https://wiki.nikhef.nl/education/api.php?action=feedcontributions&user=Rojo%40nikhef.nl&feedformat=atomEducation Wiki - User contributions [en]2024-03-28T11:48:27ZUser contributionsMediaWiki 1.35.3https://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=975Master Projects2024-03-04T17:41:27Z<p>Rojo@nikhef.nl: /* Theoretical Particle Physics: Unravelling proton structure with machine learning */</p>
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<div>'''Master Thesis Research Projects'''<br />
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The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
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== Projects with a 2024 start [WORK IN PROGRESS, please look below for older projects] ==<br />
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=== ATLAS: A new timing detector - the HGTD ===<br />
The ATLAS is going to get a new ability: a timing detector. This allows us to reconstruct tracks not only in the 3 dimensions of space but adds the ability of measuring very precisely also the time (at picosecond level) at which the particles pass the sensitive layers of the HGTD detector. The added information helps to construct the trajectories of the particles created at the LHC in 4 dimensions and ultimately will lead to a better reconstruction of physics at ATLAS. The new HGTD detector is still in construction and work needs to be done on different levels such as understanding the detector response (taking measurements in the lab and performing simulations) or developing algorithms to reconstruct the particle trajectories (programming and analysis work). <br />
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'''Several projects are available within the context of the new HGTD detector:''' <br />
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# One can choose to either focus on '''''the impact on physics analysis performance''''' by studying how the timing measurements can be included in the reconstruction of tracks, and what effect this has on how much better we can understand the physical processes occurring in the particles produced in the LHC collisions. With this work you will be part of the Atlas group at Nikhef.<br />
# The second possibility is to '''''test the sensors in our lab''''' and in test-beam setups at CERN/DESY. The analysis performed will be in context of the ATLAS HGTD test beam group in connection to both the Atlas group and the R&D department at Nikhef.<br />
# The third is to contribute in an ongoing effort '''''to precisely simulate/model the silicon avalanche detectors''''' in the Allpix2 framework. There are several models that try to describe the detectors response. The models have depend on operation temperature, field strenghts and radiation damage. We are getting close in being able to model our detector - but not there yet. This work will be within the ATLAS group.<br />
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If you are interested, contact me to discuss the possibilities. <br />
Contact: ''[mailto:hella.snoek@nikhef.nl Hella Snoek]''<br />
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=== Dark Matter: Building better Dark Matter Detectors - the XAMS R&D Setup ===<br />
The Amsterdam Dark Matter group operates an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 0.5kg of ultra-pure liquid xenon in the central volume. We use this detector for the development of new detection techniques - such as utilizing our newly installed silicon photomultipliers - and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENONnT experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory, or for future Dark Matter experiments like DARWIN. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data themselves You will "own" this experiment. <br />
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''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
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===Dark Matter: Searching for Dark Matter Particles - XENONnT Data Analysis ===<br />
The XENON collaboration has used the XENON1T detector to achieve the world’s most sensitive direct detection dark matter results and is currently operating the XENONnT successor experiment. The detectors operate at the Gran Sasso underground laboratory and consist of so-called dual-phase xenon time-projection chambers filled with ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the new data coming from the XENONnT detector. The work will consist of understanding the detector signals and applying a deep neural network to improve the (gas-) background discrimination in our Python-based analysis tool to improve the sensitivity for low-mass dark matter particles. The work will continue a study started by a recent graduate. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy.<br />
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''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
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=== Dark Matter: Signal reconstruction and correction in XENONnT ===<br />
XENONnT is a low background experiment operating at the INFN - Gran Sasso underground laboratory with the main goal of detecting Dark Matter interactions with xenon target nuclei. The detector, consisting of a dual-phase time projection chamber, is filled with ultra-pure xenon, which acts as a target and detection medium. Understanding the detector's response to various calibration sources is a mandatory step in exploiting the scientific data acquired. This MSc thesis aims to develop new methods to improve the reconstruction and correction of scintillation/ ionization signals from calibration data. The student will work with modern analysis techniques (python-based) and will collaborate with other analysts within the international XENON Collaboration.<br />
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''Contact: [mailto:mpierre@nikhef.nl Maxime Pierre], [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
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===Dark Matter: The Ultimate Dark Matter Experiment - DARWIN Sensitivity Studies===<br />
DARWIN is the “ultimate” direct detection dark matter experiment, with the goal to reach the so-called “neutrino floor”, when neutrinos become a hard-to-reduce background. The large and exquisitely clean xenon mass will allow DARWIN to also be sensitive to other physics signals such as solar neutrinos, double-beta decay from Xe-136, axions and axion-like particles etc. While the experiment will only start in 2027, we are in the midst of optimizing the experiment, which is driven by simulations. We have an opening for a student to work on the GEANT4 Monte Carlo simulations for DARWIN. We are also working on a “fast simulation” that could be included in this framework. It is your opportunity to steer the optimization of a large and unique experiment. This project requires good programming skills (Python and C++) and data analysis/physics interpretation skills.<br />
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''Contact: [mailto:t.pollmann@nikhef.nl Tina Pollmann], [mailto:decowski@nikhef.nl Patrick Decowski] or [mailto:z37@nikhef.nl Auke Colijn]''<br />
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=== Dark Matter: Exploring new background sources for DARWIN ===<br />
Experiments based on the xenon dual-phase time projection chamber detection technology have already demonstrated their leading role in the search for Dark Matter. The unprecedented low level of background reached by the current generation, such as XENONnT, allows such experiments to be sensitive to new rare-events physics searches, broadening their physics program. The next generation of experiments is already under consideration with the DARWIN observatory, which aims to surpass its predecessors in terms of background level and mass of xenon target. With the increased sensitivity to new physics channels, such as the study of neutrino properties, new sources of backgrounds may arise. This MSc thesis aims to investigate potential new sources of background for DARWIN and is a good opportunity for the student to contribute to the design of the experiment. This project will rely on Monte Carlo simulation tools such as GEANT4 and FLUKA, and good programming skills (Python and C++) are advantageous.<br />
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''Contact: [mailto:mpierre@nikhef.nl Maxime Pierre], [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
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===Dark Matter: Sensitive tests of wavelength-shifting properties of materials for dark matter detectors===<br />
Rare event search experiments that look for neutrino and dark matter interactions are performed with highly sensitive detector systems, often relying on scintillators, especially liquid noble gases, to detect particle interactions. Detectors consist of structural materials that are assumed to be optically passive, and light detection systems that use reflectors, light detectors, and sometimes, wavelength-shifting materials. MSc theses are available related to measuring the efficiency of light detection systems that might be used in future detectors. Furthermore, measurements to ensure that presumably passive materials do not fluoresce, at the low level relevant to the detectors, can be done. Part of the thesis work can include Monte Carlo simulations and data analysis for current and upcoming dark matter detectors, to study the effect of different levels of desired and nuisance wavelength shifting. In this project, students will acquire skills in photon detection, wavelength shifting technologies, vacuum systems, UV and extreme-UV optics, detector design, and optionally in Python and C++ programming, data analysis, and Monte Carlo techniques.<br />
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''Contact: [mailto:Tina.Pollmann@tum.de Tina Pollmann]''<br />
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===Theoretical Particle Physics: High-energy neutrino physics at the LHC ===<br />
High-energy collisions at the LHC and its High-Luminosity upgrade (HL-LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing experiments. The FASER experiment has in 2023, for the first team, detected neutrinos produced in LHC collisions, and is now starting to elucidate their properties. In this context, the proposed Forward Physics Facility (FPF) to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe Standard Model (SM) processes and search for physics beyond the Standard Model (BSM). High statistics neutrino detection will provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. The FPF has the promising potential to probe our understanding of the strong interactions as well as of proton and nuclear structure, providing access to both the very low-x and the very high-x regions of the colliding protons. The former regime is sensitive to novel QCD production mechanisms, such as BFKL effects and non-linear dynamics, as well as the gluon parton distribution function (PDF) down to x=1e-7, well beyond the coverage of other experiments and providing key inputs for astroparticle physics. In addition, the FPF acts as a neutrino-induced deep-inelastic scattering (DIS) experiment with TeV-scale neutrino beams. The resulting measurements of neutrino DIS structure functions represent a valuable handle on the partonic structure of nucleons and nuclei, particularly their quark flavour separation, that is fully complementary to the charged-lepton DIS measurements expected at the upcoming Electron-Ion Collider (EIC).<br />
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In this project, the student will carry out updated predictions for the neutrino fluxes expected at the FPF, assess the precision with which neutrino cross-sections will be measured, develop novel monte carlo event generation tools for high-energy neutrino scattering, and quantify their impact on proton and nuclear structure by means of machine learning tools within the NNPDF framework and state-of-the-art calculations in perturbative Quantum Chromodynamics. This project contributes to ongoing work within the FPF Initiative towards a Conceptual Design Report (CDR) to be presented within two years. Topics that can be considered as part of this project include the assessment of to which extent nuclear modifications of the free-proton PDFs can be constrained by FPF measurements, the determination of the small-x gluon PDF from suitably defined observables at the FPF and the implications for ultra-high-energy particle astrophysics, the study of the intrinsic charm content in the proton and its consequences for the FPF physics program, and the validation of models for neutrino-nucleon cross-sections in the region beyond the validity of perturbative QCD.<br />
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References: https://arxiv.org/abs/2203.05090, https://arxiv.org/abs/2109.10905 ,https://arxiv.org/abs/2208.08372 , https://arxiv.org/abs/2201.12363 , https://arxiv.org/abs/2109.02653, https://github.com/NNPDF/ see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description].<br />
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''Contacts: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
===Theoretical Particle Physics: Unravelling proton structure with machine learning===<br />
At energy-frontier facilities such as the Large Hadron Collider (LHC), scientists study the laws of nature in their quest for novel phenomena both within and beyond the Standard Model of particle physics. An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions from the nature of the Higgs boson to the origin of cosmic neutrinos. The key to address some of these questions is carrying out a global analysis of nucleon structure by combining an extensive experimental dataset and cutting-edge theory calculations. Within the NNPDF approach, this is achieved by means of a machine learning framework where neural networks parametrise the underlying physical laws while minimising ad-hoc model assumptions. In addition to the LHC, the upcoming Electron Ion Collider (EIC), to start taking data in 2029, will be the world's first ever polarised lepton-hadron collider and will offer a plethora of opportunities to address key open questions in our understanding of the strong nuclear force, such as the origin of the mass and the intrinsic angular momentum (spin) of hadrons and whether there exists a state of matter which is entirely dominated by gluons. <br />
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In this project, the student will develop novel machine learning and AI approaches aimed to improve global analyses of proton structure and better predictions for the LHC, the EIC, and astroparticle physics experiments. These new approaches will be implemented within the machine learning tools provided by the NNPDF open-source fitting framework and use state-of-the-art calculations in perturbative Quantum Chromodynamics. Techniques that will be considered include normalising flows, graph neural networks, gaussian processes, and kernel methods for unsupervised learning. Particular emphasis will be devoted to the automated determination of model hyperparameters, as well as to the estimate of the associated model uncertainties and their systematic validation with a battery of statistical tests. The outcome of the project will benefit the ongoing program of high-precision theory predictions for ongoing and future experiments in particle physics.<br />
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References: https://arxiv.org/abs/2201.12363, https://arxiv.org/abs/2109.02653 , https://arxiv.org/abs/2103.05419, https://arxiv.org/abs/1404.4293 , https://inspirehep.net/literature/1302398, https://github.com/NNPDF/ see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description].<br />
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''Contacts: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
== Projects with a 2023 start ==<br />
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=== ALICE: The next-generation multi-purpose detector at the LHC ===<br />
This main goal of this project is to focus on the next-generation multi-purpose detector planned to be built at the LHC. Its core will be a nearly massless barrel detector consisting of truly cylindrical layers based on curved wafer-scale ultra-thin silicon sensors with MAPS technology, featuring an unprecedented low material budget of 0.05% X0 per layer, with the innermost layers possibly positioned inside the beam pipe. The proposed detector is conceived for studies of pp, pA and AA collisions at luminosities a factor of 20 to 50 times higher than possible with the upgraded ALICE detector, enabling a rich physics program ranging from measurements with electromagnetic probes at ultra-low transverse momenta to precision physics in the charm and beauty sector. <br />
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''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli] and [mailto:marco.van.leeuwen@cern.ch Marco van Leeuwen]''<br />
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=== ALICE: Searching for the strongest magnetic field in nature ===<br />
In a non-central collision between two Pb ions, with a large value of impact parameter, the charged nucleons that do not participate in the interaction (called spectators) create strong magnetic fields. A back of the envelope calculation using the Biot-Savart law brings the magnitude of this filed close to 10^19Gauss in agreement with state of the art theoretical calculation, making it the strongest magnetic field in nature. The presence of this field could have direct implications in the motion of final state particles. The magnetic field, however, decays rapidly. The decay rate depends on the electric conductivity of the medium which is experimentally poorly constrained. Overall, the presence of the magnetic field, the main goal of this project, is so far not confirmed experimentally.<br />
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''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
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=== ALICE: Looking for parity violating effects in strong interactions ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions, in the presence of a deconfined state, gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, what is called the Chiral Magnetic Effect (CME).<br />
The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, however further studies are needed to constrain background effects. These highly anticipated results have the potential to reveal exiting, new physics.<br />
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''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
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=== ALICE: Machine learning techniques as a tool to study the production of heavy flavour particles ===<br />
There was recently a shift in the field of heavy-ion physics triggered by experimental results obtained in collisions between small systems (e.g. protons on protons). These results resemble the ones obtained in collisions between heavy ions. This consequently raises the question of whether we create the smallest QGP droplet in collisions between small systems. The main objective of this project will be to study the production of charm particles such as D-mesons and Λc-baryons in pp collisions at the LHC. This will be done with the help of a new and innovative technique which is based on machine learning (ML). The student will also extend the studies to investigate how this production rate depends on the event activity e.g. on how many particles are created after every collision.<br />
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''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli]''<br />
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=== ALICE: Search for new physics with 4D tracking at the most sensitive vertex detector at the LHC ===<br />
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With the newly installed Inner Tracking System consisting fully of monolithic detectors, ALICE is very sensitive to particles with low transverse momenta, more so than ATLAS and CMS. This will be even more so for the ALICE upgrade detector in 2033. This detector could potentially be even more sensitive to longlived particles that leave peculiar tracks such as disappearing or kinked tracks in the tracker by using timing information along a track. In this project you will investigate how timing information in the different tracking layers can improve or even enable a search for new physics beyond the Standard Model in ALICE. If you show a possibility for major improvements, this can have real consequences for the choice of sensors for this ALICE inner tracker upgrade.<br />
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''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld] and [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
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=== ATLAS: The Higgs boson's self-coupling ===<br />
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The coupling of the Higgs boson to itself is one of the main unobserved interactions of the Standard Model and its observation is crucial to understand the shape of the Higgs potential. Here we propose to study the 'ttHH' final state: two top quarks and two Higgs bosons produced in a single collision. This topology is yet unexplored at the ATLAS experiment and the project consists of setting up the new analysis (including multivariate analysis techniques to recognise the complicated final state), optimising the sensitivity and including the result in the full ATLAS study of the Higgs boson's coupling to itself. With the LHC data from the upcoming Run-3, we might be able to see its first glimpses! <br />
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''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree] and [mailto:cpandini@nikhef.nl Carlo Pandini]'' <br />
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=== ATLAS: Triple-Higgs production as a probe of the Higgs potential ===<br />
So far, the investigation of Higgs self-couplings (the coupling of the Higgs boson to itself) at the LHC has focused on the measurement of the Higgs tri-linear coupling λ3 mainly through direct double-Higgs production searches. In this research project we propose the investigation of Higgs tri-linear and quartic coupling parameters λ3 and λ4, via a novel measurement of triple-Higgs production at the LHC (HHH) with the ATLAS experiment. While in the SM these parameters are expected to be identical, only a combined measurement can provide an answer regarding how the Higgs potential is realised in Nature. Processes in which three Higgs bosons are produced simultaneously are extremely rare, and very difficult to measure and disentangle from background. In this project we plan to investigate different decay channels (to bottom quarks and tau leptons), and to study advanced machine learning techniques to reconstruct such a complex hadronic final state. This kind of processes is still quite unexplored in ATLAS, and the goal of this project is to put the basis for the first measurement of HHH production at the LHC.<br />
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Furthermore, we'd like to study the possible implication of a precise measurement of the self-coupling parameters from HHH production from a phenomenological point of view: what could be the impact of a deviation in the HHH measurements on the big open questions in physics (for instance, the mechanisms at the root of baryogenesis)?<br />
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Contact: ''[mailto:tdupree@nikhef.nl Tristan du Pree] and [mailto:cpandini@nikhef.nl Carlo Pandini]''<br />
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=== ATLAS: The Next Generation ===<br />
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After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks is very new [1] and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays) and advanced analysis techiques (using deep learning methods).<br />
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[https://atlas.cern/updates/briefing/charming-Higgs-decay][https://arxiv.org/abs/1802.04329 https://atlas.cern/updates/briefing/charming-Higgs-decay]<br />
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''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
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=== ATLAS: Searching for new particles in very energetic diboson production ===<br />
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The discovery of new phenomena in high-energy proton–proton collisions is one of the main goals of the Large Hadron Collider (LHC). New heavy particles decaying into a pair of vector bosons (WW, WZ, ZZ) are predicted in several extensions to the Standard Model (e.g. extended gauge-symmetry models, Grand Unified theories, theories with warped extra dimensions, etc). In this project we will investigate new ideas to look for these resonances in promising regions. We will focus on final states where both vector bosons decay into quarks, or where one decays into quarks and one into leptons. These have the potential to bring the highest sensitivity to the search for Beyond the Standard Model physics [1, 2]. We will try to reconstruct and exploit new ways to identify vector bosons (using machine learning methods) and then tackle the problem of estimating contributions from beyond the Standard Model processes in the tails of the mass distribution.<br />
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[1] https://arxiv.org/abs/1906.08589<br />
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[2] https://arxiv.org/abs/2004.14636<br />
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''Contact: [mailto:f.dias@nikhef.nl Flavia de Almeida Dias], [mailto:rhayes@nikhef.nl Robin Hayes], Elizaveta Cherepanova and Dylan van Arneman''<br />
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=== ATLAS: Top-quark and Higgs-boson analysis combination, and Effective Field Theory interpretation (also in 2023) ===<br />
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We are looking for a master student with interest in theory and data-analysis in the search for physics beyond the Standard Model in the top-quark and Higgs-boson sectors.<br />
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Your master-project starts just at the right time for preparing the Run-3 analysis of the ATLAS experiment at the LHC. In Run-3 (2022-2026), three times more data becomes available, enabling analysis of rare processes with innovative software tools and techniques.<br />
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This project aims to explore the newest strategy to combine the top-quark and Higgs-boson measurements in the perspective of constraining the existence of new physics beyond the Standard Model (SM) of Particle Physics. We selected the pp->tZq and gg->HZ processes as promising candidates for a combination to constrain new physics in the context of Standard Model Effective Field Theory (SMEFT). SMEFT is the state-of-the-art framework for theoretical interpretation of LHC data. In particular, you will study the SMEFT OtZ and Ophit operators, which are not well constrained by current measurements.<br />
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Besides affinity with particle physics theory, the ideal candidate for this project has developed python/C++ skills and is eager to learn advanced techniques. You start with a simulation of the signal and background samples using existing software tools. Then, an event selection study is required using Machine Learning techniques. To evaluate the SMEFT effects, a fitting procedure based on the innovative Morphing technique is foreseen, for which the basic tools in the ROOT and RooFit framework are available. The work is carried out in the ATLAS group at Nikhef and may lead to an ATLAS note.<br />
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''Contact: [mailto:o.rieger@nikhef.nl Oliver Rieger] and [mailto:h73@nikhef.nl Marcel Vreeswijk]''<br />
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=== ATLAS: Machine learning to search for very rare Higgs decays ===<br />
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Since the Higgs boson discovery in 2012 at the ATLAS experiment, the investigation of the properties of the Higgs boson has been a priority for research at the Large Hadron Collider (LHC). However, there are still a many open questions: Is the Higgs boson the only origin of Electroweak Symmetry Breaking? Is there a mechanism which can explain the observed mass pattern of SM particles? Many of these questions are linked to the Higgs boson coupling structure. <br />
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While the Higgs boson coupling to fermions of the third generation has been established experimentally, the investigation of the Higgs boson coupling to the light fermions of the second generation will be a major project for the upcoming data-taking period (2022-2025). The Higgs boson decay to muons is the most sensitive channel for probing this coupling. In this project, you will optimize the event selection for Higgs boson decays to muons in the Vector Boson Fusion (VBF) production channel with a focus on distinguishing signal events from background processes like Drell-Yan and electroweak Z boson production. For this purpose, you will develop, implement and validate advanced machine learning and deep learning algorithms. <br />
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''Contact: [mailto:oliver.rieger@nikhef.nl Oliver Rieger] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:s01@nikhef.nl Peter Kluit]''<br />
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=== ATLAS: Interpretation of experimental data using SMEFT ===<br />
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The Standard Model Effective Field Theory (SMEFT) provides a systematic approach to test the impact of new physics at the energy scale of the LHC through higher-dimensional operators. The interpretation of experimental data using SMEFT requires a particular interest in solving complex technical challenges, advanced statistical techniques, and a deep understanding of particle physics. We would be happy to discuss different project opportunities based on your interests with you.<br />
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''Contact: [mailto:oliver.rieger@nikhef.nl Oliver Rieger] and [mailto:verkerke@nikhef.nl Wouter Verkerke]''<br />
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=== ATLAS: Reconstructing tracks from particle physics detector hits with state-of-the-art machine learning techniques ===<br />
This project concerns the application of new machine learning techniques to tackle the problem of track reconstruction at the ATLAS detector in CERN. While algorithms to construct particle tracks from low-level detector information such as particle hits and timestamps have been around for decades, recent developments in the field of machine learning open up new opportunities to improve these algorithms significantly. Some recent developments that could help in this context include graph-based neural networks, which embed the input data in the format of a graph and as such have the capability to enhance underlying correlations within events. Transformer neural networks are a particular extension of graph-based neural networks proposed only in 2017 which could also provide helpful in this case. Another option would be to build upon some of the work done within the field of computer vision and see if image segmentation networks can help solve this problem. There are a range of available options and this project includes the freedom for the student to choose particular types of networks, but more explicit guidance could be provided in case it is desired.<br />
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In this project the student will develop and compare the performance of various machine learning models to initially reconstruct tracks from simplified test data. Upon successful completion of this, simulated data from the actual ATLAS detector can be analysed as well in the scope of this project. The student will need some familiarity with programming in python and an interest in machine learning, but a physics background is not required. In this project the student will be able to contribute to fundamental physics research and will familiarize themselves with state-of-the-art machine learning models.<br />
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Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
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=== ATLAS: New machine learning approaches to target Higgs interference signatures in LHC data ===<br />
In this project we aim to improve an ongoing analysis to determine the lifetime of the Higgs Boson through state-of-the-art machine learning techniques, in particular by addressing a ''novel solution to an as of yet unsolved fundamental problem in modeling quantum interference''. While the Higgs is an elusive particle that generally only appears in physics processes with small cross sections, its signature can be amplified in the Large Hadron Collider (LHC) through quantum interference with larger background (non-Higgs) processes. This is the effect that the Higgs’ lifetime analysis relies on to be able to measure the relevant Higgs signature. A fundamental physics modelling problem arises though in the simulation of individual events for this interference due to the fact that these events are in reality described by a superposition of underlying Higgs and non-Higgs processes.<br />
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Since machine learning models in particle physics are typically trained to characterise individual physics events, the fact that interference events cannot currently be generated is a significant problem when interference is the target. In the currently existing Higgs lifetime analysis, a machine learning model was trained which instead focuses only on the explicit Higgs-mediated processes as a proxy, which is suboptimal. The aim of this project is to improve upon this current machine learning strategy used in this analysis by implementing either of the inference-aware approaches suggested in [1] and [2]. The idea behind these inference-aware machine learning algorithms is that they do not optimise for a simplified goal such as the loss function which is common in traditional machine learning, but rather for the end-goal of the analysis. In this case, this would omit the need for interference event generation altogether and allow the machine learning models to be trained optimally regardless.<br />
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The first checkpoint of this project is to use either of the frameworks used in [1] and [2] (which are both publicly available) and run them with a simplified dataset from the aforementioned analysis. After this proof-of-principle is achieved, the next goal would be to actually implement the newly developed machine learning models in the full analysis and to determine the improvement upon the existing result. A successful completion of these tasks would not only benefit the Higgs lifetime analysis, but would be an important stepping stone to future developments to make machine learning approaches also aware of other hard to model effects such as systematic uncertainties. Finally, there are further options to improve this analysis such as the generation of actual interference training data, which could be attempted in case the primary project finishes earlier than expected.<br />
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[1] De Castro, P., & Dorigo, T. (2019). INFERNO: inference-aware neural optimisation. ''Computer Physics Communications'', ''244'', 170-179.<br />
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[2] Simpson, N., & Heinrich, L. (2023, February). neos: End-to-end-optimised summary statistics for high energy physics. In ''Journal of Physics: Conference Series'' (Vol. 2438, No. 1, p. 012105). IOP Publishing.<br />
<br />
Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
=== ATLAS: Development of state-of-the art modeling techniques to generate Higgs interference events ===<br />
In this project we aim to improve an ongoing analysis to determine the lifetime of the Higgs Boson through new event generation strategies, in particular by addressing a novel solution to an as of yet unsolved fundamental problem in modeling quantum interference. While the Higgs is an elusive particle that generally only appears in physics processes with small cross sections, its signature can be amplified in the Large Hadron Collider (LHC) through quantum interference with larger background (non-Higgs) processes. This is the effect that the Higgs’ lifetime analysis relies on to be able to measure the relevant Higgs signature. A fundamental physics modelling problem arises though in the simulation of individual events for this interference due to the fact that these events are in reality described by a superposition of underlying Higgs and non-Higgs processes.<br />
<br />
The current approach to deal with this problem is to ignore the interference in analysis optimization and instead optimize only for explicitly Higgs mediated processes, but this severely impacts analysis performance. In the context of Effective Field Theories (EFT) however, a similar problem arises and has been solved for simple (leading order) processes. In this project we plan to take the machinery developed for EFT and apply it to the Higgs lifetime analysis. Furthermore, with the recent development of a Next-to-Leading Order (NLO) Higgs event generation tool [1] a subsequent goal would be to use this to also generate interference at the NLO level. Successful completion of this project would lead to a much improved analysis result, significantly constraining the lifetime of the Higgs Boson. Besides, the techniques developed would almost certainly be used in future analyses on Large Hadron Collider (LHC) run 3 data.<br />
<br />
[1] Alioli, S., Ravasio, S. F., Lindert, J. M., & Röntsch, R. (2021). Four-lepton production in gluon fusion at NLO matched to parton showers. ''The European Physical Journal C'', ''81''(8), 687.<br />
<br />
Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák], [mailto:b.kortman@nikhef.nl Bryan Kortman] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
=== ATLAS: Approaching the Higgs from a new direction: Constraining new physics with off shell Higgs data from the LHC ===<br />
The Heisenberg uncertainly principle allows for all elementary particles---including the Higgs Boson---to momentarily disobey the fundamental energy-momentum relation, allowing the particle in question to have a significantly larger mass than usual. A description of the Higgs Boson in this state (“off shell Higgs Boson”) can provide a portal to the discovery of potential new physics, albeit very difficult to do due to its infrequent appearance. The goal of this project is to constrain or hint at new physics by estimating parameters of a generalized model which allows for new physics, Effective Field Theory (EFT), using off shell Higgs data.<br />
<br />
Most of the underlying analysis to measure the prevalence of off shell Higgs bosons has already been set up, so the goal of this project is to do the aforementioned EFT interpretation on top of this existing analysis. From a theoretical point of view much of the groundwork has also been done on simulated data which showed the potential for this EFT interpretation to constrain new physics [1]. Being on the interface between experimental and theoretical physics this project allows the student to gain a deeper understanding of both, furthermore its successful completion could be one of the first hints towards as of yet not understood physics.<br />
<br />
[1] Azatov, A., de Blas, J., Falkowski, A., Gritsan, A. V., Grojean, C., Kang, L., ... & Vryonidou, E. (2022). Off-shell Higgs Interpretations Task Force: Models and Effective Field Theories Subgroup Report. arXiv preprint arXiv:2203.02418.<br />
<br />
Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák], [mailto:b.kortman@nikhef.nl Bryan Kortman] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
=== ATLAS: A new timing detector - the HGTD ===<br />
The ATLAS is going to get a new ability: a timing detector. This allows us to reconstruct tracks not only in the 3 dimensions of space but adds the ability of measuring very precisely also the time (at picosecond level) at which the particles pass the sensitive layers of the HGTD detector. This allows to construct the trajectories of the particles created at the LHC in 4 dimensions and ultimately will lead to a better reconstruction of physics at ATLAS. The new HGTD detector is still in construction and work needs to be done on different levels such as understanding the detector response (taking measurements in the lab and performing simulations) or developing algorithms to reconstruct the particle trajectories (programming and analysis work). <br />
<br />
'''Several projects are available within the context of the new HGTD detector:''' <br />
<br />
# One can choose to either focus on '''''the impact on physics analysis performance''''' by studying how the timing measurements can be included in the reconstruction of tracks, and what effect this has on how much better we can understand the physical processes occurring in the particles produced in the LHC collisions. With this work you will be part of the Atlas group at Nikhef.<br />
# The second possibility is to '''''test the sensors in our lab''''' and in test-beam setups at CERN. The analysis performed will be in context of the ATLAS HGTD test beam group in connection to both the Atlas group and the R&D department at Nikhef.<br />
# The third is to contribute in an ongoing effort '''''to precisely simulate/model he silicon avalanche detectors''''' in the Allpix2 frameword. There are several models that try to describe the detectors response. There are several dependencies to operation temperature, field strenghts and radiation damage. We are getting close in being able to model our detector - but not there yet. This work will be within the ATLAS group together with Hella Snoek and Andrea Visibile<br />
<br />
If you are interested, contact me to discuss the possibilities. <br />
Contact: ''[mailto:hella.snoek@nikhef.nl Hella Snoek]''<br />
<br />
<br />
=== ATLAS: The next full-silicon Inner Tracker: ITk ===<br />
[[File:ITk endcap structure.jpg|210x210px|thumb|alt=]]The inner detector of the present ATLAS experiment has been designed and developed to function in the environment of the present Large Hadron Collider (LHC). At the ATLAS Phase-II Upgrade, the particle densities and radiation levels will exceed current levels by a factor of ten. The instantaneous luminosity is expected to reach unprecedented values, resulting in up to 200 proton-proton interactions in a typical bunch crossing. The new detectors must be faster and they need to be more highly segmented. The sensors used also need to be far more resistant to radiation, and they require much greater power delivery to the front-end systems. At the same time, they cannot introduce excess material which could undermine tracking performance. For those reasons, the inner tracker of the ATLAS detector (ITk) was redesigned and will be rebuilt completely.<br />
<br />
Nikhef is one of the sites in charge of building and integrating some big parts of ITk. One of the next steps consists of testing the sensors that we will install in the structures we have built (check one of the structures in the picture of our cleanroom). This project offers the possibility of working on a full hardware project, doing something completely new, by testing the sensors of a future component of the next ATLAS detector.<br />
<br />
''Contact'': ''[mailto:aalonso@nikhef.nl Andrea García Alonso]''<br />
<br />
=== Cosmic Rays/Neutrinos: Seasonal muon flux variations and the pion/kaon ratio ===<br />
The KM3NeT ARCA and ORCA detectors, located kilometers deep in the Mediterranean Sea, have neutrinos as primary probes. Muons from cosmic ray interactions reach the detectors in relatively large quantities too. These muons, exploiting the capabilities and location of the detectors allow the study of cosmic rays and their interactions. In this way, questions about their origin, type, propagation can be addressed. In particular these muons are tracers of hadronic interactions at energies inaccessible at particle accelerators.<br />
<br />
The muons reaching the depths of the detectors result from decays of mesons, mostly pions and kaons, created in interactions of high-energy cosmic rays with atoms in the upper atmosphere. Seasonal changes of the temperature – and thus density - profile of the atmosphere modulate the balance between the probability for these mesons to decay (producing muons) or to re-interact. Pions and kaons are affected differently, allowing to extract their production ratio by determining how changes in muon rate depend on changes in the effective temperature – an integral over the atmospheric temperature profile weighted by a depth dependent meson production rate.<br />
<br />
In this project, the aim is to measure the rate of muons in the detectors and to calculate the effective temperature above the KM3NeT detectors from atmospheric data, both as function of time. The relation between these two can be used to extract the pion to kaon ratio.<br />
<br />
''Contact: [mailto:rbruijn@nikhef.nl Ronald Bruijn]''<br />
=== Detector R&D: Studies of wafer-scale sensors for ALICE detector upgrade and beyond===<br />
One of the biggest milestones of the ALICE detector upgrade (foreseen in 2026) is the implementation of wafer-scale (~ 28 cm x 18 cm) monolithic silicon active pixel sensors in the tracking detector, with the goal of having truly cylindrical barrels around the beam pipe. To demonstrate such an unprecedented technology in high energy physics detectors, few chips will be soon available in Nikhef laboratories for testing and characterization purposes.<br />
The goal of the project is to contribute to the validation of the samples against the ALICE tracking detector requirements, with a focus on timing performance in view of other applications in future high energy physics experiments beyond ALICE.<br />
We are looking for a student with a focus on lab work and interested in high precision measurements with cutting-edge instrumentation. You will be part of the Nikhef Detector R&D group and you will have, at the same time, the chance to work in an international collaboration where you will report about the performance of these novel sensors. There may even be the opportunity to join beam tests at CERN or DESY facilities. Besides interest in hardware, some proficiency in computing is required (Python or C++/ROOT).<br />
<br />
''Contact: [mailto:(jory.sonneveld@nikhef.nl Jory Sonneveld ], [mailto:rrusso@nikhef.nl Roberto Russo]''<br />
<br />
=== Detector R&D: Time resolution of monolithic silicon detectors ===<br />
Monolithic silicon detectors based on industrial Complementary Metal Oxide Semiconductor (CMOS) processes offer a promising approach for large scale detectors due to their ease of production and low material budget. Until recently, their low radiation tolerance has hindered their applicability in high energy particle physics experiments. However, new prototypes ~~such as the one in this project~~ have overcome these hurdles, making them feasible candidates for future experiments in high energy particle physics. Achieving the required radiation tolerance has brought the spatial and temporal resolution of these detectors to the forefront. In this project, you will investigate the temporal performance of a radiation hard monolithic detector prototype, using laser setups in the laboratory. You will also participate in meetings with the international collaboration working on this detector, where you will report on the prototype's performance. Depending on the progress of the work, there may be a chance to participate in test beams performed at the CERN accelerator complex and a first full three dimensional characterization of the prototypes performance using a state-of-the-art two-photon absorption laser setup at Nikhef. This project is looking for someone interested in working hands on with cutting edge detector and laser systems at the Nikhef laboratory. Python programming skills and linux experience are an advantage.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld], [mailto:uwe.kraemer@nikhef.nl Uwe Kraemer]''<br />
<br />
=== Detector R&D: Improving a Laser Setup for Testing Fast Silicon Pixel Detectors ===<br />
For the upgrades of the innermost detectors of experiments at the Large Hadron Collider in Geneva, in particular to cope with the large number of collisions per second from 2027, the Detector R&D group at Nikhef tests new pixel detector prototypes with a variety of laser equipment with several wavelengths. The lasers can be focused down to a small spot to scan over the pixels on a pixel chip. Since the laser penetrates the silicon, the pixels will not be illuminated by just the focal spot, but by the entire three dimensional hourglass or double cone like light intensity distribution. So, how well defined is the volume in which charge is released? And can that be made much smaller than a pixel? And, if so, what would the optimum focus be? For this project the student will first estimate the intensity distribution inside a sensor that can be expected. This will correspond to the density of released charge within the silicon. To verify predictions, you will measure real pixel sensors for the LHC experiments.<br />
This project will involve a lot of 'hands on work' in the lab and involve programming and work on unix machines.<br />
<br />
''Contact: [mailto:martinfr@nikhef.nl Martin Fransen]''<br />
<br />
=== Detector R&D: Time resolution of hybrid pixel detectors with the Timepix4 chip ===<br />
Precise time measurements with silicon pixel detectors are very important for experiments at the High-Luminosity LHC and the future circular collider. The spatial resolution of current silicon trackers will not be sufficient to distinguish the large number of collisions that will occur within individual bunch crossings. In a new method, typically referred to as 4D tracking, spatial measurements of pixel detectors will be combined with time measurements to better distinguish collision vertices that occur close together.<br />
New sensor technologies are being explored to reach the required time measurement resolution of tens of picoseconds, and the results are promising. However, the signals that these pixelated sensors produce have to be processed by front-end electronics, which hence also play a role in the total time resolution of the detector. An important contribution comes from the systematic differences between the front-end electronics of different pixels. Many of these systematic effects can be corrected by performing detailed calibrations of the readout electronics. To achieve the required time resolution at future experiments, it is vital that these effects are understood and corrected.<br />
In this project you will be working with the Timepix4 chip. This is a so-called application specific integrated circuit (ASIC) that is designed to read out pixelated sensors. This ASIC will be used extensively in detector R&D for the characterisation of new sensor technologies requiring precise timing (< 50 ps). In order to do so, it is necessary to first study the systematic differences between the pixels, which you will do using a laser setup in our lab. This will be combined with data analysis of proton beam measurements, or with measurements performed using the built-in test-pulse mechanism of the Timepix4 ASIC. Your work will enable further research performed with this ASIC, <br />
and serve as input to the design and operation of future ASICs for experiments at the High-Luminosity LHC.<br />
<br />
''Contact: [mailto:k.heijhoff@nikhef.nl Kevin Heijhoff] and [mailto:martinb@nikhef.nl Martin van Beuzekom]''<br />
<br />
===Detector R&D: Performance studies of Trench Isolated Low Gain Avalanche Detectors (TI-LGAD) ===<br />
The future vertex detector of the LHCb Experiment needs to measure the spatial coordinates and time of the particles originating in the LHC proton-proton collisions with resolutions better than 10 um and 50 ps, respectively. Several technologies are being considered to achieve these resolutions. Among those is a novel sensor technology called Trench Isolated Low Gain Avalanche Detector. <br />
Prototype pixelated sensors have been manufactured recently and have to be characterised. Therefore these new sensors will be bump bonded to a Timepix4 ASIC which provides charge and time measurements in each of 230 thousand pixels. Characterisation will be done using a lab setup at Nikhef, and includes tests with a micro-focused laser beam, radioactive sources, and possibly with particle tracks obtained in a test-beam. This project involves data taking with these new devices and analysing the data to determine the performance parameters such as the spatial and temporal resolution. as function of temperature and other operational conditions. <br />
<br />
''Contacts: [mailto:kazu.akiba@nikhef.nl Kazu Akiba] and [mailto:martinb@nikhef.nl Martin van Beuzekom]''<br />
<br />
===Detector R&D: A Telescope with Ultrathin Sensors for Beam Tests ===<br />
To measure the performance of new prototypes for upgrades of the LHC experiments and beyond, typically a telescope is used in a beam line of charged particles that can be used to compare the results in the prototype to particle tracks measured with this telescope. In this project, you will continue work on a very lightweight, compact telescope using ALICE PIxel DEtectors (ALPIDEs). This includes work on the mechanics, data acquisition software, and a moveable stage. You will foreseeably test this telescope in the Delft Proton Therapy Center. If time allows, you will add a timing plane and perform a measurement with one of our prototypes. Apart from travel to Delft, there is a possiblity to travel to other beam line facilities.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
===Detector R&D: Laser Interferometer Space Antenna (LISA) - the first gravitational wave detector in space ===<br />
<br />
The space-based gravitational wave antenna LISA is one of the most challenging space missions ever proposed. ESA plans to launch around 2034 three spacecraft separated by a few million kilometres. This constellation measures tiny variations in the distances between test-masses located in each satellite to detect gravitational waves from sources such as supermassive black holes. LISA is based on laser interferometry, and the three satellites form a giant Michelson interferometer. LISA measures a relative phase shift between one local laser and one distant laser by light interference. The phase shift measurement requires sensitive sensors. The Nikhef DR&D group fabricated prototype sensors in 2020 together with the Photonics industry and the Dutch institute for space research SRON. Nikhef & SRON are responsible for the Quadrant PhotoReceiver (QPR) system: the sensors, the housing including a complex mount to align the sensors with 10's of nanometer accuracy, various environmental tests at the European Space Research and Technology Centre (ESTEC), and the overall performance of the QPR in the LISA instrument. Currently we are discussing possible sensor improvements for a second fabrication run in 2022, optimizing the mechanics and preparing environmental tests. As a MSc student, you will work on various aspects of the wavefront sensor development: study the performance of the epitaxial stacks of Indium-Gallium-Arsenide, setting up test benches to characterize the sensors and QPR system, performing the actual tests and data analysis, in combination with performance studies and simulations of the LISA instrument.<br />
<br />
''Contact: [mailto:nielsvb@nikhef.nl Niels van Bakel]''<br />
<br />
===Detector R&D: Other projects ===<br />
Are you looking for a slightly different project? Are the above projects already taken? Are you coming in at an unusual time of the year? Do not hesitate to contact us! We always have new projects coming up at different times in the year and we are open to your ideas.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
===FCC: The Next Collider===<br />
<br />
After the LHC, the next planned large collider at CERN is the proposed 100 kilometer circular collider "FCC". In the first stage of the project, as a high-luminosity electron-positron collider, precision measurements of the Higgs boson are the main goal. One of the channels that will improve by orders of magnitude at this new accelerator is the decay of the Higgs boson to a pair of charm quarks. This project will estimate a projected sensitivity for the coupling of the Higgs boson to second generation quarks, and in particular target the improved reconstruction of the topology of long-lived mesons in the clean environment of a precision e+e- machine.<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
===Gravitational Waves: Computer modelling to design the laser interferometers for the Einstein telescope===<br />
<br />
A new field of instrument science led to the successful detection of gravitational waves by the LIGO detectors in 2015. We are now preparing the next generation of gravitational wave observatories, such as the Einstein Telescope, with the aim to increase the detector sensitivity by a factor of ten, which would allow, for example, to detect stellar-mass black holes from early in the universe when the first stars began to form. This ambitious goal requires us to find ways to significantly improve the best laser interferometers in the world.<br />
<br />
Gravitational wave detectors, such as LIGO and VIRGO, are complex Michelson-type interferometers enhanced with optical cavities. We develop and use numerical models to study these laser interferometers, to invent new optical techniques and to quantify their performance. For example, we synthesize virtual mirror surfaces to study the effects of higher-order optical modes in the interferometers, and we use opto-mechanical models to test schemes for suppressing quantum fluctuations of the light field. We can offer several projects based on numerical modelling of laser interferometers. All projects will be directly linked to the ongoing design of the Einstein Telescope.<br />
<br />
''Contact: [mailto:a.freise@nikhef.nl Andreas Freise]''<br />
<br />
===LHCb: Search for light dark particles===<br />
The Standard Model of elementary particles does not contain a proper Dark Matter candidate. One of the most tantalizing theoretical developments is the so-called ''Hidden Valley models'': a mirror-like copy of the ''Standard Model'', with dark particles that communicate with standard ones via a very feeble interaction. These models predict the existence of ''dark hadrons'' – composite particles that are bound similarly to ordinary hadrons in the ''Standard Model''. Such ''dark hadrons'' can be abundantly produced in high-energy proton-proton collisions, making the LHC a unique place to search for them. Some ''dark hadrons'' are stable like a proton, which makes them excellent ''Dark Matter'' candidates, while others decay to ordinary particles after flying a certain distance in the collider experiment. The LHCb detector has a unique capability to identify such decays, particularly if the new particles have a mass below ten times the proton mass. <br />
<br />
This project assumes a unique search for light ''dark hadrons'' that covers a mass range not accessible to other experiments. It assumes an interesting program on data analysis (python-based) with non-trivial machine learning solutions and phenomenology research using fast simulation framework. Depending on the interest, there is quite a bit of flexibility in the precise focus of the project.<br />
<br />
''Contact: [mailto:andrii.usachov@nikhef.nl Andrii Usachov]''<br />
<br />
===LHCb: Searching for dark matter in exotic six-quark particles===<br />
<br />
Three quarters of the mass in the Universe is of unknown type. Many hypotheses about this dark matter have been proposed, but none confirmed. Recently it has been proposed that it could be made of particles made of the six quarks uuddss, which would be a Standard-Model solution to the dark matter problem. This idea has recently gained credibility as many similar multi-quarks states are being discovered by the LHCb experiment. Such a particle could be produced in decays of heavy baryons, or directly in proton-proton collisions. The anti-particle, made of six antiquarks, could be seen when annihilating with detector material. It is also proposed to use Xi_b baryons produced at LHCb to search for such a state where the state would appear as missing 4-momentum in a kinematically constrained decay. The project consists in defining a selection and applying it to LHCb data. See [https://arxiv.org/abs/2007.10378 arXiv:2007.10378].<br />
<br />
Contact: ''[mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
<br />
===LHCb: Measuring lepton flavour universality with excited Ds states in semileptonic Bs decays===<br />
One of the most striking discrepancies between the Standard Model and measurements are the lepton flavour universality (LFU) measurements with tau decays. At the moment, we have observed an excess of 3-4 sigma in ''B → Dτν'' decays. This could point even to a new force of nature! To understand this discrepancy, we need to make further measurements. <br />
<br />
One very exciting (pun intended) projects to verify these discrepancies involves measuring the ''B<sub>s</sub> → D<sub>s2</sub><sup>*</sup>τν'' and/or ''B<sub>s</sub> → D<sub>s1</sub><sup>*</sup>τν'' decays. These decays with excited states of the ''D<sub>s</sub>'' meson have not been observed before in the tau decay mode, and have a unique way of coupling to potential new physics candidates that can only be measured in ''B<sub>s</sub>'' decays [1]. See slides for more detail: [[File:LHCbLFUwithExcitedDs.pdf|thumb]]<br />
<br />
[1] https://arxiv.org/abs/1606.09300<br />
<br />
''Contact: [mailto:suzannek@nikhef.nl Suzanne Klaver]''<br />
<br />
===LHCb: New physics in the angular distributions of B decays to K*ee===<br />
<br />
Lepton flavour violation in B decays can be explained by a variety of non-standard model interactions. Angular distributions in decays of a B meson to a hadron and two leptons are an important source of information to understand which model is correct. Previous analyses at the LHCb experiment have considered final states with a pair of muons. Our LHCb group at Nikhef concentrates on a new measurement of angular distributions in decays with two electrons. The main challenge in this measurement is the calibration of the detection efficiency. In this project you will confront estimates of the detection efficiency derived from simulation with decay distributions in a well known B decay. Once the calibration is understood, the very first analysis of the angular distributions in the electron final state can be performed. <br />
<br />
Contact: [mailto:m.senghi.soares@nikhef.nl Mara Soares] and [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
<br />
===LHCb: Discovering heavy neutrinos in B decays===<br />
<br />
Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, much heavier, neutral leptons. If the mass of these new neutrinos is below the b-quark mass, they can be observed in B hadron decays.<br />
<br />
In this project we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undiscovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The analysis will be performed within the LHCb group at Nikhef using LHCb run-2 data.<br />
<br />
===LHCb: Scintillating Fibre tracker software===<br />
The installation of the scintillating-fibre tracker in LHCb’s underground cavern was recently completed. This detector uses 10000 km of fibres to track particle trajectories in the LHCb detector when the LHC starts up again later this year. The light emitted by the scintillating fibres when a particle interacts with them is measured using photon multiplier tubes. The studies proposed for this project will focus on software, and could include writing a framework to monitor the detector output, improving the detector simulation or working on the data processing.<br />
<br />
''Contact: [mailto:e.gabriel@nikhef.nl Emmy Gabriel]''<br />
<br />
===LHCb: Vertex detector calibration===<br />
In summer 2022 LHCb has started data taking will an almost entirely new detector. At the point closest to the interaction point, the trajectories of charge particles are reconstructed with a so-called silicon pixel detector. The design hit resolution of this detector is about 15 micron. However, to actually reach this resolution a precise calibration of the spatial positions of the silicon sensors needs to be performed. In this project, you will use the first data of the new LHCb detector to perform this calibration and measure the detector performance.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen]''<br />
<br />
<br />
===Neutrinos: Neutrino scattering: the ultimate resolution===<br />
<br />
Neutrino telescopes like IceCube and KM3NeT aim at detecting neutrinos from cosmic sources. The neutrinos are detected with the best resolution when charged current interactions with nucleons produce a muon, which can be detected with high accuracy (depending on the detector). A crucial ingredient in the ultimate achievable pointing accuracy of neutrino telescopes is the scattering angle between the neutrino and the muon. While published computations have investigated the cross-section of the process in great detail, this important scattering angle has not received much attention. The aim of the project is to compute and characterize the distribution of this angle, and that the ultimate resolution of a neutrino telescope. If successful, the results of this project can lead to publication of interest to the neutrino telescope community.<br />
<br />
Depending on your interests, the study could be based on a first-principles calculation (using the deep-inelastic scattering formalism), include state-of-the-art parton distribution functions, and/or exploit existing event-generation software for a more experimental approach. <br />
<br />
''Contacts: [mailto:aart.heijboer@nikhef.nl Aart Heijboer]''<br />
<br />
===Neutrinos: acoustic detection of ultra-high energy neutrinos===<br />
<br />
The study of the cosmic neutrinos of energies above 1017 eV, the so-called ultra-high energy neutrinos, provides a unique view on the universe and may provide insight in the origin of the most violent astrophysical sources, such as gamma ray bursts, supernovae or even dark matter. In addition, the observation of high energy neutrinos may provide a unique tool to study interactions at high energies. The energy deposition of these extreme neutrinos in water induce a thermo-acoustic signal, which can be detected using sensitive hydrophones. The expected neutrino flux is however extremely low and the signal that neutrinos induce is small. TNO is presently developing sensitive hydrophone technology based on fiber optics. Optical fibers form a natural way to create a distributed sensing system. Using this technology a large scale neutrino telescope can be built in the deep sea. TNO is aiming for a prototype hydrophone which will form the building block of a future telescope.<br />
<br />
The work will be executed at the Nikhef institute and/or the TNO laboratories in Delft. In this project master students have the opportunity to contribute in the following ways:<br />
<br />
'''Project 1:''' Hardware development on fiber optics hydrophones technology Goal: characterize existing prototype optical fibre hydrophones in an anechoic basin at TNO laboratory. Data collection, calibration, characterization, analysis of consequences for design future acoustic hydrophone neutrino telescopes;<br />
Keywords: Optical fiber technology, signal processing, electronics, lab.<br />
<br />
'''Project 2:''' Investigation of ultra-high energy neutrinos and their interactions with matter. Goal: Discriminate the neutrino signals from the background noises, in particular clicks from whales and dolphins in the deep sea. Study impact on physics reach for future acoustic hydrophone neutrino telescopes;<br />
Keywords: Monte Carlo simulations, particle physics, neutrino physics, data analysis algorithms.<br />
<br />
Further information: Info on ultra-high energy neutrinos can be found at: http://arxiv.org/abs/1102.3591; Info on acoustic detection of neutrinos can be found at: http://arxiv.org/abs/1311.7588<br />
<br />
''Contact: [mailto:ernst-jan.buis@tno.nl Ernst Jan Buis]'' or ''[mailto:ivo.van.vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
===Neutrinos: Oscillation analysis with the first data of KM3NeT===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first few strings with sensitive photodetectors have been deployed at both the Italian and the French detector sites. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In this project the available data will be used together with simulations to best reconstruct the event topologies and optimally identify and reconstruct the first neutrino interactions in the KM3NeT detector. The data will then be used to measure neutrino oscillation parameters, and prepare for a future neutrino mass ordering determination.<br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
''Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn] [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
<br />
===Neutrinos: the Deep Underground Neutrino Experiment (DUNE)===<br />
<br />
The Deep Underground Neutrino Experiment (DUNE) is under construction in the USA, and will consist of a powerful neutrino beam originating at Fermilab, a near detector at Fermilab, and a far detector in the SURF facility in Lead, South Dakota, 1300 km away. During travelling, neutrinos oscillate and a fraction of the neutrino beam changes flavour; DUNE will determine the neutrino oscillation parameters to unrivaled precision, and try and make a first detection of CP-violation in neutrinos. In this project, various elements of DUNE can be studied, including the neutrino oscillation fit, neutrino physics with the near detector, event reconstruction and classification (including machine learning), or elements of data selection and triggering.<br />
<br />
''Contact: [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
===Neutrinos: Searching for Majorana Neutrinos with KamLAND-Zen===<br />
The KamLAND-Zen experiment, located in the Kamioka mine in Japan, is a large liquid scintillator experiment with 750kg of ultra-pure Xe-136 to search for neutrinoless double-beta decay (0n2b). The observation of the 0n2b process would be evidence for lepton number violation and the Majorana nature of neutrinos, i.e. that neutrinos are their own anti-particles. Current limits on this extraordinary rare hypothetical decay process are presented as a half-life, with a lower limit of 10^26 years. KamLAND-Zen, the world’s most sensitive 0n2b experiment, is currently taking data and there is an opportunity to work on the data analysis, analyzing data with the possibility of taking part in a ground-breaking discovery. The main focus will be on developing new techniques to filter the spallation backgrounds, i.e. the production of radioactive isotopes by passing muons. There will be close collaboration with groups in the US (MIT, Berkeley, UW) and Japan (Tohoku Univ). <br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
===Neutrinos: relic neutrino detection with PTOLEMY ===<br />
PTOLEMY aims to make the first direct observation of the Big Bang relic neutrinos (the cosmic neutrino background, CνB) by resolving the β-decay endpoint of atomic tritium (neutrino capture target) to O(meV) precision. This remains an outstanding test of the Standard Model in an expanding universe. Not only does the CνB carry with it a signal from the hot dense universe only one second after the Big Bang but helps to constrain the balance of hot versus cold dark matter responsible for its evolution. In doing so, the PTOLEMY experiment would also measure the lowest neutrino mass, an as-of-yet unknown fundamental constant. The experiment is currently in the prototyping phase and the group at Nikhef is responsible for developing the radio-frequency (RF) system used for cyclotron radiation (CR) based trigger and tracking. This component will provide the trajectory of electrons entering the novel transverse drift filter, constraining the electrons' energy losses before they reach the cryogenic calorimeter which in turn records their final energy. The focus of this project will be modelling CR and its detection for the purposes of single electron spectroscopy and optimised trajectory reconstruction. There is also the opportunity to test hardware and readout electronics for the prototype RF-system. <br />
''Contact: [mailto:jmead@nikhef.nl James Vincent Mead]''<br />
<br />
=== Theoretical Particle Physics: Effective Field Theories of Particle Physics from low- to high-energies===<br />
Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations” seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature. The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Standard Model Effective Field Theory (SMEFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes with minimal assumptions on the nature of an eventual UV-complete theory that replaces the Standard Model. Specifically, the goal is to connect measurements from ATLAS, CMS, and LHCb experiments at the CERN's LHC among them and to jointly interpret this information with that provided by other experiments including very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
<br />
This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories. Depending on the student profile, sub-projects with a strong computational and/or machine learning component are also possible, for instance to construct new operators with optimal sensitivity to New Physics effects as encoded by the SMEFT higher-dimensional operators. Topics that can be considered in this project include the interpretation of novel physical observables at the LHC and their integration into the global SMEFiT analysis, matching of EFTs to UV-complete theories and their phenomenological analyses, projections for the impact in the SMEFT parameter space of data for future colliders, the synergies between EFT studies and proton structure fits, and the matching to the Weak Effective Field Theory to include data on flavour observables such as B-meson decays.<br />
<br />
References: https://arxiv.org/abs/2105.00006 , https://arxiv.org/abs/2302.06660, https://arxiv.org/abs/2211.02058 , https://arxiv.org/abs/1901.05965 , https://arxiv.org/abs/1906.05296 , https://arxiv.org/abs/1908.05588, https://arxiv.org/abs/1905.05215. see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description].<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theoretical Particle Physics: High-energy neutrino-nucleon interactions at the Forward Physics Facility ===<br />
High-energy collisions at the High-Luminosity Large Hadron Collider (HL-LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing experiments. The proposed Forward Physics Facility (FPF) to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe Standard Model (SM) processes and search for physics beyond the Standard Model (BSM). High statistics neutrino detection will provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. The FPF has the promising potential to probe our understanding of the strong interactions as well as of proton and nuclear structure, providing access to both the very low-x and the very high-x regions of the colliding protons. The former regime is sensitive to novel QCD production mechanisms, such as BFKL effects and non-linear dynamics, as well as the gluon parton distribution function (PDF) down to x=1e-7, well beyond the coverage of other experiments and providing key inputs for astroparticle physics. In addition, the FPF acts as a neutrino-induced deep-inelastic scattering (DIS) experiment with TeV-scale neutrino beams. The resulting measurements of neutrino DIS structure functions represent a valuable handle on the partonic structure of nucleons and nuclei, particularly their quark flavour separation, that is fully complementary to the charged-lepton DIS measurements expected at the upcoming Electron-Ion Collider (EIC).<br />
<br />
In this project, the student will carry out updated predictions for the neutrino fluxes expected at the FPF, assess the precision with which neutrino cross-sections will be measured, and quantify their impact on proton and nuclear structure by means of machine learning tools within the NNPDF framework and state-of-the-art calculations in perturbative Quantum Chromodynamics. This project contributes to ongoing work within the FPF Initiative towards a Conceptual Design Report (CDR) to be presented within two years. Topics that can be considered as part of this project include the assessment of to which extent nuclear modifications of the free-proton PDFs can be constrained by FPF measurements, the determination of the small-x gluon PDF from suitably defined observables at the FPF and the implications for ultra-high-energy particle astrophysics, the study of the intrinsic charm content in the proton and its consequences for the FPF physics program, and the validation of models for neutrino-nucleon cross-sections in the region beyond the validity of perturbative QCD.<br />
<br />
References: https://arxiv.org/abs/2203.05090, https://arxiv.org/abs/2109.10905 ,https://arxiv.org/abs/2208.08372 , https://arxiv.org/abs/2201.12363 , https://arxiv.org/abs/2109.02653, https://github.com/NNPDF/ see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description]. <br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theoretical Particle Physics: Probing the origin of the proton spin with machine learning===<br />
At energy-frontier facilities such as the Large Hadron Collider (LHC), scientists study the laws of nature in their quest for novel phenomena both within and beyond the Standard Model of particle physics. An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions from the nature of the Higgs boson to the origin of cosmic neutrinos. The key to address some of these questions is by carrying out an universal analysis of nucleon structure from the simultaneous determination of the momentum and spin distributions of quarks and gluons and their fragmentation into hadrons. This effort requires combining an extensive experimental dataset and cutting-edge theory calculations within a machine learning framework where neural networks parametrise the underlying physical laws while minimising ad-hoc model assumptions. The upcoming Electron Ion Collider (EIC), to start taking data in 2029, will be the world's first ever polarised lepton-hadron collider and will offer a plethora of opportunities to address key open questions in our understanding of the strong nuclear force, such as the origin of the mass and the intrinsic angular momentum (spin) of hadrons and whether there exists a state of matter which is entirely dominated by gluons. To fully exploit this scientific potential, novel analysis methodologies need to be develop that make it possible to carry out large-scale, coherent interpretations of measurements from the EIC and other high-energy colliders.<br />
<br />
In this project, the student will carry out a new global analysis of the spin structure of the proton by means of the machine learning tools provided by the NNPDF open-source fitting framework and state-of-the-art calculations in perturbative Quantum Chromodynamics, and integrate it within the corresponding global NNPDF analyses of unpolarised proton and nuclear structure in the framework of a combined integrated global analysis of non-perturbative QCD. Specifically, the project aims to realise a NNLO global fit of polarised quark and gluon PDFs that combines all available data and state-of-the-art perturbative QCD calculations, and study the phenomenological implications for other experiments, including the EIC, for the spin content of the proton, for comparisons with lattice QCD calculations, and for nonpperturbative models of hadron structure.<br />
<br />
References: https://arxiv.org/abs/2201.12363, https://arxiv.org/abs/2109.02653 , https://arxiv.org/abs/2103.05419, https://arxiv.org/abs/1404.4293 , https://inspirehep.net/literature/1302398, https://github.com/NNPDF/ see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description].<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== '''Theoretical Particle Physics''': Charged lepton flavor violation in neutrino mass models ===<br />
The nonzero value of neutrino masses requires an explanation beyond the Standard Model of particle physics. A promising solution involves the existence of extra neutrinos, often called right-handed or sterile neutrinos. These models elegantly explain neutrino masses and can also be connected to other puzzles such as the absence of anti-matter in our universe. In this project you will investigate potential experimental signatures of sterile neutrinos through decays that are extremely rare in the Standard Model. Examples are muon decays to electrons and photons, or muon + neutron -> electron + neutron. You will perform Quantum Field Theory calculations within the neutrino-extended Standard Model to compute the rates of these processes and compare them to experimental sensitivities. <br />
<br />
''Contacts: [Mailto:j.devries4@uva.nl Jordy de Vries]''<br />
<br />
=== '''Theoretical Particle Physics''': The electric dipole moment of paramagnetic systems in the Standard Model ===<br />
Electric dipole moments (EDMs) of elementary particles, hadrons, nuclei, atoms, and molecules would indicate the violation of CP violation. The Standard Model (SM) contains CP violation in the weak interaction in the so-called CKM matrix (the quark-mixing matrix) but it leads to EDMs that are too small to be seen. At least this is often claimed. In this work we will reinvestigate the computation of the EDMs of systems that are used in state-of-the-art experiments. In particular we will compute a CP-violating interaction between electrons and nucleons mitigated by the SM weak interaction. During this project you will obtain a deep understanding of the Standard Model and explicit quantum field theory calculations across a wider range of energy scales. <br />
<br />
''Contacts: [Mailto:j.devries4@uva.nl Jordy de Vries]''<br />
------------------------------------------------------------------<br />
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== Finished master projects ==<br />
<br />
See: <br />
* https://wiki.nikhef.nl/education/Master_Theses<br />
* https://www.nikhef.nl/master-theses-2021/<br />
* https://www.nikhef.nl/facts-figures-2020/master-theses-2020/<br />
<br />
<br />
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----<br />
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<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=974Master Projects2024-03-04T17:32:40Z<p>Rojo@nikhef.nl: /* Theoretical Particle Physics: High-energy neutrino physics at the LHC */</p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
== Projects with a 2024 start [WORK IN PROGRESS, please look below for older projects] ==<br />
<br />
=== ATLAS: A new timing detector - the HGTD ===<br />
The ATLAS is going to get a new ability: a timing detector. This allows us to reconstruct tracks not only in the 3 dimensions of space but adds the ability of measuring very precisely also the time (at picosecond level) at which the particles pass the sensitive layers of the HGTD detector. The added information helps to construct the trajectories of the particles created at the LHC in 4 dimensions and ultimately will lead to a better reconstruction of physics at ATLAS. The new HGTD detector is still in construction and work needs to be done on different levels such as understanding the detector response (taking measurements in the lab and performing simulations) or developing algorithms to reconstruct the particle trajectories (programming and analysis work). <br />
<br />
'''Several projects are available within the context of the new HGTD detector:''' <br />
<br />
# One can choose to either focus on '''''the impact on physics analysis performance''''' by studying how the timing measurements can be included in the reconstruction of tracks, and what effect this has on how much better we can understand the physical processes occurring in the particles produced in the LHC collisions. With this work you will be part of the Atlas group at Nikhef.<br />
# The second possibility is to '''''test the sensors in our lab''''' and in test-beam setups at CERN/DESY. The analysis performed will be in context of the ATLAS HGTD test beam group in connection to both the Atlas group and the R&D department at Nikhef.<br />
# The third is to contribute in an ongoing effort '''''to precisely simulate/model the silicon avalanche detectors''''' in the Allpix2 framework. There are several models that try to describe the detectors response. The models have depend on operation temperature, field strenghts and radiation damage. We are getting close in being able to model our detector - but not there yet. This work will be within the ATLAS group.<br />
<br />
If you are interested, contact me to discuss the possibilities. <br />
Contact: ''[mailto:hella.snoek@nikhef.nl Hella Snoek]''<br />
<br />
=== Dark Matter: Building better Dark Matter Detectors - the XAMS R&D Setup ===<br />
The Amsterdam Dark Matter group operates an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 0.5kg of ultra-pure liquid xenon in the central volume. We use this detector for the development of new detection techniques - such as utilizing our newly installed silicon photomultipliers - and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENONnT experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory, or for future Dark Matter experiments like DARWIN. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data themselves You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
===Dark Matter: Searching for Dark Matter Particles - XENONnT Data Analysis ===<br />
The XENON collaboration has used the XENON1T detector to achieve the world’s most sensitive direct detection dark matter results and is currently operating the XENONnT successor experiment. The detectors operate at the Gran Sasso underground laboratory and consist of so-called dual-phase xenon time-projection chambers filled with ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the new data coming from the XENONnT detector. The work will consist of understanding the detector signals and applying a deep neural network to improve the (gas-) background discrimination in our Python-based analysis tool to improve the sensitivity for low-mass dark matter particles. The work will continue a study started by a recent graduate. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy.<br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter: Signal reconstruction and correction in XENONnT ===<br />
XENONnT is a low background experiment operating at the INFN - Gran Sasso underground laboratory with the main goal of detecting Dark Matter interactions with xenon target nuclei. The detector, consisting of a dual-phase time projection chamber, is filled with ultra-pure xenon, which acts as a target and detection medium. Understanding the detector's response to various calibration sources is a mandatory step in exploiting the scientific data acquired. This MSc thesis aims to develop new methods to improve the reconstruction and correction of scintillation/ ionization signals from calibration data. The student will work with modern analysis techniques (python-based) and will collaborate with other analysts within the international XENON Collaboration.<br />
<br />
''Contact: [mailto:mpierre@nikhef.nl Maxime Pierre], [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
===Dark Matter: The Ultimate Dark Matter Experiment - DARWIN Sensitivity Studies===<br />
DARWIN is the “ultimate” direct detection dark matter experiment, with the goal to reach the so-called “neutrino floor”, when neutrinos become a hard-to-reduce background. The large and exquisitely clean xenon mass will allow DARWIN to also be sensitive to other physics signals such as solar neutrinos, double-beta decay from Xe-136, axions and axion-like particles etc. While the experiment will only start in 2027, we are in the midst of optimizing the experiment, which is driven by simulations. We have an opening for a student to work on the GEANT4 Monte Carlo simulations for DARWIN. We are also working on a “fast simulation” that could be included in this framework. It is your opportunity to steer the optimization of a large and unique experiment. This project requires good programming skills (Python and C++) and data analysis/physics interpretation skills.<br />
<br />
''Contact: [mailto:t.pollmann@nikhef.nl Tina Pollmann], [mailto:decowski@nikhef.nl Patrick Decowski] or [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter: Exploring new background sources for DARWIN ===<br />
Experiments based on the xenon dual-phase time projection chamber detection technology have already demonstrated their leading role in the search for Dark Matter. The unprecedented low level of background reached by the current generation, such as XENONnT, allows such experiments to be sensitive to new rare-events physics searches, broadening their physics program. The next generation of experiments is already under consideration with the DARWIN observatory, which aims to surpass its predecessors in terms of background level and mass of xenon target. With the increased sensitivity to new physics channels, such as the study of neutrino properties, new sources of backgrounds may arise. This MSc thesis aims to investigate potential new sources of background for DARWIN and is a good opportunity for the student to contribute to the design of the experiment. This project will rely on Monte Carlo simulation tools such as GEANT4 and FLUKA, and good programming skills (Python and C++) are advantageous.<br />
<br />
''Contact: [mailto:mpierre@nikhef.nl Maxime Pierre], [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
===Dark Matter: Sensitive tests of wavelength-shifting properties of materials for dark matter detectors===<br />
Rare event search experiments that look for neutrino and dark matter interactions are performed with highly sensitive detector systems, often relying on scintillators, especially liquid noble gases, to detect particle interactions. Detectors consist of structural materials that are assumed to be optically passive, and light detection systems that use reflectors, light detectors, and sometimes, wavelength-shifting materials. MSc theses are available related to measuring the efficiency of light detection systems that might be used in future detectors. Furthermore, measurements to ensure that presumably passive materials do not fluoresce, at the low level relevant to the detectors, can be done. Part of the thesis work can include Monte Carlo simulations and data analysis for current and upcoming dark matter detectors, to study the effect of different levels of desired and nuisance wavelength shifting. In this project, students will acquire skills in photon detection, wavelength shifting technologies, vacuum systems, UV and extreme-UV optics, detector design, and optionally in Python and C++ programming, data analysis, and Monte Carlo techniques.<br />
<br />
''Contact: [mailto:Tina.Pollmann@tum.de Tina Pollmann]''<br />
<br />
===Theoretical Particle Physics: High-energy neutrino physics at the LHC ===<br />
High-energy collisions at the LHC and its High-Luminosity upgrade (HL-LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing experiments. The FASER experiment has in 2023, for the first team, detected neutrinos produced in LHC collisions, and is now starting to elucidate their properties. In this context, the proposed Forward Physics Facility (FPF) to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe Standard Model (SM) processes and search for physics beyond the Standard Model (BSM). High statistics neutrino detection will provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. The FPF has the promising potential to probe our understanding of the strong interactions as well as of proton and nuclear structure, providing access to both the very low-x and the very high-x regions of the colliding protons. The former regime is sensitive to novel QCD production mechanisms, such as BFKL effects and non-linear dynamics, as well as the gluon parton distribution function (PDF) down to x=1e-7, well beyond the coverage of other experiments and providing key inputs for astroparticle physics. In addition, the FPF acts as a neutrino-induced deep-inelastic scattering (DIS) experiment with TeV-scale neutrino beams. The resulting measurements of neutrino DIS structure functions represent a valuable handle on the partonic structure of nucleons and nuclei, particularly their quark flavour separation, that is fully complementary to the charged-lepton DIS measurements expected at the upcoming Electron-Ion Collider (EIC).<br />
<br />
In this project, the student will carry out updated predictions for the neutrino fluxes expected at the FPF, assess the precision with which neutrino cross-sections will be measured, develop novel monte carlo event generation tools for high-energy neutrino scattering, and quantify their impact on proton and nuclear structure by means of machine learning tools within the NNPDF framework and state-of-the-art calculations in perturbative Quantum Chromodynamics. This project contributes to ongoing work within the FPF Initiative towards a Conceptual Design Report (CDR) to be presented within two years. Topics that can be considered as part of this project include the assessment of to which extent nuclear modifications of the free-proton PDFs can be constrained by FPF measurements, the determination of the small-x gluon PDF from suitably defined observables at the FPF and the implications for ultra-high-energy particle astrophysics, the study of the intrinsic charm content in the proton and its consequences for the FPF physics program, and the validation of models for neutrino-nucleon cross-sections in the region beyond the validity of perturbative QCD.<br />
<br />
References: https://arxiv.org/abs/2203.05090, https://arxiv.org/abs/2109.10905 ,https://arxiv.org/abs/2208.08372 , https://arxiv.org/abs/2201.12363 , https://arxiv.org/abs/2109.02653, https://github.com/NNPDF/ see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description].<br />
<br />
''Contacts: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
===Theoretical Particle Physics: Unravelling proton structure with machine learning===<br />
At energy-frontier facilities such as the Large Hadron Collider (LHC), scientists study the laws of nature in their quest for novel phenomena both within and beyond the Standard Model of particle physics. An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions from the nature of the Higgs boson to the origin of cosmic neutrinos. The key to address some of these questions is by carrying out an universal analysis of nucleon structure from the simultaneous determination of the momentum and spin distributions of quarks and gluons and their fragmentation into hadrons. This effort requires combining an extensive experimental dataset and cutting-edge theory calculations within a machine learning framework where neural networks parametrise the underlying physical laws while minimising ad-hoc model assumptions. The upcoming Electron Ion Collider (EIC), to start taking data in 2029, will be the world's first ever polarised lepton-hadron collider and will offer a plethora of opportunities to address key open questions in our understanding of the strong nuclear force, such as the origin of the mass and the intrinsic angular momentum (spin) of hadrons and whether there exists a state of matter which is entirely dominated by gluons. To fully exploit this scientific potential, novel analysis methodologies need to be develop that make it possible to carry out large-scale, coherent interpretations of measurements from the EIC and other high-energy colliders.<br />
<br />
In this project, the student will carry out a new global analysis of the spin structure of the proton by means of the machine learning tools provided by the NNPDF open-source fitting framework and state-of-the-art calculations in perturbative Quantum Chromodynamics, and integrate it within the corresponding global NNPDF analyses of unpolarised proton and nuclear structure in the framework of a combined integrated global analysis of non-perturbative QCD. Specifically, the project aims to realise a NNLO global fit of polarised quark and gluon PDFs that combines all available data and state-of-the-art perturbative QCD calculations, and study the phenomenological implications for other experiments, including the EIC, for the spin content of the proton, for comparisons with lattice QCD calculations, and for nonpperturbative models of hadron structure.<br />
<br />
References: https://arxiv.org/abs/2201.12363, https://arxiv.org/abs/2109.02653 , https://arxiv.org/abs/2103.05419, https://arxiv.org/abs/1404.4293 , https://inspirehep.net/literature/1302398, https://github.com/NNPDF/ see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description].<br />
<br />
''Contacts: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
== Projects with a 2023 start ==<br />
<br />
=== ALICE: The next-generation multi-purpose detector at the LHC ===<br />
This main goal of this project is to focus on the next-generation multi-purpose detector planned to be built at the LHC. Its core will be a nearly massless barrel detector consisting of truly cylindrical layers based on curved wafer-scale ultra-thin silicon sensors with MAPS technology, featuring an unprecedented low material budget of 0.05% X0 per layer, with the innermost layers possibly positioned inside the beam pipe. The proposed detector is conceived for studies of pp, pA and AA collisions at luminosities a factor of 20 to 50 times higher than possible with the upgraded ALICE detector, enabling a rich physics program ranging from measurements with electromagnetic probes at ultra-low transverse momenta to precision physics in the charm and beauty sector. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli] and [mailto:marco.van.leeuwen@cern.ch Marco van Leeuwen]''<br />
<br />
=== ALICE: Searching for the strongest magnetic field in nature ===<br />
In a non-central collision between two Pb ions, with a large value of impact parameter, the charged nucleons that do not participate in the interaction (called spectators) create strong magnetic fields. A back of the envelope calculation using the Biot-Savart law brings the magnitude of this filed close to 10^19Gauss in agreement with state of the art theoretical calculation, making it the strongest magnetic field in nature. The presence of this field could have direct implications in the motion of final state particles. The magnetic field, however, decays rapidly. The decay rate depends on the electric conductivity of the medium which is experimentally poorly constrained. Overall, the presence of the magnetic field, the main goal of this project, is so far not confirmed experimentally.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Looking for parity violating effects in strong interactions ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions, in the presence of a deconfined state, gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, what is called the Chiral Magnetic Effect (CME).<br />
The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, however further studies are needed to constrain background effects. These highly anticipated results have the potential to reveal exiting, new physics.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Machine learning techniques as a tool to study the production of heavy flavour particles ===<br />
There was recently a shift in the field of heavy-ion physics triggered by experimental results obtained in collisions between small systems (e.g. protons on protons). These results resemble the ones obtained in collisions between heavy ions. This consequently raises the question of whether we create the smallest QGP droplet in collisions between small systems. The main objective of this project will be to study the production of charm particles such as D-mesons and Λc-baryons in pp collisions at the LHC. This will be done with the help of a new and innovative technique which is based on machine learning (ML). The student will also extend the studies to investigate how this production rate depends on the event activity e.g. on how many particles are created after every collision.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli]''<br />
<br />
=== ALICE: Search for new physics with 4D tracking at the most sensitive vertex detector at the LHC ===<br />
<br />
With the newly installed Inner Tracking System consisting fully of monolithic detectors, ALICE is very sensitive to particles with low transverse momenta, more so than ATLAS and CMS. This will be even more so for the ALICE upgrade detector in 2033. This detector could potentially be even more sensitive to longlived particles that leave peculiar tracks such as disappearing or kinked tracks in the tracker by using timing information along a track. In this project you will investigate how timing information in the different tracking layers can improve or even enable a search for new physics beyond the Standard Model in ALICE. If you show a possibility for major improvements, this can have real consequences for the choice of sensors for this ALICE inner tracker upgrade.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld] and [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ATLAS: The Higgs boson's self-coupling ===<br />
<br />
The coupling of the Higgs boson to itself is one of the main unobserved interactions of the Standard Model and its observation is crucial to understand the shape of the Higgs potential. Here we propose to study the 'ttHH' final state: two top quarks and two Higgs bosons produced in a single collision. This topology is yet unexplored at the ATLAS experiment and the project consists of setting up the new analysis (including multivariate analysis techniques to recognise the complicated final state), optimising the sensitivity and including the result in the full ATLAS study of the Higgs boson's coupling to itself. With the LHC data from the upcoming Run-3, we might be able to see its first glimpses! <br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree] and [mailto:cpandini@nikhef.nl Carlo Pandini]'' <br />
<br />
=== ATLAS: Triple-Higgs production as a probe of the Higgs potential ===<br />
So far, the investigation of Higgs self-couplings (the coupling of the Higgs boson to itself) at the LHC has focused on the measurement of the Higgs tri-linear coupling λ3 mainly through direct double-Higgs production searches. In this research project we propose the investigation of Higgs tri-linear and quartic coupling parameters λ3 and λ4, via a novel measurement of triple-Higgs production at the LHC (HHH) with the ATLAS experiment. While in the SM these parameters are expected to be identical, only a combined measurement can provide an answer regarding how the Higgs potential is realised in Nature. Processes in which three Higgs bosons are produced simultaneously are extremely rare, and very difficult to measure and disentangle from background. In this project we plan to investigate different decay channels (to bottom quarks and tau leptons), and to study advanced machine learning techniques to reconstruct such a complex hadronic final state. This kind of processes is still quite unexplored in ATLAS, and the goal of this project is to put the basis for the first measurement of HHH production at the LHC.<br />
<br />
Furthermore, we'd like to study the possible implication of a precise measurement of the self-coupling parameters from HHH production from a phenomenological point of view: what could be the impact of a deviation in the HHH measurements on the big open questions in physics (for instance, the mechanisms at the root of baryogenesis)?<br />
<br />
Contact: ''[mailto:tdupree@nikhef.nl Tristan du Pree] and [mailto:cpandini@nikhef.nl Carlo Pandini]''<br />
<br />
=== ATLAS: The Next Generation ===<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks is very new [1] and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays) and advanced analysis techiques (using deep learning methods).<br />
<br />
[https://atlas.cern/updates/briefing/charming-Higgs-decay][https://arxiv.org/abs/1802.04329 https://atlas.cern/updates/briefing/charming-Higgs-decay]<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
=== ATLAS: Searching for new particles in very energetic diboson production ===<br />
<br />
The discovery of new phenomena in high-energy proton–proton collisions is one of the main goals of the Large Hadron Collider (LHC). New heavy particles decaying into a pair of vector bosons (WW, WZ, ZZ) are predicted in several extensions to the Standard Model (e.g. extended gauge-symmetry models, Grand Unified theories, theories with warped extra dimensions, etc). In this project we will investigate new ideas to look for these resonances in promising regions. We will focus on final states where both vector bosons decay into quarks, or where one decays into quarks and one into leptons. These have the potential to bring the highest sensitivity to the search for Beyond the Standard Model physics [1, 2]. We will try to reconstruct and exploit new ways to identify vector bosons (using machine learning methods) and then tackle the problem of estimating contributions from beyond the Standard Model processes in the tails of the mass distribution.<br />
<br />
[1] https://arxiv.org/abs/1906.08589<br />
<br />
[2] https://arxiv.org/abs/2004.14636<br />
<br />
''Contact: [mailto:f.dias@nikhef.nl Flavia de Almeida Dias], [mailto:rhayes@nikhef.nl Robin Hayes], Elizaveta Cherepanova and Dylan van Arneman''<br />
<br />
=== ATLAS: Top-quark and Higgs-boson analysis combination, and Effective Field Theory interpretation (also in 2023) ===<br />
<br />
We are looking for a master student with interest in theory and data-analysis in the search for physics beyond the Standard Model in the top-quark and Higgs-boson sectors.<br />
<br />
Your master-project starts just at the right time for preparing the Run-3 analysis of the ATLAS experiment at the LHC. In Run-3 (2022-2026), three times more data becomes available, enabling analysis of rare processes with innovative software tools and techniques.<br />
<br />
This project aims to explore the newest strategy to combine the top-quark and Higgs-boson measurements in the perspective of constraining the existence of new physics beyond the Standard Model (SM) of Particle Physics. We selected the pp->tZq and gg->HZ processes as promising candidates for a combination to constrain new physics in the context of Standard Model Effective Field Theory (SMEFT). SMEFT is the state-of-the-art framework for theoretical interpretation of LHC data. In particular, you will study the SMEFT OtZ and Ophit operators, which are not well constrained by current measurements.<br />
<br />
Besides affinity with particle physics theory, the ideal candidate for this project has developed python/C++ skills and is eager to learn advanced techniques. You start with a simulation of the signal and background samples using existing software tools. Then, an event selection study is required using Machine Learning techniques. To evaluate the SMEFT effects, a fitting procedure based on the innovative Morphing technique is foreseen, for which the basic tools in the ROOT and RooFit framework are available. The work is carried out in the ATLAS group at Nikhef and may lead to an ATLAS note.<br />
<br />
''Contact: [mailto:o.rieger@nikhef.nl Oliver Rieger] and [mailto:h73@nikhef.nl Marcel Vreeswijk]''<br />
<br />
=== ATLAS: Machine learning to search for very rare Higgs decays ===<br />
<br />
Since the Higgs boson discovery in 2012 at the ATLAS experiment, the investigation of the properties of the Higgs boson has been a priority for research at the Large Hadron Collider (LHC). However, there are still a many open questions: Is the Higgs boson the only origin of Electroweak Symmetry Breaking? Is there a mechanism which can explain the observed mass pattern of SM particles? Many of these questions are linked to the Higgs boson coupling structure. <br />
<br />
While the Higgs boson coupling to fermions of the third generation has been established experimentally, the investigation of the Higgs boson coupling to the light fermions of the second generation will be a major project for the upcoming data-taking period (2022-2025). The Higgs boson decay to muons is the most sensitive channel for probing this coupling. In this project, you will optimize the event selection for Higgs boson decays to muons in the Vector Boson Fusion (VBF) production channel with a focus on distinguishing signal events from background processes like Drell-Yan and electroweak Z boson production. For this purpose, you will develop, implement and validate advanced machine learning and deep learning algorithms. <br />
<br />
''Contact: [mailto:oliver.rieger@nikhef.nl Oliver Rieger] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:s01@nikhef.nl Peter Kluit]''<br />
<br />
=== ATLAS: Interpretation of experimental data using SMEFT ===<br />
<br />
The Standard Model Effective Field Theory (SMEFT) provides a systematic approach to test the impact of new physics at the energy scale of the LHC through higher-dimensional operators. The interpretation of experimental data using SMEFT requires a particular interest in solving complex technical challenges, advanced statistical techniques, and a deep understanding of particle physics. We would be happy to discuss different project opportunities based on your interests with you.<br />
<br />
''Contact: [mailto:oliver.rieger@nikhef.nl Oliver Rieger] and [mailto:verkerke@nikhef.nl Wouter Verkerke]''<br />
<br />
=== ATLAS: Reconstructing tracks from particle physics detector hits with state-of-the-art machine learning techniques ===<br />
This project concerns the application of new machine learning techniques to tackle the problem of track reconstruction at the ATLAS detector in CERN. While algorithms to construct particle tracks from low-level detector information such as particle hits and timestamps have been around for decades, recent developments in the field of machine learning open up new opportunities to improve these algorithms significantly. Some recent developments that could help in this context include graph-based neural networks, which embed the input data in the format of a graph and as such have the capability to enhance underlying correlations within events. Transformer neural networks are a particular extension of graph-based neural networks proposed only in 2017 which could also provide helpful in this case. Another option would be to build upon some of the work done within the field of computer vision and see if image segmentation networks can help solve this problem. There are a range of available options and this project includes the freedom for the student to choose particular types of networks, but more explicit guidance could be provided in case it is desired.<br />
<br />
In this project the student will develop and compare the performance of various machine learning models to initially reconstruct tracks from simplified test data. Upon successful completion of this, simulated data from the actual ATLAS detector can be analysed as well in the scope of this project. The student will need some familiarity with programming in python and an interest in machine learning, but a physics background is not required. In this project the student will be able to contribute to fundamental physics research and will familiarize themselves with state-of-the-art machine learning models.<br />
<br />
Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
=== ATLAS: New machine learning approaches to target Higgs interference signatures in LHC data ===<br />
In this project we aim to improve an ongoing analysis to determine the lifetime of the Higgs Boson through state-of-the-art machine learning techniques, in particular by addressing a ''novel solution to an as of yet unsolved fundamental problem in modeling quantum interference''. While the Higgs is an elusive particle that generally only appears in physics processes with small cross sections, its signature can be amplified in the Large Hadron Collider (LHC) through quantum interference with larger background (non-Higgs) processes. This is the effect that the Higgs’ lifetime analysis relies on to be able to measure the relevant Higgs signature. A fundamental physics modelling problem arises though in the simulation of individual events for this interference due to the fact that these events are in reality described by a superposition of underlying Higgs and non-Higgs processes.<br />
<br />
Since machine learning models in particle physics are typically trained to characterise individual physics events, the fact that interference events cannot currently be generated is a significant problem when interference is the target. In the currently existing Higgs lifetime analysis, a machine learning model was trained which instead focuses only on the explicit Higgs-mediated processes as a proxy, which is suboptimal. The aim of this project is to improve upon this current machine learning strategy used in this analysis by implementing either of the inference-aware approaches suggested in [1] and [2]. The idea behind these inference-aware machine learning algorithms is that they do not optimise for a simplified goal such as the loss function which is common in traditional machine learning, but rather for the end-goal of the analysis. In this case, this would omit the need for interference event generation altogether and allow the machine learning models to be trained optimally regardless.<br />
<br />
The first checkpoint of this project is to use either of the frameworks used in [1] and [2] (which are both publicly available) and run them with a simplified dataset from the aforementioned analysis. After this proof-of-principle is achieved, the next goal would be to actually implement the newly developed machine learning models in the full analysis and to determine the improvement upon the existing result. A successful completion of these tasks would not only benefit the Higgs lifetime analysis, but would be an important stepping stone to future developments to make machine learning approaches also aware of other hard to model effects such as systematic uncertainties. Finally, there are further options to improve this analysis such as the generation of actual interference training data, which could be attempted in case the primary project finishes earlier than expected.<br />
<br />
[1] De Castro, P., & Dorigo, T. (2019). INFERNO: inference-aware neural optimisation. ''Computer Physics Communications'', ''244'', 170-179.<br />
<br />
[2] Simpson, N., & Heinrich, L. (2023, February). neos: End-to-end-optimised summary statistics for high energy physics. In ''Journal of Physics: Conference Series'' (Vol. 2438, No. 1, p. 012105). IOP Publishing.<br />
<br />
Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
=== ATLAS: Development of state-of-the art modeling techniques to generate Higgs interference events ===<br />
In this project we aim to improve an ongoing analysis to determine the lifetime of the Higgs Boson through new event generation strategies, in particular by addressing a novel solution to an as of yet unsolved fundamental problem in modeling quantum interference. While the Higgs is an elusive particle that generally only appears in physics processes with small cross sections, its signature can be amplified in the Large Hadron Collider (LHC) through quantum interference with larger background (non-Higgs) processes. This is the effect that the Higgs’ lifetime analysis relies on to be able to measure the relevant Higgs signature. A fundamental physics modelling problem arises though in the simulation of individual events for this interference due to the fact that these events are in reality described by a superposition of underlying Higgs and non-Higgs processes.<br />
<br />
The current approach to deal with this problem is to ignore the interference in analysis optimization and instead optimize only for explicitly Higgs mediated processes, but this severely impacts analysis performance. In the context of Effective Field Theories (EFT) however, a similar problem arises and has been solved for simple (leading order) processes. In this project we plan to take the machinery developed for EFT and apply it to the Higgs lifetime analysis. Furthermore, with the recent development of a Next-to-Leading Order (NLO) Higgs event generation tool [1] a subsequent goal would be to use this to also generate interference at the NLO level. Successful completion of this project would lead to a much improved analysis result, significantly constraining the lifetime of the Higgs Boson. Besides, the techniques developed would almost certainly be used in future analyses on Large Hadron Collider (LHC) run 3 data.<br />
<br />
[1] Alioli, S., Ravasio, S. F., Lindert, J. M., & Röntsch, R. (2021). Four-lepton production in gluon fusion at NLO matched to parton showers. ''The European Physical Journal C'', ''81''(8), 687.<br />
<br />
Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák], [mailto:b.kortman@nikhef.nl Bryan Kortman] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
=== ATLAS: Approaching the Higgs from a new direction: Constraining new physics with off shell Higgs data from the LHC ===<br />
The Heisenberg uncertainly principle allows for all elementary particles---including the Higgs Boson---to momentarily disobey the fundamental energy-momentum relation, allowing the particle in question to have a significantly larger mass than usual. A description of the Higgs Boson in this state (“off shell Higgs Boson”) can provide a portal to the discovery of potential new physics, albeit very difficult to do due to its infrequent appearance. The goal of this project is to constrain or hint at new physics by estimating parameters of a generalized model which allows for new physics, Effective Field Theory (EFT), using off shell Higgs data.<br />
<br />
Most of the underlying analysis to measure the prevalence of off shell Higgs bosons has already been set up, so the goal of this project is to do the aforementioned EFT interpretation on top of this existing analysis. From a theoretical point of view much of the groundwork has also been done on simulated data which showed the potential for this EFT interpretation to constrain new physics [1]. Being on the interface between experimental and theoretical physics this project allows the student to gain a deeper understanding of both, furthermore its successful completion could be one of the first hints towards as of yet not understood physics.<br />
<br />
[1] Azatov, A., de Blas, J., Falkowski, A., Gritsan, A. V., Grojean, C., Kang, L., ... & Vryonidou, E. (2022). Off-shell Higgs Interpretations Task Force: Models and Effective Field Theories Subgroup Report. arXiv preprint arXiv:2203.02418.<br />
<br />
Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák], [mailto:b.kortman@nikhef.nl Bryan Kortman] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
=== ATLAS: A new timing detector - the HGTD ===<br />
The ATLAS is going to get a new ability: a timing detector. This allows us to reconstruct tracks not only in the 3 dimensions of space but adds the ability of measuring very precisely also the time (at picosecond level) at which the particles pass the sensitive layers of the HGTD detector. This allows to construct the trajectories of the particles created at the LHC in 4 dimensions and ultimately will lead to a better reconstruction of physics at ATLAS. The new HGTD detector is still in construction and work needs to be done on different levels such as understanding the detector response (taking measurements in the lab and performing simulations) or developing algorithms to reconstruct the particle trajectories (programming and analysis work). <br />
<br />
'''Several projects are available within the context of the new HGTD detector:''' <br />
<br />
# One can choose to either focus on '''''the impact on physics analysis performance''''' by studying how the timing measurements can be included in the reconstruction of tracks, and what effect this has on how much better we can understand the physical processes occurring in the particles produced in the LHC collisions. With this work you will be part of the Atlas group at Nikhef.<br />
# The second possibility is to '''''test the sensors in our lab''''' and in test-beam setups at CERN. The analysis performed will be in context of the ATLAS HGTD test beam group in connection to both the Atlas group and the R&D department at Nikhef.<br />
# The third is to contribute in an ongoing effort '''''to precisely simulate/model he silicon avalanche detectors''''' in the Allpix2 frameword. There are several models that try to describe the detectors response. There are several dependencies to operation temperature, field strenghts and radiation damage. We are getting close in being able to model our detector - but not there yet. This work will be within the ATLAS group together with Hella Snoek and Andrea Visibile<br />
<br />
If you are interested, contact me to discuss the possibilities. <br />
Contact: ''[mailto:hella.snoek@nikhef.nl Hella Snoek]''<br />
<br />
<br />
=== ATLAS: The next full-silicon Inner Tracker: ITk ===<br />
[[File:ITk endcap structure.jpg|210x210px|thumb|alt=]]The inner detector of the present ATLAS experiment has been designed and developed to function in the environment of the present Large Hadron Collider (LHC). At the ATLAS Phase-II Upgrade, the particle densities and radiation levels will exceed current levels by a factor of ten. The instantaneous luminosity is expected to reach unprecedented values, resulting in up to 200 proton-proton interactions in a typical bunch crossing. The new detectors must be faster and they need to be more highly segmented. The sensors used also need to be far more resistant to radiation, and they require much greater power delivery to the front-end systems. At the same time, they cannot introduce excess material which could undermine tracking performance. For those reasons, the inner tracker of the ATLAS detector (ITk) was redesigned and will be rebuilt completely.<br />
<br />
Nikhef is one of the sites in charge of building and integrating some big parts of ITk. One of the next steps consists of testing the sensors that we will install in the structures we have built (check one of the structures in the picture of our cleanroom). This project offers the possibility of working on a full hardware project, doing something completely new, by testing the sensors of a future component of the next ATLAS detector.<br />
<br />
''Contact'': ''[mailto:aalonso@nikhef.nl Andrea García Alonso]''<br />
<br />
=== Cosmic Rays/Neutrinos: Seasonal muon flux variations and the pion/kaon ratio ===<br />
The KM3NeT ARCA and ORCA detectors, located kilometers deep in the Mediterranean Sea, have neutrinos as primary probes. Muons from cosmic ray interactions reach the detectors in relatively large quantities too. These muons, exploiting the capabilities and location of the detectors allow the study of cosmic rays and their interactions. In this way, questions about their origin, type, propagation can be addressed. In particular these muons are tracers of hadronic interactions at energies inaccessible at particle accelerators.<br />
<br />
The muons reaching the depths of the detectors result from decays of mesons, mostly pions and kaons, created in interactions of high-energy cosmic rays with atoms in the upper atmosphere. Seasonal changes of the temperature – and thus density - profile of the atmosphere modulate the balance between the probability for these mesons to decay (producing muons) or to re-interact. Pions and kaons are affected differently, allowing to extract their production ratio by determining how changes in muon rate depend on changes in the effective temperature – an integral over the atmospheric temperature profile weighted by a depth dependent meson production rate.<br />
<br />
In this project, the aim is to measure the rate of muons in the detectors and to calculate the effective temperature above the KM3NeT detectors from atmospheric data, both as function of time. The relation between these two can be used to extract the pion to kaon ratio.<br />
<br />
''Contact: [mailto:rbruijn@nikhef.nl Ronald Bruijn]''<br />
=== Detector R&D: Studies of wafer-scale sensors for ALICE detector upgrade and beyond===<br />
One of the biggest milestones of the ALICE detector upgrade (foreseen in 2026) is the implementation of wafer-scale (~ 28 cm x 18 cm) monolithic silicon active pixel sensors in the tracking detector, with the goal of having truly cylindrical barrels around the beam pipe. To demonstrate such an unprecedented technology in high energy physics detectors, few chips will be soon available in Nikhef laboratories for testing and characterization purposes.<br />
The goal of the project is to contribute to the validation of the samples against the ALICE tracking detector requirements, with a focus on timing performance in view of other applications in future high energy physics experiments beyond ALICE.<br />
We are looking for a student with a focus on lab work and interested in high precision measurements with cutting-edge instrumentation. You will be part of the Nikhef Detector R&D group and you will have, at the same time, the chance to work in an international collaboration where you will report about the performance of these novel sensors. There may even be the opportunity to join beam tests at CERN or DESY facilities. Besides interest in hardware, some proficiency in computing is required (Python or C++/ROOT).<br />
<br />
''Contact: [mailto:(jory.sonneveld@nikhef.nl Jory Sonneveld ], [mailto:rrusso@nikhef.nl Roberto Russo]''<br />
<br />
=== Detector R&D: Time resolution of monolithic silicon detectors ===<br />
Monolithic silicon detectors based on industrial Complementary Metal Oxide Semiconductor (CMOS) processes offer a promising approach for large scale detectors due to their ease of production and low material budget. Until recently, their low radiation tolerance has hindered their applicability in high energy particle physics experiments. However, new prototypes ~~such as the one in this project~~ have overcome these hurdles, making them feasible candidates for future experiments in high energy particle physics. Achieving the required radiation tolerance has brought the spatial and temporal resolution of these detectors to the forefront. In this project, you will investigate the temporal performance of a radiation hard monolithic detector prototype, using laser setups in the laboratory. You will also participate in meetings with the international collaboration working on this detector, where you will report on the prototype's performance. Depending on the progress of the work, there may be a chance to participate in test beams performed at the CERN accelerator complex and a first full three dimensional characterization of the prototypes performance using a state-of-the-art two-photon absorption laser setup at Nikhef. This project is looking for someone interested in working hands on with cutting edge detector and laser systems at the Nikhef laboratory. Python programming skills and linux experience are an advantage.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld], [mailto:uwe.kraemer@nikhef.nl Uwe Kraemer]''<br />
<br />
=== Detector R&D: Improving a Laser Setup for Testing Fast Silicon Pixel Detectors ===<br />
For the upgrades of the innermost detectors of experiments at the Large Hadron Collider in Geneva, in particular to cope with the large number of collisions per second from 2027, the Detector R&D group at Nikhef tests new pixel detector prototypes with a variety of laser equipment with several wavelengths. The lasers can be focused down to a small spot to scan over the pixels on a pixel chip. Since the laser penetrates the silicon, the pixels will not be illuminated by just the focal spot, but by the entire three dimensional hourglass or double cone like light intensity distribution. So, how well defined is the volume in which charge is released? And can that be made much smaller than a pixel? And, if so, what would the optimum focus be? For this project the student will first estimate the intensity distribution inside a sensor that can be expected. This will correspond to the density of released charge within the silicon. To verify predictions, you will measure real pixel sensors for the LHC experiments.<br />
This project will involve a lot of 'hands on work' in the lab and involve programming and work on unix machines.<br />
<br />
''Contact: [mailto:martinfr@nikhef.nl Martin Fransen]''<br />
<br />
=== Detector R&D: Time resolution of hybrid pixel detectors with the Timepix4 chip ===<br />
Precise time measurements with silicon pixel detectors are very important for experiments at the High-Luminosity LHC and the future circular collider. The spatial resolution of current silicon trackers will not be sufficient to distinguish the large number of collisions that will occur within individual bunch crossings. In a new method, typically referred to as 4D tracking, spatial measurements of pixel detectors will be combined with time measurements to better distinguish collision vertices that occur close together.<br />
New sensor technologies are being explored to reach the required time measurement resolution of tens of picoseconds, and the results are promising. However, the signals that these pixelated sensors produce have to be processed by front-end electronics, which hence also play a role in the total time resolution of the detector. An important contribution comes from the systematic differences between the front-end electronics of different pixels. Many of these systematic effects can be corrected by performing detailed calibrations of the readout electronics. To achieve the required time resolution at future experiments, it is vital that these effects are understood and corrected.<br />
In this project you will be working with the Timepix4 chip. This is a so-called application specific integrated circuit (ASIC) that is designed to read out pixelated sensors. This ASIC will be used extensively in detector R&D for the characterisation of new sensor technologies requiring precise timing (< 50 ps). In order to do so, it is necessary to first study the systematic differences between the pixels, which you will do using a laser setup in our lab. This will be combined with data analysis of proton beam measurements, or with measurements performed using the built-in test-pulse mechanism of the Timepix4 ASIC. Your work will enable further research performed with this ASIC, <br />
and serve as input to the design and operation of future ASICs for experiments at the High-Luminosity LHC.<br />
<br />
''Contact: [mailto:k.heijhoff@nikhef.nl Kevin Heijhoff] and [mailto:martinb@nikhef.nl Martin van Beuzekom]''<br />
<br />
===Detector R&D: Performance studies of Trench Isolated Low Gain Avalanche Detectors (TI-LGAD) ===<br />
The future vertex detector of the LHCb Experiment needs to measure the spatial coordinates and time of the particles originating in the LHC proton-proton collisions with resolutions better than 10 um and 50 ps, respectively. Several technologies are being considered to achieve these resolutions. Among those is a novel sensor technology called Trench Isolated Low Gain Avalanche Detector. <br />
Prototype pixelated sensors have been manufactured recently and have to be characterised. Therefore these new sensors will be bump bonded to a Timepix4 ASIC which provides charge and time measurements in each of 230 thousand pixels. Characterisation will be done using a lab setup at Nikhef, and includes tests with a micro-focused laser beam, radioactive sources, and possibly with particle tracks obtained in a test-beam. This project involves data taking with these new devices and analysing the data to determine the performance parameters such as the spatial and temporal resolution. as function of temperature and other operational conditions. <br />
<br />
''Contacts: [mailto:kazu.akiba@nikhef.nl Kazu Akiba] and [mailto:martinb@nikhef.nl Martin van Beuzekom]''<br />
<br />
===Detector R&D: A Telescope with Ultrathin Sensors for Beam Tests ===<br />
To measure the performance of new prototypes for upgrades of the LHC experiments and beyond, typically a telescope is used in a beam line of charged particles that can be used to compare the results in the prototype to particle tracks measured with this telescope. In this project, you will continue work on a very lightweight, compact telescope using ALICE PIxel DEtectors (ALPIDEs). This includes work on the mechanics, data acquisition software, and a moveable stage. You will foreseeably test this telescope in the Delft Proton Therapy Center. If time allows, you will add a timing plane and perform a measurement with one of our prototypes. Apart from travel to Delft, there is a possiblity to travel to other beam line facilities.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
===Detector R&D: Laser Interferometer Space Antenna (LISA) - the first gravitational wave detector in space ===<br />
<br />
The space-based gravitational wave antenna LISA is one of the most challenging space missions ever proposed. ESA plans to launch around 2034 three spacecraft separated by a few million kilometres. This constellation measures tiny variations in the distances between test-masses located in each satellite to detect gravitational waves from sources such as supermassive black holes. LISA is based on laser interferometry, and the three satellites form a giant Michelson interferometer. LISA measures a relative phase shift between one local laser and one distant laser by light interference. The phase shift measurement requires sensitive sensors. The Nikhef DR&D group fabricated prototype sensors in 2020 together with the Photonics industry and the Dutch institute for space research SRON. Nikhef & SRON are responsible for the Quadrant PhotoReceiver (QPR) system: the sensors, the housing including a complex mount to align the sensors with 10's of nanometer accuracy, various environmental tests at the European Space Research and Technology Centre (ESTEC), and the overall performance of the QPR in the LISA instrument. Currently we are discussing possible sensor improvements for a second fabrication run in 2022, optimizing the mechanics and preparing environmental tests. As a MSc student, you will work on various aspects of the wavefront sensor development: study the performance of the epitaxial stacks of Indium-Gallium-Arsenide, setting up test benches to characterize the sensors and QPR system, performing the actual tests and data analysis, in combination with performance studies and simulations of the LISA instrument.<br />
<br />
''Contact: [mailto:nielsvb@nikhef.nl Niels van Bakel]''<br />
<br />
===Detector R&D: Other projects ===<br />
Are you looking for a slightly different project? Are the above projects already taken? Are you coming in at an unusual time of the year? Do not hesitate to contact us! We always have new projects coming up at different times in the year and we are open to your ideas.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
===FCC: The Next Collider===<br />
<br />
After the LHC, the next planned large collider at CERN is the proposed 100 kilometer circular collider "FCC". In the first stage of the project, as a high-luminosity electron-positron collider, precision measurements of the Higgs boson are the main goal. One of the channels that will improve by orders of magnitude at this new accelerator is the decay of the Higgs boson to a pair of charm quarks. This project will estimate a projected sensitivity for the coupling of the Higgs boson to second generation quarks, and in particular target the improved reconstruction of the topology of long-lived mesons in the clean environment of a precision e+e- machine.<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
===Gravitational Waves: Computer modelling to design the laser interferometers for the Einstein telescope===<br />
<br />
A new field of instrument science led to the successful detection of gravitational waves by the LIGO detectors in 2015. We are now preparing the next generation of gravitational wave observatories, such as the Einstein Telescope, with the aim to increase the detector sensitivity by a factor of ten, which would allow, for example, to detect stellar-mass black holes from early in the universe when the first stars began to form. This ambitious goal requires us to find ways to significantly improve the best laser interferometers in the world.<br />
<br />
Gravitational wave detectors, such as LIGO and VIRGO, are complex Michelson-type interferometers enhanced with optical cavities. We develop and use numerical models to study these laser interferometers, to invent new optical techniques and to quantify their performance. For example, we synthesize virtual mirror surfaces to study the effects of higher-order optical modes in the interferometers, and we use opto-mechanical models to test schemes for suppressing quantum fluctuations of the light field. We can offer several projects based on numerical modelling of laser interferometers. All projects will be directly linked to the ongoing design of the Einstein Telescope.<br />
<br />
''Contact: [mailto:a.freise@nikhef.nl Andreas Freise]''<br />
<br />
===LHCb: Search for light dark particles===<br />
The Standard Model of elementary particles does not contain a proper Dark Matter candidate. One of the most tantalizing theoretical developments is the so-called ''Hidden Valley models'': a mirror-like copy of the ''Standard Model'', with dark particles that communicate with standard ones via a very feeble interaction. These models predict the existence of ''dark hadrons'' – composite particles that are bound similarly to ordinary hadrons in the ''Standard Model''. Such ''dark hadrons'' can be abundantly produced in high-energy proton-proton collisions, making the LHC a unique place to search for them. Some ''dark hadrons'' are stable like a proton, which makes them excellent ''Dark Matter'' candidates, while others decay to ordinary particles after flying a certain distance in the collider experiment. The LHCb detector has a unique capability to identify such decays, particularly if the new particles have a mass below ten times the proton mass. <br />
<br />
This project assumes a unique search for light ''dark hadrons'' that covers a mass range not accessible to other experiments. It assumes an interesting program on data analysis (python-based) with non-trivial machine learning solutions and phenomenology research using fast simulation framework. Depending on the interest, there is quite a bit of flexibility in the precise focus of the project.<br />
<br />
''Contact: [mailto:andrii.usachov@nikhef.nl Andrii Usachov]''<br />
<br />
===LHCb: Searching for dark matter in exotic six-quark particles===<br />
<br />
Three quarters of the mass in the Universe is of unknown type. Many hypotheses about this dark matter have been proposed, but none confirmed. Recently it has been proposed that it could be made of particles made of the six quarks uuddss, which would be a Standard-Model solution to the dark matter problem. This idea has recently gained credibility as many similar multi-quarks states are being discovered by the LHCb experiment. Such a particle could be produced in decays of heavy baryons, or directly in proton-proton collisions. The anti-particle, made of six antiquarks, could be seen when annihilating with detector material. It is also proposed to use Xi_b baryons produced at LHCb to search for such a state where the state would appear as missing 4-momentum in a kinematically constrained decay. The project consists in defining a selection and applying it to LHCb data. See [https://arxiv.org/abs/2007.10378 arXiv:2007.10378].<br />
<br />
Contact: ''[mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
<br />
===LHCb: Measuring lepton flavour universality with excited Ds states in semileptonic Bs decays===<br />
One of the most striking discrepancies between the Standard Model and measurements are the lepton flavour universality (LFU) measurements with tau decays. At the moment, we have observed an excess of 3-4 sigma in ''B → Dτν'' decays. This could point even to a new force of nature! To understand this discrepancy, we need to make further measurements. <br />
<br />
One very exciting (pun intended) projects to verify these discrepancies involves measuring the ''B<sub>s</sub> → D<sub>s2</sub><sup>*</sup>τν'' and/or ''B<sub>s</sub> → D<sub>s1</sub><sup>*</sup>τν'' decays. These decays with excited states of the ''D<sub>s</sub>'' meson have not been observed before in the tau decay mode, and have a unique way of coupling to potential new physics candidates that can only be measured in ''B<sub>s</sub>'' decays [1]. See slides for more detail: [[File:LHCbLFUwithExcitedDs.pdf|thumb]]<br />
<br />
[1] https://arxiv.org/abs/1606.09300<br />
<br />
''Contact: [mailto:suzannek@nikhef.nl Suzanne Klaver]''<br />
<br />
===LHCb: New physics in the angular distributions of B decays to K*ee===<br />
<br />
Lepton flavour violation in B decays can be explained by a variety of non-standard model interactions. Angular distributions in decays of a B meson to a hadron and two leptons are an important source of information to understand which model is correct. Previous analyses at the LHCb experiment have considered final states with a pair of muons. Our LHCb group at Nikhef concentrates on a new measurement of angular distributions in decays with two electrons. The main challenge in this measurement is the calibration of the detection efficiency. In this project you will confront estimates of the detection efficiency derived from simulation with decay distributions in a well known B decay. Once the calibration is understood, the very first analysis of the angular distributions in the electron final state can be performed. <br />
<br />
Contact: [mailto:m.senghi.soares@nikhef.nl Mara Soares] and [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
<br />
===LHCb: Discovering heavy neutrinos in B decays===<br />
<br />
Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, much heavier, neutral leptons. If the mass of these new neutrinos is below the b-quark mass, they can be observed in B hadron decays.<br />
<br />
In this project we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undiscovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The analysis will be performed within the LHCb group at Nikhef using LHCb run-2 data.<br />
<br />
===LHCb: Scintillating Fibre tracker software===<br />
The installation of the scintillating-fibre tracker in LHCb’s underground cavern was recently completed. This detector uses 10000 km of fibres to track particle trajectories in the LHCb detector when the LHC starts up again later this year. The light emitted by the scintillating fibres when a particle interacts with them is measured using photon multiplier tubes. The studies proposed for this project will focus on software, and could include writing a framework to monitor the detector output, improving the detector simulation or working on the data processing.<br />
<br />
''Contact: [mailto:e.gabriel@nikhef.nl Emmy Gabriel]''<br />
<br />
===LHCb: Vertex detector calibration===<br />
In summer 2022 LHCb has started data taking will an almost entirely new detector. At the point closest to the interaction point, the trajectories of charge particles are reconstructed with a so-called silicon pixel detector. The design hit resolution of this detector is about 15 micron. However, to actually reach this resolution a precise calibration of the spatial positions of the silicon sensors needs to be performed. In this project, you will use the first data of the new LHCb detector to perform this calibration and measure the detector performance.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen]''<br />
<br />
<br />
===Neutrinos: Neutrino scattering: the ultimate resolution===<br />
<br />
Neutrino telescopes like IceCube and KM3NeT aim at detecting neutrinos from cosmic sources. The neutrinos are detected with the best resolution when charged current interactions with nucleons produce a muon, which can be detected with high accuracy (depending on the detector). A crucial ingredient in the ultimate achievable pointing accuracy of neutrino telescopes is the scattering angle between the neutrino and the muon. While published computations have investigated the cross-section of the process in great detail, this important scattering angle has not received much attention. The aim of the project is to compute and characterize the distribution of this angle, and that the ultimate resolution of a neutrino telescope. If successful, the results of this project can lead to publication of interest to the neutrino telescope community.<br />
<br />
Depending on your interests, the study could be based on a first-principles calculation (using the deep-inelastic scattering formalism), include state-of-the-art parton distribution functions, and/or exploit existing event-generation software for a more experimental approach. <br />
<br />
''Contacts: [mailto:aart.heijboer@nikhef.nl Aart Heijboer]''<br />
<br />
===Neutrinos: acoustic detection of ultra-high energy neutrinos===<br />
<br />
The study of the cosmic neutrinos of energies above 1017 eV, the so-called ultra-high energy neutrinos, provides a unique view on the universe and may provide insight in the origin of the most violent astrophysical sources, such as gamma ray bursts, supernovae or even dark matter. In addition, the observation of high energy neutrinos may provide a unique tool to study interactions at high energies. The energy deposition of these extreme neutrinos in water induce a thermo-acoustic signal, which can be detected using sensitive hydrophones. The expected neutrino flux is however extremely low and the signal that neutrinos induce is small. TNO is presently developing sensitive hydrophone technology based on fiber optics. Optical fibers form a natural way to create a distributed sensing system. Using this technology a large scale neutrino telescope can be built in the deep sea. TNO is aiming for a prototype hydrophone which will form the building block of a future telescope.<br />
<br />
The work will be executed at the Nikhef institute and/or the TNO laboratories in Delft. In this project master students have the opportunity to contribute in the following ways:<br />
<br />
'''Project 1:''' Hardware development on fiber optics hydrophones technology Goal: characterize existing prototype optical fibre hydrophones in an anechoic basin at TNO laboratory. Data collection, calibration, characterization, analysis of consequences for design future acoustic hydrophone neutrino telescopes;<br />
Keywords: Optical fiber technology, signal processing, electronics, lab.<br />
<br />
'''Project 2:''' Investigation of ultra-high energy neutrinos and their interactions with matter. Goal: Discriminate the neutrino signals from the background noises, in particular clicks from whales and dolphins in the deep sea. Study impact on physics reach for future acoustic hydrophone neutrino telescopes;<br />
Keywords: Monte Carlo simulations, particle physics, neutrino physics, data analysis algorithms.<br />
<br />
Further information: Info on ultra-high energy neutrinos can be found at: http://arxiv.org/abs/1102.3591; Info on acoustic detection of neutrinos can be found at: http://arxiv.org/abs/1311.7588<br />
<br />
''Contact: [mailto:ernst-jan.buis@tno.nl Ernst Jan Buis]'' or ''[mailto:ivo.van.vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
===Neutrinos: Oscillation analysis with the first data of KM3NeT===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first few strings with sensitive photodetectors have been deployed at both the Italian and the French detector sites. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In this project the available data will be used together with simulations to best reconstruct the event topologies and optimally identify and reconstruct the first neutrino interactions in the KM3NeT detector. The data will then be used to measure neutrino oscillation parameters, and prepare for a future neutrino mass ordering determination.<br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
''Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn] [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
<br />
===Neutrinos: the Deep Underground Neutrino Experiment (DUNE)===<br />
<br />
The Deep Underground Neutrino Experiment (DUNE) is under construction in the USA, and will consist of a powerful neutrino beam originating at Fermilab, a near detector at Fermilab, and a far detector in the SURF facility in Lead, South Dakota, 1300 km away. During travelling, neutrinos oscillate and a fraction of the neutrino beam changes flavour; DUNE will determine the neutrino oscillation parameters to unrivaled precision, and try and make a first detection of CP-violation in neutrinos. In this project, various elements of DUNE can be studied, including the neutrino oscillation fit, neutrino physics with the near detector, event reconstruction and classification (including machine learning), or elements of data selection and triggering.<br />
<br />
''Contact: [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
===Neutrinos: Searching for Majorana Neutrinos with KamLAND-Zen===<br />
The KamLAND-Zen experiment, located in the Kamioka mine in Japan, is a large liquid scintillator experiment with 750kg of ultra-pure Xe-136 to search for neutrinoless double-beta decay (0n2b). The observation of the 0n2b process would be evidence for lepton number violation and the Majorana nature of neutrinos, i.e. that neutrinos are their own anti-particles. Current limits on this extraordinary rare hypothetical decay process are presented as a half-life, with a lower limit of 10^26 years. KamLAND-Zen, the world’s most sensitive 0n2b experiment, is currently taking data and there is an opportunity to work on the data analysis, analyzing data with the possibility of taking part in a ground-breaking discovery. The main focus will be on developing new techniques to filter the spallation backgrounds, i.e. the production of radioactive isotopes by passing muons. There will be close collaboration with groups in the US (MIT, Berkeley, UW) and Japan (Tohoku Univ). <br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
===Neutrinos: relic neutrino detection with PTOLEMY ===<br />
PTOLEMY aims to make the first direct observation of the Big Bang relic neutrinos (the cosmic neutrino background, CνB) by resolving the β-decay endpoint of atomic tritium (neutrino capture target) to O(meV) precision. This remains an outstanding test of the Standard Model in an expanding universe. Not only does the CνB carry with it a signal from the hot dense universe only one second after the Big Bang but helps to constrain the balance of hot versus cold dark matter responsible for its evolution. In doing so, the PTOLEMY experiment would also measure the lowest neutrino mass, an as-of-yet unknown fundamental constant. The experiment is currently in the prototyping phase and the group at Nikhef is responsible for developing the radio-frequency (RF) system used for cyclotron radiation (CR) based trigger and tracking. This component will provide the trajectory of electrons entering the novel transverse drift filter, constraining the electrons' energy losses before they reach the cryogenic calorimeter which in turn records their final energy. The focus of this project will be modelling CR and its detection for the purposes of single electron spectroscopy and optimised trajectory reconstruction. There is also the opportunity to test hardware and readout electronics for the prototype RF-system. <br />
''Contact: [mailto:jmead@nikhef.nl James Vincent Mead]''<br />
<br />
=== Theoretical Particle Physics: Effective Field Theories of Particle Physics from low- to high-energies===<br />
Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations” seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature. The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Standard Model Effective Field Theory (SMEFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes with minimal assumptions on the nature of an eventual UV-complete theory that replaces the Standard Model. Specifically, the goal is to connect measurements from ATLAS, CMS, and LHCb experiments at the CERN's LHC among them and to jointly interpret this information with that provided by other experiments including very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
<br />
This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories. Depending on the student profile, sub-projects with a strong computational and/or machine learning component are also possible, for instance to construct new operators with optimal sensitivity to New Physics effects as encoded by the SMEFT higher-dimensional operators. Topics that can be considered in this project include the interpretation of novel physical observables at the LHC and their integration into the global SMEFiT analysis, matching of EFTs to UV-complete theories and their phenomenological analyses, projections for the impact in the SMEFT parameter space of data for future colliders, the synergies between EFT studies and proton structure fits, and the matching to the Weak Effective Field Theory to include data on flavour observables such as B-meson decays.<br />
<br />
References: https://arxiv.org/abs/2105.00006 , https://arxiv.org/abs/2302.06660, https://arxiv.org/abs/2211.02058 , https://arxiv.org/abs/1901.05965 , https://arxiv.org/abs/1906.05296 , https://arxiv.org/abs/1908.05588, https://arxiv.org/abs/1905.05215. see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description].<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theoretical Particle Physics: High-energy neutrino-nucleon interactions at the Forward Physics Facility ===<br />
High-energy collisions at the High-Luminosity Large Hadron Collider (HL-LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing experiments. The proposed Forward Physics Facility (FPF) to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe Standard Model (SM) processes and search for physics beyond the Standard Model (BSM). High statistics neutrino detection will provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. The FPF has the promising potential to probe our understanding of the strong interactions as well as of proton and nuclear structure, providing access to both the very low-x and the very high-x regions of the colliding protons. The former regime is sensitive to novel QCD production mechanisms, such as BFKL effects and non-linear dynamics, as well as the gluon parton distribution function (PDF) down to x=1e-7, well beyond the coverage of other experiments and providing key inputs for astroparticle physics. In addition, the FPF acts as a neutrino-induced deep-inelastic scattering (DIS) experiment with TeV-scale neutrino beams. The resulting measurements of neutrino DIS structure functions represent a valuable handle on the partonic structure of nucleons and nuclei, particularly their quark flavour separation, that is fully complementary to the charged-lepton DIS measurements expected at the upcoming Electron-Ion Collider (EIC).<br />
<br />
In this project, the student will carry out updated predictions for the neutrino fluxes expected at the FPF, assess the precision with which neutrino cross-sections will be measured, and quantify their impact on proton and nuclear structure by means of machine learning tools within the NNPDF framework and state-of-the-art calculations in perturbative Quantum Chromodynamics. This project contributes to ongoing work within the FPF Initiative towards a Conceptual Design Report (CDR) to be presented within two years. Topics that can be considered as part of this project include the assessment of to which extent nuclear modifications of the free-proton PDFs can be constrained by FPF measurements, the determination of the small-x gluon PDF from suitably defined observables at the FPF and the implications for ultra-high-energy particle astrophysics, the study of the intrinsic charm content in the proton and its consequences for the FPF physics program, and the validation of models for neutrino-nucleon cross-sections in the region beyond the validity of perturbative QCD.<br />
<br />
References: https://arxiv.org/abs/2203.05090, https://arxiv.org/abs/2109.10905 ,https://arxiv.org/abs/2208.08372 , https://arxiv.org/abs/2201.12363 , https://arxiv.org/abs/2109.02653, https://github.com/NNPDF/ see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description]. <br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theoretical Particle Physics: Probing the origin of the proton spin with machine learning===<br />
At energy-frontier facilities such as the Large Hadron Collider (LHC), scientists study the laws of nature in their quest for novel phenomena both within and beyond the Standard Model of particle physics. An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions from the nature of the Higgs boson to the origin of cosmic neutrinos. The key to address some of these questions is by carrying out an universal analysis of nucleon structure from the simultaneous determination of the momentum and spin distributions of quarks and gluons and their fragmentation into hadrons. This effort requires combining an extensive experimental dataset and cutting-edge theory calculations within a machine learning framework where neural networks parametrise the underlying physical laws while minimising ad-hoc model assumptions. The upcoming Electron Ion Collider (EIC), to start taking data in 2029, will be the world's first ever polarised lepton-hadron collider and will offer a plethora of opportunities to address key open questions in our understanding of the strong nuclear force, such as the origin of the mass and the intrinsic angular momentum (spin) of hadrons and whether there exists a state of matter which is entirely dominated by gluons. To fully exploit this scientific potential, novel analysis methodologies need to be develop that make it possible to carry out large-scale, coherent interpretations of measurements from the EIC and other high-energy colliders.<br />
<br />
In this project, the student will carry out a new global analysis of the spin structure of the proton by means of the machine learning tools provided by the NNPDF open-source fitting framework and state-of-the-art calculations in perturbative Quantum Chromodynamics, and integrate it within the corresponding global NNPDF analyses of unpolarised proton and nuclear structure in the framework of a combined integrated global analysis of non-perturbative QCD. Specifically, the project aims to realise a NNLO global fit of polarised quark and gluon PDFs that combines all available data and state-of-the-art perturbative QCD calculations, and study the phenomenological implications for other experiments, including the EIC, for the spin content of the proton, for comparisons with lattice QCD calculations, and for nonpperturbative models of hadron structure.<br />
<br />
References: https://arxiv.org/abs/2201.12363, https://arxiv.org/abs/2109.02653 , https://arxiv.org/abs/2103.05419, https://arxiv.org/abs/1404.4293 , https://inspirehep.net/literature/1302398, https://github.com/NNPDF/ see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description].<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== '''Theoretical Particle Physics''': Charged lepton flavor violation in neutrino mass models ===<br />
The nonzero value of neutrino masses requires an explanation beyond the Standard Model of particle physics. A promising solution involves the existence of extra neutrinos, often called right-handed or sterile neutrinos. These models elegantly explain neutrino masses and can also be connected to other puzzles such as the absence of anti-matter in our universe. In this project you will investigate potential experimental signatures of sterile neutrinos through decays that are extremely rare in the Standard Model. Examples are muon decays to electrons and photons, or muon + neutron -> electron + neutron. You will perform Quantum Field Theory calculations within the neutrino-extended Standard Model to compute the rates of these processes and compare them to experimental sensitivities. <br />
<br />
''Contacts: [Mailto:j.devries4@uva.nl Jordy de Vries]''<br />
<br />
=== '''Theoretical Particle Physics''': The electric dipole moment of paramagnetic systems in the Standard Model ===<br />
Electric dipole moments (EDMs) of elementary particles, hadrons, nuclei, atoms, and molecules would indicate the violation of CP violation. The Standard Model (SM) contains CP violation in the weak interaction in the so-called CKM matrix (the quark-mixing matrix) but it leads to EDMs that are too small to be seen. At least this is often claimed. In this work we will reinvestigate the computation of the EDMs of systems that are used in state-of-the-art experiments. In particular we will compute a CP-violating interaction between electrons and nucleons mitigated by the SM weak interaction. During this project you will obtain a deep understanding of the Standard Model and explicit quantum field theory calculations across a wider range of energy scales. <br />
<br />
''Contacts: [Mailto:j.devries4@uva.nl Jordy de Vries]''<br />
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== Finished master projects ==<br />
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See: <br />
* https://wiki.nikhef.nl/education/Master_Theses<br />
* https://www.nikhef.nl/master-theses-2021/<br />
* https://www.nikhef.nl/facts-figures-2020/master-theses-2020/<br />
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[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=973Master Projects2024-03-04T17:24:51Z<p>Rojo@nikhef.nl: /* Projects with a 2024 start [WORK IN PROGRESS, please look below for older projects] */</p>
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<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
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== Projects with a 2024 start [WORK IN PROGRESS, please look below for older projects] ==<br />
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=== ATLAS: A new timing detector - the HGTD ===<br />
The ATLAS is going to get a new ability: a timing detector. This allows us to reconstruct tracks not only in the 3 dimensions of space but adds the ability of measuring very precisely also the time (at picosecond level) at which the particles pass the sensitive layers of the HGTD detector. The added information helps to construct the trajectories of the particles created at the LHC in 4 dimensions and ultimately will lead to a better reconstruction of physics at ATLAS. The new HGTD detector is still in construction and work needs to be done on different levels such as understanding the detector response (taking measurements in the lab and performing simulations) or developing algorithms to reconstruct the particle trajectories (programming and analysis work). <br />
<br />
'''Several projects are available within the context of the new HGTD detector:''' <br />
<br />
# One can choose to either focus on '''''the impact on physics analysis performance''''' by studying how the timing measurements can be included in the reconstruction of tracks, and what effect this has on how much better we can understand the physical processes occurring in the particles produced in the LHC collisions. With this work you will be part of the Atlas group at Nikhef.<br />
# The second possibility is to '''''test the sensors in our lab''''' and in test-beam setups at CERN/DESY. The analysis performed will be in context of the ATLAS HGTD test beam group in connection to both the Atlas group and the R&D department at Nikhef.<br />
# The third is to contribute in an ongoing effort '''''to precisely simulate/model the silicon avalanche detectors''''' in the Allpix2 framework. There are several models that try to describe the detectors response. The models have depend on operation temperature, field strenghts and radiation damage. We are getting close in being able to model our detector - but not there yet. This work will be within the ATLAS group.<br />
<br />
If you are interested, contact me to discuss the possibilities. <br />
Contact: ''[mailto:hella.snoek@nikhef.nl Hella Snoek]''<br />
<br />
=== Dark Matter: Building better Dark Matter Detectors - the XAMS R&D Setup ===<br />
The Amsterdam Dark Matter group operates an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 0.5kg of ultra-pure liquid xenon in the central volume. We use this detector for the development of new detection techniques - such as utilizing our newly installed silicon photomultipliers - and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENONnT experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory, or for future Dark Matter experiments like DARWIN. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data themselves You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
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===Dark Matter: Searching for Dark Matter Particles - XENONnT Data Analysis ===<br />
The XENON collaboration has used the XENON1T detector to achieve the world’s most sensitive direct detection dark matter results and is currently operating the XENONnT successor experiment. The detectors operate at the Gran Sasso underground laboratory and consist of so-called dual-phase xenon time-projection chambers filled with ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the new data coming from the XENONnT detector. The work will consist of understanding the detector signals and applying a deep neural network to improve the (gas-) background discrimination in our Python-based analysis tool to improve the sensitivity for low-mass dark matter particles. The work will continue a study started by a recent graduate. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy.<br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter: Signal reconstruction and correction in XENONnT ===<br />
XENONnT is a low background experiment operating at the INFN - Gran Sasso underground laboratory with the main goal of detecting Dark Matter interactions with xenon target nuclei. The detector, consisting of a dual-phase time projection chamber, is filled with ultra-pure xenon, which acts as a target and detection medium. Understanding the detector's response to various calibration sources is a mandatory step in exploiting the scientific data acquired. This MSc thesis aims to develop new methods to improve the reconstruction and correction of scintillation/ ionization signals from calibration data. The student will work with modern analysis techniques (python-based) and will collaborate with other analysts within the international XENON Collaboration.<br />
<br />
''Contact: [mailto:mpierre@nikhef.nl Maxime Pierre], [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
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===Dark Matter: The Ultimate Dark Matter Experiment - DARWIN Sensitivity Studies===<br />
DARWIN is the “ultimate” direct detection dark matter experiment, with the goal to reach the so-called “neutrino floor”, when neutrinos become a hard-to-reduce background. The large and exquisitely clean xenon mass will allow DARWIN to also be sensitive to other physics signals such as solar neutrinos, double-beta decay from Xe-136, axions and axion-like particles etc. While the experiment will only start in 2027, we are in the midst of optimizing the experiment, which is driven by simulations. We have an opening for a student to work on the GEANT4 Monte Carlo simulations for DARWIN. We are also working on a “fast simulation” that could be included in this framework. It is your opportunity to steer the optimization of a large and unique experiment. This project requires good programming skills (Python and C++) and data analysis/physics interpretation skills.<br />
<br />
''Contact: [mailto:t.pollmann@nikhef.nl Tina Pollmann], [mailto:decowski@nikhef.nl Patrick Decowski] or [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter: Exploring new background sources for DARWIN ===<br />
Experiments based on the xenon dual-phase time projection chamber detection technology have already demonstrated their leading role in the search for Dark Matter. The unprecedented low level of background reached by the current generation, such as XENONnT, allows such experiments to be sensitive to new rare-events physics searches, broadening their physics program. The next generation of experiments is already under consideration with the DARWIN observatory, which aims to surpass its predecessors in terms of background level and mass of xenon target. With the increased sensitivity to new physics channels, such as the study of neutrino properties, new sources of backgrounds may arise. This MSc thesis aims to investigate potential new sources of background for DARWIN and is a good opportunity for the student to contribute to the design of the experiment. This project will rely on Monte Carlo simulation tools such as GEANT4 and FLUKA, and good programming skills (Python and C++) are advantageous.<br />
<br />
''Contact: [mailto:mpierre@nikhef.nl Maxime Pierre], [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
===Dark Matter: Sensitive tests of wavelength-shifting properties of materials for dark matter detectors===<br />
Rare event search experiments that look for neutrino and dark matter interactions are performed with highly sensitive detector systems, often relying on scintillators, especially liquid noble gases, to detect particle interactions. Detectors consist of structural materials that are assumed to be optically passive, and light detection systems that use reflectors, light detectors, and sometimes, wavelength-shifting materials. MSc theses are available related to measuring the efficiency of light detection systems that might be used in future detectors. Furthermore, measurements to ensure that presumably passive materials do not fluoresce, at the low level relevant to the detectors, can be done. Part of the thesis work can include Monte Carlo simulations and data analysis for current and upcoming dark matter detectors, to study the effect of different levels of desired and nuisance wavelength shifting. In this project, students will acquire skills in photon detection, wavelength shifting technologies, vacuum systems, UV and extreme-UV optics, detector design, and optionally in Python and C++ programming, data analysis, and Monte Carlo techniques.<br />
<br />
''Contact: [mailto:Tina.Pollmann@tum.de Tina Pollmann]''<br />
<br />
===Theoretical Particle Physics: High-energy neutrino physics at the LHC ===<br />
High-energy collisions at the High-Luminosity Large Hadron Collider (HL-LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing experiments. The proposed Forward Physics Facility (FPF) to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe Standard Model (SM) processes and search for physics beyond the Standard Model (BSM). High statistics neutrino detection will provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. The FPF has the promising potential to probe our understanding of the strong interactions as well as of proton and nuclear structure, providing access to both the very low-x and the very high-x regions of the colliding protons. The former regime is sensitive to novel QCD production mechanisms, such as BFKL effects and non-linear dynamics, as well as the gluon parton distribution function (PDF) down to x=1e-7, well beyond the coverage of other experiments and providing key inputs for astroparticle physics. In addition, the FPF acts as a neutrino-induced deep-inelastic scattering (DIS) experiment with TeV-scale neutrino beams. The resulting measurements of neutrino DIS structure functions represent a valuable handle on the partonic structure of nucleons and nuclei, particularly their quark flavour separation, that is fully complementary to the charged-lepton DIS measurements expected at the upcoming Electron-Ion Collider (EIC).<br />
<br />
In this project, the student will carry out updated predictions for the neutrino fluxes expected at the FPF, assess the precision with which neutrino cross-sections will be measured, and quantify their impact on proton and nuclear structure by means of machine learning tools within the NNPDF framework and state-of-the-art calculations in perturbative Quantum Chromodynamics. This project contributes to ongoing work within the FPF Initiative towards a Conceptual Design Report (CDR) to be presented within two years. Topics that can be considered as part of this project include the assessment of to which extent nuclear modifications of the free-proton PDFs can be constrained by FPF measurements, the determination of the small-x gluon PDF from suitably defined observables at the FPF and the implications for ultra-high-energy particle astrophysics, the study of the intrinsic charm content in the proton and its consequences for the FPF physics program, and the validation of models for neutrino-nucleon cross-sections in the region beyond the validity of perturbative QCD.<br />
<br />
References: https://arxiv.org/abs/2203.05090, https://arxiv.org/abs/2109.10905 ,https://arxiv.org/abs/2208.08372 , https://arxiv.org/abs/2201.12363 , https://arxiv.org/abs/2109.02653, https://github.com/NNPDF/ see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description].<br />
<br />
''Contacts: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
===Theoretical Particle Physics: Unravelling proton structure with machine learning===<br />
At energy-frontier facilities such as the Large Hadron Collider (LHC), scientists study the laws of nature in their quest for novel phenomena both within and beyond the Standard Model of particle physics. An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions from the nature of the Higgs boson to the origin of cosmic neutrinos. The key to address some of these questions is by carrying out an universal analysis of nucleon structure from the simultaneous determination of the momentum and spin distributions of quarks and gluons and their fragmentation into hadrons. This effort requires combining an extensive experimental dataset and cutting-edge theory calculations within a machine learning framework where neural networks parametrise the underlying physical laws while minimising ad-hoc model assumptions. The upcoming Electron Ion Collider (EIC), to start taking data in 2029, will be the world's first ever polarised lepton-hadron collider and will offer a plethora of opportunities to address key open questions in our understanding of the strong nuclear force, such as the origin of the mass and the intrinsic angular momentum (spin) of hadrons and whether there exists a state of matter which is entirely dominated by gluons. To fully exploit this scientific potential, novel analysis methodologies need to be develop that make it possible to carry out large-scale, coherent interpretations of measurements from the EIC and other high-energy colliders.<br />
<br />
In this project, the student will carry out a new global analysis of the spin structure of the proton by means of the machine learning tools provided by the NNPDF open-source fitting framework and state-of-the-art calculations in perturbative Quantum Chromodynamics, and integrate it within the corresponding global NNPDF analyses of unpolarised proton and nuclear structure in the framework of a combined integrated global analysis of non-perturbative QCD. Specifically, the project aims to realise a NNLO global fit of polarised quark and gluon PDFs that combines all available data and state-of-the-art perturbative QCD calculations, and study the phenomenological implications for other experiments, including the EIC, for the spin content of the proton, for comparisons with lattice QCD calculations, and for nonpperturbative models of hadron structure.<br />
<br />
References: https://arxiv.org/abs/2201.12363, https://arxiv.org/abs/2109.02653 , https://arxiv.org/abs/2103.05419, https://arxiv.org/abs/1404.4293 , https://inspirehep.net/literature/1302398, https://github.com/NNPDF/ see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description].<br />
<br />
''Contacts: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
== Projects with a 2023 start ==<br />
<br />
=== ALICE: The next-generation multi-purpose detector at the LHC ===<br />
This main goal of this project is to focus on the next-generation multi-purpose detector planned to be built at the LHC. Its core will be a nearly massless barrel detector consisting of truly cylindrical layers based on curved wafer-scale ultra-thin silicon sensors with MAPS technology, featuring an unprecedented low material budget of 0.05% X0 per layer, with the innermost layers possibly positioned inside the beam pipe. The proposed detector is conceived for studies of pp, pA and AA collisions at luminosities a factor of 20 to 50 times higher than possible with the upgraded ALICE detector, enabling a rich physics program ranging from measurements with electromagnetic probes at ultra-low transverse momenta to precision physics in the charm and beauty sector. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli] and [mailto:marco.van.leeuwen@cern.ch Marco van Leeuwen]''<br />
<br />
=== ALICE: Searching for the strongest magnetic field in nature ===<br />
In a non-central collision between two Pb ions, with a large value of impact parameter, the charged nucleons that do not participate in the interaction (called spectators) create strong magnetic fields. A back of the envelope calculation using the Biot-Savart law brings the magnitude of this filed close to 10^19Gauss in agreement with state of the art theoretical calculation, making it the strongest magnetic field in nature. The presence of this field could have direct implications in the motion of final state particles. The magnetic field, however, decays rapidly. The decay rate depends on the electric conductivity of the medium which is experimentally poorly constrained. Overall, the presence of the magnetic field, the main goal of this project, is so far not confirmed experimentally.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Looking for parity violating effects in strong interactions ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions, in the presence of a deconfined state, gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, what is called the Chiral Magnetic Effect (CME).<br />
The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, however further studies are needed to constrain background effects. These highly anticipated results have the potential to reveal exiting, new physics.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Machine learning techniques as a tool to study the production of heavy flavour particles ===<br />
There was recently a shift in the field of heavy-ion physics triggered by experimental results obtained in collisions between small systems (e.g. protons on protons). These results resemble the ones obtained in collisions between heavy ions. This consequently raises the question of whether we create the smallest QGP droplet in collisions between small systems. The main objective of this project will be to study the production of charm particles such as D-mesons and Λc-baryons in pp collisions at the LHC. This will be done with the help of a new and innovative technique which is based on machine learning (ML). The student will also extend the studies to investigate how this production rate depends on the event activity e.g. on how many particles are created after every collision.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli]''<br />
<br />
=== ALICE: Search for new physics with 4D tracking at the most sensitive vertex detector at the LHC ===<br />
<br />
With the newly installed Inner Tracking System consisting fully of monolithic detectors, ALICE is very sensitive to particles with low transverse momenta, more so than ATLAS and CMS. This will be even more so for the ALICE upgrade detector in 2033. This detector could potentially be even more sensitive to longlived particles that leave peculiar tracks such as disappearing or kinked tracks in the tracker by using timing information along a track. In this project you will investigate how timing information in the different tracking layers can improve or even enable a search for new physics beyond the Standard Model in ALICE. If you show a possibility for major improvements, this can have real consequences for the choice of sensors for this ALICE inner tracker upgrade.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld] and [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ATLAS: The Higgs boson's self-coupling ===<br />
<br />
The coupling of the Higgs boson to itself is one of the main unobserved interactions of the Standard Model and its observation is crucial to understand the shape of the Higgs potential. Here we propose to study the 'ttHH' final state: two top quarks and two Higgs bosons produced in a single collision. This topology is yet unexplored at the ATLAS experiment and the project consists of setting up the new analysis (including multivariate analysis techniques to recognise the complicated final state), optimising the sensitivity and including the result in the full ATLAS study of the Higgs boson's coupling to itself. With the LHC data from the upcoming Run-3, we might be able to see its first glimpses! <br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree] and [mailto:cpandini@nikhef.nl Carlo Pandini]'' <br />
<br />
=== ATLAS: Triple-Higgs production as a probe of the Higgs potential ===<br />
So far, the investigation of Higgs self-couplings (the coupling of the Higgs boson to itself) at the LHC has focused on the measurement of the Higgs tri-linear coupling λ3 mainly through direct double-Higgs production searches. In this research project we propose the investigation of Higgs tri-linear and quartic coupling parameters λ3 and λ4, via a novel measurement of triple-Higgs production at the LHC (HHH) with the ATLAS experiment. While in the SM these parameters are expected to be identical, only a combined measurement can provide an answer regarding how the Higgs potential is realised in Nature. Processes in which three Higgs bosons are produced simultaneously are extremely rare, and very difficult to measure and disentangle from background. In this project we plan to investigate different decay channels (to bottom quarks and tau leptons), and to study advanced machine learning techniques to reconstruct such a complex hadronic final state. This kind of processes is still quite unexplored in ATLAS, and the goal of this project is to put the basis for the first measurement of HHH production at the LHC.<br />
<br />
Furthermore, we'd like to study the possible implication of a precise measurement of the self-coupling parameters from HHH production from a phenomenological point of view: what could be the impact of a deviation in the HHH measurements on the big open questions in physics (for instance, the mechanisms at the root of baryogenesis)?<br />
<br />
Contact: ''[mailto:tdupree@nikhef.nl Tristan du Pree] and [mailto:cpandini@nikhef.nl Carlo Pandini]''<br />
<br />
=== ATLAS: The Next Generation ===<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks is very new [1] and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays) and advanced analysis techiques (using deep learning methods).<br />
<br />
[https://atlas.cern/updates/briefing/charming-Higgs-decay][https://arxiv.org/abs/1802.04329 https://atlas.cern/updates/briefing/charming-Higgs-decay]<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
=== ATLAS: Searching for new particles in very energetic diboson production ===<br />
<br />
The discovery of new phenomena in high-energy proton–proton collisions is one of the main goals of the Large Hadron Collider (LHC). New heavy particles decaying into a pair of vector bosons (WW, WZ, ZZ) are predicted in several extensions to the Standard Model (e.g. extended gauge-symmetry models, Grand Unified theories, theories with warped extra dimensions, etc). In this project we will investigate new ideas to look for these resonances in promising regions. We will focus on final states where both vector bosons decay into quarks, or where one decays into quarks and one into leptons. These have the potential to bring the highest sensitivity to the search for Beyond the Standard Model physics [1, 2]. We will try to reconstruct and exploit new ways to identify vector bosons (using machine learning methods) and then tackle the problem of estimating contributions from beyond the Standard Model processes in the tails of the mass distribution.<br />
<br />
[1] https://arxiv.org/abs/1906.08589<br />
<br />
[2] https://arxiv.org/abs/2004.14636<br />
<br />
''Contact: [mailto:f.dias@nikhef.nl Flavia de Almeida Dias], [mailto:rhayes@nikhef.nl Robin Hayes], Elizaveta Cherepanova and Dylan van Arneman''<br />
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=== ATLAS: Top-quark and Higgs-boson analysis combination, and Effective Field Theory interpretation (also in 2023) ===<br />
<br />
We are looking for a master student with interest in theory and data-analysis in the search for physics beyond the Standard Model in the top-quark and Higgs-boson sectors.<br />
<br />
Your master-project starts just at the right time for preparing the Run-3 analysis of the ATLAS experiment at the LHC. In Run-3 (2022-2026), three times more data becomes available, enabling analysis of rare processes with innovative software tools and techniques.<br />
<br />
This project aims to explore the newest strategy to combine the top-quark and Higgs-boson measurements in the perspective of constraining the existence of new physics beyond the Standard Model (SM) of Particle Physics. We selected the pp->tZq and gg->HZ processes as promising candidates for a combination to constrain new physics in the context of Standard Model Effective Field Theory (SMEFT). SMEFT is the state-of-the-art framework for theoretical interpretation of LHC data. In particular, you will study the SMEFT OtZ and Ophit operators, which are not well constrained by current measurements.<br />
<br />
Besides affinity with particle physics theory, the ideal candidate for this project has developed python/C++ skills and is eager to learn advanced techniques. You start with a simulation of the signal and background samples using existing software tools. Then, an event selection study is required using Machine Learning techniques. To evaluate the SMEFT effects, a fitting procedure based on the innovative Morphing technique is foreseen, for which the basic tools in the ROOT and RooFit framework are available. The work is carried out in the ATLAS group at Nikhef and may lead to an ATLAS note.<br />
<br />
''Contact: [mailto:o.rieger@nikhef.nl Oliver Rieger] and [mailto:h73@nikhef.nl Marcel Vreeswijk]''<br />
<br />
=== ATLAS: Machine learning to search for very rare Higgs decays ===<br />
<br />
Since the Higgs boson discovery in 2012 at the ATLAS experiment, the investigation of the properties of the Higgs boson has been a priority for research at the Large Hadron Collider (LHC). However, there are still a many open questions: Is the Higgs boson the only origin of Electroweak Symmetry Breaking? Is there a mechanism which can explain the observed mass pattern of SM particles? Many of these questions are linked to the Higgs boson coupling structure. <br />
<br />
While the Higgs boson coupling to fermions of the third generation has been established experimentally, the investigation of the Higgs boson coupling to the light fermions of the second generation will be a major project for the upcoming data-taking period (2022-2025). The Higgs boson decay to muons is the most sensitive channel for probing this coupling. In this project, you will optimize the event selection for Higgs boson decays to muons in the Vector Boson Fusion (VBF) production channel with a focus on distinguishing signal events from background processes like Drell-Yan and electroweak Z boson production. For this purpose, you will develop, implement and validate advanced machine learning and deep learning algorithms. <br />
<br />
''Contact: [mailto:oliver.rieger@nikhef.nl Oliver Rieger] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:s01@nikhef.nl Peter Kluit]''<br />
<br />
=== ATLAS: Interpretation of experimental data using SMEFT ===<br />
<br />
The Standard Model Effective Field Theory (SMEFT) provides a systematic approach to test the impact of new physics at the energy scale of the LHC through higher-dimensional operators. The interpretation of experimental data using SMEFT requires a particular interest in solving complex technical challenges, advanced statistical techniques, and a deep understanding of particle physics. We would be happy to discuss different project opportunities based on your interests with you.<br />
<br />
''Contact: [mailto:oliver.rieger@nikhef.nl Oliver Rieger] and [mailto:verkerke@nikhef.nl Wouter Verkerke]''<br />
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=== ATLAS: Reconstructing tracks from particle physics detector hits with state-of-the-art machine learning techniques ===<br />
This project concerns the application of new machine learning techniques to tackle the problem of track reconstruction at the ATLAS detector in CERN. While algorithms to construct particle tracks from low-level detector information such as particle hits and timestamps have been around for decades, recent developments in the field of machine learning open up new opportunities to improve these algorithms significantly. Some recent developments that could help in this context include graph-based neural networks, which embed the input data in the format of a graph and as such have the capability to enhance underlying correlations within events. Transformer neural networks are a particular extension of graph-based neural networks proposed only in 2017 which could also provide helpful in this case. Another option would be to build upon some of the work done within the field of computer vision and see if image segmentation networks can help solve this problem. There are a range of available options and this project includes the freedom for the student to choose particular types of networks, but more explicit guidance could be provided in case it is desired.<br />
<br />
In this project the student will develop and compare the performance of various machine learning models to initially reconstruct tracks from simplified test data. Upon successful completion of this, simulated data from the actual ATLAS detector can be analysed as well in the scope of this project. The student will need some familiarity with programming in python and an interest in machine learning, but a physics background is not required. In this project the student will be able to contribute to fundamental physics research and will familiarize themselves with state-of-the-art machine learning models.<br />
<br />
Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
=== ATLAS: New machine learning approaches to target Higgs interference signatures in LHC data ===<br />
In this project we aim to improve an ongoing analysis to determine the lifetime of the Higgs Boson through state-of-the-art machine learning techniques, in particular by addressing a ''novel solution to an as of yet unsolved fundamental problem in modeling quantum interference''. While the Higgs is an elusive particle that generally only appears in physics processes with small cross sections, its signature can be amplified in the Large Hadron Collider (LHC) through quantum interference with larger background (non-Higgs) processes. This is the effect that the Higgs’ lifetime analysis relies on to be able to measure the relevant Higgs signature. A fundamental physics modelling problem arises though in the simulation of individual events for this interference due to the fact that these events are in reality described by a superposition of underlying Higgs and non-Higgs processes.<br />
<br />
Since machine learning models in particle physics are typically trained to characterise individual physics events, the fact that interference events cannot currently be generated is a significant problem when interference is the target. In the currently existing Higgs lifetime analysis, a machine learning model was trained which instead focuses only on the explicit Higgs-mediated processes as a proxy, which is suboptimal. The aim of this project is to improve upon this current machine learning strategy used in this analysis by implementing either of the inference-aware approaches suggested in [1] and [2]. The idea behind these inference-aware machine learning algorithms is that they do not optimise for a simplified goal such as the loss function which is common in traditional machine learning, but rather for the end-goal of the analysis. In this case, this would omit the need for interference event generation altogether and allow the machine learning models to be trained optimally regardless.<br />
<br />
The first checkpoint of this project is to use either of the frameworks used in [1] and [2] (which are both publicly available) and run them with a simplified dataset from the aforementioned analysis. After this proof-of-principle is achieved, the next goal would be to actually implement the newly developed machine learning models in the full analysis and to determine the improvement upon the existing result. A successful completion of these tasks would not only benefit the Higgs lifetime analysis, but would be an important stepping stone to future developments to make machine learning approaches also aware of other hard to model effects such as systematic uncertainties. Finally, there are further options to improve this analysis such as the generation of actual interference training data, which could be attempted in case the primary project finishes earlier than expected.<br />
<br />
[1] De Castro, P., & Dorigo, T. (2019). INFERNO: inference-aware neural optimisation. ''Computer Physics Communications'', ''244'', 170-179.<br />
<br />
[2] Simpson, N., & Heinrich, L. (2023, February). neos: End-to-end-optimised summary statistics for high energy physics. In ''Journal of Physics: Conference Series'' (Vol. 2438, No. 1, p. 012105). IOP Publishing.<br />
<br />
Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
=== ATLAS: Development of state-of-the art modeling techniques to generate Higgs interference events ===<br />
In this project we aim to improve an ongoing analysis to determine the lifetime of the Higgs Boson through new event generation strategies, in particular by addressing a novel solution to an as of yet unsolved fundamental problem in modeling quantum interference. While the Higgs is an elusive particle that generally only appears in physics processes with small cross sections, its signature can be amplified in the Large Hadron Collider (LHC) through quantum interference with larger background (non-Higgs) processes. This is the effect that the Higgs’ lifetime analysis relies on to be able to measure the relevant Higgs signature. A fundamental physics modelling problem arises though in the simulation of individual events for this interference due to the fact that these events are in reality described by a superposition of underlying Higgs and non-Higgs processes.<br />
<br />
The current approach to deal with this problem is to ignore the interference in analysis optimization and instead optimize only for explicitly Higgs mediated processes, but this severely impacts analysis performance. In the context of Effective Field Theories (EFT) however, a similar problem arises and has been solved for simple (leading order) processes. In this project we plan to take the machinery developed for EFT and apply it to the Higgs lifetime analysis. Furthermore, with the recent development of a Next-to-Leading Order (NLO) Higgs event generation tool [1] a subsequent goal would be to use this to also generate interference at the NLO level. Successful completion of this project would lead to a much improved analysis result, significantly constraining the lifetime of the Higgs Boson. Besides, the techniques developed would almost certainly be used in future analyses on Large Hadron Collider (LHC) run 3 data.<br />
<br />
[1] Alioli, S., Ravasio, S. F., Lindert, J. M., & Röntsch, R. (2021). Four-lepton production in gluon fusion at NLO matched to parton showers. ''The European Physical Journal C'', ''81''(8), 687.<br />
<br />
Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák], [mailto:b.kortman@nikhef.nl Bryan Kortman] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
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=== ATLAS: Approaching the Higgs from a new direction: Constraining new physics with off shell Higgs data from the LHC ===<br />
The Heisenberg uncertainly principle allows for all elementary particles---including the Higgs Boson---to momentarily disobey the fundamental energy-momentum relation, allowing the particle in question to have a significantly larger mass than usual. A description of the Higgs Boson in this state (“off shell Higgs Boson”) can provide a portal to the discovery of potential new physics, albeit very difficult to do due to its infrequent appearance. The goal of this project is to constrain or hint at new physics by estimating parameters of a generalized model which allows for new physics, Effective Field Theory (EFT), using off shell Higgs data.<br />
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Most of the underlying analysis to measure the prevalence of off shell Higgs bosons has already been set up, so the goal of this project is to do the aforementioned EFT interpretation on top of this existing analysis. From a theoretical point of view much of the groundwork has also been done on simulated data which showed the potential for this EFT interpretation to constrain new physics [1]. Being on the interface between experimental and theoretical physics this project allows the student to gain a deeper understanding of both, furthermore its successful completion could be one of the first hints towards as of yet not understood physics.<br />
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[1] Azatov, A., de Blas, J., Falkowski, A., Gritsan, A. V., Grojean, C., Kang, L., ... & Vryonidou, E. (2022). Off-shell Higgs Interpretations Task Force: Models and Effective Field Theories Subgroup Report. arXiv preprint arXiv:2203.02418.<br />
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Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák], [mailto:b.kortman@nikhef.nl Bryan Kortman] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
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=== ATLAS: A new timing detector - the HGTD ===<br />
The ATLAS is going to get a new ability: a timing detector. This allows us to reconstruct tracks not only in the 3 dimensions of space but adds the ability of measuring very precisely also the time (at picosecond level) at which the particles pass the sensitive layers of the HGTD detector. This allows to construct the trajectories of the particles created at the LHC in 4 dimensions and ultimately will lead to a better reconstruction of physics at ATLAS. The new HGTD detector is still in construction and work needs to be done on different levels such as understanding the detector response (taking measurements in the lab and performing simulations) or developing algorithms to reconstruct the particle trajectories (programming and analysis work). <br />
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'''Several projects are available within the context of the new HGTD detector:''' <br />
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# One can choose to either focus on '''''the impact on physics analysis performance''''' by studying how the timing measurements can be included in the reconstruction of tracks, and what effect this has on how much better we can understand the physical processes occurring in the particles produced in the LHC collisions. With this work you will be part of the Atlas group at Nikhef.<br />
# The second possibility is to '''''test the sensors in our lab''''' and in test-beam setups at CERN. The analysis performed will be in context of the ATLAS HGTD test beam group in connection to both the Atlas group and the R&D department at Nikhef.<br />
# The third is to contribute in an ongoing effort '''''to precisely simulate/model he silicon avalanche detectors''''' in the Allpix2 frameword. There are several models that try to describe the detectors response. There are several dependencies to operation temperature, field strenghts and radiation damage. We are getting close in being able to model our detector - but not there yet. This work will be within the ATLAS group together with Hella Snoek and Andrea Visibile<br />
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If you are interested, contact me to discuss the possibilities. <br />
Contact: ''[mailto:hella.snoek@nikhef.nl Hella Snoek]''<br />
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=== ATLAS: The next full-silicon Inner Tracker: ITk ===<br />
[[File:ITk endcap structure.jpg|210x210px|thumb|alt=]]The inner detector of the present ATLAS experiment has been designed and developed to function in the environment of the present Large Hadron Collider (LHC). At the ATLAS Phase-II Upgrade, the particle densities and radiation levels will exceed current levels by a factor of ten. The instantaneous luminosity is expected to reach unprecedented values, resulting in up to 200 proton-proton interactions in a typical bunch crossing. The new detectors must be faster and they need to be more highly segmented. The sensors used also need to be far more resistant to radiation, and they require much greater power delivery to the front-end systems. At the same time, they cannot introduce excess material which could undermine tracking performance. For those reasons, the inner tracker of the ATLAS detector (ITk) was redesigned and will be rebuilt completely.<br />
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Nikhef is one of the sites in charge of building and integrating some big parts of ITk. One of the next steps consists of testing the sensors that we will install in the structures we have built (check one of the structures in the picture of our cleanroom). This project offers the possibility of working on a full hardware project, doing something completely new, by testing the sensors of a future component of the next ATLAS detector.<br />
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''Contact'': ''[mailto:aalonso@nikhef.nl Andrea García Alonso]''<br />
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=== Cosmic Rays/Neutrinos: Seasonal muon flux variations and the pion/kaon ratio ===<br />
The KM3NeT ARCA and ORCA detectors, located kilometers deep in the Mediterranean Sea, have neutrinos as primary probes. Muons from cosmic ray interactions reach the detectors in relatively large quantities too. These muons, exploiting the capabilities and location of the detectors allow the study of cosmic rays and their interactions. In this way, questions about their origin, type, propagation can be addressed. In particular these muons are tracers of hadronic interactions at energies inaccessible at particle accelerators.<br />
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The muons reaching the depths of the detectors result from decays of mesons, mostly pions and kaons, created in interactions of high-energy cosmic rays with atoms in the upper atmosphere. Seasonal changes of the temperature – and thus density - profile of the atmosphere modulate the balance between the probability for these mesons to decay (producing muons) or to re-interact. Pions and kaons are affected differently, allowing to extract their production ratio by determining how changes in muon rate depend on changes in the effective temperature – an integral over the atmospheric temperature profile weighted by a depth dependent meson production rate.<br />
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In this project, the aim is to measure the rate of muons in the detectors and to calculate the effective temperature above the KM3NeT detectors from atmospheric data, both as function of time. The relation between these two can be used to extract the pion to kaon ratio.<br />
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''Contact: [mailto:rbruijn@nikhef.nl Ronald Bruijn]''<br />
=== Detector R&D: Studies of wafer-scale sensors for ALICE detector upgrade and beyond===<br />
One of the biggest milestones of the ALICE detector upgrade (foreseen in 2026) is the implementation of wafer-scale (~ 28 cm x 18 cm) monolithic silicon active pixel sensors in the tracking detector, with the goal of having truly cylindrical barrels around the beam pipe. To demonstrate such an unprecedented technology in high energy physics detectors, few chips will be soon available in Nikhef laboratories for testing and characterization purposes.<br />
The goal of the project is to contribute to the validation of the samples against the ALICE tracking detector requirements, with a focus on timing performance in view of other applications in future high energy physics experiments beyond ALICE.<br />
We are looking for a student with a focus on lab work and interested in high precision measurements with cutting-edge instrumentation. You will be part of the Nikhef Detector R&D group and you will have, at the same time, the chance to work in an international collaboration where you will report about the performance of these novel sensors. There may even be the opportunity to join beam tests at CERN or DESY facilities. Besides interest in hardware, some proficiency in computing is required (Python or C++/ROOT).<br />
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''Contact: [mailto:(jory.sonneveld@nikhef.nl Jory Sonneveld ], [mailto:rrusso@nikhef.nl Roberto Russo]''<br />
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=== Detector R&D: Time resolution of monolithic silicon detectors ===<br />
Monolithic silicon detectors based on industrial Complementary Metal Oxide Semiconductor (CMOS) processes offer a promising approach for large scale detectors due to their ease of production and low material budget. Until recently, their low radiation tolerance has hindered their applicability in high energy particle physics experiments. However, new prototypes ~~such as the one in this project~~ have overcome these hurdles, making them feasible candidates for future experiments in high energy particle physics. Achieving the required radiation tolerance has brought the spatial and temporal resolution of these detectors to the forefront. In this project, you will investigate the temporal performance of a radiation hard monolithic detector prototype, using laser setups in the laboratory. You will also participate in meetings with the international collaboration working on this detector, where you will report on the prototype's performance. Depending on the progress of the work, there may be a chance to participate in test beams performed at the CERN accelerator complex and a first full three dimensional characterization of the prototypes performance using a state-of-the-art two-photon absorption laser setup at Nikhef. This project is looking for someone interested in working hands on with cutting edge detector and laser systems at the Nikhef laboratory. Python programming skills and linux experience are an advantage.<br />
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''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld], [mailto:uwe.kraemer@nikhef.nl Uwe Kraemer]''<br />
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=== Detector R&D: Improving a Laser Setup for Testing Fast Silicon Pixel Detectors ===<br />
For the upgrades of the innermost detectors of experiments at the Large Hadron Collider in Geneva, in particular to cope with the large number of collisions per second from 2027, the Detector R&D group at Nikhef tests new pixel detector prototypes with a variety of laser equipment with several wavelengths. The lasers can be focused down to a small spot to scan over the pixels on a pixel chip. Since the laser penetrates the silicon, the pixels will not be illuminated by just the focal spot, but by the entire three dimensional hourglass or double cone like light intensity distribution. So, how well defined is the volume in which charge is released? And can that be made much smaller than a pixel? And, if so, what would the optimum focus be? For this project the student will first estimate the intensity distribution inside a sensor that can be expected. This will correspond to the density of released charge within the silicon. To verify predictions, you will measure real pixel sensors for the LHC experiments.<br />
This project will involve a lot of 'hands on work' in the lab and involve programming and work on unix machines.<br />
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''Contact: [mailto:martinfr@nikhef.nl Martin Fransen]''<br />
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=== Detector R&D: Time resolution of hybrid pixel detectors with the Timepix4 chip ===<br />
Precise time measurements with silicon pixel detectors are very important for experiments at the High-Luminosity LHC and the future circular collider. The spatial resolution of current silicon trackers will not be sufficient to distinguish the large number of collisions that will occur within individual bunch crossings. In a new method, typically referred to as 4D tracking, spatial measurements of pixel detectors will be combined with time measurements to better distinguish collision vertices that occur close together.<br />
New sensor technologies are being explored to reach the required time measurement resolution of tens of picoseconds, and the results are promising. However, the signals that these pixelated sensors produce have to be processed by front-end electronics, which hence also play a role in the total time resolution of the detector. An important contribution comes from the systematic differences between the front-end electronics of different pixels. Many of these systematic effects can be corrected by performing detailed calibrations of the readout electronics. To achieve the required time resolution at future experiments, it is vital that these effects are understood and corrected.<br />
In this project you will be working with the Timepix4 chip. This is a so-called application specific integrated circuit (ASIC) that is designed to read out pixelated sensors. This ASIC will be used extensively in detector R&D for the characterisation of new sensor technologies requiring precise timing (< 50 ps). In order to do so, it is necessary to first study the systematic differences between the pixels, which you will do using a laser setup in our lab. This will be combined with data analysis of proton beam measurements, or with measurements performed using the built-in test-pulse mechanism of the Timepix4 ASIC. Your work will enable further research performed with this ASIC, <br />
and serve as input to the design and operation of future ASICs for experiments at the High-Luminosity LHC.<br />
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''Contact: [mailto:k.heijhoff@nikhef.nl Kevin Heijhoff] and [mailto:martinb@nikhef.nl Martin van Beuzekom]''<br />
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===Detector R&D: Performance studies of Trench Isolated Low Gain Avalanche Detectors (TI-LGAD) ===<br />
The future vertex detector of the LHCb Experiment needs to measure the spatial coordinates and time of the particles originating in the LHC proton-proton collisions with resolutions better than 10 um and 50 ps, respectively. Several technologies are being considered to achieve these resolutions. Among those is a novel sensor technology called Trench Isolated Low Gain Avalanche Detector. <br />
Prototype pixelated sensors have been manufactured recently and have to be characterised. Therefore these new sensors will be bump bonded to a Timepix4 ASIC which provides charge and time measurements in each of 230 thousand pixels. Characterisation will be done using a lab setup at Nikhef, and includes tests with a micro-focused laser beam, radioactive sources, and possibly with particle tracks obtained in a test-beam. This project involves data taking with these new devices and analysing the data to determine the performance parameters such as the spatial and temporal resolution. as function of temperature and other operational conditions. <br />
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''Contacts: [mailto:kazu.akiba@nikhef.nl Kazu Akiba] and [mailto:martinb@nikhef.nl Martin van Beuzekom]''<br />
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===Detector R&D: A Telescope with Ultrathin Sensors for Beam Tests ===<br />
To measure the performance of new prototypes for upgrades of the LHC experiments and beyond, typically a telescope is used in a beam line of charged particles that can be used to compare the results in the prototype to particle tracks measured with this telescope. In this project, you will continue work on a very lightweight, compact telescope using ALICE PIxel DEtectors (ALPIDEs). This includes work on the mechanics, data acquisition software, and a moveable stage. You will foreseeably test this telescope in the Delft Proton Therapy Center. If time allows, you will add a timing plane and perform a measurement with one of our prototypes. Apart from travel to Delft, there is a possiblity to travel to other beam line facilities.<br />
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''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
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===Detector R&D: Laser Interferometer Space Antenna (LISA) - the first gravitational wave detector in space ===<br />
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The space-based gravitational wave antenna LISA is one of the most challenging space missions ever proposed. ESA plans to launch around 2034 three spacecraft separated by a few million kilometres. This constellation measures tiny variations in the distances between test-masses located in each satellite to detect gravitational waves from sources such as supermassive black holes. LISA is based on laser interferometry, and the three satellites form a giant Michelson interferometer. LISA measures a relative phase shift between one local laser and one distant laser by light interference. The phase shift measurement requires sensitive sensors. The Nikhef DR&D group fabricated prototype sensors in 2020 together with the Photonics industry and the Dutch institute for space research SRON. Nikhef & SRON are responsible for the Quadrant PhotoReceiver (QPR) system: the sensors, the housing including a complex mount to align the sensors with 10's of nanometer accuracy, various environmental tests at the European Space Research and Technology Centre (ESTEC), and the overall performance of the QPR in the LISA instrument. Currently we are discussing possible sensor improvements for a second fabrication run in 2022, optimizing the mechanics and preparing environmental tests. As a MSc student, you will work on various aspects of the wavefront sensor development: study the performance of the epitaxial stacks of Indium-Gallium-Arsenide, setting up test benches to characterize the sensors and QPR system, performing the actual tests and data analysis, in combination with performance studies and simulations of the LISA instrument.<br />
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''Contact: [mailto:nielsvb@nikhef.nl Niels van Bakel]''<br />
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===Detector R&D: Other projects ===<br />
Are you looking for a slightly different project? Are the above projects already taken? Are you coming in at an unusual time of the year? Do not hesitate to contact us! We always have new projects coming up at different times in the year and we are open to your ideas.<br />
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''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
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===FCC: The Next Collider===<br />
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After the LHC, the next planned large collider at CERN is the proposed 100 kilometer circular collider "FCC". In the first stage of the project, as a high-luminosity electron-positron collider, precision measurements of the Higgs boson are the main goal. One of the channels that will improve by orders of magnitude at this new accelerator is the decay of the Higgs boson to a pair of charm quarks. This project will estimate a projected sensitivity for the coupling of the Higgs boson to second generation quarks, and in particular target the improved reconstruction of the topology of long-lived mesons in the clean environment of a precision e+e- machine.<br />
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''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
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===Gravitational Waves: Computer modelling to design the laser interferometers for the Einstein telescope===<br />
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A new field of instrument science led to the successful detection of gravitational waves by the LIGO detectors in 2015. We are now preparing the next generation of gravitational wave observatories, such as the Einstein Telescope, with the aim to increase the detector sensitivity by a factor of ten, which would allow, for example, to detect stellar-mass black holes from early in the universe when the first stars began to form. This ambitious goal requires us to find ways to significantly improve the best laser interferometers in the world.<br />
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Gravitational wave detectors, such as LIGO and VIRGO, are complex Michelson-type interferometers enhanced with optical cavities. We develop and use numerical models to study these laser interferometers, to invent new optical techniques and to quantify their performance. For example, we synthesize virtual mirror surfaces to study the effects of higher-order optical modes in the interferometers, and we use opto-mechanical models to test schemes for suppressing quantum fluctuations of the light field. We can offer several projects based on numerical modelling of laser interferometers. All projects will be directly linked to the ongoing design of the Einstein Telescope.<br />
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''Contact: [mailto:a.freise@nikhef.nl Andreas Freise]''<br />
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===LHCb: Search for light dark particles===<br />
The Standard Model of elementary particles does not contain a proper Dark Matter candidate. One of the most tantalizing theoretical developments is the so-called ''Hidden Valley models'': a mirror-like copy of the ''Standard Model'', with dark particles that communicate with standard ones via a very feeble interaction. These models predict the existence of ''dark hadrons'' – composite particles that are bound similarly to ordinary hadrons in the ''Standard Model''. Such ''dark hadrons'' can be abundantly produced in high-energy proton-proton collisions, making the LHC a unique place to search for them. Some ''dark hadrons'' are stable like a proton, which makes them excellent ''Dark Matter'' candidates, while others decay to ordinary particles after flying a certain distance in the collider experiment. The LHCb detector has a unique capability to identify such decays, particularly if the new particles have a mass below ten times the proton mass. <br />
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This project assumes a unique search for light ''dark hadrons'' that covers a mass range not accessible to other experiments. It assumes an interesting program on data analysis (python-based) with non-trivial machine learning solutions and phenomenology research using fast simulation framework. Depending on the interest, there is quite a bit of flexibility in the precise focus of the project.<br />
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''Contact: [mailto:andrii.usachov@nikhef.nl Andrii Usachov]''<br />
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===LHCb: Searching for dark matter in exotic six-quark particles===<br />
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Three quarters of the mass in the Universe is of unknown type. Many hypotheses about this dark matter have been proposed, but none confirmed. Recently it has been proposed that it could be made of particles made of the six quarks uuddss, which would be a Standard-Model solution to the dark matter problem. This idea has recently gained credibility as many similar multi-quarks states are being discovered by the LHCb experiment. Such a particle could be produced in decays of heavy baryons, or directly in proton-proton collisions. The anti-particle, made of six antiquarks, could be seen when annihilating with detector material. It is also proposed to use Xi_b baryons produced at LHCb to search for such a state where the state would appear as missing 4-momentum in a kinematically constrained decay. The project consists in defining a selection and applying it to LHCb data. See [https://arxiv.org/abs/2007.10378 arXiv:2007.10378].<br />
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Contact: ''[mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
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===LHCb: Measuring lepton flavour universality with excited Ds states in semileptonic Bs decays===<br />
One of the most striking discrepancies between the Standard Model and measurements are the lepton flavour universality (LFU) measurements with tau decays. At the moment, we have observed an excess of 3-4 sigma in ''B → Dτν'' decays. This could point even to a new force of nature! To understand this discrepancy, we need to make further measurements. <br />
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One very exciting (pun intended) projects to verify these discrepancies involves measuring the ''B<sub>s</sub> → D<sub>s2</sub><sup>*</sup>τν'' and/or ''B<sub>s</sub> → D<sub>s1</sub><sup>*</sup>τν'' decays. These decays with excited states of the ''D<sub>s</sub>'' meson have not been observed before in the tau decay mode, and have a unique way of coupling to potential new physics candidates that can only be measured in ''B<sub>s</sub>'' decays [1]. See slides for more detail: [[File:LHCbLFUwithExcitedDs.pdf|thumb]]<br />
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[1] https://arxiv.org/abs/1606.09300<br />
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''Contact: [mailto:suzannek@nikhef.nl Suzanne Klaver]''<br />
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===LHCb: New physics in the angular distributions of B decays to K*ee===<br />
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Lepton flavour violation in B decays can be explained by a variety of non-standard model interactions. Angular distributions in decays of a B meson to a hadron and two leptons are an important source of information to understand which model is correct. Previous analyses at the LHCb experiment have considered final states with a pair of muons. Our LHCb group at Nikhef concentrates on a new measurement of angular distributions in decays with two electrons. The main challenge in this measurement is the calibration of the detection efficiency. In this project you will confront estimates of the detection efficiency derived from simulation with decay distributions in a well known B decay. Once the calibration is understood, the very first analysis of the angular distributions in the electron final state can be performed. <br />
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Contact: [mailto:m.senghi.soares@nikhef.nl Mara Soares] and [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
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===LHCb: Discovering heavy neutrinos in B decays===<br />
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Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, much heavier, neutral leptons. If the mass of these new neutrinos is below the b-quark mass, they can be observed in B hadron decays.<br />
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In this project we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undiscovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The analysis will be performed within the LHCb group at Nikhef using LHCb run-2 data.<br />
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===LHCb: Scintillating Fibre tracker software===<br />
The installation of the scintillating-fibre tracker in LHCb’s underground cavern was recently completed. This detector uses 10000 km of fibres to track particle trajectories in the LHCb detector when the LHC starts up again later this year. The light emitted by the scintillating fibres when a particle interacts with them is measured using photon multiplier tubes. The studies proposed for this project will focus on software, and could include writing a framework to monitor the detector output, improving the detector simulation or working on the data processing.<br />
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''Contact: [mailto:e.gabriel@nikhef.nl Emmy Gabriel]''<br />
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===LHCb: Vertex detector calibration===<br />
In summer 2022 LHCb has started data taking will an almost entirely new detector. At the point closest to the interaction point, the trajectories of charge particles are reconstructed with a so-called silicon pixel detector. The design hit resolution of this detector is about 15 micron. However, to actually reach this resolution a precise calibration of the spatial positions of the silicon sensors needs to be performed. In this project, you will use the first data of the new LHCb detector to perform this calibration and measure the detector performance.<br />
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''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen]''<br />
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===Neutrinos: Neutrino scattering: the ultimate resolution===<br />
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Neutrino telescopes like IceCube and KM3NeT aim at detecting neutrinos from cosmic sources. The neutrinos are detected with the best resolution when charged current interactions with nucleons produce a muon, which can be detected with high accuracy (depending on the detector). A crucial ingredient in the ultimate achievable pointing accuracy of neutrino telescopes is the scattering angle between the neutrino and the muon. While published computations have investigated the cross-section of the process in great detail, this important scattering angle has not received much attention. The aim of the project is to compute and characterize the distribution of this angle, and that the ultimate resolution of a neutrino telescope. If successful, the results of this project can lead to publication of interest to the neutrino telescope community.<br />
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Depending on your interests, the study could be based on a first-principles calculation (using the deep-inelastic scattering formalism), include state-of-the-art parton distribution functions, and/or exploit existing event-generation software for a more experimental approach. <br />
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''Contacts: [mailto:aart.heijboer@nikhef.nl Aart Heijboer]''<br />
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===Neutrinos: acoustic detection of ultra-high energy neutrinos===<br />
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The study of the cosmic neutrinos of energies above 1017 eV, the so-called ultra-high energy neutrinos, provides a unique view on the universe and may provide insight in the origin of the most violent astrophysical sources, such as gamma ray bursts, supernovae or even dark matter. In addition, the observation of high energy neutrinos may provide a unique tool to study interactions at high energies. The energy deposition of these extreme neutrinos in water induce a thermo-acoustic signal, which can be detected using sensitive hydrophones. The expected neutrino flux is however extremely low and the signal that neutrinos induce is small. TNO is presently developing sensitive hydrophone technology based on fiber optics. Optical fibers form a natural way to create a distributed sensing system. Using this technology a large scale neutrino telescope can be built in the deep sea. TNO is aiming for a prototype hydrophone which will form the building block of a future telescope.<br />
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The work will be executed at the Nikhef institute and/or the TNO laboratories in Delft. In this project master students have the opportunity to contribute in the following ways:<br />
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'''Project 1:''' Hardware development on fiber optics hydrophones technology Goal: characterize existing prototype optical fibre hydrophones in an anechoic basin at TNO laboratory. Data collection, calibration, characterization, analysis of consequences for design future acoustic hydrophone neutrino telescopes;<br />
Keywords: Optical fiber technology, signal processing, electronics, lab.<br />
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'''Project 2:''' Investigation of ultra-high energy neutrinos and their interactions with matter. Goal: Discriminate the neutrino signals from the background noises, in particular clicks from whales and dolphins in the deep sea. Study impact on physics reach for future acoustic hydrophone neutrino telescopes;<br />
Keywords: Monte Carlo simulations, particle physics, neutrino physics, data analysis algorithms.<br />
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Further information: Info on ultra-high energy neutrinos can be found at: http://arxiv.org/abs/1102.3591; Info on acoustic detection of neutrinos can be found at: http://arxiv.org/abs/1311.7588<br />
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''Contact: [mailto:ernst-jan.buis@tno.nl Ernst Jan Buis]'' or ''[mailto:ivo.van.vulpen@nikhef.nl Ivo van Vulpen]''<br />
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===Neutrinos: Oscillation analysis with the first data of KM3NeT===<br />
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The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first few strings with sensitive photodetectors have been deployed at both the Italian and the French detector sites. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In this project the available data will be used together with simulations to best reconstruct the event topologies and optimally identify and reconstruct the first neutrino interactions in the KM3NeT detector. The data will then be used to measure neutrino oscillation parameters, and prepare for a future neutrino mass ordering determination.<br />
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Programming skills are essential, mostly root and C++ will be used.<br />
''Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn] [mailto:h26@nikhef.nl Paul de Jong]''<br />
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===Neutrinos: the Deep Underground Neutrino Experiment (DUNE)===<br />
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The Deep Underground Neutrino Experiment (DUNE) is under construction in the USA, and will consist of a powerful neutrino beam originating at Fermilab, a near detector at Fermilab, and a far detector in the SURF facility in Lead, South Dakota, 1300 km away. During travelling, neutrinos oscillate and a fraction of the neutrino beam changes flavour; DUNE will determine the neutrino oscillation parameters to unrivaled precision, and try and make a first detection of CP-violation in neutrinos. In this project, various elements of DUNE can be studied, including the neutrino oscillation fit, neutrino physics with the near detector, event reconstruction and classification (including machine learning), or elements of data selection and triggering.<br />
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''Contact: [mailto:h26@nikhef.nl Paul de Jong]''<br />
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===Neutrinos: Searching for Majorana Neutrinos with KamLAND-Zen===<br />
The KamLAND-Zen experiment, located in the Kamioka mine in Japan, is a large liquid scintillator experiment with 750kg of ultra-pure Xe-136 to search for neutrinoless double-beta decay (0n2b). The observation of the 0n2b process would be evidence for lepton number violation and the Majorana nature of neutrinos, i.e. that neutrinos are their own anti-particles. Current limits on this extraordinary rare hypothetical decay process are presented as a half-life, with a lower limit of 10^26 years. KamLAND-Zen, the world’s most sensitive 0n2b experiment, is currently taking data and there is an opportunity to work on the data analysis, analyzing data with the possibility of taking part in a ground-breaking discovery. The main focus will be on developing new techniques to filter the spallation backgrounds, i.e. the production of radioactive isotopes by passing muons. There will be close collaboration with groups in the US (MIT, Berkeley, UW) and Japan (Tohoku Univ). <br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
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===Neutrinos: relic neutrino detection with PTOLEMY ===<br />
PTOLEMY aims to make the first direct observation of the Big Bang relic neutrinos (the cosmic neutrino background, CνB) by resolving the β-decay endpoint of atomic tritium (neutrino capture target) to O(meV) precision. This remains an outstanding test of the Standard Model in an expanding universe. Not only does the CνB carry with it a signal from the hot dense universe only one second after the Big Bang but helps to constrain the balance of hot versus cold dark matter responsible for its evolution. In doing so, the PTOLEMY experiment would also measure the lowest neutrino mass, an as-of-yet unknown fundamental constant. The experiment is currently in the prototyping phase and the group at Nikhef is responsible for developing the radio-frequency (RF) system used for cyclotron radiation (CR) based trigger and tracking. This component will provide the trajectory of electrons entering the novel transverse drift filter, constraining the electrons' energy losses before they reach the cryogenic calorimeter which in turn records their final energy. The focus of this project will be modelling CR and its detection for the purposes of single electron spectroscopy and optimised trajectory reconstruction. There is also the opportunity to test hardware and readout electronics for the prototype RF-system. <br />
''Contact: [mailto:jmead@nikhef.nl James Vincent Mead]''<br />
<br />
=== Theoretical Particle Physics: Effective Field Theories of Particle Physics from low- to high-energies===<br />
Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations” seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature. The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Standard Model Effective Field Theory (SMEFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes with minimal assumptions on the nature of an eventual UV-complete theory that replaces the Standard Model. Specifically, the goal is to connect measurements from ATLAS, CMS, and LHCb experiments at the CERN's LHC among them and to jointly interpret this information with that provided by other experiments including very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
<br />
This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories. Depending on the student profile, sub-projects with a strong computational and/or machine learning component are also possible, for instance to construct new operators with optimal sensitivity to New Physics effects as encoded by the SMEFT higher-dimensional operators. Topics that can be considered in this project include the interpretation of novel physical observables at the LHC and their integration into the global SMEFiT analysis, matching of EFTs to UV-complete theories and their phenomenological analyses, projections for the impact in the SMEFT parameter space of data for future colliders, the synergies between EFT studies and proton structure fits, and the matching to the Weak Effective Field Theory to include data on flavour observables such as B-meson decays.<br />
<br />
References: https://arxiv.org/abs/2105.00006 , https://arxiv.org/abs/2302.06660, https://arxiv.org/abs/2211.02058 , https://arxiv.org/abs/1901.05965 , https://arxiv.org/abs/1906.05296 , https://arxiv.org/abs/1908.05588, https://arxiv.org/abs/1905.05215. see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description].<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theoretical Particle Physics: High-energy neutrino-nucleon interactions at the Forward Physics Facility ===<br />
High-energy collisions at the High-Luminosity Large Hadron Collider (HL-LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing experiments. The proposed Forward Physics Facility (FPF) to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe Standard Model (SM) processes and search for physics beyond the Standard Model (BSM). High statistics neutrino detection will provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. The FPF has the promising potential to probe our understanding of the strong interactions as well as of proton and nuclear structure, providing access to both the very low-x and the very high-x regions of the colliding protons. The former regime is sensitive to novel QCD production mechanisms, such as BFKL effects and non-linear dynamics, as well as the gluon parton distribution function (PDF) down to x=1e-7, well beyond the coverage of other experiments and providing key inputs for astroparticle physics. In addition, the FPF acts as a neutrino-induced deep-inelastic scattering (DIS) experiment with TeV-scale neutrino beams. The resulting measurements of neutrino DIS structure functions represent a valuable handle on the partonic structure of nucleons and nuclei, particularly their quark flavour separation, that is fully complementary to the charged-lepton DIS measurements expected at the upcoming Electron-Ion Collider (EIC).<br />
<br />
In this project, the student will carry out updated predictions for the neutrino fluxes expected at the FPF, assess the precision with which neutrino cross-sections will be measured, and quantify their impact on proton and nuclear structure by means of machine learning tools within the NNPDF framework and state-of-the-art calculations in perturbative Quantum Chromodynamics. This project contributes to ongoing work within the FPF Initiative towards a Conceptual Design Report (CDR) to be presented within two years. Topics that can be considered as part of this project include the assessment of to which extent nuclear modifications of the free-proton PDFs can be constrained by FPF measurements, the determination of the small-x gluon PDF from suitably defined observables at the FPF and the implications for ultra-high-energy particle astrophysics, the study of the intrinsic charm content in the proton and its consequences for the FPF physics program, and the validation of models for neutrino-nucleon cross-sections in the region beyond the validity of perturbative QCD.<br />
<br />
References: https://arxiv.org/abs/2203.05090, https://arxiv.org/abs/2109.10905 ,https://arxiv.org/abs/2208.08372 , https://arxiv.org/abs/2201.12363 , https://arxiv.org/abs/2109.02653, https://github.com/NNPDF/ see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description]. <br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theoretical Particle Physics: Probing the origin of the proton spin with machine learning===<br />
At energy-frontier facilities such as the Large Hadron Collider (LHC), scientists study the laws of nature in their quest for novel phenomena both within and beyond the Standard Model of particle physics. An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions from the nature of the Higgs boson to the origin of cosmic neutrinos. The key to address some of these questions is by carrying out an universal analysis of nucleon structure from the simultaneous determination of the momentum and spin distributions of quarks and gluons and their fragmentation into hadrons. This effort requires combining an extensive experimental dataset and cutting-edge theory calculations within a machine learning framework where neural networks parametrise the underlying physical laws while minimising ad-hoc model assumptions. The upcoming Electron Ion Collider (EIC), to start taking data in 2029, will be the world's first ever polarised lepton-hadron collider and will offer a plethora of opportunities to address key open questions in our understanding of the strong nuclear force, such as the origin of the mass and the intrinsic angular momentum (spin) of hadrons and whether there exists a state of matter which is entirely dominated by gluons. To fully exploit this scientific potential, novel analysis methodologies need to be develop that make it possible to carry out large-scale, coherent interpretations of measurements from the EIC and other high-energy colliders.<br />
<br />
In this project, the student will carry out a new global analysis of the spin structure of the proton by means of the machine learning tools provided by the NNPDF open-source fitting framework and state-of-the-art calculations in perturbative Quantum Chromodynamics, and integrate it within the corresponding global NNPDF analyses of unpolarised proton and nuclear structure in the framework of a combined integrated global analysis of non-perturbative QCD. Specifically, the project aims to realise a NNLO global fit of polarised quark and gluon PDFs that combines all available data and state-of-the-art perturbative QCD calculations, and study the phenomenological implications for other experiments, including the EIC, for the spin content of the proton, for comparisons with lattice QCD calculations, and for nonpperturbative models of hadron structure.<br />
<br />
References: https://arxiv.org/abs/2201.12363, https://arxiv.org/abs/2109.02653 , https://arxiv.org/abs/2103.05419, https://arxiv.org/abs/1404.4293 , https://inspirehep.net/literature/1302398, https://github.com/NNPDF/ see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description].<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== '''Theoretical Particle Physics''': Charged lepton flavor violation in neutrino mass models ===<br />
The nonzero value of neutrino masses requires an explanation beyond the Standard Model of particle physics. A promising solution involves the existence of extra neutrinos, often called right-handed or sterile neutrinos. These models elegantly explain neutrino masses and can also be connected to other puzzles such as the absence of anti-matter in our universe. In this project you will investigate potential experimental signatures of sterile neutrinos through decays that are extremely rare in the Standard Model. Examples are muon decays to electrons and photons, or muon + neutron -> electron + neutron. You will perform Quantum Field Theory calculations within the neutrino-extended Standard Model to compute the rates of these processes and compare them to experimental sensitivities. <br />
<br />
''Contacts: [Mailto:j.devries4@uva.nl Jordy de Vries]''<br />
<br />
=== '''Theoretical Particle Physics''': The electric dipole moment of paramagnetic systems in the Standard Model ===<br />
Electric dipole moments (EDMs) of elementary particles, hadrons, nuclei, atoms, and molecules would indicate the violation of CP violation. The Standard Model (SM) contains CP violation in the weak interaction in the so-called CKM matrix (the quark-mixing matrix) but it leads to EDMs that are too small to be seen. At least this is often claimed. In this work we will reinvestigate the computation of the EDMs of systems that are used in state-of-the-art experiments. In particular we will compute a CP-violating interaction between electrons and nucleons mitigated by the SM weak interaction. During this project you will obtain a deep understanding of the Standard Model and explicit quantum field theory calculations across a wider range of energy scales. <br />
<br />
''Contacts: [Mailto:j.devries4@uva.nl Jordy de Vries]''<br />
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== Finished master projects ==<br />
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See: <br />
* https://wiki.nikhef.nl/education/Master_Theses<br />
* https://www.nikhef.nl/master-theses-2021/<br />
* https://www.nikhef.nl/facts-figures-2020/master-theses-2020/<br />
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[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Bachelor_Projects&diff=942Bachelor Projects2024-02-09T13:50:47Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>== Bachelor Projects 2024 ==<br />
<br />
=== Detector R&D ===<br />
<br />
=== KM3NeT ===<br />
<br />
=== Dark Matter ===<br />
<br />
=== ATLAS ===<br />
<br />
=== LHCb ===<br />
<br />
=== Gravitational waves ===<br />
<br />
=== Theoretical Physics ===<br />
<br />
====The Schiff theorem for Electric Dipole Moments (Jordy de Vries)====<br />
<br />
Electric Dipole Moments (EDMs) of nucleons, atoms and molecules are important experimental observables to look for beyond-the-Standard-Model sources of fundamental symmetry violation. Specifically, the violation of Charge-Parity (CP) symmetry, which is present in the SM but not in sufficient amounts to explain the observed matter-antimatter asymmetry in the universe, can be probed through EDMs. To understand what EDM measurements on larger systems tell us about the fundamental physics at the elemental particle scale, and to assess what systems are most promising for EDM experiments, the Schiff theorem is essential. This theorem describes how, under certain simplifications, the EDMs of atoms and molecules vanish due to screening. In this project, you will investigate the theory behind Schiff screening, including possible violations of the theorem which lead to interesting systems with which to probe EDMs. For this project, the courses Advanced Quantum Physics & Atomic Physics are useful, but not strictly necessary.<br />
<br />
<br />
====High-energy neutrino-nucleon interactions at the LHC with FASER ====<br />
<br />
High-energy collisions at the Large Hadron Collider (LHC) produce an unprecedented number of light particles along the beam collision axis, outside of the acceptance of existing experiments. The FASER experiment, located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, provides new opportunities to probe Standard Model (SM) processes, in particular high-energy neutrino physics, and search for physics beyond the Standard Model (BSM). In this project, the student(s) will carry out updated theoretical predictions and numerical simulations for relevant physical processes at FASER, in particular concerning neutrino production and scattering, and assess their implications for our current models of proton structure and of QCD, the quantum field theory of the strong nuclear force. The project will also involve studying the implications of these results for ultra-high-energy particle astrophysics such as at the KM3NET and AUGER experiments. For this project, having followed the elective courses "Introduction to (astro-)particle physics" and "Standard Model of Elementary Particles" is required.<br />
<br />
''Contact: [[Mailto:j.rojo@vu.nl Juan Rojo]] (''VU Amsterdam & Nikhef Theory)<br />
<br />
==== Probing the proton spin with machine learning at future colliders ====<br />
<br />
An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions in particle physics from the nature of the Higgs boson to the origin of cosmic neutrinos. This effort requires combining an extensive experimental dataset and cutting-edge theory calculations within a machine learning framework where neural networks parametrise the underlying physical laws while minimising ad-hoc model assumptions. The upcoming Electron Ion Collider (EIC), to start taking data in 2030, will be the world's first ever polarised lepton-hadron collider and will offer a plethora of opportunities to address key open questions in our understanding of the strong nuclear force, such as the origin of the mass and the intrinsic angular momentum (spin) of hadrons and whether there exists a state of matter which is entirely dominated by gluons. In this project, the student will carry out a determination of the polarised quark and gluon substructure of the proton by means of the machine learning tools provided by the NNPDF open-source fitting framework and include projections for the impact of future EIC data on the spin content of the proton and on non-perturbative models of hadron structure. For this project, having followed the elective courses "Introduction to (astro-)particle physics" and "Standard Model of Elementary Particles" is required.<br />
<br />
''Contact: [[Mailto:j.rojo@vu.nl Juan Rojo]] (VU Amsterdam & Nikhef Theory)''<br />
<br />
== Bachelor Projects 2023 ==<br />
<br />
=== KM3NeT ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along 200-700m long vertical lines, called detection units.<br />
<br />
<br />
==== Search for cosmic neutrinos with the first KM3NeT data ====<br />
<br />
The KM3NeT/ARCA block is tuned for the detection of cosmic neutrinos and search for their sources. The first data of ARCA will be used to search for cosmic neutrino sources, and to search for a neutrino signal in response to external alerts for transients (gamma-ray bursts, IceCube neutrinos, gravitational wave events). Furthermore there is the opportunity to search for a neutrino signal from dark matter annihilation in the galactic halo and in dwarf spheroidal galaxies.<br />
<br />
Supervisors: Thijs van Eeden, Jhilik Majumdar, Clara Gatius, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
<br />
==== Neutrino oscillations with KM3NeT/ORCA ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope is able to measure the oscillations of neutrinos produced in interactions of cosmic rays with the earth atmosphere. Fundamental neutrino properties can be deduced from these oscillations measurements. In this project we will use the first data of ORCA to study neutrino oscillations and fit neutrino mixing parameters and mass differences between neutrino mass states. We will study data selection, event reconstruction, and effects of systematic uncertainties on the results. <br />
<br />
Supervisors: Bouke Jung, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
<br />
==== Multi-messenger astronomy with neutrinos and radio signals ====<br />
The main goal of neutrino telescopes, such as ANTARES, KM3NeT and IceCube, is to detect cosmic neutrinos from astrophysical sources. When an interesting neutrino candidate is detected they send out a message to alert the scientific community. Other scientific instruments, like the Murchison Widefield Array (MWA) radio telescope, can then do a follow-up observation, to see if there are other messengers coming from the same source as the neutrinos. In this project you will analyse MWA data that were taken after the reception of neutrino alerts, to search for a radio source that can be associated with a neutrino source.<br />
<br />
Supervisor: Mieke Bouwhuis (mieke.bouwhuis at nikhef.nl)<br />
<br />
<br />
<br />
=== Dark Matter ===<br />
<br />
==== Investigating muon spallation backgrounds in KamLAND neutrino detector ====<br />
The KamLAND neutrino detector in Japan is designed to measure among other things neutrinoless double beta decay, an important process in particle physics that, should it be observed, would confirm that neutrinos might be their own antiparticles. However, the lack of detection of this process can be blamed on various backgrounds, one of which is muon spallation. Only recently did we start studying these spallation backgrounds in detail and we are looking for a student that has a strong interest in programming, simulations and data analysis to help the progression. The goal of this project is to allow for a better understanding of the behaviour of spallation events and to contribute to the simulation of the background that will be used in KamLAND, as well as future neutrino and dark matter experiments.<br />
<br />
Supervisors: Kelly Weerman and Patrick Decowski (decowski@nikhef.nl)<br />
<br />
==== First measurements with new VULCAN detectors ====<br />
At Nikhef we have a brand new experiment designed to measure the reflectance, transmission, and fluorescence properties of materials at vacuum ultraviolet (VUV) wavelengths. The materials to be studied are used to construct the XENONnT dark matter and the DUNE neutrino detectors. <br />
<br />
In this project, you will calibrate the characteristics of the VUV lamp and of the SiPM photon sensors used in VULCAN. Lab work at the Nikhef building will be a main part of the project, but you will also analyse the data you collect using modern analysis tools.<br />
<br />
You will gain experience with VUV optics, vacuum systems, single-photon sensors, and data analysis using Python and/or C++ tools.<br />
<br />
Supervisors: Marjolein van Nuland and Tina Pollmann (t.pollmann@nikhef.nl)<br />
<br />
==== The XAMS dark matter R&D setup at Nikhef ====<br />
The Nikhef dark matter group has a small version of the XENONnT dark matter detector in our Nikhef lab. With this detector we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENONnT experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso. We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with recently upgraded hardware to test a novel concept for UV light detection. The goal of this project will be to do the first measurements and analyze the data. Depending on the progress with the hardware we intend to complete the first measurements with our upgraded setup.<br />
<br />
Supervisors: Patrick Decowski (decowski@nikhef.nl) and A.P. Colijn (colijn@nikhef.nl)<br />
<br />
==== Reconstruction software for the XENONnT dark matter experiment ====<br />
The XENONnT dark matter experiment became operational in 2021. The experiment is in the Gran Sasso underground laboratory in Italy and the hardware is not being touched. However, we keep on developing and perfecting our reconstruction software. For this project we are looking for a student with a keen interest in and talent for writing physics-based event reconstruction software (we use python). Specifically we have an idea to improve the localization of events inside the XENONnT for which proto-type software exists. The proto-type software needs to be implemented in the XENONnT reconstruction framework and subsequently it needs to be validated on the first data from the experiment. The final goal of the project is to deliver the reconstruction software to the collaboration to be used during the lifetime of the experiment.<br />
<br />
Supervisors: Patrick Decowski and A.P. Colijn (colijn@nikhef.nl)<br />
<br />
=== ATLAS ===<br />
<br />
==== Machine-Learning in Top-Quark physics ====<br />
As the heaviest elementary particle the top quarks plays a key role in the Standard Model. Discovered in 1995 at the Tevatron accelerator, top quarks are now abundantly produced at the Large Hadron Collider (LHC) located at the European Organization for Nuclear Research (CERN) . But do these produced top quarks behave as predicted by the Standard Model or are there signs of new physics? To describe possible deviations, we use calculations from Effective Field Theory (EFT) that allows to add new interactions. For this project simulated data samples with deviations predicted by EFT are available.<br />
<br />
The candidate applies new techniques involving machine-learning to separate backgrounds from top quark production, aware for signs of new physics. Existing tools can be used to quantify the improvements on finding new interactions involving top quarks. Depending on the candidates interest, the focus of the project can be put more on machine-learning or top quark physics. For this project, we use the Python computing language and the ROOT package. Therefore, some proficiency with Python is required. Knowledge of C++ and root is advantageous but not required. <br />
<br />
Supervisors: Jordy Degens (PhD candidate) and Marcel Vreeswijk (h73@nikhef.nl).<br />
<br />
==== '''New machine learning approaches to target Higgs interference signatures in LHC data''' ====<br />
In this project we aim to improve an ongoing analysis to determine the lifetime of the Higgs Boson through state-of-the-art machine learning techniques, in particular by addressing a novel solution to an as of yet unsolved fundamental problem in modeling quantum interference. While the Higgs is an elusive particle that generally only appears in physics processes with small cross sections, its signature can be amplified in the Large Hadron Collider (LHC) through quantum interference with larger background (non-Higgs) processes. This is the effect that the Higgs’ lifetime analysis relies on to be able to measure the relevant Higgs signature. A fundamental physics modelling problem arises though in the simulation of individual events for this interference due to the fact that these events are in reality described by a superposition of underlying Higgs and non-Higgs processes.<br />
<br />
Since machine learning models in particle physics are typically trained to characterise individual physics events, the fact that interference events cannot currently be generated is a significant problem when interference is the target. In the currently existing Higgs lifetime analysis, a machine learning model was trained which instead focuses only on the explicit Higgs-mediated processes as a proxy, which is suboptimal. The aim of this project is to improve upon this current machine learning strategy used in this analysis by implementing either of the inference-aware approaches suggested in [1] and [2]. The idea behind these inference-aware machine learning algorithms is that they do not optimise for a simplified goal such as the loss function which is common in traditional machine learning, but rather for the end-goal of the analysis. In this case, this would omit the need for interference event generation altogether and allow the machine learning models to be trained optimally regardless.<br />
<br />
The goal of this project is to use either of the frameworks used in [1] and [2] (which are both publicly available) and run them with a simplified dataset from the aforementioned analysis as a proof-of-principle. In case this goal is achieved, the next goal would be to actually implement the newly developed machine learning models in the full analysis and to determine the improvement upon the existing result. Successful completion of these tasks would not only benefit the Higgs lifetime analysis, but would be an important stepping stone to future developments to make machine learning approaches deal better with other hard to model effects such as systematic uncertainties.<br />
<br />
Supervisors: Zef Wolffs, Ivo van Vulpen and Matous Vozak (matous.vozak@cern.ch)<br />
<br />
==== '''Reconstructing tracks from particle physics detector hits with state-of-the-art machine learning techniques''' ====<br />
This project concerns the application of new machine learning techniques to tackle the problem of track reconstruction at the ATLAS detector in CERN. While algorithms to construct particle tracks from low-level detector information such as particle hits and timestamps have been around for decades, recent developments in the field of machine learning open up new opportunities to improve these algorithms significantly. In particular graph-based neural networks and attention architectures prove promising candidates for solving these problems based on preliminary studies. <br />
<br />
In this project the student will develop machine learning models to initially reconstruct tracks from simplified test data. If time allows, real data from the ATLAS detector can be analyzed as well in the scope of this project. The student will need some familiarity with programming in python and an interest in machine learning, but a physics background is not required. In this project the student will be able to contribute to fundamental physics research and will familiarize themselves with state-of-the-art machine learning models.<br />
<br />
Supervisors: Zef Wolffs, Ivo van Vulpen and Matous Vozak (matous.vozak@cern.ch)<br />
<br />
=== LHCb ===<br />
<br />
=== Gravitational Waves ===<br />
<br />
====Staying in shape====<br />
Nikhef is co-leading the current effort to realise the Einstein Telescope (ET), a future 10km-scale underground observatory for gravitational waves. Numerical modelling software forms a crucial subsystem for the design and operation of the GW detectors. Our interferometer simulation software Finesse was developed for the design and commissioning of gravitational wave detectors and has become the main interferometer software tool in the community world wide. In our group we use Finesse to predict the shape of the laser beam and how this affects the GW data. You will join our group using Python-based scripts to model mis-shaped lasers and see how the interferometer reacts.<br />
<br />
Required knowledge:<br />
<br />
Good knowledge of Python is required.<br />
<br />
Knowledge of optics will be useful but is not required.<br />
<br />
Supervisors: Anna Green (agreen@nikhef.nl) and Andreas Freise (a.freise@nikhef.nl)<br />
<br />
====Riding the wave====<br />
Theoretical predictions of gravitational-wave (GW) signals provide essential tools to detect and analyse transient GW events in the data of GW instruments like LIGO and Virgo. Over the last few years, there has been significant effort to develop signal models that accurately describe the complex morphology of GWs from merging neutron-star and black-hole binaries. Our work focusses on a particular class of GW binary sources: those that come from two black holes meeting at close separation in dense stellar environments. Here, we expect the merging binary to be in a non-circular orbit and to have arbitrary spin orientations, which significantly complicates the prediction of its GW signal.<br />
<br />
We are looking for '''two''' students who are interested in the development of accurate and efficient GW models and their application in GW data analysis. We are offering '''two separate projects''' that aim to improve signal modeling at the interface of perturbation theory, numerical relativity simulations and fast phenomenological descriptions. Some proficiency in computing is required (Mathematica, Python or C++).<br />
<br />
Supervisor: Maria Haney (mhaney@nikhef.nl)<br />
<br />
=== Detector R&D ===<br />
<br />
====Charge collection study of fast monolithic detectors====<br />
In view of the upgrade of the ALICE tracking detector, innovative ultrathin monolithic silicon sensors are developed for testing. These devices are provided with analogue outputs to study in detail the charge collection and the timing properties of the sensor.<br />
The goal of the project is to contribute to the study of the charge collection features of the samples by measuring the response of the sensor to Fe55 X-rays.<br />
We are looking for a student with a focus on lab work and interested in contributing to the python-based data analysis.<br />
Depending on the progress with the intended measurement and the availability of the hardware, further studies with Sr90 electrons and a laser setup could be possible.<br />
<br />
Contacts: Jory Sonneveld (jory.sonneveld@nikhef.nl), Roberto Russo (rrusso@nikhef.nl)<br />
<br />
====Laser setup for silicon sensor studies====<br />
The Detector R&D group at Nikhef develops and tests detector concepts before they are used in scientific programs at Nikhef. To achieve such a goal, advanced instrumentation and setups are required.<br />
The goal of the project is to contribute to the design and construction of a fast infrared laser setup aimed at the characterization of silicon sensors for high energy physics experiments.<br />
We are looking for a student with a focus on lab work and interest in instrumentation and optics. Besides contributing to the setup construction, measurements finalised at the characterization of the laser beam (e.g. spot size, intensity) are foreseen.<br />
<br />
Contacts: Jory Sonneveld (jory.sonneveld@nikhef.nl), Roberto Russo (rrusso@nikhef.nl)<br />
<br />
==== Characterization of monolithic silicon sensors ====<br />
As part of the ongoing efforts for the design of ultimate tracking detectors, an excellent understanding of the basic performance of the detectors is required. To do so, the silicon detectors can be tested by making an electrical contact with the sensor using a probe station, a device for micrometer precision placement of temporary electrical contacts to acquire signals from internal nodes of semiconductor devices, to investigate aspects such as it's depletion voltage, depletion depth, the dark current and more which are essential for understanding the results gathered by the sensors later in the laboratory and allow the investigation of aspects that can be improved in further chip iterations. The goal of the project is to investigate the performance of monolithic sensors, where electronics is integrated into the sensor, developed for collider experiments like those at the large hadron collider at CERN and beyond. Depending on the progress with the planned measurements, further tests with the electronics and readout of the chip, as well as measurements with advanced laster instrumentation are also possible.<br />
<br />
Contacts: Jory Sonneveld (jory.sonneveld@nikhef.nl), Uwe Kraemer (uwe.kraemer@nikhef.nl)<br />
<br />
=== Theory ===<br />
'''Axion-Electrodynamics (Jordy de Vries and Arghavan Safavi-Nani)'''<br />
<br />
Axions are hypothetical particles that are introduced to solve the so-called strong CP problem. Being very light, axion can be described as a coherent classical field similar to electromagnetic fields. In this project, you will develop the modifications of Maxwell’s equations to include axion fields. Reference: arXiv:1401.0709 . <br />
<br />
'''Axions in a Paul-trap (Jordy de Vries and Arghavan Safavi-Nani)'''<br />
<br />
Axions are hypothetical particles that are introduced to solve the so-called strong CP problem. If axions form the dark matter in our universe, they can be described by a coherent oscillating background field. This oscillating field interacts with charged particles and it possible to detect axions by the motion of ions in a Paul trap. In this project, you will investigate how these interactions work and what are the observables associated to the detection of axions in ion traps.<br />
<br />
'''Phase space integrals for double-weak processes (Jordy de Vries)'''<br />
<br />
The rarest processes ever measured are so-called double weak processes in which two neutrons undergo beta decay at the same time in a nucleus. Lifetimes of these processes are in the 10^22 years range. Theoretical computations of these rates involve so-called phase space integrals that take into account the possible momentum configurations of the outgoing electrons and neutrinos. In this project you will investigate these phase space integrals and develop a method to compute them. <br />
<br />
<br />
<br />
<br />
<br />
<br />
== Bachelor Projects 2022 ==<br />
<br />
=== Dark Matter ===<br />
<br />
==== Response of materials to scintillation light from liquid noble gasses ====<br />
<br />
The liquid form of the noble gases argon and xenon is a popular target material for neutrino and dark matter detectors. The scintillation light from noble gases is in the vacuum UV spectral region. Air and many materials used for optical studies are not transparent to these photons. Measurements of the optical properties of detector materials, such as their reflectivity for example, thus have to be performed with dedicated VUV optics and in vacuum. Additionally, to reproduce the conditions in the detectors, the samples must be cooled to cryogenic temperatures. In this BSc project, you will calibrate the photon detectors in an experimental setup designed to study the optical response of materials excited with VUV photons. You will learn about material requirements for rare event search detectors, vacuum instrumentation, vacuum UV optics including monochromators and spectrometers, and single-photon sensors.<br />
<br />
Supervisors: T. Pollmann (t.pollmann_at_nikhef.nl)<br />
====XAMS====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENONnT detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENONnT experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso. We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with recently upgraded hardware to test a novel concept for UV light detection. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complete the first measurements with our upgraded setup.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
==== XENONnT reconstruction software ====<br />
The XENONnT experiment becomes operational during 2021. While the hwardware is finished we keep on developing and perfecting our reconstruction software. For this project we are looking for a student with a keen interest in and talent for writing physics based event reconstruction software (we use python). Specifically we have an idea to improve the localization of events inside the XENONnT for which proto-type software exists. The proto-type software needs to be implemented in the XENONnT reconstruction framework and subsequently it needs to be validated on the first data from the experiment. The final goal of the project is to deliver the reconstruction software to the collaboration that will be used during teh full lifetime of the experiment.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
=== ATLAS ===<br />
<br />
==== The Higgs boson - did we miss anything and can we do better? ====<br />
<br />
The Higgs boson is a key element of the Standard Model (SM) of particle physics, however, it can also represent a link between yet unexplored 'new' physics beyond the SM. What is the Higgs boson life-time? How precisely can we measure its mass? Is there an additional heavy Higgs boson? Do other particles, not contained in the SM, couple to the Higgs? All these questions can be studied by measuring Higgs properties using one of the Higgs decay modes to photons, vector bosons, quarks and leptons and comparing them with the (beyond) SM predictions. <br />
<br />
As the restart of the Large Hadron Collider (LHC) is imminent, it is essential to develop and test new physics ideas and strategies. '''The ATLAS open data project''' will allow students to work on a real analysis digging through the LHC data collected during Run2. Students will go through all the key aspects of a Higgs analysis performed also by ATLAS physicists. They will learn about Higgs boson theory and its simulation, what objects are reconstructed in the ATLAS experiment, how well do we understand them and finally how does this project into our understanding of the Higgs boson and its properties. <br />
<br />
The exact focus of the topic is flexible depending on the interest of a student. For instance, a student can delve into how precisely can we determine objects' energy and their positions and see whether we can '''improve our estimate of the Higgs mass (project 1)'''. Another possibility is to focus on trying to find out whether there is '''an additional (heavier) Higgs (project 2)''' in the data and how confident we can be of that. Each of these projects will most likely yield new questions, so feel free to take a tangent and walk into yet unexplored territory and see what the data tells you.<br />
<br />
Supervisor: Matouš Vozak (m.vozak_at_nikhef.nl) & Ivo van Vulpen (Ivo.van.Vulpen_at_nikhef.nl)<br />
<br />
==== The Higgs boson life-time ====<br />
<br />
The Higgs particle does not have eternal life. The Standard Model (SM) predicts that it decays into other particles and as these couplings are fixed we can predict its life-time with very high precision. Determining this life-time is a crucial test for the Standard Model. If the Higgs boson life-time is shorter that we expect this could mean that the Higgs boson could decay into non-SM particles. In this project we investigate a) how we can identify Higgs particles in the detector and b) how we plan to use quantum-interference to get a handle on the Higgs boson's life-time. <br />
<br />
Supervisor: Wouter Verkerke (verkerke_at_nikhef.nl)<br />
<br />
==== Higgs interferentie ====<br />
In 2012 hebben het ATLAS en het CMS experiment het Higgs deeltje gevonden. Inmiddels zijn we het Higgs boson aan het bestuderen, hoe gedraagt het zich precies, bestaan er meer soorten Higgs bosonen of is er echt maar eentje van? In dit project leer je hoe we een Higgs boson kunnen herkennen in de detector en gaan we kijken naar hoe de signalen veranderen als er meer Higgs bosonen bestaan of misschien wel andere exotische nieuwe deeltjes. <br />
Dit doen we door gebruik te maken van quantum interferentie wat plaats vindt tussen het Higgs boson en achtergrondprocessen. Hoe dit precies werkt leer je in het project. Supervisor: Hella Snoek (h.snoek_at_nikhef.nl)<br />
<br />
<br />
=== LHCb ===<br />
<br />
<br />
==== Exotic neutrinos in B decays====<br />
<br />
Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, heavier, neutral leptons. In the LHCb group at Nikhef we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undisovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The bachelor project will contribute with the optimization of the selection using state-of-the-art tools for the multi-variate analysis.<br />
<br />
Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
<br />
<br />
=== Gravitational Waves ===<br />
<br />
=== Detector R&D ===<br />
Answering big elementary particle physics questions requires pioneering experiments. The Detector R&D program at Nikhef is aimed at conceptualizing and testing of instrumentation concepts before they are implemented in scientific programs at Nikhef. <br />
<br />
==== Time resolution of monolithic timing detectors ====<br />
For the upgrade of the vertex detectors of the large LHC experiments like LHCb and ALICE, new silicon pixel detectors will developed now that can register the passing particles with a time precision of tens of picoseconds. ALICE is the first experiment at the LHC to have installed monolithic sensors where electronics is integrated into the sensor resulting in ultrathin, low-material detectors, that will soon see it's first particles from LHC collisions. In this project you will measure the time resolution of these promising integrated sensors with a laser setup in our laboratory.<br />
<br />
Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
==== Modeling radiation damage in silicon sensors ====<br />
In the coming years, the ATLAS experiment at the LHC works on upgrades to prepare for the high-luminosity LHC, where many more collisions will take place than today. Analyses of LHC data rely heavily on simulations of the detector. It may sound counterintuitive, but particle detectors do not actually like particles: after many collisions at the LHC, a silicon pixel detector has seen so many particles that its bulk gathers defects. Charge generated by traversing particles can get trapped in defects resulting in less charge induced in the readout electrodes, reducing detector performance in resolution and efficiency. In this project, you will be part of the international ATLAS collaboration and compare different models of radiation damage with measured data and you will contribute to the open source program Allpix Squared that is widely used for simulations in many areas of particle physics.<br />
<br />
Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
==== Time resolution of a new digital pixel test structure from test beam data ====<br />
For the upgrade of the ALICE detector, ultrathin picosecond timing integrated sensors are developed. To reduce power consumption, asynchronous readout is implemented in this prototype sensor in a digital pixel test structure. This structure was studied in test beams with an ALPIDE (ALICE PIxel DEtector) telescope at CERN. You will measure the efficiency and time resolution of this new sensor with the latest data from test beams at CERN.<br />
<br />
Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
<br />
==== Fast timing detectoren ====<br />
Op dit moment maken we veel gebruik van silicon detectoren in onze deeltjes experimenten. Deze zijn gevoelig voor geladen deeltjes en zijn bij uitstek geschikt om de paden vast te leggen die de deeltjes maken die in de botsingen worden gemaakt. Bijvoorbeeld in de Atlas en LHCb experimenten worden tientallen tot honderden deeltjes gemaakt bij elk botsingsgebeurtenis (event) die met 40MHz plaatsvinden. Voor toekomstige deeltjesdetectoren willen we niet alleen het traject vastleggen maar ook met grote precisie een tijdsmeting toevoegen. We hebben hiervoor dus nieuwe detectoren nodig die behalve met een hele hoge snelheid en efficientie de posities van de langsvliegende deeltjes kunnen vastleggen, maar hier ook een zeer nauwkeurige tijdsmeting (in orde van picosecondes) aan kunnen toevoegen. We hebben met verschillende detectoren metingen gedaan, in testbundels op CERN, maar ook in het lab op Nikhef kunnen we metingen doen. In dit project ga je samen met het fast-timing detectoren team op het Nikhef metingen verrichten en de resultaten hiervan bekijken. Contact: Hella Snoek (h.snoek@nikhef.nl)<br />
<br />
<br />
=== KM3NeT ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along 200-700m long vertical lines, called detection units.<br />
<br />
==== Neutrino oscillation measurements with the first KM3NeT data ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope is able to measure the oscillations of neutrinos produced in interactions of cosmic rays with the earth atmosphere. Fundamental neutrino properties can be deduced from these oscillations measurements. In this project we will use the first data of ORCA (more than one year with six detection units) to study neutrino oscillations and fit neutrino mixing parameters and mass differences between neutrino mass states. We will study data selection, event reconstruction, and effects of systematic uncertainties on the results. <br />
<br />
Supervisors: Brian O'Fearraigh, Ronald Bruijn, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
==== Search for sterile neutrinos with KM3NeT. ====<br />
A detailed study of neutrino oscillations in the KM3NeT detector is sensitive to the existence of so-called sterile neutrinos: neutrinos that are not part of the Standard Model of particle physics, and have no ordinary interactions with matter. We will use a mixture of data and simulations to estimate KM3NeT sensitivity.<br />
<br />
Supervisors: Alba Domi, Paul de Jong<br />
<br />
==== Machine learning for event classification in KM3NeT ====<br />
The classification of neutrino events recorded in the KM3NeT detector in terms of originating from electron neutrinos, muon neutrinos, or tau neutrinos, is very well suited for machine learning techniques. We will study the performance of a few advanced machine learning techniques on simulated high-energy neutrino events.<br />
<br />
Supervisors: Alba Domi, Paul de Jong<br />
<br />
==== Multi-messenger astronomy with neutrinos and radio signals ====<br />
The main goal of neutrino telescopes, such as ANTARES, KM3NeT and IceCube, is to detect cosmic neutrinos from astrophysical sources. When an interesting neutrino candidate is detected they send out a message to alert the scientific community. Other scientific instruments, like the Murchison Widefield Array (MWA) radio telescope, can then do a follow-up observation, to see if there are other messengers coming from the same source as the neutrinos. In this project you will analyse MWA data that were taken after the reception of neutrino alerts, to search for a radio source that can be associated with a neutrino source.<br />
<br />
Supervisor: Mieke Bouwhuis (mieke.bouwhuis at nikhef.nl)<br />
<br />
=== Theory ===<br />
<br />
==== Effective Field Theories of Particle Physics from low- to high-energies (2022 not yet determined if available in 2023) ====<br />
<br />
Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations<nowiki>''</nowiki> seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature.<br />
<br />
Until recently, it was widely assumed that matter particles from each of the three generations interact with the same (“universal”) strength. This hypothesis is being challenged by new measurements at the Large Hadron Collider (LHC) at CERN, which hint towards non-universal interactions. If confirmed, these measurements will be the first signs of new particles and interactions in high-energy colliders. These exciting findings indicate the urgent need to explore such phenomena in depth.<br />
<br />
The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Effective Field Theory (EFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes. Specifically, the goal is to connect measurements from ATLAS and LHCb among them and to jointly interpret this information with that provided by other experiments, from CMS and Belle-II to very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
<br />
''Methodology and workplan''<br />
<br />
This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories.<br />
<br />
This project accommodates several students, who would work together in developing the main formalism while each of them focuses on a specific sub-project. The maximum capacity of this project is 5 students. <br />
<br />
Depending on the student profile, sub-projects with a strong computational / machine learning component are also possible.<br />
<br />
During the first four weeks of the project, students will learn the required background material on effective field theories, following the guidelines from the supervisors. Afterwards, they will focus on different sub-projects, each covering a different aspect of the same global EFT program.<br />
<br />
Required knowledge<br />
<br />
Quantum Mechanics 2, Particle Physics 1 (required)<br />
<br />
Advanced Quantum Mechanics, Particle Physics 2, Machine Learning (optional)<br />
<br />
Available subprojects<br />
<br />
Here we list the available subprojects, including the corresponding daily supervisor(s) in each case.<br />
<br />
''Subproject #1: SMEFT & Flavour symmetries'' <br />
<br />
Daily supervisors: Jordy de Vries (UvA), Keri Vos (Maastricht University), Jaco ter Hoeve (VU), Giacomo Magni (VU)<br />
<br />
While the power of the Standard Model EFT (named SMEFT) framework is its generality and lack of assumptions, the number of operators is somewhat daunting. A popular way to trim the number of operators is to assume flavour symmetries that relate operators with different quark and lepton flavours. In this project you will investigate the theoretical basis for commonly-used flavour symmetries and what they imply for the connection between high-energy observables involving third-generation particles (top and bottom quarks and tau leptons) and low-energy precision tests involving first- and second-generation particles. The investigations of this project are connected with Subproject #2.<br />
<br />
''Subproject #2: SMEFT & magnetic moment of the muon''<br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU)<br />
<br />
The magnetic moment of the muon appears to differ from the Standard Model expectations by a large amount, well beyond the known experimental and theoretical uncertainties. Recent experiments have only strengthened the significance of this anomaly. In this project, the students will investigate the feasibility of implementing the measurement of the magnetic moment of the muon into a global SMEFT analysis, by exploiting recently provided calculations. Special attention will be devoted to the flavour assumptions required to consistently match this measurement with the LHC data, also at the light of the connection with Subproject #1. The SMEFiT analysis framework will be used to connect the g-2 data with high-energy LHC measurements.<br />
<br />
''Subproject #3: CP Violation and low-energy precision experiments''<br />
<br />
Most analyses of LHC data are performed under the assumption that CP symmetry (charge conjugation + parity, essentially the symmetry between particles and anti-particles) is conserved. More recent analyses attempt to also measure possible new sources of CP violation in SMEFT operators in the Higgs and top sector. <br />
<br />
''Subproject #3a: CP Violation and low-energy precision experiments''<br />
<br />
Daily supervisors: Jordy de Vries (UvA), Juan Rojo (VU)<br />
<br />
Low-energy precision experiments can also set stringent constraints on new mechanisms of CP violation. In this project you will try to combine high- and low-energy data to put CP symmetry to the test. <br />
<br />
''Subproject #3b: CP Violation and flavour physics experiments''<br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU)<br />
<br />
Besides low-energy precision experiments, also B-meson decays are excellent probes of CP violation. Unlike most low-energy experiments, this allows us to probe CP violation in the third generation. In this project you will link constraints on CP violation at high-energy to those from B meson decays. <br />
<br />
''Subproject #4: SMEFT & optimal observables'' <br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU), Tommaso Giani (VU & Nikhef)<br />
<br />
In full generality, the number of operators in SMEFT spans a very large parameter space. These parameters are constrained by experimental inputs from ATLAS and CMS, depending on the precise parameters these constraints may be more or less stringent. In order to fully exploit the whole parameters space in SMEFT, it is necessary to devise statistically optimal observables that have a large constraining power. In this project, we will define such observables. This project has a strong computational / machine learning component and may involve simulations based on tools such as MadGraph and Pythia8.<br />
<br />
Contacts:<br />
<br />
Juan Rojo (VU Amsterdam & Nikhef): j.rojo at vu.nl<br />
<br />
Keri Vos (UM & Nikhef): k.vos at maastrichtuniversity.nl <br />
<br />
Jordy de Vries (UvA & Nikhef): j.devries4 at uva.nl<br />
<br />
== Bachelor Projects 2021 ==<br />
=== Dark Matter ===<br />
<br />
==== XAMS ====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso.<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with recently upgraded hardware to test a novel concept for UV light detection. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complete the first measurements with our upgraded setup.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== XENONnT reconstruction software ====<br />
The XENONnT experiment becomes operational during 2021. While the hwardware is finished we keep on developing and perfecting our reconstruction software. For this project we are looking for a student with a keen interest in and talent for writing physics based event reconstruction software (we use python). Specifically we have an idea to improve the localization of events inside the XENONnT for which proto-type software exists. The proto-type software needs to be implemented in the XENONnT reconstruction framework and subsequently it needs to be validated on the first data from the experiment. The final goal of the project is to deliver the reconstruction software to the collaboration that will be used during teh full lifetime of the experiment.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Backgrounds in Radioactive Decay Measurements ====<br />
At Nikhef, the XENON group has a working setup, continuously monitoring the<br />
radioactive decay of Cobalt-60, Caesium-137 and Titanium-44. This beautiful setup is<br />
however not shielded perfectly; it is still vulnerable to background radioactivity. Our<br />
current way of working around this background radiation is to subtract it from our<br />
waveforms. You as a BSc student could help us hands-on and with analyses:<br />
together, we can disassemble the setup, measure background spectra and<br />
implement this in the data analysis. You can use all the data to validate the<br />
lifetime of our isotopes!<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Detection of scintillation light from liquid noble gasses ====<br />
<br />
The liquid form of the noble gases argon and xenon is a popular target material for neutrino and dark matter detectors. The scintillation light from noble gases is in the vacuum UV spectral region. Air and many materials used for optics studies are not transparent to these photons. Measurements of the optical properties of detector materials, such as their reflectivity for example, thus have to be performed with dedicated VUV optics and in vacuum. Additionally, to reproduce the conditions in the detectors, the samples must be cooled to cryogenic temperatures. In this BSc project, you will design, using professional hardware design software, a vacuum chamber to hold the detector materials whose optical properties are to be investigated, as well as the cooling system and photon detectors. You will learn about material requirements for rare event search detectors, vacuum instrumentation, vacuum UV optics including monochromators and spectrometers, and single-photon sensors.<br />
<br />
Supervisors: T. Pollmann (t.pollmann_at_nikhef.nl)<br />
<br />
=== Detector R&D ===<br />
<br />
==== Characterization of the new ultrathin ALPIDE monolithic active pixel sensor ====<br />
At the Large Hadron Collider at CERN, major upgrades of experiments take place in the long shutdown years where particle collisions are paused. The ALICE inner tracking system (ITS) 2, the part of the ALICE experiment closest to the beam pipe, is currently being installed at CERN. This detector makes use of ultra-lightweight monolithic active pixel sensors, the first to use this technology at particle colliders after the STAR experiment at RHIC in Brookhaven. These very thin pixel detectors have a low power consumption, result in very little material in the detector, and still have optimal timing and resolution -- and are a promising technology for future experiments. To characterize the performance of these sensors, you will learn to set up experiments, carry out measurements, and analyze data using various instruments available in the detector R&D lab at Nikhef. This could lead to novel insights of monolithic active pixel sensors. It is also possible to do measurements from home using data from the first test beams with bent (yes, with a curvature!) ALPIDE sensors. You will work in an international, stimulating research environment in the detector R&D group at Nikhef at the forefront of silicon detector technologies for high energy physics. ''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
==== Simulation of 3D silicon sensors ====<br />
<br />
For the upgrade of the vertex detector of the LHCb experiment novel silicon pixel detectors have to be developed that can register the passing particles with a time precision of tens of picoseconds. Given the harsh radiation environment very close to the LHCb interaction point only a limited number of technologies can be applied. One of the most promising technologies are the so-called 3D sensors whose readout electrodes are pillars that are placed into the sensor perpendicular to the surface; this in contrast to ’standard’ planar silicon sensors where the pixel electrodes are at the surface, similar to the camera in your smartphone. To understand the time response of these 3D sensors, simulations with TCAD software have to be performed and the results will be compared to measured data. These simulations involve the creation/adaptation of the 3D structures of the model, optimising the simulation speed, and analysing the signals as function voltage, track impact point and deposited charge. If time and Covid regulations permit, gaining some hands-on experience with such 3D sensors in the R&D labs at Nikhef is possible. ''Contacts: [mailto:martinb@nikhef.nl Martin van Beuzekom] [mailto:k.heijhoff@cern.ch Kevin Heijhoff] ''<br />
<br />
<br />
=== Theory ===<br />
<br />
==== Standard Model Effective Field Theory analysis of Z+dijet production ====<br />
The goal of this project is to study the effect of higher dimensional operators from the Standard Model Effective Field Theory in Z-boson production measured at LHC. The ATLAS collaboration has just reported in 2020 the measurement of Z production alongside with a pair of jets, based on the full Run II luminosity. In this project we aim to study the effect of dimension six SMEFT operators on the signal (EW-induced) and/or background (QCD-induced), finding which is the kinematic variable that maximises the possible effect of beyond the SM operators and thus may provide the best constraint on New Physics. The outcome of this project may be the first step of the inclusion of Vector production in a global SMEFT fit. <br />
<br />
References: https://arxiv.org/pdf/2006.15458.pdf, https://www.hepdata.net/record/ins1803608<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Maximum precision on new physics through information theory ====<br />
One way to look for physics beyond the standard model is through the framework of effective field theory. In this framework, deviations from the standard model are described by a set of continuous parameters. Finding constraints on these parameters might point to the discovery of new physics. With the large number of LHC experiments we currently face, we want to be able to quantify the maximum knowledge that (future) experiments can provide on new physics parameters. In this project, the student will study and quantify the maximum information that is contained in particle physics experiments through information theory. The central object of study will be the Fisher information matrix. The idea is to work with a simple toy experiment that describes Higgs physics and compute its associated Fisher information matrix to quantify the optimal bounds on new physics. The project will start with studying central objects from statistics and information theory. Later, we will apply these to open problems in particle physics.<br />
<br />
Reference: https://arxiv.org/pdf/1612.05261.pdf<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Seesaw mechanism and neutrino mass ==== <br />
Many unsolved questions in particle physics are related to the nature of the neutrino and its mass generation. The goal of this theoretical project is to understand and review one of the possible candidate theories that describe how neutrinos mix and get massive, namely the Seesaw mechanism. Among the many possible Seesaw mechanisms that can generate new phenomenology including lepton number non-conservation, the student will focus on one minimal model to understand the key processes that are currently used to probe the validity of the given theory. <br />
<br />
References: https://cds.cern.ch/record/408119/files/9911364.pdf, https://arxiv.org/pdf/1711.02180.pdf<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Mixing of sterile neutrinos ====<br />
<br />
Neutrino oscillation experiments demonstrate that neutrinos are massive particles. However, the mass mechanism of neutrinos is unknown. A<br />
minimal solution requires the existence of so-called sterile neutrinos: neutrinos that are even more elusive than ordinary neutrinos. <br />
We will investigate how to parametrize the matrix that describes the mixing between ordinary and sterile neutrinos. We will then use this<br />
to calculate how sterile neutrinos induce rare nuclear decays and determine the sensitivity of ongoing experiments to observe sterile<br />
neutrinos.<br />
<br />
Supervisor: Jordy de Vries (devries.jordy at gmail.com)<br />
<br />
<br />
=== KM3NeT ===<br />
<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
==== Data analysis of the first deployed KM3NeT detection lines ====<br />
<br />
First detection lines of the KM3NeT neutrino telescope have been deployed<br />
in the Mediterranean Sea, and a first data set is available. The lines consist<br />
of light-sensitive detectors that record the time of arrival of photons<br />
produced by relativistic particles in the deep sea, and their number.<br />
In this project we will study the first data to separate various components:<br />
photons from potassium decay, bioluminesence, sparks in the photomultipliers,<br />
downgoing muons from cosmic rays, and first neutrinos.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben (paul.de.jong at nikhef.nl)<br />
<br />
==== Neutrino oscillation measurements with the KM3NeT neutrino telescope ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope currently under construction<br />
will be able to measure the oscillations of neutrinos produced in interactions<br />
of cosmic rays with the earth atmosphere. Fundamental neutrino properties can<br />
be deduced from these oscillations measurements, in particular the so-called<br />
mass hierarchy of neutrinos. In this project we will simulate the ORCA measurements<br />
of neutrino oscillations, and study the dependence of the sensitivity on<br />
experimental uncertainties, such as energy resolution and neutrino flavour<br />
identification, and theoretical uncertainties, such as the atmospheric neutrino<br />
flux and neutrino cross sections. The results will help ORCA to identify<br />
the main sources of uncertainty, and therefore to actively try to reduce these<br />
and improve the final measurement.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
==== Performance Studies of ORCA for Dark Matter Detection ====<br />
<br />
The interactions of neutrinos in KM3NeT-ORCA give different signatures which are categorised as track and shower events. This project involves the studies of muon, electron and tau neutrino interactions for the reconstruction performance of ORCA. Efficient reconstruction of such signals is important for Dark Matter searches in the low-mass regime. We will work on understanding the detector performance, e.g. effective acceptance, energy and angular resolution, with different configurations of the detector setup. The result of this study will be very useful to improve the sensitivity of the experiment for Dark Matter detection and its possible location. The student will have the opportunity to work closely with KM3NeT members at Nikhef and gain skills of analyzing data. <br />
<br />
Supervisors: Suzan Basegmez du Pree, Aart Heijboer (s.basegmez.du.pree at nikhef.nl)<br />
<br />
==== Study of Optical Properties of Sea Water using Hit Coincidences in MC Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
By studying coincidences of L1 hits between neighbouring DOMs, for various Monte Carlo (MC) data sets with different sea water optical properties such as scattering and absorption coefficients, in this project we try to figure out if and how well we can quantify optical sea water properties by studying L1 hit coincidences in real KM3NeT data.<br />
<br />
Supervisor: Daan van Eijk (dveijk at nikhef.nl)<br />
<br />
==== Determination of Inter-DOM Distances using Hit Coincidences in KM3NeT Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
The number of L1 hit coincidences from atmospheric muons between neighbouring DOMs on a DU is expected to decrease exponentially. By fitting the observed number of L1 hit coincidences between neighbouring DOMs in real data to the expected exponential decay, in this project we study how accurately we can determine the distances between DOMs on a single DU. In addition, we try to determine the distances between DUs by looking for L1 hit coincidences between DOMs on neighbouring DUs.<br />
<br />
Supervisor: Daan van Eijk (dveijk at nikhef.nl)<br />
<br />
<br />
=== ATLAS ===<br />
<br />
==== The Higgs boson life-time ====<br />
<br />
The Higgs particle does not have eternal life. The Standard Model (SM) predicts that it decays into other particles and as these couplings are fixed we can predict its life-time with very high precision. Determining this life-time is a crucial test for the Standard Model. If the Higgs boson life-time is shorter that we expect this could mean that the Higgs boson could decay into non-SM particles. In this project we investigate a) how we can identify Higgs particles in the detector and b) how we plan to use quantum-interference to get a handle on the Higgs boson's life-time. <br />
<br />
Supervisor: Wouter Verkerke (verkerke_at_nikhef.nl)<br />
<br />
==== The Higgs boson decaying to photons ====<br />
<br />
One of the main channels used to analyse the properties of the Higgs boson is when the Higgs boson decays into two photons. The crucial building block in this analysis is our ability to reconstruct the energy and the direction of the photons in the ATLAS detector and in this project we will revisit the photon reconstruction. We will start by studying simulations and learning about photon reconstruction in general. Then our goal is to determine the energy and position resolution of photons in the ATLAS detector and see if we can exploit our knowledge on the photon resolution to get an (improved) estimate of the Higgs boson mass. For the analysis we will use the '''real data from the LHC''' - the ATLAS open data project.<br />
<br />
Supervisor: Ashley McDougall and Ivo van Vulpen (Ivo.van.Vulpen_at_nikhef.nl)<br />
<br />
<br />
=== LHCb (1) ===<br />
<br />
One of the most fascinating mysteries in physics today is: how is it possible that universe is filled with matter? If the Big Bang produced equal amounts of matter and antimatter, we still do not understand the mechanism that lead to the excess of matter over antimatter that we observe today.<br />
<br />
One interesting feature of some particles is that they can transform themselves into their antiparticles, then back to particle, and so forth, in an oscillatory way until they finally decay. In particular, beauty mesons (B) can oscillate into their antiparticle (B ̄). The parameters of this oscillation, such as amplitude, frequency and phase, are calculable mathematically: predictions for it are available in the standard model (SM) of particle physics. But the oscillations according to the SM alone would not lead to the imbalance of matter in the universe – we still need to find a new type of physics that may be able to explain it.<br />
<br />
In this context, it is very important to measure B oscillations in the laboratory, and compare these observations with the expectations from the SM. Are the experimental data in good agreement with the SM, as we expect? If the aswer is not, i.e. if there are features of the oscillation that we do not understand well, then we may be observing “new physics”. In other words, the data may reveal a new mechanism that generates a different matter-antimatter balance than predicted by the SM, that may potentially solve the puzzle.<br />
<br />
The LHCb experiment at CERN is dedicated to such studies: LHCb detectors are placed in a region along the LHC collider beamline, where a large number of B mesons are produced, arising from the proton-proton collision data from the LHC collider. Looking at the LHCb data we can obtain large samples of B mesons, and observe their oscillations.<br />
In this project we will learn how to select a sample of B mesons out of the data taken with the LHCb detector, measure the parameters that govern their oscillation and compare them with the SM.<br />
<br />
For more information, please contact Mara Soares (msoares_at_nikhef.nl).<br />
<br />
== Bachelor Projects 2020 ==<br />
<br />
<br />
=== Dark Matter ===<br />
<br />
==== XAMS ====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso.<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source and liquid scintillatorneutron detector we have acquired for the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study of neutron transport in xenon.<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Backgrounds in Radioactive Decay Measurements ====<br />
At Nikhef, the XENON group has a working setup, continuously monitoring the<br />
radioactive decay of Cobalt-60, Caesium-137 and Titanium-44. This beautiful setup is<br />
however not shielded perfectly; it is still vulnerable to background radioactivity. Our<br />
current way of working around this background radiation is to subtract it from our<br />
waveforms. You as a BSc student could help us hands-on and with analyses:<br />
together, we can disassemble the setup, measure background spectra and<br />
implement this in the data analysis. You can use all the data to validate the<br />
lifetime of our isotopes!<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
=== ATLAS ===<br />
<br />
==== Project ATLAS-ITk ====<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
==== The Most Energetic Higgs Boson ====<br />
A common approach to search for physics beyond the standard model is by searching for the direct production of new particles. Alternatively, indirect quantum effects on the production of known particles -such as the Higgs Boson- could reveal the first cracks in the theory. Processes with high energy transfer are of particular potential since possible deviations are expected to increase with the square of the involved energy scale. Using the entire data-set collected by the ATLAS experiment at CERN during the four years of the LHC’s Run 2, a proof-of-principle analysis, targeting transverse momenta of the above 400 GeV, has been developed by Nikhef researchers. The first results of this Higgs boson study are expected to be published this year and this project aims to develop refinements of the analysis techniques. We will investigate the usage of sophisticated machine learning tools such as artificial neural networks, the search for new variables that can help discriminating the signal from its background, revisiting the analysis categorisation and improving the reconstruction techniques at these extreme momenta. Supervisors: Brian Moser and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs: The Next Generation ====<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks has been developed by Nikhef researchers and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays), advanced analysis techiques (using deep learning methods) and expanding the theory interpretation. Another opportunity would be the development of a new statistical combination with various independent searches, which could significantly improve the discovery potential. Supervisors: Marko Stamenkovic and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs interferentie ====<br />
In 2012 hebben het ATLAS en het CMS experiment het Higgs deeltje gevonden. Inmiddels zijn we het Higgs boson aan het bestuderen, hoe gedraagt het zich precies, bestaan er meer soorten Higgs bosonen of is er echt maar eentje van? In dit project leer je hoe we een Higgs boson kunnen herkennen in de detector en gaan we kijken naar hoe de signalen veranderen als er meer Higgs bosonen bestaan of misschien wel andere exotische nieuwe deeltjes. <br />
Dit doen we door gebruik te maken van quantum interferentie wat plaats vindt tussen het Higgs boson en achtergrondprocessen. Hoe dit precies werkt leer je in het project. Supervisor: Hella Snoek (h.snoek_at_nikhef.nl)<br />
<br />
=== B-Physics - LHCb ===<br />
<br />
==== Time dependent CP violation ====<br />
The LHCb experiment studies CP violation withB-meson decays.<br />
The project focusses on the measurement of the unitarity angle gamma using decays of the Bs mesons to Ds K.<br />
Supervisors: Sevda Esen & Michele Veronesi<br />
<br />
==== Machine learning ====<br />
Machine learning has proven to be an indispensable tool in the selection of interesting events in high energy physics. Such technologies will become increasingly important as detector upgrades are introduced and data rates increase by orders of magnitude. HEPDrone is a toolkit to enable the creation of a drone classifier from any machine learning classifier, such that different classifiers may be standardised into a single form and executed in parallel. A detailed evaluation of the performance of different drone models in the real production environment of LHCb will give the collaboration a complete idea of not only the advantages of the drone model, but also the limits of drone complexity given the available computing resources.<br />
Requirements: Advanced python and Advanced C++<br />
Supervisor: Sean Benson<br />
<br />
==== LHCb simulations of physics beyond the Standard Model ====<br />
This project is of relatively theoretical and computing nature and performs simulation studies for physics beyond the Standard Model in the context of long lived particles. It is related to test the sensitivity of the LHCb experiment to detect specific signals of physics beyond the Standard Model.<br />
supervisor: Carlos Vazquez Sierra<br />
<br />
=== Detector R&D ===<br />
<br />
==== Fast timing detectoren ====<br />
Op dit moment maken we veel gebruik van silicon detectoren in onze deeltjes experimenten. Deze zijn gevoelig voor geladen deeltjes en zijn bij uitstek geschikt om de paden vast te leggen die de deeltjes maken die in de botsingen worden gemaakt. Bijvoorbeeld in de Atlas en LHCb experimenten worden tientallen tot honderden deeltjes gemaakt bij elk botsingsgebeurtenis (event) die met 40MHz plaatsvinden. Voor toekomstige deeltjesdetectoren willen we niet alleen het traject vastleggen maar ook met grote precisie een tijdsmeting toevoegen. We hebben hiervoor dus nieuwe detectoren nodig die behalve met een hele hoge snelheid en efficientie de posities van de langsvliegende deeltjes kunnen vastleggen, maar hier ook een zeer nauwkeurige tijdsmeting (in orde van picosecondes) aan kunnen toevoegen. We hebben met verschillende detectoren metingen gedaan, in testbundels op CERN, maar ook in het lab op Nikhef kunnen we metingen doen. In dit project ga je samen met het fast-timing detectoren team op het Nikhef metingen verrichten en de resultaten hiervan bekijken. Contact: Hella Snoek (h.snoek@nikhef.nl)<br />
<br />
==== Muon tomography ====<br />
In this project we are not looking for where cosmic rays come from. We are looking for what we can use them for instead. The muons in cosmic rays can be used to ‘probe’ massive objects. Muons are short lived particles that carry the same charge as electrons, have a high penetrating power and can be detected relatively easy. It is possible to reconstruct a density distribution within an object by measuring muon scattering and absorption. In this context the objects may be freight containers, buildings, melting furnaces, etc… <br />
<br />
Systems that scan objects through the use of muons are often large (objects often need to be enclosed by the system) and complex. The question we want to answer is: Can we develop a smaller, simpler and cheaper system for muon tomography? <br />
<br />
A method to detect muons is by using a material that scintillates (emits light) when hit by an ionising particle. When this light emission is prompt after the passage of the muon, timing information of the light can be used to reconstruct the path of the muon.<br />
In this experiment we make a muon tracker based on two sheets of scintillating material and photo multiplier tubes (PMTs). Photo multiplier tubes are fast responding and very sensitive light detectors (capable of detecting single photons).<br />
<br />
The big question is: How well does this system perform?<br />
<br />
Currently a set-up is being build. You have a lot of freedom to choose a focus in this project (theory, simulation, hardware, or a combination of those).<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Spectral X-ray imaging - Looking at colours the eyes can't see ====<br />
When a conventional X-ray image is made to analyse the composition of a sample, or to perform a medical examination on a patient, one acquires an image that only shows intensities. One obtains a ‘black and white’ image. Most of the information carried by the photon energy is lost. Lacking spectral information can result in an ambiguity between material composition and amount of material in the sample. If the X-ray intensity as a function of the energy can be measured (i.e. a ‘colour’ X-ray image) more information can be obtained from a sample. This translates to less required dose and/or to a better understanding of the sample that is being investigated. For example, two fields that can benefit from spectral X-ray imaging are mammography and real time CT.<br />
<br />
X-ray detectors based on Medipix/Timepix pixel chips have spectral resolving capabilities and can be used to make polychromatic X-ray images. Medipix and Timepix chips have branched from pixel chips developed for detectors for high energy physics collider experiments.<br />
<br />
Some themes that students can work on: <br />
<br />
- Optimising methods to acquire spectral X-ray images.<br />
<br />
- Determining how much existing applications benefit from spectral X-ray imaging and looking for potential new applications.<br />
<br />
- Characterising, calibrating, optimising X-ray imaging detector systems.<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Holographic emitter ====<br />
A difficulty in generating holograms (based on the interference of light) is the required dense spatial light field sampling. One would need pixels of less than 200 nanometer. With larger pixels artefacts occur due to spatial under sampling. A pixel pitch of 200 nm or less is difficult, if not, impossible, to achieve, especially for larger areas. Another challenge is the massive amount of computing power that is required to control such a dense pixel matrix. <br />
<br />
A new holographic projection method has been developed that reduces under sampling artefacts, regardless of spatial sample density. The trick is to create 'pixels' at random but known positions, resulting in an array that lacks any spatial periodicity. As a result a holographic emitter can be built with a significantly lower sample density and less required computing power. This could bring holography in reach for many applications like display, lithography, 3D printing, metrology, etc...<br />
<br />
The big question: How does the performance of the holographic emitter depend on sample density and sample positions?<br />
<br />
The aspects of a holographic image we are interested in are:<br />
<br />
- Noise<br />
<br />
- Contrast<br />
<br />
- Suppression of under sampling artefacts<br />
<br />
- Resolution <br />
<br />
For this project we are building a proof of concept holographic emitter. This set-up will be used to verify simulation results (and to make some cool holograms of course). <br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
=== KM3NeT ===<br />
<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
==== Data analysis of the first deployed KM3NeT detection lines ====<br />
<br />
First detection lines of the KM3NeT neutrino telescope have been deployed<br />
in the Mediterranean Sea, and a first data set is available. The lines consist<br />
of light-sensitive detectors that record the time of arrival of photons<br />
produced by relativistic particles in the deep sea, and their number.<br />
In this project we will study the first data to separate various components:<br />
photons from potassium decay, bioluminesence, sparks in the photomultipliers,<br />
downgoing muons from cosmic rays, and perhaps first neutrinos.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Neutrino oscillation measurements with the KM3NeT neutrino telescope ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope currently under construction<br />
will be able to measure the oscillations of neutrinos produced in interactions<br />
of cosmic rays with the earth atmosphere. Fundamental neutrino properties can<br />
be deduced from these oscillations measurements, in particular the so-called<br />
mass hierarchy of neutrinos. In this project we will simulate the ORCA measurements<br />
of neutrino oscillations, and study the dependence of the sensitivity on<br />
experimental uncertainties, such as energy resolution and neutrino flavour<br />
identification, and theoretical uncertainties, such as the atmospheric neutrino<br />
flux and neutrino cross sections. The results will help ORCA to identify<br />
the main sources of uncertainty, and therefore to actively try to reduce these<br />
and improve the final measurement.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Performance Studies of ORCA for Dark Matter Detection ====<br />
<br />
The interactions of neutrinos in KM3NeT-ORCA give different signatures which are categorised as track and shower events. This project involves the studies of muon, electron and tau neutrino interactions for the reconstruction performance of ORCA. Efficient reconstruction of such signals is important for Dark Matter searches in the low-mass regime. We will work on understanding the detector performance, e.g. effective acceptance, energy and angular resolution, with different configurations of the detector setup. The result of this study will be very useful to improve the sensitivity of the experiment for Dark Matter detection and its possible location. The student will have the opportunity to work closely with KM3NeT members at Nikhef and gain skills of analyzing data. <br />
<br />
Supervisors: Suzan Basegmez du Pree, Aart Heijboer<br />
<br />
==== A search for periodic sources in Antares data ====<br />
<br />
The Antares deep-sea neutrino telescope has been operated for more then ten years. A search for periodic sources is proposed by applying a fast Fourier transformation (FFT) analysis on the available low-level data. This search will be combined with a (literature) study of pulsars which are thought to emit neutrinos.<br />
<br />
Supervisor: Maarten de Jong<br />
<br />
==== Study of Optical Properties of Sea Water using Hit Coincidences in MC Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
By studying coincidences of L1 hits between neighbouring DOMs, for various Monte Carlo (MC) data sets with different sea water optical properties such as scattering and absorption coefficients, in this project we try to figure out if and how well we can quantify optical sea water properties by studying L1 hit coincidences in real KM3NeT data.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
==== Determination of Inter-DOM Distances using Hit Coincidences in KM3NeT Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
The number of L1 hit coincidences from atmospheric muons between neighbouring DOMs on a DU is expected to decrease exponentially. By fitting the observed number of L1 hit coincidences between neighbouring DOMs in real data to the expected exponential decay, in this project we study how accurately we can determine the distances between DOMs on a single DU. In addition, we try to determine the distances between DUs by looking for L1 hit coincidences between DOMs on neighbouring DUs.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
=== VIRGO ===<br />
<br />
The Advanced LIGO and Advanced Virgo interferometers have recently observed gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results.<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Frank Linde (frank.linde_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
<br><br><br><br />
<br />
== Bachelor Projects 2017 ==<br />
<br />
=== Extreme Astronomy – Preparing for CTA, the Next-Generation Gamma-Ray Observatory ===<br />
<br />
The Cherenkov Telescope Array (CTA) is a planned facility for measuring gamma rays from space covering more than four orders of magnitude in energy, up to energies exceeding 100 TeV. CTA employs the imaging atmospheric Cherenkov technique to measure properties of cosmic gamma rays. This technique is based on measuring Cherenkov light emitted during the development of a gamma-ray air shower. CTA will be built at two experimental sites, one in the Northern, one in the Southern hemisphere, and will consist of up to 100 telescopes. It represents a major leap forward in sensitivity and precision for gamma-ray astronomy, and will allow us to explore very-high-energy processes of the extreme Universe at an unprecedented level.<br />
<br />
Two projects for students are available at the CTA group of UvA in the field of optical and photonic R&D contributing to the starting phase of CTA. For the first project the student will conduct measurements to characterise novel kinds of single-photon detectors, referred to as silicon photomultipliers, and evaluate different types of these sensors for their use for CTA. For the second project the student will develop and test an imaging system making use of a liquid crystal display. This flexible light source will be able to mimic images from different light sources of the night sky as seen by cameras of CTA, for instance gamma-ray air showers or stars, and will be used for camera tests and calibration.<br />
<br />
<br />
Supervisors: David Berge, Maurice Stephan (postdoc)<br />
<br />
=== Dark Matter ===<br />
<br />
<!--<br />
==== XENON1T - the world's most sensitive dark matter detector ====<br />
<br />
Finding the mysterious dark matter particles is one of the most challenging enterprises in physics today. Soon we will get first data from the world's most sensitive dark matter detector yet: the XENON1T experiment.<br />
<br />
The first goal of this project is to understand why dak matter is necessary to understand the universe, and how we could detect it with XENON1T. Then, you can contribute to our group's efforts preparing for <br />
and analyzing the XENON1T data by, for example: examining XENON1T's calibration signals to check for problems in the experiment, testing our data analysis software with simulated dark matter signals, or studying the physics behind XENON1T's detection process to learn how to better distinguish dark matter signals from backgrounds. For data analyis, experience with or willingness to learn programming in python is essential.<br />
<br />
<br />
Supervisors: M.P. Decowski & J. Aalbers --><br />
<br />
==== Neutrinoless double beta decay sensitivity study in future dark matter detectors ====<br />
<br />
The discovery of neutrino oscillation (Nobel Physics 2015) means that neutrinos have mass. We already know that their masses are tiny, more than one million times smaller than the next-lightest particle in the standard model, the electron. This raises the question if the mass-generation mechanism is the same for neutrinos as it is for the other subatomic particles. In particular, since neutrinos are electrically neutral, they could be their own anti-particles - we call these types of particles Majorana. The only practical way to discover if neutrinos are Majorana is through the search of an extremely rare radioactive decay called neutrinoless double beta decay (0n2b). A few isotopes are candidates for this process, among them Xe-136. The natural abundance of Xe-136 in natural xenon is about 9%, and this gives the opportunity to look for a 0n2b signal in xenon-based dark matter detectors like XENON1T and the future XENONnT and DARWIN detectors. <br />
<br />
We are looking for a student interested in doing a sensitivity study for 0n2b in XENONnT and the DARWIN experiments. The first goal will be to understand the physics addressed in neutrinoless double beta decay. Then the student will inventory possible backgrounds for the signal, use a (controversial) claim of a 0n2b signal as a benchmark and finally obtain the sensitivity of these future detectors. The work will involve simulations and analysis, building on an existing framework developed in our group. <br />
<br />
Supervisors: M.P. Decowski & A. Tiseni<br />
<br />
==== Shaking Dark Matter detectors ====<br />
<br />
Our XENON1T detector is built in the lab underneath the Gran Sasso mountains in central Italy. The lab is very well suited for low-background experiments due to the 1.5km of rock overburden. <br />
However, as you may know, cental Italy has been plagued by earthqaukes over the past decade, with the most recentones occurring in January 2017. We need a BSc student to investigate the <br />
details of such earthquakes in our underground lab. What are the magnitdues by which stuff is moving underground? What are the accelerations? What is the potential effect on our experimental<br />
setup? What would ahppen if an earthquake happens much closer to our lab? Furthermore we are interested to find out whether Earthquakes can be predicted. Some papers claim that before<br />
an earthquake the radon emanating from rock increases. In our lab we measure the radon concentration as a function of time: can you find a correlation between the measurements and recent <br />
earthquakes?<br />
<br />
If you are interested in finding out more about earthquakes, please contact M.P. Decowski or A.P. Colijn<br />
<br />
==== XAMS - a baby dark matter detector ====<br />
<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso<br />
we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector<br />
are identical to its big sibling in Gran Sasso.<br />
<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source we have acquired<br />
before the start of the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project<br />
will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study<br />
of neutron transport in xenon.<br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
==== Radon is bad for Dark Matter ====<br />
<br />
Radon is the dominant background for xenon based dark matter detectors, like the XENON1T experiment. In our lab at Nikhef we are investigating ways to reduce or eliminate the effect of radon<br />
on our sensitivity. For our lab setup XAMS we have designed and constructed a radon detector, that can be used in xenon systems at high-pressure. This completely new detector<br />
is now waiting for a BSc student to fully chracterize and use it. During this project you will first study the effect that radon contaminations have on dark matter detectors, then you will start working to<br />
understand our new radon detector in detail. You will learn howto use a radioactive source to calibrate the detector: this is something which is not easy and has not been done before in our lab. <br />
If you manage to succesfully calibrate the detector, we then want to incorporate it into our lab xenon system at Nikhef and maybe at some later stage in the real XENON1T detector!<br />
<br />
The profile of the student to work on this project is broad. I expect a good theoretical knowledge in order to quickly get upto speed with understanding dark mater detectors, and in addition I <br />
need 'lab-creativity' in order to develop methods for calibrating the new detector. If a good method is developed, it will be used for many years by the Nikhef dark matter group and beyond. <br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
=== ATLAS ===<br />
<br />
<br />
==== ATLAS (1): Searching for new physics with the Higgs and W bosons ====<br />
<br />
The strength of the Higgs interactions with electroweak bosons are precisely defined in the<br />
Standard Model. Therefore they are sensitive probes of the mechanism of electroweak symmetry<br />
breaking and enable searches for new physics beyond the SM. With the data collected by the ATLAS<br />
experiment in years 2015-2016 we plan to measure separately the Higgs coupling to<br />
longitudinally and transversely polarised W bosons in a process of weak boson fusion. To<br />
maximise experimental sensitivity we are developing techniques to separate the signal from<br />
background processes. You will take part in investigating possible improvements from<br />
reconstructing events in reference frames boosted with respect to the detector. During the<br />
project you will learn modern experimental analysis techniques. This project is a part of Vector<br />
Boson Scattering Coordination and Action Network (VBSCan) which connects researchers studying<br />
this and related topics worldwide.<br />
<br />
Supervisors: Pamela Ferrari, Magdalena Slawinska, Bob van Eijk<br />
<br />
<br />
==== ATLAS (2): Dark-matter-motivated searches for supersymmetric particles at the LHC ====<br />
<br />
Supersymmetry, a symmetry between fermions and bosons in particle physics,<br />
may provide a particle that could be the dark matter in the universe.<br />
The observation of an excess of gamma rays originating from the centre of our<br />
galaxy could be explained in a model where supersymmetric dark matter<br />
particles annihilate each other in the galactic centre, leading to gamma rays.<br />
<br />
Given the model parameters, it should also be possible to produce such<br />
particles at the LHC, at CERN in Geneva. But it is not so easy to observe<br />
them: the signal is small, and the noise (background) is large.<br />
In this project, we will use simulations of signal and background to<br />
optimize experimental searches for such particles with the ATLAS detector,<br />
apply them to the data collected in 2015, and prepare for the new data in<br />
2016 and later.Where possible, we will explore new machine learning techniques.<br />
<br />
Supervisors: Paul de Jong, Broos Vermeulen<br />
<br />
<br />
==== ATLAS (3): Simulations / Quality tests for the ATLAS High-Luminosity LHC Upgrade ====<br />
<br />
One of the key sub-systems of the ATLAS experiment at the Large<br />
Hadron Collider (LHC) is the Inner Detector (ID), designed to provide<br />
excellent charged particles momentum and vertex resolution measurements.<br />
<br />
At Phase-2 of the LHC run, in ~2025, the operating luminosity of<br />
the collider will be increased significantly.<br />
This will imply an upgrade of all ATLAS subsystems. In particular,<br />
the ID will be fully replaced with a tracker completely made of<br />
Silicon, having higher granularity and radiation hardness.<br />
The R&D process for the new ATLAS ID is now ongoing.<br />
Different geometrical layouts are simulated and their performance is<br />
studied under different operating conditions in search for the optimal<br />
detector architecture. Also, the performance of the new<br />
Si-sensors/modules is under investigation with dedicated laboratory tests.<br />
<br />
The focus of the project could be on the simulation of the High-Luminosity LHC<br />
version of the ATLAS Inner Detector. The student will learn how a<br />
high-energy physics experiment is designed and optimized.<br />
Alternatively, if possible at that moment, the student could<br />
work on a project at the Nikhef Silicon laboratory at the test-bench for<br />
new ATLAS Si-strip detectors and participate in the quality<br />
assurance procedure for the new ATLAS Si detectors.<br />
<br />
==== ATLAS (4): Higgs productie in Run-2 van de LHC ====<br />
In de eerste run van de LHC is onder andere bij het ATLAS experiment het Higgs deeltje gevonden. Nu is de tweede run begonnen en kan het Higgs deeltje worden bevestigd. Door de verhoogde energie ziet de achtergrond er echter heel anders uit, dus is de optimalisatie van het wegsnijden van de achtergronden qua fysica anders. Voor je bachelor project kan met behulp van de ATLAS detector het Higgs deeltje in run twee komen vinden. <br />
<br />
Supervisors: Lydia Brenner, Wouter Verkerke<br />
<br />
==== ATLAS (5): De lange staart van het Higgs boson ====<br />
<br />
[[File:HiggsMassa.png |thumb|left|upright=1.25]]<br />
<br />
<br><br />
Na de ontdekking van het Higgs boson in 2012 zijn we druk bezig om te kijken of zijn eigenschappen overeenkomen met de voorspellingen van het Standaard Model. Een van de belangrijkste eigenschappen is de zogenaamde breedte van het Higgs boson. Als het Higgs boson naast de Standaard Model deeltjes ook in exotische nieuwe speeltje uit elkaar kan vallen (bijvoorbeeld donkere materie) dan zal dat ale eerste zichtbaar worden in een afwijking van de breedte tov de verwachting. We gaan in dit project uitzoeken hoe de strategie die nu gebruikt wordt (meten van de hoeveelheid Higgs bosonen met een extreem hoge massa) precies werkt en kijken of we door het toevoegen van nieuwe ideeën een verbetering kunnen aanbrengen. <br />
<br />
<br><br />
Specifiek: We gaan eerst in detail de eigenschappen bekijken van het Higgs signaal en de twee achtergronden die er het meest op lijken. Daarna gaan we op zoek naar de verschillen en een manier waarop we onze kennis daarover kunnen gebruiken om gevoeliger te worden voor het Higgs signaal.<br />
<br />
Supervisors: Hella Snoek, Ivo van Vulpen<br />
<br />
E-mail: H.Snoek_at_nikhef.nl & Ivo.van.Vulpen_at_nikhef.nl<br />
<br><br><br><br><br><br><br />
<br />
=== ATLAS (6): Project ATLAS-ITk ===<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
<br><br />
<br />
=== KM3Net ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierachy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
The first phase of the KM3NeT neutrino telescope is currently under construction, with the first two detection units operational at 3500m depth in the Mediterranean Sea, 100 km off the coast of Sicily.<br />
<br />
<br />
==== KM3NeT (1): Photon counting in KM3NeT ====<br />
<br />
The details of a neutrino interaction, such as its incoming direction and energy, determine the pattern, time and amount, of recorded photons (´hits´) by the photo-multplier tubes. The time of arrival is recorded with nanosecond accuracy and the amount of photons is encoded in the length of the pulse(time-over-threshold, ToT). Currently, only the photon arrival time and the number of photo-multipliers that record a hit are used in reconstructing event properties.<br />
In this project, the distributions of the ToT mainly originating from photons from potassium-40 decays in the sea-water and from atmospheric muons passing through the water will be studied. The goals are to investigate the properties of the ToT distributions obtained from data and simulation, in particular the dependence on the photo-multiplier efficiency and atmospheric muon flux.<br />
In this project we will be extensively using the programming language C++ to analyse the data, so a reasonable proficiency is required.<br />
<br />
Supervisors: Ronald Bruijn & Karel Melis<br />
<br />
Email: rbruijn_at_nikhef.nl<br />
<br />
<br />
<br />
<br><br><br><br />
<br />
=== VIRGO ===<br />
<br />
"It is anticipated that in the next few years, Advanced LIGO and Advanced Virgo will start observing gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results."<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Jo van den Brand (jo_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
=== LHCb ===<br />
<br />
Begeleider: Sean Benson<br />
<br />
Title: <br />
Searching for physics beyond the Standard Model with LHCb<br />
<br />
The LHCb experiment is designed to study the "The Flavour Problem" in particle physics:<br />
Why is the universe dominated by matter over antimatter? Why are there three generations of elementary particles? What is the origin of quark flavour changing interactions.<br />
<br />
To solve these riddles, LHCb performs precision measurements on b-quark particle decays.<br />
An intriguing signal has recently been observed in the decay of a B-meson to a K* and two muons: Bd→K*μμ, which does not seem to behave according to the predictions of the Standard Model<br />
In this project the bachelor student will investigate this further by studying the case where the K* particle decays to a so-called k-short particle and a π0. The observation of such a final state will provide valuable information in the search for physics beyond the Standard Model.<br />
<br />
In this ambitious project the student is expected to study both a theory on the mechanism of CP violation with B mesons, in addition to data analysis with B decays. Programming experience in python is required.<br />
<br />
The LHCb experiment at CERN analyzes the properties of B-hadrons produced in proton-proton collisions at the LHC. For projects in the LHCb group, please contact Marcel Mark (marcel.merk_at_nikhef.nl)<br />
<br />
<br />
=== LHCb (1) ===<br />
<br />
One of the most fascinating mysteries in physics today is: how is it possible that universe is filled with matter? If the Big Bang produced equal amounts of matter and antimatter, we still do not understand the mechanism that lead to the excess of matter over antimatter that we observe today.<br />
<br />
One interesting feature of some particles is that they can transform themselves into their antiparticles, then back to particle, and so forth, in an oscillatory way until they finally decay. In particular, beauty mesons (B) can oscillate into their antiparticle (B ̄). The parameters of this oscillation, such as amplitude, frequency and phase, are calculable mathematically: predictions for it are available in the standard model (SM) of particle physics. But the oscillations according to the SM alone would not lead to the imbalance of matter in the universe – we still need to find a new type of physics that may be able to explain it.<br />
<br />
In this context, it is very important to measure B oscillations in the laboratory, and compare these observations with the expectations from the SM. Are the experimental data in good agreement with the SM, as we expect? If the aswer is not, i.e. if there are features of the oscillation that we do not understand well, then we may be observing “new physics”. In other words, the data may reveal a new mechanism that generates a different matter-antimatter balance than predicted by the SM, that may potentially solve the puzzle.<br />
<br />
The LHCb experiment at CERN is dedicated to such studies: LHCb detectors are placed in a region along the LHC collider beamline, where a large number of B mesons are produced, arising from the proton-proton collision data from the LHC collider. Looking at the LHCb data we can obtain large samples of B mesons, and observe their oscillations.<br />
In this project we will learn how to select a sample of B mesons out of the data taken with the LHCb detector, measure the parameters that govern their oscillation and compare them with the SM.<br />
<br />
For more information, please contact Mara Soares (msoares_at_nikhef.nl).</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Bachelor_Projects&diff=941Bachelor Projects2024-02-09T13:50:28Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>== Bachelor Projects 2024 ==<br />
<br />
=== Detector R&D ===<br />
<br />
=== KM3NeT ===<br />
<br />
=== Dark Matter ===<br />
<br />
=== ATLAS ===<br />
<br />
=== LHCb ===<br />
<br />
=== Gravitational waves ===<br />
<br />
=== Theory ===<br />
<br />
====The Schiff theorem for Electric Dipole Moments (Jordy de Vries)====<br />
<br />
Electric Dipole Moments (EDMs) of nucleons, atoms and molecules are important experimental observables to look for beyond-the-Standard-Model sources of fundamental symmetry violation. Specifically, the violation of Charge-Parity (CP) symmetry, which is present in the SM but not in sufficient amounts to explain the observed matter-antimatter asymmetry in the universe, can be probed through EDMs. To understand what EDM measurements on larger systems tell us about the fundamental physics at the elemental particle scale, and to assess what systems are most promising for EDM experiments, the Schiff theorem is essential. This theorem describes how, under certain simplifications, the EDMs of atoms and molecules vanish due to screening. In this project, you will investigate the theory behind Schiff screening, including possible violations of the theorem which lead to interesting systems with which to probe EDMs. For this project, the courses Advanced Quantum Physics & Atomic Physics are useful, but not strictly necessary.<br />
<br />
<br />
====High-energy neutrino-nucleon interactions at the LHC with FASER ====<br />
<br />
High-energy collisions at the Large Hadron Collider (LHC) produce an unprecedented number of light particles along the beam collision axis, outside of the acceptance of existing experiments. The FASER experiment, located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, provides new opportunities to probe Standard Model (SM) processes, in particular high-energy neutrino physics, and search for physics beyond the Standard Model (BSM). In this project, the student(s) will carry out updated theoretical predictions and numerical simulations for relevant physical processes at FASER, in particular concerning neutrino production and scattering, and assess their implications for our current models of proton structure and of QCD, the quantum field theory of the strong nuclear force. The project will also involve studying the implications of these results for ultra-high-energy particle astrophysics such as at the KM3NET and AUGER experiments. For this project, having followed the elective courses "Introduction to (astro-)particle physics" and "Standard Model of Elementary Particles" is required.<br />
<br />
''Contact: [[Mailto:j.rojo@vu.nl Juan Rojo]] (''VU Amsterdam & Nikhef Theory)<br />
<br />
==== Probing the proton spin with machine learning at future colliders ====<br />
<br />
An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions in particle physics from the nature of the Higgs boson to the origin of cosmic neutrinos. This effort requires combining an extensive experimental dataset and cutting-edge theory calculations within a machine learning framework where neural networks parametrise the underlying physical laws while minimising ad-hoc model assumptions. The upcoming Electron Ion Collider (EIC), to start taking data in 2030, will be the world's first ever polarised lepton-hadron collider and will offer a plethora of opportunities to address key open questions in our understanding of the strong nuclear force, such as the origin of the mass and the intrinsic angular momentum (spin) of hadrons and whether there exists a state of matter which is entirely dominated by gluons. In this project, the student will carry out a determination of the polarised quark and gluon substructure of the proton by means of the machine learning tools provided by the NNPDF open-source fitting framework and include projections for the impact of future EIC data on the spin content of the proton and on non-perturbative models of hadron structure. For this project, having followed the elective courses "Introduction to (astro-)particle physics" and "Standard Model of Elementary Particles" is required.<br />
<br />
''Contact: [[Mailto:j.rojo@vu.nl Juan Rojo]] (VU Amsterdam & Nikhef Theory)''<br />
<br />
== Bachelor Projects 2023 ==<br />
<br />
=== KM3NeT ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along 200-700m long vertical lines, called detection units.<br />
<br />
<br />
==== Search for cosmic neutrinos with the first KM3NeT data ====<br />
<br />
The KM3NeT/ARCA block is tuned for the detection of cosmic neutrinos and search for their sources. The first data of ARCA will be used to search for cosmic neutrino sources, and to search for a neutrino signal in response to external alerts for transients (gamma-ray bursts, IceCube neutrinos, gravitational wave events). Furthermore there is the opportunity to search for a neutrino signal from dark matter annihilation in the galactic halo and in dwarf spheroidal galaxies.<br />
<br />
Supervisors: Thijs van Eeden, Jhilik Majumdar, Clara Gatius, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
<br />
==== Neutrino oscillations with KM3NeT/ORCA ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope is able to measure the oscillations of neutrinos produced in interactions of cosmic rays with the earth atmosphere. Fundamental neutrino properties can be deduced from these oscillations measurements. In this project we will use the first data of ORCA to study neutrino oscillations and fit neutrino mixing parameters and mass differences between neutrino mass states. We will study data selection, event reconstruction, and effects of systematic uncertainties on the results. <br />
<br />
Supervisors: Bouke Jung, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
<br />
==== Multi-messenger astronomy with neutrinos and radio signals ====<br />
The main goal of neutrino telescopes, such as ANTARES, KM3NeT and IceCube, is to detect cosmic neutrinos from astrophysical sources. When an interesting neutrino candidate is detected they send out a message to alert the scientific community. Other scientific instruments, like the Murchison Widefield Array (MWA) radio telescope, can then do a follow-up observation, to see if there are other messengers coming from the same source as the neutrinos. In this project you will analyse MWA data that were taken after the reception of neutrino alerts, to search for a radio source that can be associated with a neutrino source.<br />
<br />
Supervisor: Mieke Bouwhuis (mieke.bouwhuis at nikhef.nl)<br />
<br />
<br />
<br />
=== Dark Matter ===<br />
<br />
==== Investigating muon spallation backgrounds in KamLAND neutrino detector ====<br />
The KamLAND neutrino detector in Japan is designed to measure among other things neutrinoless double beta decay, an important process in particle physics that, should it be observed, would confirm that neutrinos might be their own antiparticles. However, the lack of detection of this process can be blamed on various backgrounds, one of which is muon spallation. Only recently did we start studying these spallation backgrounds in detail and we are looking for a student that has a strong interest in programming, simulations and data analysis to help the progression. The goal of this project is to allow for a better understanding of the behaviour of spallation events and to contribute to the simulation of the background that will be used in KamLAND, as well as future neutrino and dark matter experiments.<br />
<br />
Supervisors: Kelly Weerman and Patrick Decowski (decowski@nikhef.nl)<br />
<br />
==== First measurements with new VULCAN detectors ====<br />
At Nikhef we have a brand new experiment designed to measure the reflectance, transmission, and fluorescence properties of materials at vacuum ultraviolet (VUV) wavelengths. The materials to be studied are used to construct the XENONnT dark matter and the DUNE neutrino detectors. <br />
<br />
In this project, you will calibrate the characteristics of the VUV lamp and of the SiPM photon sensors used in VULCAN. Lab work at the Nikhef building will be a main part of the project, but you will also analyse the data you collect using modern analysis tools.<br />
<br />
You will gain experience with VUV optics, vacuum systems, single-photon sensors, and data analysis using Python and/or C++ tools.<br />
<br />
Supervisors: Marjolein van Nuland and Tina Pollmann (t.pollmann@nikhef.nl)<br />
<br />
==== The XAMS dark matter R&D setup at Nikhef ====<br />
The Nikhef dark matter group has a small version of the XENONnT dark matter detector in our Nikhef lab. With this detector we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENONnT experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso. We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with recently upgraded hardware to test a novel concept for UV light detection. The goal of this project will be to do the first measurements and analyze the data. Depending on the progress with the hardware we intend to complete the first measurements with our upgraded setup.<br />
<br />
Supervisors: Patrick Decowski (decowski@nikhef.nl) and A.P. Colijn (colijn@nikhef.nl)<br />
<br />
==== Reconstruction software for the XENONnT dark matter experiment ====<br />
The XENONnT dark matter experiment became operational in 2021. The experiment is in the Gran Sasso underground laboratory in Italy and the hardware is not being touched. However, we keep on developing and perfecting our reconstruction software. For this project we are looking for a student with a keen interest in and talent for writing physics-based event reconstruction software (we use python). Specifically we have an idea to improve the localization of events inside the XENONnT for which proto-type software exists. The proto-type software needs to be implemented in the XENONnT reconstruction framework and subsequently it needs to be validated on the first data from the experiment. The final goal of the project is to deliver the reconstruction software to the collaboration to be used during the lifetime of the experiment.<br />
<br />
Supervisors: Patrick Decowski and A.P. Colijn (colijn@nikhef.nl)<br />
<br />
=== ATLAS ===<br />
<br />
==== Machine-Learning in Top-Quark physics ====<br />
As the heaviest elementary particle the top quarks plays a key role in the Standard Model. Discovered in 1995 at the Tevatron accelerator, top quarks are now abundantly produced at the Large Hadron Collider (LHC) located at the European Organization for Nuclear Research (CERN) . But do these produced top quarks behave as predicted by the Standard Model or are there signs of new physics? To describe possible deviations, we use calculations from Effective Field Theory (EFT) that allows to add new interactions. For this project simulated data samples with deviations predicted by EFT are available.<br />
<br />
The candidate applies new techniques involving machine-learning to separate backgrounds from top quark production, aware for signs of new physics. Existing tools can be used to quantify the improvements on finding new interactions involving top quarks. Depending on the candidates interest, the focus of the project can be put more on machine-learning or top quark physics. For this project, we use the Python computing language and the ROOT package. Therefore, some proficiency with Python is required. Knowledge of C++ and root is advantageous but not required. <br />
<br />
Supervisors: Jordy Degens (PhD candidate) and Marcel Vreeswijk (h73@nikhef.nl).<br />
<br />
==== '''New machine learning approaches to target Higgs interference signatures in LHC data''' ====<br />
In this project we aim to improve an ongoing analysis to determine the lifetime of the Higgs Boson through state-of-the-art machine learning techniques, in particular by addressing a novel solution to an as of yet unsolved fundamental problem in modeling quantum interference. While the Higgs is an elusive particle that generally only appears in physics processes with small cross sections, its signature can be amplified in the Large Hadron Collider (LHC) through quantum interference with larger background (non-Higgs) processes. This is the effect that the Higgs’ lifetime analysis relies on to be able to measure the relevant Higgs signature. A fundamental physics modelling problem arises though in the simulation of individual events for this interference due to the fact that these events are in reality described by a superposition of underlying Higgs and non-Higgs processes.<br />
<br />
Since machine learning models in particle physics are typically trained to characterise individual physics events, the fact that interference events cannot currently be generated is a significant problem when interference is the target. In the currently existing Higgs lifetime analysis, a machine learning model was trained which instead focuses only on the explicit Higgs-mediated processes as a proxy, which is suboptimal. The aim of this project is to improve upon this current machine learning strategy used in this analysis by implementing either of the inference-aware approaches suggested in [1] and [2]. The idea behind these inference-aware machine learning algorithms is that they do not optimise for a simplified goal such as the loss function which is common in traditional machine learning, but rather for the end-goal of the analysis. In this case, this would omit the need for interference event generation altogether and allow the machine learning models to be trained optimally regardless.<br />
<br />
The goal of this project is to use either of the frameworks used in [1] and [2] (which are both publicly available) and run them with a simplified dataset from the aforementioned analysis as a proof-of-principle. In case this goal is achieved, the next goal would be to actually implement the newly developed machine learning models in the full analysis and to determine the improvement upon the existing result. Successful completion of these tasks would not only benefit the Higgs lifetime analysis, but would be an important stepping stone to future developments to make machine learning approaches deal better with other hard to model effects such as systematic uncertainties.<br />
<br />
Supervisors: Zef Wolffs, Ivo van Vulpen and Matous Vozak (matous.vozak@cern.ch)<br />
<br />
==== '''Reconstructing tracks from particle physics detector hits with state-of-the-art machine learning techniques''' ====<br />
This project concerns the application of new machine learning techniques to tackle the problem of track reconstruction at the ATLAS detector in CERN. While algorithms to construct particle tracks from low-level detector information such as particle hits and timestamps have been around for decades, recent developments in the field of machine learning open up new opportunities to improve these algorithms significantly. In particular graph-based neural networks and attention architectures prove promising candidates for solving these problems based on preliminary studies. <br />
<br />
In this project the student will develop machine learning models to initially reconstruct tracks from simplified test data. If time allows, real data from the ATLAS detector can be analyzed as well in the scope of this project. The student will need some familiarity with programming in python and an interest in machine learning, but a physics background is not required. In this project the student will be able to contribute to fundamental physics research and will familiarize themselves with state-of-the-art machine learning models.<br />
<br />
Supervisors: Zef Wolffs, Ivo van Vulpen and Matous Vozak (matous.vozak@cern.ch)<br />
<br />
=== LHCb ===<br />
<br />
=== Gravitational Waves ===<br />
<br />
====Staying in shape====<br />
Nikhef is co-leading the current effort to realise the Einstein Telescope (ET), a future 10km-scale underground observatory for gravitational waves. Numerical modelling software forms a crucial subsystem for the design and operation of the GW detectors. Our interferometer simulation software Finesse was developed for the design and commissioning of gravitational wave detectors and has become the main interferometer software tool in the community world wide. In our group we use Finesse to predict the shape of the laser beam and how this affects the GW data. You will join our group using Python-based scripts to model mis-shaped lasers and see how the interferometer reacts.<br />
<br />
Required knowledge:<br />
<br />
Good knowledge of Python is required.<br />
<br />
Knowledge of optics will be useful but is not required.<br />
<br />
Supervisors: Anna Green (agreen@nikhef.nl) and Andreas Freise (a.freise@nikhef.nl)<br />
<br />
====Riding the wave====<br />
Theoretical predictions of gravitational-wave (GW) signals provide essential tools to detect and analyse transient GW events in the data of GW instruments like LIGO and Virgo. Over the last few years, there has been significant effort to develop signal models that accurately describe the complex morphology of GWs from merging neutron-star and black-hole binaries. Our work focusses on a particular class of GW binary sources: those that come from two black holes meeting at close separation in dense stellar environments. Here, we expect the merging binary to be in a non-circular orbit and to have arbitrary spin orientations, which significantly complicates the prediction of its GW signal.<br />
<br />
We are looking for '''two''' students who are interested in the development of accurate and efficient GW models and their application in GW data analysis. We are offering '''two separate projects''' that aim to improve signal modeling at the interface of perturbation theory, numerical relativity simulations and fast phenomenological descriptions. Some proficiency in computing is required (Mathematica, Python or C++).<br />
<br />
Supervisor: Maria Haney (mhaney@nikhef.nl)<br />
<br />
=== Detector R&D ===<br />
<br />
====Charge collection study of fast monolithic detectors====<br />
In view of the upgrade of the ALICE tracking detector, innovative ultrathin monolithic silicon sensors are developed for testing. These devices are provided with analogue outputs to study in detail the charge collection and the timing properties of the sensor.<br />
The goal of the project is to contribute to the study of the charge collection features of the samples by measuring the response of the sensor to Fe55 X-rays.<br />
We are looking for a student with a focus on lab work and interested in contributing to the python-based data analysis.<br />
Depending on the progress with the intended measurement and the availability of the hardware, further studies with Sr90 electrons and a laser setup could be possible.<br />
<br />
Contacts: Jory Sonneveld (jory.sonneveld@nikhef.nl), Roberto Russo (rrusso@nikhef.nl)<br />
<br />
====Laser setup for silicon sensor studies====<br />
The Detector R&D group at Nikhef develops and tests detector concepts before they are used in scientific programs at Nikhef. To achieve such a goal, advanced instrumentation and setups are required.<br />
The goal of the project is to contribute to the design and construction of a fast infrared laser setup aimed at the characterization of silicon sensors for high energy physics experiments.<br />
We are looking for a student with a focus on lab work and interest in instrumentation and optics. Besides contributing to the setup construction, measurements finalised at the characterization of the laser beam (e.g. spot size, intensity) are foreseen.<br />
<br />
Contacts: Jory Sonneveld (jory.sonneveld@nikhef.nl), Roberto Russo (rrusso@nikhef.nl)<br />
<br />
==== Characterization of monolithic silicon sensors ====<br />
As part of the ongoing efforts for the design of ultimate tracking detectors, an excellent understanding of the basic performance of the detectors is required. To do so, the silicon detectors can be tested by making an electrical contact with the sensor using a probe station, a device for micrometer precision placement of temporary electrical contacts to acquire signals from internal nodes of semiconductor devices, to investigate aspects such as it's depletion voltage, depletion depth, the dark current and more which are essential for understanding the results gathered by the sensors later in the laboratory and allow the investigation of aspects that can be improved in further chip iterations. The goal of the project is to investigate the performance of monolithic sensors, where electronics is integrated into the sensor, developed for collider experiments like those at the large hadron collider at CERN and beyond. Depending on the progress with the planned measurements, further tests with the electronics and readout of the chip, as well as measurements with advanced laster instrumentation are also possible.<br />
<br />
Contacts: Jory Sonneveld (jory.sonneveld@nikhef.nl), Uwe Kraemer (uwe.kraemer@nikhef.nl)<br />
<br />
=== Theory ===<br />
'''Axion-Electrodynamics (Jordy de Vries and Arghavan Safavi-Nani)'''<br />
<br />
Axions are hypothetical particles that are introduced to solve the so-called strong CP problem. Being very light, axion can be described as a coherent classical field similar to electromagnetic fields. In this project, you will develop the modifications of Maxwell’s equations to include axion fields. Reference: arXiv:1401.0709 . <br />
<br />
'''Axions in a Paul-trap (Jordy de Vries and Arghavan Safavi-Nani)'''<br />
<br />
Axions are hypothetical particles that are introduced to solve the so-called strong CP problem. If axions form the dark matter in our universe, they can be described by a coherent oscillating background field. This oscillating field interacts with charged particles and it possible to detect axions by the motion of ions in a Paul trap. In this project, you will investigate how these interactions work and what are the observables associated to the detection of axions in ion traps.<br />
<br />
'''Phase space integrals for double-weak processes (Jordy de Vries)'''<br />
<br />
The rarest processes ever measured are so-called double weak processes in which two neutrons undergo beta decay at the same time in a nucleus. Lifetimes of these processes are in the 10^22 years range. Theoretical computations of these rates involve so-called phase space integrals that take into account the possible momentum configurations of the outgoing electrons and neutrinos. In this project you will investigate these phase space integrals and develop a method to compute them. <br />
<br />
<br />
<br />
<br />
<br />
<br />
== Bachelor Projects 2022 ==<br />
<br />
=== Dark Matter ===<br />
<br />
==== Response of materials to scintillation light from liquid noble gasses ====<br />
<br />
The liquid form of the noble gases argon and xenon is a popular target material for neutrino and dark matter detectors. The scintillation light from noble gases is in the vacuum UV spectral region. Air and many materials used for optical studies are not transparent to these photons. Measurements of the optical properties of detector materials, such as their reflectivity for example, thus have to be performed with dedicated VUV optics and in vacuum. Additionally, to reproduce the conditions in the detectors, the samples must be cooled to cryogenic temperatures. In this BSc project, you will calibrate the photon detectors in an experimental setup designed to study the optical response of materials excited with VUV photons. You will learn about material requirements for rare event search detectors, vacuum instrumentation, vacuum UV optics including monochromators and spectrometers, and single-photon sensors.<br />
<br />
Supervisors: T. Pollmann (t.pollmann_at_nikhef.nl)<br />
====XAMS====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENONnT detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENONnT experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso. We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with recently upgraded hardware to test a novel concept for UV light detection. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complete the first measurements with our upgraded setup.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
==== XENONnT reconstruction software ====<br />
The XENONnT experiment becomes operational during 2021. While the hwardware is finished we keep on developing and perfecting our reconstruction software. For this project we are looking for a student with a keen interest in and talent for writing physics based event reconstruction software (we use python). Specifically we have an idea to improve the localization of events inside the XENONnT for which proto-type software exists. The proto-type software needs to be implemented in the XENONnT reconstruction framework and subsequently it needs to be validated on the first data from the experiment. The final goal of the project is to deliver the reconstruction software to the collaboration that will be used during teh full lifetime of the experiment.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
=== ATLAS ===<br />
<br />
==== The Higgs boson - did we miss anything and can we do better? ====<br />
<br />
The Higgs boson is a key element of the Standard Model (SM) of particle physics, however, it can also represent a link between yet unexplored 'new' physics beyond the SM. What is the Higgs boson life-time? How precisely can we measure its mass? Is there an additional heavy Higgs boson? Do other particles, not contained in the SM, couple to the Higgs? All these questions can be studied by measuring Higgs properties using one of the Higgs decay modes to photons, vector bosons, quarks and leptons and comparing them with the (beyond) SM predictions. <br />
<br />
As the restart of the Large Hadron Collider (LHC) is imminent, it is essential to develop and test new physics ideas and strategies. '''The ATLAS open data project''' will allow students to work on a real analysis digging through the LHC data collected during Run2. Students will go through all the key aspects of a Higgs analysis performed also by ATLAS physicists. They will learn about Higgs boson theory and its simulation, what objects are reconstructed in the ATLAS experiment, how well do we understand them and finally how does this project into our understanding of the Higgs boson and its properties. <br />
<br />
The exact focus of the topic is flexible depending on the interest of a student. For instance, a student can delve into how precisely can we determine objects' energy and their positions and see whether we can '''improve our estimate of the Higgs mass (project 1)'''. Another possibility is to focus on trying to find out whether there is '''an additional (heavier) Higgs (project 2)''' in the data and how confident we can be of that. Each of these projects will most likely yield new questions, so feel free to take a tangent and walk into yet unexplored territory and see what the data tells you.<br />
<br />
Supervisor: Matouš Vozak (m.vozak_at_nikhef.nl) & Ivo van Vulpen (Ivo.van.Vulpen_at_nikhef.nl)<br />
<br />
==== The Higgs boson life-time ====<br />
<br />
The Higgs particle does not have eternal life. The Standard Model (SM) predicts that it decays into other particles and as these couplings are fixed we can predict its life-time with very high precision. Determining this life-time is a crucial test for the Standard Model. If the Higgs boson life-time is shorter that we expect this could mean that the Higgs boson could decay into non-SM particles. In this project we investigate a) how we can identify Higgs particles in the detector and b) how we plan to use quantum-interference to get a handle on the Higgs boson's life-time. <br />
<br />
Supervisor: Wouter Verkerke (verkerke_at_nikhef.nl)<br />
<br />
==== Higgs interferentie ====<br />
In 2012 hebben het ATLAS en het CMS experiment het Higgs deeltje gevonden. Inmiddels zijn we het Higgs boson aan het bestuderen, hoe gedraagt het zich precies, bestaan er meer soorten Higgs bosonen of is er echt maar eentje van? In dit project leer je hoe we een Higgs boson kunnen herkennen in de detector en gaan we kijken naar hoe de signalen veranderen als er meer Higgs bosonen bestaan of misschien wel andere exotische nieuwe deeltjes. <br />
Dit doen we door gebruik te maken van quantum interferentie wat plaats vindt tussen het Higgs boson en achtergrondprocessen. Hoe dit precies werkt leer je in het project. Supervisor: Hella Snoek (h.snoek_at_nikhef.nl)<br />
<br />
<br />
=== LHCb ===<br />
<br />
<br />
==== Exotic neutrinos in B decays====<br />
<br />
Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, heavier, neutral leptons. In the LHCb group at Nikhef we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undisovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The bachelor project will contribute with the optimization of the selection using state-of-the-art tools for the multi-variate analysis.<br />
<br />
Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
<br />
<br />
=== Gravitational Waves ===<br />
<br />
=== Detector R&D ===<br />
Answering big elementary particle physics questions requires pioneering experiments. The Detector R&D program at Nikhef is aimed at conceptualizing and testing of instrumentation concepts before they are implemented in scientific programs at Nikhef. <br />
<br />
==== Time resolution of monolithic timing detectors ====<br />
For the upgrade of the vertex detectors of the large LHC experiments like LHCb and ALICE, new silicon pixel detectors will developed now that can register the passing particles with a time precision of tens of picoseconds. ALICE is the first experiment at the LHC to have installed monolithic sensors where electronics is integrated into the sensor resulting in ultrathin, low-material detectors, that will soon see it's first particles from LHC collisions. In this project you will measure the time resolution of these promising integrated sensors with a laser setup in our laboratory.<br />
<br />
Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
==== Modeling radiation damage in silicon sensors ====<br />
In the coming years, the ATLAS experiment at the LHC works on upgrades to prepare for the high-luminosity LHC, where many more collisions will take place than today. Analyses of LHC data rely heavily on simulations of the detector. It may sound counterintuitive, but particle detectors do not actually like particles: after many collisions at the LHC, a silicon pixel detector has seen so many particles that its bulk gathers defects. Charge generated by traversing particles can get trapped in defects resulting in less charge induced in the readout electrodes, reducing detector performance in resolution and efficiency. In this project, you will be part of the international ATLAS collaboration and compare different models of radiation damage with measured data and you will contribute to the open source program Allpix Squared that is widely used for simulations in many areas of particle physics.<br />
<br />
Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
==== Time resolution of a new digital pixel test structure from test beam data ====<br />
For the upgrade of the ALICE detector, ultrathin picosecond timing integrated sensors are developed. To reduce power consumption, asynchronous readout is implemented in this prototype sensor in a digital pixel test structure. This structure was studied in test beams with an ALPIDE (ALICE PIxel DEtector) telescope at CERN. You will measure the efficiency and time resolution of this new sensor with the latest data from test beams at CERN.<br />
<br />
Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
<br />
==== Fast timing detectoren ====<br />
Op dit moment maken we veel gebruik van silicon detectoren in onze deeltjes experimenten. Deze zijn gevoelig voor geladen deeltjes en zijn bij uitstek geschikt om de paden vast te leggen die de deeltjes maken die in de botsingen worden gemaakt. Bijvoorbeeld in de Atlas en LHCb experimenten worden tientallen tot honderden deeltjes gemaakt bij elk botsingsgebeurtenis (event) die met 40MHz plaatsvinden. Voor toekomstige deeltjesdetectoren willen we niet alleen het traject vastleggen maar ook met grote precisie een tijdsmeting toevoegen. We hebben hiervoor dus nieuwe detectoren nodig die behalve met een hele hoge snelheid en efficientie de posities van de langsvliegende deeltjes kunnen vastleggen, maar hier ook een zeer nauwkeurige tijdsmeting (in orde van picosecondes) aan kunnen toevoegen. We hebben met verschillende detectoren metingen gedaan, in testbundels op CERN, maar ook in het lab op Nikhef kunnen we metingen doen. In dit project ga je samen met het fast-timing detectoren team op het Nikhef metingen verrichten en de resultaten hiervan bekijken. Contact: Hella Snoek (h.snoek@nikhef.nl)<br />
<br />
<br />
=== KM3NeT ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along 200-700m long vertical lines, called detection units.<br />
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==== Neutrino oscillation measurements with the first KM3NeT data ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope is able to measure the oscillations of neutrinos produced in interactions of cosmic rays with the earth atmosphere. Fundamental neutrino properties can be deduced from these oscillations measurements. In this project we will use the first data of ORCA (more than one year with six detection units) to study neutrino oscillations and fit neutrino mixing parameters and mass differences between neutrino mass states. We will study data selection, event reconstruction, and effects of systematic uncertainties on the results. <br />
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Supervisors: Brian O'Fearraigh, Ronald Bruijn, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
==== Search for sterile neutrinos with KM3NeT. ====<br />
A detailed study of neutrino oscillations in the KM3NeT detector is sensitive to the existence of so-called sterile neutrinos: neutrinos that are not part of the Standard Model of particle physics, and have no ordinary interactions with matter. We will use a mixture of data and simulations to estimate KM3NeT sensitivity.<br />
<br />
Supervisors: Alba Domi, Paul de Jong<br />
<br />
==== Machine learning for event classification in KM3NeT ====<br />
The classification of neutrino events recorded in the KM3NeT detector in terms of originating from electron neutrinos, muon neutrinos, or tau neutrinos, is very well suited for machine learning techniques. We will study the performance of a few advanced machine learning techniques on simulated high-energy neutrino events.<br />
<br />
Supervisors: Alba Domi, Paul de Jong<br />
<br />
==== Multi-messenger astronomy with neutrinos and radio signals ====<br />
The main goal of neutrino telescopes, such as ANTARES, KM3NeT and IceCube, is to detect cosmic neutrinos from astrophysical sources. When an interesting neutrino candidate is detected they send out a message to alert the scientific community. Other scientific instruments, like the Murchison Widefield Array (MWA) radio telescope, can then do a follow-up observation, to see if there are other messengers coming from the same source as the neutrinos. In this project you will analyse MWA data that were taken after the reception of neutrino alerts, to search for a radio source that can be associated with a neutrino source.<br />
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Supervisor: Mieke Bouwhuis (mieke.bouwhuis at nikhef.nl)<br />
<br />
=== Theory ===<br />
<br />
==== Effective Field Theories of Particle Physics from low- to high-energies (2022 not yet determined if available in 2023) ====<br />
<br />
Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations<nowiki>''</nowiki> seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature.<br />
<br />
Until recently, it was widely assumed that matter particles from each of the three generations interact with the same (“universal”) strength. This hypothesis is being challenged by new measurements at the Large Hadron Collider (LHC) at CERN, which hint towards non-universal interactions. If confirmed, these measurements will be the first signs of new particles and interactions in high-energy colliders. These exciting findings indicate the urgent need to explore such phenomena in depth.<br />
<br />
The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Effective Field Theory (EFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes. Specifically, the goal is to connect measurements from ATLAS and LHCb among them and to jointly interpret this information with that provided by other experiments, from CMS and Belle-II to very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
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''Methodology and workplan''<br />
<br />
This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories.<br />
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This project accommodates several students, who would work together in developing the main formalism while each of them focuses on a specific sub-project. The maximum capacity of this project is 5 students. <br />
<br />
Depending on the student profile, sub-projects with a strong computational / machine learning component are also possible.<br />
<br />
During the first four weeks of the project, students will learn the required background material on effective field theories, following the guidelines from the supervisors. Afterwards, they will focus on different sub-projects, each covering a different aspect of the same global EFT program.<br />
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Required knowledge<br />
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Quantum Mechanics 2, Particle Physics 1 (required)<br />
<br />
Advanced Quantum Mechanics, Particle Physics 2, Machine Learning (optional)<br />
<br />
Available subprojects<br />
<br />
Here we list the available subprojects, including the corresponding daily supervisor(s) in each case.<br />
<br />
''Subproject #1: SMEFT & Flavour symmetries'' <br />
<br />
Daily supervisors: Jordy de Vries (UvA), Keri Vos (Maastricht University), Jaco ter Hoeve (VU), Giacomo Magni (VU)<br />
<br />
While the power of the Standard Model EFT (named SMEFT) framework is its generality and lack of assumptions, the number of operators is somewhat daunting. A popular way to trim the number of operators is to assume flavour symmetries that relate operators with different quark and lepton flavours. In this project you will investigate the theoretical basis for commonly-used flavour symmetries and what they imply for the connection between high-energy observables involving third-generation particles (top and bottom quarks and tau leptons) and low-energy precision tests involving first- and second-generation particles. The investigations of this project are connected with Subproject #2.<br />
<br />
''Subproject #2: SMEFT & magnetic moment of the muon''<br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU)<br />
<br />
The magnetic moment of the muon appears to differ from the Standard Model expectations by a large amount, well beyond the known experimental and theoretical uncertainties. Recent experiments have only strengthened the significance of this anomaly. In this project, the students will investigate the feasibility of implementing the measurement of the magnetic moment of the muon into a global SMEFT analysis, by exploiting recently provided calculations. Special attention will be devoted to the flavour assumptions required to consistently match this measurement with the LHC data, also at the light of the connection with Subproject #1. The SMEFiT analysis framework will be used to connect the g-2 data with high-energy LHC measurements.<br />
<br />
''Subproject #3: CP Violation and low-energy precision experiments''<br />
<br />
Most analyses of LHC data are performed under the assumption that CP symmetry (charge conjugation + parity, essentially the symmetry between particles and anti-particles) is conserved. More recent analyses attempt to also measure possible new sources of CP violation in SMEFT operators in the Higgs and top sector. <br />
<br />
''Subproject #3a: CP Violation and low-energy precision experiments''<br />
<br />
Daily supervisors: Jordy de Vries (UvA), Juan Rojo (VU)<br />
<br />
Low-energy precision experiments can also set stringent constraints on new mechanisms of CP violation. In this project you will try to combine high- and low-energy data to put CP symmetry to the test. <br />
<br />
''Subproject #3b: CP Violation and flavour physics experiments''<br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU)<br />
<br />
Besides low-energy precision experiments, also B-meson decays are excellent probes of CP violation. Unlike most low-energy experiments, this allows us to probe CP violation in the third generation. In this project you will link constraints on CP violation at high-energy to those from B meson decays. <br />
<br />
''Subproject #4: SMEFT & optimal observables'' <br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU), Tommaso Giani (VU & Nikhef)<br />
<br />
In full generality, the number of operators in SMEFT spans a very large parameter space. These parameters are constrained by experimental inputs from ATLAS and CMS, depending on the precise parameters these constraints may be more or less stringent. In order to fully exploit the whole parameters space in SMEFT, it is necessary to devise statistically optimal observables that have a large constraining power. In this project, we will define such observables. This project has a strong computational / machine learning component and may involve simulations based on tools such as MadGraph and Pythia8.<br />
<br />
Contacts:<br />
<br />
Juan Rojo (VU Amsterdam & Nikhef): j.rojo at vu.nl<br />
<br />
Keri Vos (UM & Nikhef): k.vos at maastrichtuniversity.nl <br />
<br />
Jordy de Vries (UvA & Nikhef): j.devries4 at uva.nl<br />
<br />
== Bachelor Projects 2021 ==<br />
=== Dark Matter ===<br />
<br />
==== XAMS ====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso.<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with recently upgraded hardware to test a novel concept for UV light detection. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complete the first measurements with our upgraded setup.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== XENONnT reconstruction software ====<br />
The XENONnT experiment becomes operational during 2021. While the hwardware is finished we keep on developing and perfecting our reconstruction software. For this project we are looking for a student with a keen interest in and talent for writing physics based event reconstruction software (we use python). Specifically we have an idea to improve the localization of events inside the XENONnT for which proto-type software exists. The proto-type software needs to be implemented in the XENONnT reconstruction framework and subsequently it needs to be validated on the first data from the experiment. The final goal of the project is to deliver the reconstruction software to the collaboration that will be used during teh full lifetime of the experiment.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Backgrounds in Radioactive Decay Measurements ====<br />
At Nikhef, the XENON group has a working setup, continuously monitoring the<br />
radioactive decay of Cobalt-60, Caesium-137 and Titanium-44. This beautiful setup is<br />
however not shielded perfectly; it is still vulnerable to background radioactivity. Our<br />
current way of working around this background radiation is to subtract it from our<br />
waveforms. You as a BSc student could help us hands-on and with analyses:<br />
together, we can disassemble the setup, measure background spectra and<br />
implement this in the data analysis. You can use all the data to validate the<br />
lifetime of our isotopes!<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Detection of scintillation light from liquid noble gasses ====<br />
<br />
The liquid form of the noble gases argon and xenon is a popular target material for neutrino and dark matter detectors. The scintillation light from noble gases is in the vacuum UV spectral region. Air and many materials used for optics studies are not transparent to these photons. Measurements of the optical properties of detector materials, such as their reflectivity for example, thus have to be performed with dedicated VUV optics and in vacuum. Additionally, to reproduce the conditions in the detectors, the samples must be cooled to cryogenic temperatures. In this BSc project, you will design, using professional hardware design software, a vacuum chamber to hold the detector materials whose optical properties are to be investigated, as well as the cooling system and photon detectors. You will learn about material requirements for rare event search detectors, vacuum instrumentation, vacuum UV optics including monochromators and spectrometers, and single-photon sensors.<br />
<br />
Supervisors: T. Pollmann (t.pollmann_at_nikhef.nl)<br />
<br />
=== Detector R&D ===<br />
<br />
==== Characterization of the new ultrathin ALPIDE monolithic active pixel sensor ====<br />
At the Large Hadron Collider at CERN, major upgrades of experiments take place in the long shutdown years where particle collisions are paused. The ALICE inner tracking system (ITS) 2, the part of the ALICE experiment closest to the beam pipe, is currently being installed at CERN. This detector makes use of ultra-lightweight monolithic active pixel sensors, the first to use this technology at particle colliders after the STAR experiment at RHIC in Brookhaven. These very thin pixel detectors have a low power consumption, result in very little material in the detector, and still have optimal timing and resolution -- and are a promising technology for future experiments. To characterize the performance of these sensors, you will learn to set up experiments, carry out measurements, and analyze data using various instruments available in the detector R&D lab at Nikhef. This could lead to novel insights of monolithic active pixel sensors. It is also possible to do measurements from home using data from the first test beams with bent (yes, with a curvature!) ALPIDE sensors. You will work in an international, stimulating research environment in the detector R&D group at Nikhef at the forefront of silicon detector technologies for high energy physics. ''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
==== Simulation of 3D silicon sensors ====<br />
<br />
For the upgrade of the vertex detector of the LHCb experiment novel silicon pixel detectors have to be developed that can register the passing particles with a time precision of tens of picoseconds. Given the harsh radiation environment very close to the LHCb interaction point only a limited number of technologies can be applied. One of the most promising technologies are the so-called 3D sensors whose readout electrodes are pillars that are placed into the sensor perpendicular to the surface; this in contrast to ’standard’ planar silicon sensors where the pixel electrodes are at the surface, similar to the camera in your smartphone. To understand the time response of these 3D sensors, simulations with TCAD software have to be performed and the results will be compared to measured data. These simulations involve the creation/adaptation of the 3D structures of the model, optimising the simulation speed, and analysing the signals as function voltage, track impact point and deposited charge. If time and Covid regulations permit, gaining some hands-on experience with such 3D sensors in the R&D labs at Nikhef is possible. ''Contacts: [mailto:martinb@nikhef.nl Martin van Beuzekom] [mailto:k.heijhoff@cern.ch Kevin Heijhoff] ''<br />
<br />
<br />
=== Theory ===<br />
<br />
==== Standard Model Effective Field Theory analysis of Z+dijet production ====<br />
The goal of this project is to study the effect of higher dimensional operators from the Standard Model Effective Field Theory in Z-boson production measured at LHC. The ATLAS collaboration has just reported in 2020 the measurement of Z production alongside with a pair of jets, based on the full Run II luminosity. In this project we aim to study the effect of dimension six SMEFT operators on the signal (EW-induced) and/or background (QCD-induced), finding which is the kinematic variable that maximises the possible effect of beyond the SM operators and thus may provide the best constraint on New Physics. The outcome of this project may be the first step of the inclusion of Vector production in a global SMEFT fit. <br />
<br />
References: https://arxiv.org/pdf/2006.15458.pdf, https://www.hepdata.net/record/ins1803608<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Maximum precision on new physics through information theory ====<br />
One way to look for physics beyond the standard model is through the framework of effective field theory. In this framework, deviations from the standard model are described by a set of continuous parameters. Finding constraints on these parameters might point to the discovery of new physics. With the large number of LHC experiments we currently face, we want to be able to quantify the maximum knowledge that (future) experiments can provide on new physics parameters. In this project, the student will study and quantify the maximum information that is contained in particle physics experiments through information theory. The central object of study will be the Fisher information matrix. The idea is to work with a simple toy experiment that describes Higgs physics and compute its associated Fisher information matrix to quantify the optimal bounds on new physics. The project will start with studying central objects from statistics and information theory. Later, we will apply these to open problems in particle physics.<br />
<br />
Reference: https://arxiv.org/pdf/1612.05261.pdf<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Seesaw mechanism and neutrino mass ==== <br />
Many unsolved questions in particle physics are related to the nature of the neutrino and its mass generation. The goal of this theoretical project is to understand and review one of the possible candidate theories that describe how neutrinos mix and get massive, namely the Seesaw mechanism. Among the many possible Seesaw mechanisms that can generate new phenomenology including lepton number non-conservation, the student will focus on one minimal model to understand the key processes that are currently used to probe the validity of the given theory. <br />
<br />
References: https://cds.cern.ch/record/408119/files/9911364.pdf, https://arxiv.org/pdf/1711.02180.pdf<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Mixing of sterile neutrinos ====<br />
<br />
Neutrino oscillation experiments demonstrate that neutrinos are massive particles. However, the mass mechanism of neutrinos is unknown. A<br />
minimal solution requires the existence of so-called sterile neutrinos: neutrinos that are even more elusive than ordinary neutrinos. <br />
We will investigate how to parametrize the matrix that describes the mixing between ordinary and sterile neutrinos. We will then use this<br />
to calculate how sterile neutrinos induce rare nuclear decays and determine the sensitivity of ongoing experiments to observe sterile<br />
neutrinos.<br />
<br />
Supervisor: Jordy de Vries (devries.jordy at gmail.com)<br />
<br />
<br />
=== KM3NeT ===<br />
<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
==== Data analysis of the first deployed KM3NeT detection lines ====<br />
<br />
First detection lines of the KM3NeT neutrino telescope have been deployed<br />
in the Mediterranean Sea, and a first data set is available. The lines consist<br />
of light-sensitive detectors that record the time of arrival of photons<br />
produced by relativistic particles in the deep sea, and their number.<br />
In this project we will study the first data to separate various components:<br />
photons from potassium decay, bioluminesence, sparks in the photomultipliers,<br />
downgoing muons from cosmic rays, and first neutrinos.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben (paul.de.jong at nikhef.nl)<br />
<br />
==== Neutrino oscillation measurements with the KM3NeT neutrino telescope ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope currently under construction<br />
will be able to measure the oscillations of neutrinos produced in interactions<br />
of cosmic rays with the earth atmosphere. Fundamental neutrino properties can<br />
be deduced from these oscillations measurements, in particular the so-called<br />
mass hierarchy of neutrinos. In this project we will simulate the ORCA measurements<br />
of neutrino oscillations, and study the dependence of the sensitivity on<br />
experimental uncertainties, such as energy resolution and neutrino flavour<br />
identification, and theoretical uncertainties, such as the atmospheric neutrino<br />
flux and neutrino cross sections. The results will help ORCA to identify<br />
the main sources of uncertainty, and therefore to actively try to reduce these<br />
and improve the final measurement.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
==== Performance Studies of ORCA for Dark Matter Detection ====<br />
<br />
The interactions of neutrinos in KM3NeT-ORCA give different signatures which are categorised as track and shower events. This project involves the studies of muon, electron and tau neutrino interactions for the reconstruction performance of ORCA. Efficient reconstruction of such signals is important for Dark Matter searches in the low-mass regime. We will work on understanding the detector performance, e.g. effective acceptance, energy and angular resolution, with different configurations of the detector setup. The result of this study will be very useful to improve the sensitivity of the experiment for Dark Matter detection and its possible location. The student will have the opportunity to work closely with KM3NeT members at Nikhef and gain skills of analyzing data. <br />
<br />
Supervisors: Suzan Basegmez du Pree, Aart Heijboer (s.basegmez.du.pree at nikhef.nl)<br />
<br />
==== Study of Optical Properties of Sea Water using Hit Coincidences in MC Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
By studying coincidences of L1 hits between neighbouring DOMs, for various Monte Carlo (MC) data sets with different sea water optical properties such as scattering and absorption coefficients, in this project we try to figure out if and how well we can quantify optical sea water properties by studying L1 hit coincidences in real KM3NeT data.<br />
<br />
Supervisor: Daan van Eijk (dveijk at nikhef.nl)<br />
<br />
==== Determination of Inter-DOM Distances using Hit Coincidences in KM3NeT Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
The number of L1 hit coincidences from atmospheric muons between neighbouring DOMs on a DU is expected to decrease exponentially. By fitting the observed number of L1 hit coincidences between neighbouring DOMs in real data to the expected exponential decay, in this project we study how accurately we can determine the distances between DOMs on a single DU. In addition, we try to determine the distances between DUs by looking for L1 hit coincidences between DOMs on neighbouring DUs.<br />
<br />
Supervisor: Daan van Eijk (dveijk at nikhef.nl)<br />
<br />
<br />
=== ATLAS ===<br />
<br />
==== The Higgs boson life-time ====<br />
<br />
The Higgs particle does not have eternal life. The Standard Model (SM) predicts that it decays into other particles and as these couplings are fixed we can predict its life-time with very high precision. Determining this life-time is a crucial test for the Standard Model. If the Higgs boson life-time is shorter that we expect this could mean that the Higgs boson could decay into non-SM particles. In this project we investigate a) how we can identify Higgs particles in the detector and b) how we plan to use quantum-interference to get a handle on the Higgs boson's life-time. <br />
<br />
Supervisor: Wouter Verkerke (verkerke_at_nikhef.nl)<br />
<br />
==== The Higgs boson decaying to photons ====<br />
<br />
One of the main channels used to analyse the properties of the Higgs boson is when the Higgs boson decays into two photons. The crucial building block in this analysis is our ability to reconstruct the energy and the direction of the photons in the ATLAS detector and in this project we will revisit the photon reconstruction. We will start by studying simulations and learning about photon reconstruction in general. Then our goal is to determine the energy and position resolution of photons in the ATLAS detector and see if we can exploit our knowledge on the photon resolution to get an (improved) estimate of the Higgs boson mass. For the analysis we will use the '''real data from the LHC''' - the ATLAS open data project.<br />
<br />
Supervisor: Ashley McDougall and Ivo van Vulpen (Ivo.van.Vulpen_at_nikhef.nl)<br />
<br />
<br />
=== LHCb (1) ===<br />
<br />
One of the most fascinating mysteries in physics today is: how is it possible that universe is filled with matter? If the Big Bang produced equal amounts of matter and antimatter, we still do not understand the mechanism that lead to the excess of matter over antimatter that we observe today.<br />
<br />
One interesting feature of some particles is that they can transform themselves into their antiparticles, then back to particle, and so forth, in an oscillatory way until they finally decay. In particular, beauty mesons (B) can oscillate into their antiparticle (B ̄). The parameters of this oscillation, such as amplitude, frequency and phase, are calculable mathematically: predictions for it are available in the standard model (SM) of particle physics. But the oscillations according to the SM alone would not lead to the imbalance of matter in the universe – we still need to find a new type of physics that may be able to explain it.<br />
<br />
In this context, it is very important to measure B oscillations in the laboratory, and compare these observations with the expectations from the SM. Are the experimental data in good agreement with the SM, as we expect? If the aswer is not, i.e. if there are features of the oscillation that we do not understand well, then we may be observing “new physics”. In other words, the data may reveal a new mechanism that generates a different matter-antimatter balance than predicted by the SM, that may potentially solve the puzzle.<br />
<br />
The LHCb experiment at CERN is dedicated to such studies: LHCb detectors are placed in a region along the LHC collider beamline, where a large number of B mesons are produced, arising from the proton-proton collision data from the LHC collider. Looking at the LHCb data we can obtain large samples of B mesons, and observe their oscillations.<br />
In this project we will learn how to select a sample of B mesons out of the data taken with the LHCb detector, measure the parameters that govern their oscillation and compare them with the SM.<br />
<br />
For more information, please contact Mara Soares (msoares_at_nikhef.nl).<br />
<br />
== Bachelor Projects 2020 ==<br />
<br />
<br />
=== Dark Matter ===<br />
<br />
==== XAMS ====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso.<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source and liquid scintillatorneutron detector we have acquired for the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study of neutron transport in xenon.<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Backgrounds in Radioactive Decay Measurements ====<br />
At Nikhef, the XENON group has a working setup, continuously monitoring the<br />
radioactive decay of Cobalt-60, Caesium-137 and Titanium-44. This beautiful setup is<br />
however not shielded perfectly; it is still vulnerable to background radioactivity. Our<br />
current way of working around this background radiation is to subtract it from our<br />
waveforms. You as a BSc student could help us hands-on and with analyses:<br />
together, we can disassemble the setup, measure background spectra and<br />
implement this in the data analysis. You can use all the data to validate the<br />
lifetime of our isotopes!<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
=== ATLAS ===<br />
<br />
==== Project ATLAS-ITk ====<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
==== The Most Energetic Higgs Boson ====<br />
A common approach to search for physics beyond the standard model is by searching for the direct production of new particles. Alternatively, indirect quantum effects on the production of known particles -such as the Higgs Boson- could reveal the first cracks in the theory. Processes with high energy transfer are of particular potential since possible deviations are expected to increase with the square of the involved energy scale. Using the entire data-set collected by the ATLAS experiment at CERN during the four years of the LHC’s Run 2, a proof-of-principle analysis, targeting transverse momenta of the above 400 GeV, has been developed by Nikhef researchers. The first results of this Higgs boson study are expected to be published this year and this project aims to develop refinements of the analysis techniques. We will investigate the usage of sophisticated machine learning tools such as artificial neural networks, the search for new variables that can help discriminating the signal from its background, revisiting the analysis categorisation and improving the reconstruction techniques at these extreme momenta. Supervisors: Brian Moser and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs: The Next Generation ====<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks has been developed by Nikhef researchers and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays), advanced analysis techiques (using deep learning methods) and expanding the theory interpretation. Another opportunity would be the development of a new statistical combination with various independent searches, which could significantly improve the discovery potential. Supervisors: Marko Stamenkovic and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs interferentie ====<br />
In 2012 hebben het ATLAS en het CMS experiment het Higgs deeltje gevonden. Inmiddels zijn we het Higgs boson aan het bestuderen, hoe gedraagt het zich precies, bestaan er meer soorten Higgs bosonen of is er echt maar eentje van? In dit project leer je hoe we een Higgs boson kunnen herkennen in de detector en gaan we kijken naar hoe de signalen veranderen als er meer Higgs bosonen bestaan of misschien wel andere exotische nieuwe deeltjes. <br />
Dit doen we door gebruik te maken van quantum interferentie wat plaats vindt tussen het Higgs boson en achtergrondprocessen. Hoe dit precies werkt leer je in het project. Supervisor: Hella Snoek (h.snoek_at_nikhef.nl)<br />
<br />
=== B-Physics - LHCb ===<br />
<br />
==== Time dependent CP violation ====<br />
The LHCb experiment studies CP violation withB-meson decays.<br />
The project focusses on the measurement of the unitarity angle gamma using decays of the Bs mesons to Ds K.<br />
Supervisors: Sevda Esen & Michele Veronesi<br />
<br />
==== Machine learning ====<br />
Machine learning has proven to be an indispensable tool in the selection of interesting events in high energy physics. Such technologies will become increasingly important as detector upgrades are introduced and data rates increase by orders of magnitude. HEPDrone is a toolkit to enable the creation of a drone classifier from any machine learning classifier, such that different classifiers may be standardised into a single form and executed in parallel. A detailed evaluation of the performance of different drone models in the real production environment of LHCb will give the collaboration a complete idea of not only the advantages of the drone model, but also the limits of drone complexity given the available computing resources.<br />
Requirements: Advanced python and Advanced C++<br />
Supervisor: Sean Benson<br />
<br />
==== LHCb simulations of physics beyond the Standard Model ====<br />
This project is of relatively theoretical and computing nature and performs simulation studies for physics beyond the Standard Model in the context of long lived particles. It is related to test the sensitivity of the LHCb experiment to detect specific signals of physics beyond the Standard Model.<br />
supervisor: Carlos Vazquez Sierra<br />
<br />
=== Detector R&D ===<br />
<br />
==== Fast timing detectoren ====<br />
Op dit moment maken we veel gebruik van silicon detectoren in onze deeltjes experimenten. Deze zijn gevoelig voor geladen deeltjes en zijn bij uitstek geschikt om de paden vast te leggen die de deeltjes maken die in de botsingen worden gemaakt. Bijvoorbeeld in de Atlas en LHCb experimenten worden tientallen tot honderden deeltjes gemaakt bij elk botsingsgebeurtenis (event) die met 40MHz plaatsvinden. Voor toekomstige deeltjesdetectoren willen we niet alleen het traject vastleggen maar ook met grote precisie een tijdsmeting toevoegen. We hebben hiervoor dus nieuwe detectoren nodig die behalve met een hele hoge snelheid en efficientie de posities van de langsvliegende deeltjes kunnen vastleggen, maar hier ook een zeer nauwkeurige tijdsmeting (in orde van picosecondes) aan kunnen toevoegen. We hebben met verschillende detectoren metingen gedaan, in testbundels op CERN, maar ook in het lab op Nikhef kunnen we metingen doen. In dit project ga je samen met het fast-timing detectoren team op het Nikhef metingen verrichten en de resultaten hiervan bekijken. Contact: Hella Snoek (h.snoek@nikhef.nl)<br />
<br />
==== Muon tomography ====<br />
In this project we are not looking for where cosmic rays come from. We are looking for what we can use them for instead. The muons in cosmic rays can be used to ‘probe’ massive objects. Muons are short lived particles that carry the same charge as electrons, have a high penetrating power and can be detected relatively easy. It is possible to reconstruct a density distribution within an object by measuring muon scattering and absorption. In this context the objects may be freight containers, buildings, melting furnaces, etc… <br />
<br />
Systems that scan objects through the use of muons are often large (objects often need to be enclosed by the system) and complex. The question we want to answer is: Can we develop a smaller, simpler and cheaper system for muon tomography? <br />
<br />
A method to detect muons is by using a material that scintillates (emits light) when hit by an ionising particle. When this light emission is prompt after the passage of the muon, timing information of the light can be used to reconstruct the path of the muon.<br />
In this experiment we make a muon tracker based on two sheets of scintillating material and photo multiplier tubes (PMTs). Photo multiplier tubes are fast responding and very sensitive light detectors (capable of detecting single photons).<br />
<br />
The big question is: How well does this system perform?<br />
<br />
Currently a set-up is being build. You have a lot of freedom to choose a focus in this project (theory, simulation, hardware, or a combination of those).<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Spectral X-ray imaging - Looking at colours the eyes can't see ====<br />
When a conventional X-ray image is made to analyse the composition of a sample, or to perform a medical examination on a patient, one acquires an image that only shows intensities. One obtains a ‘black and white’ image. Most of the information carried by the photon energy is lost. Lacking spectral information can result in an ambiguity between material composition and amount of material in the sample. If the X-ray intensity as a function of the energy can be measured (i.e. a ‘colour’ X-ray image) more information can be obtained from a sample. This translates to less required dose and/or to a better understanding of the sample that is being investigated. For example, two fields that can benefit from spectral X-ray imaging are mammography and real time CT.<br />
<br />
X-ray detectors based on Medipix/Timepix pixel chips have spectral resolving capabilities and can be used to make polychromatic X-ray images. Medipix and Timepix chips have branched from pixel chips developed for detectors for high energy physics collider experiments.<br />
<br />
Some themes that students can work on: <br />
<br />
- Optimising methods to acquire spectral X-ray images.<br />
<br />
- Determining how much existing applications benefit from spectral X-ray imaging and looking for potential new applications.<br />
<br />
- Characterising, calibrating, optimising X-ray imaging detector systems.<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Holographic emitter ====<br />
A difficulty in generating holograms (based on the interference of light) is the required dense spatial light field sampling. One would need pixels of less than 200 nanometer. With larger pixels artefacts occur due to spatial under sampling. A pixel pitch of 200 nm or less is difficult, if not, impossible, to achieve, especially for larger areas. Another challenge is the massive amount of computing power that is required to control such a dense pixel matrix. <br />
<br />
A new holographic projection method has been developed that reduces under sampling artefacts, regardless of spatial sample density. The trick is to create 'pixels' at random but known positions, resulting in an array that lacks any spatial periodicity. As a result a holographic emitter can be built with a significantly lower sample density and less required computing power. This could bring holography in reach for many applications like display, lithography, 3D printing, metrology, etc...<br />
<br />
The big question: How does the performance of the holographic emitter depend on sample density and sample positions?<br />
<br />
The aspects of a holographic image we are interested in are:<br />
<br />
- Noise<br />
<br />
- Contrast<br />
<br />
- Suppression of under sampling artefacts<br />
<br />
- Resolution <br />
<br />
For this project we are building a proof of concept holographic emitter. This set-up will be used to verify simulation results (and to make some cool holograms of course). <br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
=== KM3NeT ===<br />
<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
==== Data analysis of the first deployed KM3NeT detection lines ====<br />
<br />
First detection lines of the KM3NeT neutrino telescope have been deployed<br />
in the Mediterranean Sea, and a first data set is available. The lines consist<br />
of light-sensitive detectors that record the time of arrival of photons<br />
produced by relativistic particles in the deep sea, and their number.<br />
In this project we will study the first data to separate various components:<br />
photons from potassium decay, bioluminesence, sparks in the photomultipliers,<br />
downgoing muons from cosmic rays, and perhaps first neutrinos.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Neutrino oscillation measurements with the KM3NeT neutrino telescope ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope currently under construction<br />
will be able to measure the oscillations of neutrinos produced in interactions<br />
of cosmic rays with the earth atmosphere. Fundamental neutrino properties can<br />
be deduced from these oscillations measurements, in particular the so-called<br />
mass hierarchy of neutrinos. In this project we will simulate the ORCA measurements<br />
of neutrino oscillations, and study the dependence of the sensitivity on<br />
experimental uncertainties, such as energy resolution and neutrino flavour<br />
identification, and theoretical uncertainties, such as the atmospheric neutrino<br />
flux and neutrino cross sections. The results will help ORCA to identify<br />
the main sources of uncertainty, and therefore to actively try to reduce these<br />
and improve the final measurement.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Performance Studies of ORCA for Dark Matter Detection ====<br />
<br />
The interactions of neutrinos in KM3NeT-ORCA give different signatures which are categorised as track and shower events. This project involves the studies of muon, electron and tau neutrino interactions for the reconstruction performance of ORCA. Efficient reconstruction of such signals is important for Dark Matter searches in the low-mass regime. We will work on understanding the detector performance, e.g. effective acceptance, energy and angular resolution, with different configurations of the detector setup. The result of this study will be very useful to improve the sensitivity of the experiment for Dark Matter detection and its possible location. The student will have the opportunity to work closely with KM3NeT members at Nikhef and gain skills of analyzing data. <br />
<br />
Supervisors: Suzan Basegmez du Pree, Aart Heijboer<br />
<br />
==== A search for periodic sources in Antares data ====<br />
<br />
The Antares deep-sea neutrino telescope has been operated for more then ten years. A search for periodic sources is proposed by applying a fast Fourier transformation (FFT) analysis on the available low-level data. This search will be combined with a (literature) study of pulsars which are thought to emit neutrinos.<br />
<br />
Supervisor: Maarten de Jong<br />
<br />
==== Study of Optical Properties of Sea Water using Hit Coincidences in MC Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
By studying coincidences of L1 hits between neighbouring DOMs, for various Monte Carlo (MC) data sets with different sea water optical properties such as scattering and absorption coefficients, in this project we try to figure out if and how well we can quantify optical sea water properties by studying L1 hit coincidences in real KM3NeT data.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
==== Determination of Inter-DOM Distances using Hit Coincidences in KM3NeT Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
The number of L1 hit coincidences from atmospheric muons between neighbouring DOMs on a DU is expected to decrease exponentially. By fitting the observed number of L1 hit coincidences between neighbouring DOMs in real data to the expected exponential decay, in this project we study how accurately we can determine the distances between DOMs on a single DU. In addition, we try to determine the distances between DUs by looking for L1 hit coincidences between DOMs on neighbouring DUs.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
=== VIRGO ===<br />
<br />
The Advanced LIGO and Advanced Virgo interferometers have recently observed gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results.<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Frank Linde (frank.linde_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
<br><br><br><br />
<br />
== Bachelor Projects 2017 ==<br />
<br />
=== Extreme Astronomy – Preparing for CTA, the Next-Generation Gamma-Ray Observatory ===<br />
<br />
The Cherenkov Telescope Array (CTA) is a planned facility for measuring gamma rays from space covering more than four orders of magnitude in energy, up to energies exceeding 100 TeV. CTA employs the imaging atmospheric Cherenkov technique to measure properties of cosmic gamma rays. This technique is based on measuring Cherenkov light emitted during the development of a gamma-ray air shower. CTA will be built at two experimental sites, one in the Northern, one in the Southern hemisphere, and will consist of up to 100 telescopes. It represents a major leap forward in sensitivity and precision for gamma-ray astronomy, and will allow us to explore very-high-energy processes of the extreme Universe at an unprecedented level.<br />
<br />
Two projects for students are available at the CTA group of UvA in the field of optical and photonic R&D contributing to the starting phase of CTA. For the first project the student will conduct measurements to characterise novel kinds of single-photon detectors, referred to as silicon photomultipliers, and evaluate different types of these sensors for their use for CTA. For the second project the student will develop and test an imaging system making use of a liquid crystal display. This flexible light source will be able to mimic images from different light sources of the night sky as seen by cameras of CTA, for instance gamma-ray air showers or stars, and will be used for camera tests and calibration.<br />
<br />
<br />
Supervisors: David Berge, Maurice Stephan (postdoc)<br />
<br />
=== Dark Matter ===<br />
<br />
<!--<br />
==== XENON1T - the world's most sensitive dark matter detector ====<br />
<br />
Finding the mysterious dark matter particles is one of the most challenging enterprises in physics today. Soon we will get first data from the world's most sensitive dark matter detector yet: the XENON1T experiment.<br />
<br />
The first goal of this project is to understand why dak matter is necessary to understand the universe, and how we could detect it with XENON1T. Then, you can contribute to our group's efforts preparing for <br />
and analyzing the XENON1T data by, for example: examining XENON1T's calibration signals to check for problems in the experiment, testing our data analysis software with simulated dark matter signals, or studying the physics behind XENON1T's detection process to learn how to better distinguish dark matter signals from backgrounds. For data analyis, experience with or willingness to learn programming in python is essential.<br />
<br />
<br />
Supervisors: M.P. Decowski & J. Aalbers --><br />
<br />
==== Neutrinoless double beta decay sensitivity study in future dark matter detectors ====<br />
<br />
The discovery of neutrino oscillation (Nobel Physics 2015) means that neutrinos have mass. We already know that their masses are tiny, more than one million times smaller than the next-lightest particle in the standard model, the electron. This raises the question if the mass-generation mechanism is the same for neutrinos as it is for the other subatomic particles. In particular, since neutrinos are electrically neutral, they could be their own anti-particles - we call these types of particles Majorana. The only practical way to discover if neutrinos are Majorana is through the search of an extremely rare radioactive decay called neutrinoless double beta decay (0n2b). A few isotopes are candidates for this process, among them Xe-136. The natural abundance of Xe-136 in natural xenon is about 9%, and this gives the opportunity to look for a 0n2b signal in xenon-based dark matter detectors like XENON1T and the future XENONnT and DARWIN detectors. <br />
<br />
We are looking for a student interested in doing a sensitivity study for 0n2b in XENONnT and the DARWIN experiments. The first goal will be to understand the physics addressed in neutrinoless double beta decay. Then the student will inventory possible backgrounds for the signal, use a (controversial) claim of a 0n2b signal as a benchmark and finally obtain the sensitivity of these future detectors. The work will involve simulations and analysis, building on an existing framework developed in our group. <br />
<br />
Supervisors: M.P. Decowski & A. Tiseni<br />
<br />
==== Shaking Dark Matter detectors ====<br />
<br />
Our XENON1T detector is built in the lab underneath the Gran Sasso mountains in central Italy. The lab is very well suited for low-background experiments due to the 1.5km of rock overburden. <br />
However, as you may know, cental Italy has been plagued by earthqaukes over the past decade, with the most recentones occurring in January 2017. We need a BSc student to investigate the <br />
details of such earthquakes in our underground lab. What are the magnitdues by which stuff is moving underground? What are the accelerations? What is the potential effect on our experimental<br />
setup? What would ahppen if an earthquake happens much closer to our lab? Furthermore we are interested to find out whether Earthquakes can be predicted. Some papers claim that before<br />
an earthquake the radon emanating from rock increases. In our lab we measure the radon concentration as a function of time: can you find a correlation between the measurements and recent <br />
earthquakes?<br />
<br />
If you are interested in finding out more about earthquakes, please contact M.P. Decowski or A.P. Colijn<br />
<br />
==== XAMS - a baby dark matter detector ====<br />
<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso<br />
we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector<br />
are identical to its big sibling in Gran Sasso.<br />
<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source we have acquired<br />
before the start of the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project<br />
will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study<br />
of neutron transport in xenon.<br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
==== Radon is bad for Dark Matter ====<br />
<br />
Radon is the dominant background for xenon based dark matter detectors, like the XENON1T experiment. In our lab at Nikhef we are investigating ways to reduce or eliminate the effect of radon<br />
on our sensitivity. For our lab setup XAMS we have designed and constructed a radon detector, that can be used in xenon systems at high-pressure. This completely new detector<br />
is now waiting for a BSc student to fully chracterize and use it. During this project you will first study the effect that radon contaminations have on dark matter detectors, then you will start working to<br />
understand our new radon detector in detail. You will learn howto use a radioactive source to calibrate the detector: this is something which is not easy and has not been done before in our lab. <br />
If you manage to succesfully calibrate the detector, we then want to incorporate it into our lab xenon system at Nikhef and maybe at some later stage in the real XENON1T detector!<br />
<br />
The profile of the student to work on this project is broad. I expect a good theoretical knowledge in order to quickly get upto speed with understanding dark mater detectors, and in addition I <br />
need 'lab-creativity' in order to develop methods for calibrating the new detector. If a good method is developed, it will be used for many years by the Nikhef dark matter group and beyond. <br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
=== ATLAS ===<br />
<br />
<br />
==== ATLAS (1): Searching for new physics with the Higgs and W bosons ====<br />
<br />
The strength of the Higgs interactions with electroweak bosons are precisely defined in the<br />
Standard Model. Therefore they are sensitive probes of the mechanism of electroweak symmetry<br />
breaking and enable searches for new physics beyond the SM. With the data collected by the ATLAS<br />
experiment in years 2015-2016 we plan to measure separately the Higgs coupling to<br />
longitudinally and transversely polarised W bosons in a process of weak boson fusion. To<br />
maximise experimental sensitivity we are developing techniques to separate the signal from<br />
background processes. You will take part in investigating possible improvements from<br />
reconstructing events in reference frames boosted with respect to the detector. During the<br />
project you will learn modern experimental analysis techniques. This project is a part of Vector<br />
Boson Scattering Coordination and Action Network (VBSCan) which connects researchers studying<br />
this and related topics worldwide.<br />
<br />
Supervisors: Pamela Ferrari, Magdalena Slawinska, Bob van Eijk<br />
<br />
<br />
==== ATLAS (2): Dark-matter-motivated searches for supersymmetric particles at the LHC ====<br />
<br />
Supersymmetry, a symmetry between fermions and bosons in particle physics,<br />
may provide a particle that could be the dark matter in the universe.<br />
The observation of an excess of gamma rays originating from the centre of our<br />
galaxy could be explained in a model where supersymmetric dark matter<br />
particles annihilate each other in the galactic centre, leading to gamma rays.<br />
<br />
Given the model parameters, it should also be possible to produce such<br />
particles at the LHC, at CERN in Geneva. But it is not so easy to observe<br />
them: the signal is small, and the noise (background) is large.<br />
In this project, we will use simulations of signal and background to<br />
optimize experimental searches for such particles with the ATLAS detector,<br />
apply them to the data collected in 2015, and prepare for the new data in<br />
2016 and later.Where possible, we will explore new machine learning techniques.<br />
<br />
Supervisors: Paul de Jong, Broos Vermeulen<br />
<br />
<br />
==== ATLAS (3): Simulations / Quality tests for the ATLAS High-Luminosity LHC Upgrade ====<br />
<br />
One of the key sub-systems of the ATLAS experiment at the Large<br />
Hadron Collider (LHC) is the Inner Detector (ID), designed to provide<br />
excellent charged particles momentum and vertex resolution measurements.<br />
<br />
At Phase-2 of the LHC run, in ~2025, the operating luminosity of<br />
the collider will be increased significantly.<br />
This will imply an upgrade of all ATLAS subsystems. In particular,<br />
the ID will be fully replaced with a tracker completely made of<br />
Silicon, having higher granularity and radiation hardness.<br />
The R&D process for the new ATLAS ID is now ongoing.<br />
Different geometrical layouts are simulated and their performance is<br />
studied under different operating conditions in search for the optimal<br />
detector architecture. Also, the performance of the new<br />
Si-sensors/modules is under investigation with dedicated laboratory tests.<br />
<br />
The focus of the project could be on the simulation of the High-Luminosity LHC<br />
version of the ATLAS Inner Detector. The student will learn how a<br />
high-energy physics experiment is designed and optimized.<br />
Alternatively, if possible at that moment, the student could<br />
work on a project at the Nikhef Silicon laboratory at the test-bench for<br />
new ATLAS Si-strip detectors and participate in the quality<br />
assurance procedure for the new ATLAS Si detectors.<br />
<br />
==== ATLAS (4): Higgs productie in Run-2 van de LHC ====<br />
In de eerste run van de LHC is onder andere bij het ATLAS experiment het Higgs deeltje gevonden. Nu is de tweede run begonnen en kan het Higgs deeltje worden bevestigd. Door de verhoogde energie ziet de achtergrond er echter heel anders uit, dus is de optimalisatie van het wegsnijden van de achtergronden qua fysica anders. Voor je bachelor project kan met behulp van de ATLAS detector het Higgs deeltje in run twee komen vinden. <br />
<br />
Supervisors: Lydia Brenner, Wouter Verkerke<br />
<br />
==== ATLAS (5): De lange staart van het Higgs boson ====<br />
<br />
[[File:HiggsMassa.png |thumb|left|upright=1.25]]<br />
<br />
<br><br />
Na de ontdekking van het Higgs boson in 2012 zijn we druk bezig om te kijken of zijn eigenschappen overeenkomen met de voorspellingen van het Standaard Model. Een van de belangrijkste eigenschappen is de zogenaamde breedte van het Higgs boson. Als het Higgs boson naast de Standaard Model deeltjes ook in exotische nieuwe speeltje uit elkaar kan vallen (bijvoorbeeld donkere materie) dan zal dat ale eerste zichtbaar worden in een afwijking van de breedte tov de verwachting. We gaan in dit project uitzoeken hoe de strategie die nu gebruikt wordt (meten van de hoeveelheid Higgs bosonen met een extreem hoge massa) precies werkt en kijken of we door het toevoegen van nieuwe ideeën een verbetering kunnen aanbrengen. <br />
<br />
<br><br />
Specifiek: We gaan eerst in detail de eigenschappen bekijken van het Higgs signaal en de twee achtergronden die er het meest op lijken. Daarna gaan we op zoek naar de verschillen en een manier waarop we onze kennis daarover kunnen gebruiken om gevoeliger te worden voor het Higgs signaal.<br />
<br />
Supervisors: Hella Snoek, Ivo van Vulpen<br />
<br />
E-mail: H.Snoek_at_nikhef.nl & Ivo.van.Vulpen_at_nikhef.nl<br />
<br><br><br><br><br><br><br />
<br />
=== ATLAS (6): Project ATLAS-ITk ===<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
<br><br />
<br />
=== KM3Net ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierachy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
The first phase of the KM3NeT neutrino telescope is currently under construction, with the first two detection units operational at 3500m depth in the Mediterranean Sea, 100 km off the coast of Sicily.<br />
<br />
<br />
==== KM3NeT (1): Photon counting in KM3NeT ====<br />
<br />
The details of a neutrino interaction, such as its incoming direction and energy, determine the pattern, time and amount, of recorded photons (´hits´) by the photo-multplier tubes. The time of arrival is recorded with nanosecond accuracy and the amount of photons is encoded in the length of the pulse(time-over-threshold, ToT). Currently, only the photon arrival time and the number of photo-multipliers that record a hit are used in reconstructing event properties.<br />
In this project, the distributions of the ToT mainly originating from photons from potassium-40 decays in the sea-water and from atmospheric muons passing through the water will be studied. The goals are to investigate the properties of the ToT distributions obtained from data and simulation, in particular the dependence on the photo-multiplier efficiency and atmospheric muon flux.<br />
In this project we will be extensively using the programming language C++ to analyse the data, so a reasonable proficiency is required.<br />
<br />
Supervisors: Ronald Bruijn & Karel Melis<br />
<br />
Email: rbruijn_at_nikhef.nl<br />
<br />
<br />
<br />
<br><br><br><br />
<br />
=== VIRGO ===<br />
<br />
"It is anticipated that in the next few years, Advanced LIGO and Advanced Virgo will start observing gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results."<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Jo van den Brand (jo_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
=== LHCb ===<br />
<br />
Begeleider: Sean Benson<br />
<br />
Title: <br />
Searching for physics beyond the Standard Model with LHCb<br />
<br />
The LHCb experiment is designed to study the "The Flavour Problem" in particle physics:<br />
Why is the universe dominated by matter over antimatter? Why are there three generations of elementary particles? What is the origin of quark flavour changing interactions.<br />
<br />
To solve these riddles, LHCb performs precision measurements on b-quark particle decays.<br />
An intriguing signal has recently been observed in the decay of a B-meson to a K* and two muons: Bd→K*μμ, which does not seem to behave according to the predictions of the Standard Model<br />
In this project the bachelor student will investigate this further by studying the case where the K* particle decays to a so-called k-short particle and a π0. The observation of such a final state will provide valuable information in the search for physics beyond the Standard Model.<br />
<br />
In this ambitious project the student is expected to study both a theory on the mechanism of CP violation with B mesons, in addition to data analysis with B decays. Programming experience in python is required.<br />
<br />
The LHCb experiment at CERN analyzes the properties of B-hadrons produced in proton-proton collisions at the LHC. For projects in the LHCb group, please contact Marcel Mark (marcel.merk_at_nikhef.nl)<br />
<br />
<br />
=== LHCb (1) ===<br />
<br />
One of the most fascinating mysteries in physics today is: how is it possible that universe is filled with matter? If the Big Bang produced equal amounts of matter and antimatter, we still do not understand the mechanism that lead to the excess of matter over antimatter that we observe today.<br />
<br />
One interesting feature of some particles is that they can transform themselves into their antiparticles, then back to particle, and so forth, in an oscillatory way until they finally decay. In particular, beauty mesons (B) can oscillate into their antiparticle (B ̄). The parameters of this oscillation, such as amplitude, frequency and phase, are calculable mathematically: predictions for it are available in the standard model (SM) of particle physics. But the oscillations according to the SM alone would not lead to the imbalance of matter in the universe – we still need to find a new type of physics that may be able to explain it.<br />
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In this context, it is very important to measure B oscillations in the laboratory, and compare these observations with the expectations from the SM. Are the experimental data in good agreement with the SM, as we expect? If the aswer is not, i.e. if there are features of the oscillation that we do not understand well, then we may be observing “new physics”. In other words, the data may reveal a new mechanism that generates a different matter-antimatter balance than predicted by the SM, that may potentially solve the puzzle.<br />
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The LHCb experiment at CERN is dedicated to such studies: LHCb detectors are placed in a region along the LHC collider beamline, where a large number of B mesons are produced, arising from the proton-proton collision data from the LHC collider. Looking at the LHCb data we can obtain large samples of B mesons, and observe their oscillations.<br />
In this project we will learn how to select a sample of B mesons out of the data taken with the LHCb detector, measure the parameters that govern their oscillation and compare them with the SM.<br />
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For more information, please contact Mara Soares (msoares_at_nikhef.nl).</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Bachelor_Projects&diff=940Bachelor Projects2024-02-09T13:49:49Z<p>Rojo@nikhef.nl: </p>
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<div>== Bachelor Projects 2024 ==<br />
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=== Detector R&D ===<br />
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=== KM3NeT ===<br />
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=== Dark Matter ===<br />
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=== ATLAS ===<br />
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=== LHCb ===<br />
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=== Gravitational waves ===<br />
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=== Theory ===<br />
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====The Schiff theorem for Electric Dipole Moments (Jordy de Vries)====<br />
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Electric Dipole Moments (EDMs) of nucleons, atoms and molecules are important experimental observables to look for beyond-the-Standard-Model sources of fundamental symmetry violation. Specifically, the violation of Charge-Parity (CP) symmetry, which is present in the SM but not in sufficient amounts to explain the observed matter-antimatter asymmetry in the universe, can be probed through EDMs. To understand what EDM measurements on larger systems tell us about the fundamental physics at the elemental particle scale, and to assess what systems are most promising for EDM experiments, the Schiff theorem is essential. This theorem describes how, under certain simplifications, the EDMs of atoms and molecules vanish due to screening. In this project, you will investigate the theory behind Schiff screening, including possible violations of the theorem which lead to interesting systems with which to probe EDMs. For this project, the courses Advanced Quantum Physics & Atomic Physics are useful, but not strictly necessary.<br />
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====High-energy neutrino-nucleon interactions at the LHC with FASER (Juan Rojo, VU Amsterdam & Nikhef Theory) ====<br />
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High-energy collisions at the Large Hadron Collider (LHC) produce an unprecedented number of light particles along the beam collision axis, outside of the acceptance of existing experiments. The FASER experiment, located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, provides new opportunities to probe Standard Model (SM) processes, in particular high-energy neutrino physics, and search for physics beyond the Standard Model (BSM). In this project, the student(s) will carry out updated theoretical predictions and numerical simulations for relevant physical processes at FASER, in particular concerning neutrino production and scattering, and assess their implications for our current models of proton structure and of QCD, the quantum field theory of the strong nuclear force. The project will also involve studying the implications of these results for ultra-high-energy particle astrophysics such as at the KM3NET and AUGER experiments. For this project, having followed the elective courses "Introduction to (astro-)particle physics" and "Standard Model of Elementary Particles" is required.<br />
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''Contact: [[Mailto:j.rojo@vu.nl Juan Rojo]]''<br />
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==== Probing the proton spin with machine learning at future colliders''' (Juan Rojo, VU Amsterdam & Nikhef Theory) ====<br />
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An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions in particle physics from the nature of the Higgs boson to the origin of cosmic neutrinos. This effort requires combining an extensive experimental dataset and cutting-edge theory calculations within a machine learning framework where neural networks parametrise the underlying physical laws while minimising ad-hoc model assumptions. The upcoming Electron Ion Collider (EIC), to start taking data in 2030, will be the world's first ever polarised lepton-hadron collider and will offer a plethora of opportunities to address key open questions in our understanding of the strong nuclear force, such as the origin of the mass and the intrinsic angular momentum (spin) of hadrons and whether there exists a state of matter which is entirely dominated by gluons. In this project, the student will carry out a determination of the polarised quark and gluon substructure of the proton by means of the machine learning tools provided by the NNPDF open-source fitting framework and include projections for the impact of future EIC data on the spin content of the proton and on non-perturbative models of hadron structure. For this project, having followed the elective courses "Introduction to (astro-)particle physics" and "Standard Model of Elementary Particles" is required.<br />
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''Contact: [[Mailto:j.rojo@vu.nl Juan Rojo]]''<br />
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== Bachelor Projects 2023 ==<br />
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=== KM3NeT ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown neutrino mass hierarchy.<br />
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The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along 200-700m long vertical lines, called detection units.<br />
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==== Search for cosmic neutrinos with the first KM3NeT data ====<br />
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The KM3NeT/ARCA block is tuned for the detection of cosmic neutrinos and search for their sources. The first data of ARCA will be used to search for cosmic neutrino sources, and to search for a neutrino signal in response to external alerts for transients (gamma-ray bursts, IceCube neutrinos, gravitational wave events). Furthermore there is the opportunity to search for a neutrino signal from dark matter annihilation in the galactic halo and in dwarf spheroidal galaxies.<br />
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Supervisors: Thijs van Eeden, Jhilik Majumdar, Clara Gatius, Paul de Jong (paul.de.jong at nikhef.nl)<br />
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==== Neutrino oscillations with KM3NeT/ORCA ====<br />
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The ORCA block of the KM3NeT neutrino telescope is able to measure the oscillations of neutrinos produced in interactions of cosmic rays with the earth atmosphere. Fundamental neutrino properties can be deduced from these oscillations measurements. In this project we will use the first data of ORCA to study neutrino oscillations and fit neutrino mixing parameters and mass differences between neutrino mass states. We will study data selection, event reconstruction, and effects of systematic uncertainties on the results. <br />
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Supervisors: Bouke Jung, Paul de Jong (paul.de.jong at nikhef.nl)<br />
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==== Multi-messenger astronomy with neutrinos and radio signals ====<br />
The main goal of neutrino telescopes, such as ANTARES, KM3NeT and IceCube, is to detect cosmic neutrinos from astrophysical sources. When an interesting neutrino candidate is detected they send out a message to alert the scientific community. Other scientific instruments, like the Murchison Widefield Array (MWA) radio telescope, can then do a follow-up observation, to see if there are other messengers coming from the same source as the neutrinos. In this project you will analyse MWA data that were taken after the reception of neutrino alerts, to search for a radio source that can be associated with a neutrino source.<br />
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Supervisor: Mieke Bouwhuis (mieke.bouwhuis at nikhef.nl)<br />
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=== Dark Matter ===<br />
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==== Investigating muon spallation backgrounds in KamLAND neutrino detector ====<br />
The KamLAND neutrino detector in Japan is designed to measure among other things neutrinoless double beta decay, an important process in particle physics that, should it be observed, would confirm that neutrinos might be their own antiparticles. However, the lack of detection of this process can be blamed on various backgrounds, one of which is muon spallation. Only recently did we start studying these spallation backgrounds in detail and we are looking for a student that has a strong interest in programming, simulations and data analysis to help the progression. The goal of this project is to allow for a better understanding of the behaviour of spallation events and to contribute to the simulation of the background that will be used in KamLAND, as well as future neutrino and dark matter experiments.<br />
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Supervisors: Kelly Weerman and Patrick Decowski (decowski@nikhef.nl)<br />
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==== First measurements with new VULCAN detectors ====<br />
At Nikhef we have a brand new experiment designed to measure the reflectance, transmission, and fluorescence properties of materials at vacuum ultraviolet (VUV) wavelengths. The materials to be studied are used to construct the XENONnT dark matter and the DUNE neutrino detectors. <br />
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In this project, you will calibrate the characteristics of the VUV lamp and of the SiPM photon sensors used in VULCAN. Lab work at the Nikhef building will be a main part of the project, but you will also analyse the data you collect using modern analysis tools.<br />
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You will gain experience with VUV optics, vacuum systems, single-photon sensors, and data analysis using Python and/or C++ tools.<br />
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Supervisors: Marjolein van Nuland and Tina Pollmann (t.pollmann@nikhef.nl)<br />
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==== The XAMS dark matter R&D setup at Nikhef ====<br />
The Nikhef dark matter group has a small version of the XENONnT dark matter detector in our Nikhef lab. With this detector we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENONnT experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso. We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with recently upgraded hardware to test a novel concept for UV light detection. The goal of this project will be to do the first measurements and analyze the data. Depending on the progress with the hardware we intend to complete the first measurements with our upgraded setup.<br />
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Supervisors: Patrick Decowski (decowski@nikhef.nl) and A.P. Colijn (colijn@nikhef.nl)<br />
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==== Reconstruction software for the XENONnT dark matter experiment ====<br />
The XENONnT dark matter experiment became operational in 2021. The experiment is in the Gran Sasso underground laboratory in Italy and the hardware is not being touched. However, we keep on developing and perfecting our reconstruction software. For this project we are looking for a student with a keen interest in and talent for writing physics-based event reconstruction software (we use python). Specifically we have an idea to improve the localization of events inside the XENONnT for which proto-type software exists. The proto-type software needs to be implemented in the XENONnT reconstruction framework and subsequently it needs to be validated on the first data from the experiment. The final goal of the project is to deliver the reconstruction software to the collaboration to be used during the lifetime of the experiment.<br />
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Supervisors: Patrick Decowski and A.P. Colijn (colijn@nikhef.nl)<br />
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=== ATLAS ===<br />
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==== Machine-Learning in Top-Quark physics ====<br />
As the heaviest elementary particle the top quarks plays a key role in the Standard Model. Discovered in 1995 at the Tevatron accelerator, top quarks are now abundantly produced at the Large Hadron Collider (LHC) located at the European Organization for Nuclear Research (CERN) . But do these produced top quarks behave as predicted by the Standard Model or are there signs of new physics? To describe possible deviations, we use calculations from Effective Field Theory (EFT) that allows to add new interactions. For this project simulated data samples with deviations predicted by EFT are available.<br />
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The candidate applies new techniques involving machine-learning to separate backgrounds from top quark production, aware for signs of new physics. Existing tools can be used to quantify the improvements on finding new interactions involving top quarks. Depending on the candidates interest, the focus of the project can be put more on machine-learning or top quark physics. For this project, we use the Python computing language and the ROOT package. Therefore, some proficiency with Python is required. Knowledge of C++ and root is advantageous but not required. <br />
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Supervisors: Jordy Degens (PhD candidate) and Marcel Vreeswijk (h73@nikhef.nl).<br />
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==== '''New machine learning approaches to target Higgs interference signatures in LHC data''' ====<br />
In this project we aim to improve an ongoing analysis to determine the lifetime of the Higgs Boson through state-of-the-art machine learning techniques, in particular by addressing a novel solution to an as of yet unsolved fundamental problem in modeling quantum interference. While the Higgs is an elusive particle that generally only appears in physics processes with small cross sections, its signature can be amplified in the Large Hadron Collider (LHC) through quantum interference with larger background (non-Higgs) processes. This is the effect that the Higgs’ lifetime analysis relies on to be able to measure the relevant Higgs signature. A fundamental physics modelling problem arises though in the simulation of individual events for this interference due to the fact that these events are in reality described by a superposition of underlying Higgs and non-Higgs processes.<br />
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Since machine learning models in particle physics are typically trained to characterise individual physics events, the fact that interference events cannot currently be generated is a significant problem when interference is the target. In the currently existing Higgs lifetime analysis, a machine learning model was trained which instead focuses only on the explicit Higgs-mediated processes as a proxy, which is suboptimal. The aim of this project is to improve upon this current machine learning strategy used in this analysis by implementing either of the inference-aware approaches suggested in [1] and [2]. The idea behind these inference-aware machine learning algorithms is that they do not optimise for a simplified goal such as the loss function which is common in traditional machine learning, but rather for the end-goal of the analysis. In this case, this would omit the need for interference event generation altogether and allow the machine learning models to be trained optimally regardless.<br />
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The goal of this project is to use either of the frameworks used in [1] and [2] (which are both publicly available) and run them with a simplified dataset from the aforementioned analysis as a proof-of-principle. In case this goal is achieved, the next goal would be to actually implement the newly developed machine learning models in the full analysis and to determine the improvement upon the existing result. Successful completion of these tasks would not only benefit the Higgs lifetime analysis, but would be an important stepping stone to future developments to make machine learning approaches deal better with other hard to model effects such as systematic uncertainties.<br />
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Supervisors: Zef Wolffs, Ivo van Vulpen and Matous Vozak (matous.vozak@cern.ch)<br />
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==== '''Reconstructing tracks from particle physics detector hits with state-of-the-art machine learning techniques''' ====<br />
This project concerns the application of new machine learning techniques to tackle the problem of track reconstruction at the ATLAS detector in CERN. While algorithms to construct particle tracks from low-level detector information such as particle hits and timestamps have been around for decades, recent developments in the field of machine learning open up new opportunities to improve these algorithms significantly. In particular graph-based neural networks and attention architectures prove promising candidates for solving these problems based on preliminary studies. <br />
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In this project the student will develop machine learning models to initially reconstruct tracks from simplified test data. If time allows, real data from the ATLAS detector can be analyzed as well in the scope of this project. The student will need some familiarity with programming in python and an interest in machine learning, but a physics background is not required. In this project the student will be able to contribute to fundamental physics research and will familiarize themselves with state-of-the-art machine learning models.<br />
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Supervisors: Zef Wolffs, Ivo van Vulpen and Matous Vozak (matous.vozak@cern.ch)<br />
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=== LHCb ===<br />
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=== Gravitational Waves ===<br />
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====Staying in shape====<br />
Nikhef is co-leading the current effort to realise the Einstein Telescope (ET), a future 10km-scale underground observatory for gravitational waves. Numerical modelling software forms a crucial subsystem for the design and operation of the GW detectors. Our interferometer simulation software Finesse was developed for the design and commissioning of gravitational wave detectors and has become the main interferometer software tool in the community world wide. In our group we use Finesse to predict the shape of the laser beam and how this affects the GW data. You will join our group using Python-based scripts to model mis-shaped lasers and see how the interferometer reacts.<br />
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Required knowledge:<br />
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Good knowledge of Python is required.<br />
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Knowledge of optics will be useful but is not required.<br />
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Supervisors: Anna Green (agreen@nikhef.nl) and Andreas Freise (a.freise@nikhef.nl)<br />
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====Riding the wave====<br />
Theoretical predictions of gravitational-wave (GW) signals provide essential tools to detect and analyse transient GW events in the data of GW instruments like LIGO and Virgo. Over the last few years, there has been significant effort to develop signal models that accurately describe the complex morphology of GWs from merging neutron-star and black-hole binaries. Our work focusses on a particular class of GW binary sources: those that come from two black holes meeting at close separation in dense stellar environments. Here, we expect the merging binary to be in a non-circular orbit and to have arbitrary spin orientations, which significantly complicates the prediction of its GW signal.<br />
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We are looking for '''two''' students who are interested in the development of accurate and efficient GW models and their application in GW data analysis. We are offering '''two separate projects''' that aim to improve signal modeling at the interface of perturbation theory, numerical relativity simulations and fast phenomenological descriptions. Some proficiency in computing is required (Mathematica, Python or C++).<br />
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Supervisor: Maria Haney (mhaney@nikhef.nl)<br />
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=== Detector R&D ===<br />
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====Charge collection study of fast monolithic detectors====<br />
In view of the upgrade of the ALICE tracking detector, innovative ultrathin monolithic silicon sensors are developed for testing. These devices are provided with analogue outputs to study in detail the charge collection and the timing properties of the sensor.<br />
The goal of the project is to contribute to the study of the charge collection features of the samples by measuring the response of the sensor to Fe55 X-rays.<br />
We are looking for a student with a focus on lab work and interested in contributing to the python-based data analysis.<br />
Depending on the progress with the intended measurement and the availability of the hardware, further studies with Sr90 electrons and a laser setup could be possible.<br />
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Contacts: Jory Sonneveld (jory.sonneveld@nikhef.nl), Roberto Russo (rrusso@nikhef.nl)<br />
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====Laser setup for silicon sensor studies====<br />
The Detector R&D group at Nikhef develops and tests detector concepts before they are used in scientific programs at Nikhef. To achieve such a goal, advanced instrumentation and setups are required.<br />
The goal of the project is to contribute to the design and construction of a fast infrared laser setup aimed at the characterization of silicon sensors for high energy physics experiments.<br />
We are looking for a student with a focus on lab work and interest in instrumentation and optics. Besides contributing to the setup construction, measurements finalised at the characterization of the laser beam (e.g. spot size, intensity) are foreseen.<br />
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Contacts: Jory Sonneveld (jory.sonneveld@nikhef.nl), Roberto Russo (rrusso@nikhef.nl)<br />
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==== Characterization of monolithic silicon sensors ====<br />
As part of the ongoing efforts for the design of ultimate tracking detectors, an excellent understanding of the basic performance of the detectors is required. To do so, the silicon detectors can be tested by making an electrical contact with the sensor using a probe station, a device for micrometer precision placement of temporary electrical contacts to acquire signals from internal nodes of semiconductor devices, to investigate aspects such as it's depletion voltage, depletion depth, the dark current and more which are essential for understanding the results gathered by the sensors later in the laboratory and allow the investigation of aspects that can be improved in further chip iterations. The goal of the project is to investigate the performance of monolithic sensors, where electronics is integrated into the sensor, developed for collider experiments like those at the large hadron collider at CERN and beyond. Depending on the progress with the planned measurements, further tests with the electronics and readout of the chip, as well as measurements with advanced laster instrumentation are also possible.<br />
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Contacts: Jory Sonneveld (jory.sonneveld@nikhef.nl), Uwe Kraemer (uwe.kraemer@nikhef.nl)<br />
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=== Theory ===<br />
'''Axion-Electrodynamics (Jordy de Vries and Arghavan Safavi-Nani)'''<br />
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Axions are hypothetical particles that are introduced to solve the so-called strong CP problem. Being very light, axion can be described as a coherent classical field similar to electromagnetic fields. In this project, you will develop the modifications of Maxwell’s equations to include axion fields. Reference: arXiv:1401.0709 . <br />
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'''Axions in a Paul-trap (Jordy de Vries and Arghavan Safavi-Nani)'''<br />
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Axions are hypothetical particles that are introduced to solve the so-called strong CP problem. If axions form the dark matter in our universe, they can be described by a coherent oscillating background field. This oscillating field interacts with charged particles and it possible to detect axions by the motion of ions in a Paul trap. In this project, you will investigate how these interactions work and what are the observables associated to the detection of axions in ion traps.<br />
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'''Phase space integrals for double-weak processes (Jordy de Vries)'''<br />
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The rarest processes ever measured are so-called double weak processes in which two neutrons undergo beta decay at the same time in a nucleus. Lifetimes of these processes are in the 10^22 years range. Theoretical computations of these rates involve so-called phase space integrals that take into account the possible momentum configurations of the outgoing electrons and neutrinos. In this project you will investigate these phase space integrals and develop a method to compute them. <br />
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== Bachelor Projects 2022 ==<br />
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=== Dark Matter ===<br />
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==== Response of materials to scintillation light from liquid noble gasses ====<br />
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The liquid form of the noble gases argon and xenon is a popular target material for neutrino and dark matter detectors. The scintillation light from noble gases is in the vacuum UV spectral region. Air and many materials used for optical studies are not transparent to these photons. Measurements of the optical properties of detector materials, such as their reflectivity for example, thus have to be performed with dedicated VUV optics and in vacuum. Additionally, to reproduce the conditions in the detectors, the samples must be cooled to cryogenic temperatures. In this BSc project, you will calibrate the photon detectors in an experimental setup designed to study the optical response of materials excited with VUV photons. You will learn about material requirements for rare event search detectors, vacuum instrumentation, vacuum UV optics including monochromators and spectrometers, and single-photon sensors.<br />
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Supervisors: T. Pollmann (t.pollmann_at_nikhef.nl)<br />
====XAMS====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENONnT detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENONnT experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso. We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with recently upgraded hardware to test a novel concept for UV light detection. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complete the first measurements with our upgraded setup.<br />
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Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
==== XENONnT reconstruction software ====<br />
The XENONnT experiment becomes operational during 2021. While the hwardware is finished we keep on developing and perfecting our reconstruction software. For this project we are looking for a student with a keen interest in and talent for writing physics based event reconstruction software (we use python). Specifically we have an idea to improve the localization of events inside the XENONnT for which proto-type software exists. The proto-type software needs to be implemented in the XENONnT reconstruction framework and subsequently it needs to be validated on the first data from the experiment. The final goal of the project is to deliver the reconstruction software to the collaboration that will be used during teh full lifetime of the experiment.<br />
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Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
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=== ATLAS ===<br />
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==== The Higgs boson - did we miss anything and can we do better? ====<br />
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The Higgs boson is a key element of the Standard Model (SM) of particle physics, however, it can also represent a link between yet unexplored 'new' physics beyond the SM. What is the Higgs boson life-time? How precisely can we measure its mass? Is there an additional heavy Higgs boson? Do other particles, not contained in the SM, couple to the Higgs? All these questions can be studied by measuring Higgs properties using one of the Higgs decay modes to photons, vector bosons, quarks and leptons and comparing them with the (beyond) SM predictions. <br />
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As the restart of the Large Hadron Collider (LHC) is imminent, it is essential to develop and test new physics ideas and strategies. '''The ATLAS open data project''' will allow students to work on a real analysis digging through the LHC data collected during Run2. Students will go through all the key aspects of a Higgs analysis performed also by ATLAS physicists. They will learn about Higgs boson theory and its simulation, what objects are reconstructed in the ATLAS experiment, how well do we understand them and finally how does this project into our understanding of the Higgs boson and its properties. <br />
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The exact focus of the topic is flexible depending on the interest of a student. For instance, a student can delve into how precisely can we determine objects' energy and their positions and see whether we can '''improve our estimate of the Higgs mass (project 1)'''. Another possibility is to focus on trying to find out whether there is '''an additional (heavier) Higgs (project 2)''' in the data and how confident we can be of that. Each of these projects will most likely yield new questions, so feel free to take a tangent and walk into yet unexplored territory and see what the data tells you.<br />
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Supervisor: Matouš Vozak (m.vozak_at_nikhef.nl) & Ivo van Vulpen (Ivo.van.Vulpen_at_nikhef.nl)<br />
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==== The Higgs boson life-time ====<br />
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The Higgs particle does not have eternal life. The Standard Model (SM) predicts that it decays into other particles and as these couplings are fixed we can predict its life-time with very high precision. Determining this life-time is a crucial test for the Standard Model. If the Higgs boson life-time is shorter that we expect this could mean that the Higgs boson could decay into non-SM particles. In this project we investigate a) how we can identify Higgs particles in the detector and b) how we plan to use quantum-interference to get a handle on the Higgs boson's life-time. <br />
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Supervisor: Wouter Verkerke (verkerke_at_nikhef.nl)<br />
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==== Higgs interferentie ====<br />
In 2012 hebben het ATLAS en het CMS experiment het Higgs deeltje gevonden. Inmiddels zijn we het Higgs boson aan het bestuderen, hoe gedraagt het zich precies, bestaan er meer soorten Higgs bosonen of is er echt maar eentje van? In dit project leer je hoe we een Higgs boson kunnen herkennen in de detector en gaan we kijken naar hoe de signalen veranderen als er meer Higgs bosonen bestaan of misschien wel andere exotische nieuwe deeltjes. <br />
Dit doen we door gebruik te maken van quantum interferentie wat plaats vindt tussen het Higgs boson en achtergrondprocessen. Hoe dit precies werkt leer je in het project. Supervisor: Hella Snoek (h.snoek_at_nikhef.nl)<br />
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=== LHCb ===<br />
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==== Exotic neutrinos in B decays====<br />
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Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, heavier, neutral leptons. In the LHCb group at Nikhef we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undisovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The bachelor project will contribute with the optimization of the selection using state-of-the-art tools for the multi-variate analysis.<br />
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Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
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=== Gravitational Waves ===<br />
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=== Detector R&D ===<br />
Answering big elementary particle physics questions requires pioneering experiments. The Detector R&D program at Nikhef is aimed at conceptualizing and testing of instrumentation concepts before they are implemented in scientific programs at Nikhef. <br />
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==== Time resolution of monolithic timing detectors ====<br />
For the upgrade of the vertex detectors of the large LHC experiments like LHCb and ALICE, new silicon pixel detectors will developed now that can register the passing particles with a time precision of tens of picoseconds. ALICE is the first experiment at the LHC to have installed monolithic sensors where electronics is integrated into the sensor resulting in ultrathin, low-material detectors, that will soon see it's first particles from LHC collisions. In this project you will measure the time resolution of these promising integrated sensors with a laser setup in our laboratory.<br />
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Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
==== Modeling radiation damage in silicon sensors ====<br />
In the coming years, the ATLAS experiment at the LHC works on upgrades to prepare for the high-luminosity LHC, where many more collisions will take place than today. Analyses of LHC data rely heavily on simulations of the detector. It may sound counterintuitive, but particle detectors do not actually like particles: after many collisions at the LHC, a silicon pixel detector has seen so many particles that its bulk gathers defects. Charge generated by traversing particles can get trapped in defects resulting in less charge induced in the readout electrodes, reducing detector performance in resolution and efficiency. In this project, you will be part of the international ATLAS collaboration and compare different models of radiation damage with measured data and you will contribute to the open source program Allpix Squared that is widely used for simulations in many areas of particle physics.<br />
<br />
Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
==== Time resolution of a new digital pixel test structure from test beam data ====<br />
For the upgrade of the ALICE detector, ultrathin picosecond timing integrated sensors are developed. To reduce power consumption, asynchronous readout is implemented in this prototype sensor in a digital pixel test structure. This structure was studied in test beams with an ALPIDE (ALICE PIxel DEtector) telescope at CERN. You will measure the efficiency and time resolution of this new sensor with the latest data from test beams at CERN.<br />
<br />
Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
<br />
==== Fast timing detectoren ====<br />
Op dit moment maken we veel gebruik van silicon detectoren in onze deeltjes experimenten. Deze zijn gevoelig voor geladen deeltjes en zijn bij uitstek geschikt om de paden vast te leggen die de deeltjes maken die in de botsingen worden gemaakt. Bijvoorbeeld in de Atlas en LHCb experimenten worden tientallen tot honderden deeltjes gemaakt bij elk botsingsgebeurtenis (event) die met 40MHz plaatsvinden. Voor toekomstige deeltjesdetectoren willen we niet alleen het traject vastleggen maar ook met grote precisie een tijdsmeting toevoegen. We hebben hiervoor dus nieuwe detectoren nodig die behalve met een hele hoge snelheid en efficientie de posities van de langsvliegende deeltjes kunnen vastleggen, maar hier ook een zeer nauwkeurige tijdsmeting (in orde van picosecondes) aan kunnen toevoegen. We hebben met verschillende detectoren metingen gedaan, in testbundels op CERN, maar ook in het lab op Nikhef kunnen we metingen doen. In dit project ga je samen met het fast-timing detectoren team op het Nikhef metingen verrichten en de resultaten hiervan bekijken. Contact: Hella Snoek (h.snoek@nikhef.nl)<br />
<br />
<br />
=== KM3NeT ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along 200-700m long vertical lines, called detection units.<br />
<br />
==== Neutrino oscillation measurements with the first KM3NeT data ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope is able to measure the oscillations of neutrinos produced in interactions of cosmic rays with the earth atmosphere. Fundamental neutrino properties can be deduced from these oscillations measurements. In this project we will use the first data of ORCA (more than one year with six detection units) to study neutrino oscillations and fit neutrino mixing parameters and mass differences between neutrino mass states. We will study data selection, event reconstruction, and effects of systematic uncertainties on the results. <br />
<br />
Supervisors: Brian O'Fearraigh, Ronald Bruijn, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
==== Search for sterile neutrinos with KM3NeT. ====<br />
A detailed study of neutrino oscillations in the KM3NeT detector is sensitive to the existence of so-called sterile neutrinos: neutrinos that are not part of the Standard Model of particle physics, and have no ordinary interactions with matter. We will use a mixture of data and simulations to estimate KM3NeT sensitivity.<br />
<br />
Supervisors: Alba Domi, Paul de Jong<br />
<br />
==== Machine learning for event classification in KM3NeT ====<br />
The classification of neutrino events recorded in the KM3NeT detector in terms of originating from electron neutrinos, muon neutrinos, or tau neutrinos, is very well suited for machine learning techniques. We will study the performance of a few advanced machine learning techniques on simulated high-energy neutrino events.<br />
<br />
Supervisors: Alba Domi, Paul de Jong<br />
<br />
==== Multi-messenger astronomy with neutrinos and radio signals ====<br />
The main goal of neutrino telescopes, such as ANTARES, KM3NeT and IceCube, is to detect cosmic neutrinos from astrophysical sources. When an interesting neutrino candidate is detected they send out a message to alert the scientific community. Other scientific instruments, like the Murchison Widefield Array (MWA) radio telescope, can then do a follow-up observation, to see if there are other messengers coming from the same source as the neutrinos. In this project you will analyse MWA data that were taken after the reception of neutrino alerts, to search for a radio source that can be associated with a neutrino source.<br />
<br />
Supervisor: Mieke Bouwhuis (mieke.bouwhuis at nikhef.nl)<br />
<br />
=== Theory ===<br />
<br />
==== Effective Field Theories of Particle Physics from low- to high-energies (2022 not yet determined if available in 2023) ====<br />
<br />
Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations<nowiki>''</nowiki> seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature.<br />
<br />
Until recently, it was widely assumed that matter particles from each of the three generations interact with the same (“universal”) strength. This hypothesis is being challenged by new measurements at the Large Hadron Collider (LHC) at CERN, which hint towards non-universal interactions. If confirmed, these measurements will be the first signs of new particles and interactions in high-energy colliders. These exciting findings indicate the urgent need to explore such phenomena in depth.<br />
<br />
The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Effective Field Theory (EFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes. Specifically, the goal is to connect measurements from ATLAS and LHCb among them and to jointly interpret this information with that provided by other experiments, from CMS and Belle-II to very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
<br />
''Methodology and workplan''<br />
<br />
This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories.<br />
<br />
This project accommodates several students, who would work together in developing the main formalism while each of them focuses on a specific sub-project. The maximum capacity of this project is 5 students. <br />
<br />
Depending on the student profile, sub-projects with a strong computational / machine learning component are also possible.<br />
<br />
During the first four weeks of the project, students will learn the required background material on effective field theories, following the guidelines from the supervisors. Afterwards, they will focus on different sub-projects, each covering a different aspect of the same global EFT program.<br />
<br />
Required knowledge<br />
<br />
Quantum Mechanics 2, Particle Physics 1 (required)<br />
<br />
Advanced Quantum Mechanics, Particle Physics 2, Machine Learning (optional)<br />
<br />
Available subprojects<br />
<br />
Here we list the available subprojects, including the corresponding daily supervisor(s) in each case.<br />
<br />
''Subproject #1: SMEFT & Flavour symmetries'' <br />
<br />
Daily supervisors: Jordy de Vries (UvA), Keri Vos (Maastricht University), Jaco ter Hoeve (VU), Giacomo Magni (VU)<br />
<br />
While the power of the Standard Model EFT (named SMEFT) framework is its generality and lack of assumptions, the number of operators is somewhat daunting. A popular way to trim the number of operators is to assume flavour symmetries that relate operators with different quark and lepton flavours. In this project you will investigate the theoretical basis for commonly-used flavour symmetries and what they imply for the connection between high-energy observables involving third-generation particles (top and bottom quarks and tau leptons) and low-energy precision tests involving first- and second-generation particles. The investigations of this project are connected with Subproject #2.<br />
<br />
''Subproject #2: SMEFT & magnetic moment of the muon''<br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU)<br />
<br />
The magnetic moment of the muon appears to differ from the Standard Model expectations by a large amount, well beyond the known experimental and theoretical uncertainties. Recent experiments have only strengthened the significance of this anomaly. In this project, the students will investigate the feasibility of implementing the measurement of the magnetic moment of the muon into a global SMEFT analysis, by exploiting recently provided calculations. Special attention will be devoted to the flavour assumptions required to consistently match this measurement with the LHC data, also at the light of the connection with Subproject #1. The SMEFiT analysis framework will be used to connect the g-2 data with high-energy LHC measurements.<br />
<br />
''Subproject #3: CP Violation and low-energy precision experiments''<br />
<br />
Most analyses of LHC data are performed under the assumption that CP symmetry (charge conjugation + parity, essentially the symmetry between particles and anti-particles) is conserved. More recent analyses attempt to also measure possible new sources of CP violation in SMEFT operators in the Higgs and top sector. <br />
<br />
''Subproject #3a: CP Violation and low-energy precision experiments''<br />
<br />
Daily supervisors: Jordy de Vries (UvA), Juan Rojo (VU)<br />
<br />
Low-energy precision experiments can also set stringent constraints on new mechanisms of CP violation. In this project you will try to combine high- and low-energy data to put CP symmetry to the test. <br />
<br />
''Subproject #3b: CP Violation and flavour physics experiments''<br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU)<br />
<br />
Besides low-energy precision experiments, also B-meson decays are excellent probes of CP violation. Unlike most low-energy experiments, this allows us to probe CP violation in the third generation. In this project you will link constraints on CP violation at high-energy to those from B meson decays. <br />
<br />
''Subproject #4: SMEFT & optimal observables'' <br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU), Tommaso Giani (VU & Nikhef)<br />
<br />
In full generality, the number of operators in SMEFT spans a very large parameter space. These parameters are constrained by experimental inputs from ATLAS and CMS, depending on the precise parameters these constraints may be more or less stringent. In order to fully exploit the whole parameters space in SMEFT, it is necessary to devise statistically optimal observables that have a large constraining power. In this project, we will define such observables. This project has a strong computational / machine learning component and may involve simulations based on tools such as MadGraph and Pythia8.<br />
<br />
Contacts:<br />
<br />
Juan Rojo (VU Amsterdam & Nikhef): j.rojo at vu.nl<br />
<br />
Keri Vos (UM & Nikhef): k.vos at maastrichtuniversity.nl <br />
<br />
Jordy de Vries (UvA & Nikhef): j.devries4 at uva.nl<br />
<br />
== Bachelor Projects 2021 ==<br />
=== Dark Matter ===<br />
<br />
==== XAMS ====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso.<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with recently upgraded hardware to test a novel concept for UV light detection. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complete the first measurements with our upgraded setup.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== XENONnT reconstruction software ====<br />
The XENONnT experiment becomes operational during 2021. While the hwardware is finished we keep on developing and perfecting our reconstruction software. For this project we are looking for a student with a keen interest in and talent for writing physics based event reconstruction software (we use python). Specifically we have an idea to improve the localization of events inside the XENONnT for which proto-type software exists. The proto-type software needs to be implemented in the XENONnT reconstruction framework and subsequently it needs to be validated on the first data from the experiment. The final goal of the project is to deliver the reconstruction software to the collaboration that will be used during teh full lifetime of the experiment.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Backgrounds in Radioactive Decay Measurements ====<br />
At Nikhef, the XENON group has a working setup, continuously monitoring the<br />
radioactive decay of Cobalt-60, Caesium-137 and Titanium-44. This beautiful setup is<br />
however not shielded perfectly; it is still vulnerable to background radioactivity. Our<br />
current way of working around this background radiation is to subtract it from our<br />
waveforms. You as a BSc student could help us hands-on and with analyses:<br />
together, we can disassemble the setup, measure background spectra and<br />
implement this in the data analysis. You can use all the data to validate the<br />
lifetime of our isotopes!<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Detection of scintillation light from liquid noble gasses ====<br />
<br />
The liquid form of the noble gases argon and xenon is a popular target material for neutrino and dark matter detectors. The scintillation light from noble gases is in the vacuum UV spectral region. Air and many materials used for optics studies are not transparent to these photons. Measurements of the optical properties of detector materials, such as their reflectivity for example, thus have to be performed with dedicated VUV optics and in vacuum. Additionally, to reproduce the conditions in the detectors, the samples must be cooled to cryogenic temperatures. In this BSc project, you will design, using professional hardware design software, a vacuum chamber to hold the detector materials whose optical properties are to be investigated, as well as the cooling system and photon detectors. You will learn about material requirements for rare event search detectors, vacuum instrumentation, vacuum UV optics including monochromators and spectrometers, and single-photon sensors.<br />
<br />
Supervisors: T. Pollmann (t.pollmann_at_nikhef.nl)<br />
<br />
=== Detector R&D ===<br />
<br />
==== Characterization of the new ultrathin ALPIDE monolithic active pixel sensor ====<br />
At the Large Hadron Collider at CERN, major upgrades of experiments take place in the long shutdown years where particle collisions are paused. The ALICE inner tracking system (ITS) 2, the part of the ALICE experiment closest to the beam pipe, is currently being installed at CERN. This detector makes use of ultra-lightweight monolithic active pixel sensors, the first to use this technology at particle colliders after the STAR experiment at RHIC in Brookhaven. These very thin pixel detectors have a low power consumption, result in very little material in the detector, and still have optimal timing and resolution -- and are a promising technology for future experiments. To characterize the performance of these sensors, you will learn to set up experiments, carry out measurements, and analyze data using various instruments available in the detector R&D lab at Nikhef. This could lead to novel insights of monolithic active pixel sensors. It is also possible to do measurements from home using data from the first test beams with bent (yes, with a curvature!) ALPIDE sensors. You will work in an international, stimulating research environment in the detector R&D group at Nikhef at the forefront of silicon detector technologies for high energy physics. ''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
==== Simulation of 3D silicon sensors ====<br />
<br />
For the upgrade of the vertex detector of the LHCb experiment novel silicon pixel detectors have to be developed that can register the passing particles with a time precision of tens of picoseconds. Given the harsh radiation environment very close to the LHCb interaction point only a limited number of technologies can be applied. One of the most promising technologies are the so-called 3D sensors whose readout electrodes are pillars that are placed into the sensor perpendicular to the surface; this in contrast to ’standard’ planar silicon sensors where the pixel electrodes are at the surface, similar to the camera in your smartphone. To understand the time response of these 3D sensors, simulations with TCAD software have to be performed and the results will be compared to measured data. These simulations involve the creation/adaptation of the 3D structures of the model, optimising the simulation speed, and analysing the signals as function voltage, track impact point and deposited charge. If time and Covid regulations permit, gaining some hands-on experience with such 3D sensors in the R&D labs at Nikhef is possible. ''Contacts: [mailto:martinb@nikhef.nl Martin van Beuzekom] [mailto:k.heijhoff@cern.ch Kevin Heijhoff] ''<br />
<br />
<br />
=== Theory ===<br />
<br />
==== Standard Model Effective Field Theory analysis of Z+dijet production ====<br />
The goal of this project is to study the effect of higher dimensional operators from the Standard Model Effective Field Theory in Z-boson production measured at LHC. The ATLAS collaboration has just reported in 2020 the measurement of Z production alongside with a pair of jets, based on the full Run II luminosity. In this project we aim to study the effect of dimension six SMEFT operators on the signal (EW-induced) and/or background (QCD-induced), finding which is the kinematic variable that maximises the possible effect of beyond the SM operators and thus may provide the best constraint on New Physics. The outcome of this project may be the first step of the inclusion of Vector production in a global SMEFT fit. <br />
<br />
References: https://arxiv.org/pdf/2006.15458.pdf, https://www.hepdata.net/record/ins1803608<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Maximum precision on new physics through information theory ====<br />
One way to look for physics beyond the standard model is through the framework of effective field theory. In this framework, deviations from the standard model are described by a set of continuous parameters. Finding constraints on these parameters might point to the discovery of new physics. With the large number of LHC experiments we currently face, we want to be able to quantify the maximum knowledge that (future) experiments can provide on new physics parameters. In this project, the student will study and quantify the maximum information that is contained in particle physics experiments through information theory. The central object of study will be the Fisher information matrix. The idea is to work with a simple toy experiment that describes Higgs physics and compute its associated Fisher information matrix to quantify the optimal bounds on new physics. The project will start with studying central objects from statistics and information theory. Later, we will apply these to open problems in particle physics.<br />
<br />
Reference: https://arxiv.org/pdf/1612.05261.pdf<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Seesaw mechanism and neutrino mass ==== <br />
Many unsolved questions in particle physics are related to the nature of the neutrino and its mass generation. The goal of this theoretical project is to understand and review one of the possible candidate theories that describe how neutrinos mix and get massive, namely the Seesaw mechanism. Among the many possible Seesaw mechanisms that can generate new phenomenology including lepton number non-conservation, the student will focus on one minimal model to understand the key processes that are currently used to probe the validity of the given theory. <br />
<br />
References: https://cds.cern.ch/record/408119/files/9911364.pdf, https://arxiv.org/pdf/1711.02180.pdf<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Mixing of sterile neutrinos ====<br />
<br />
Neutrino oscillation experiments demonstrate that neutrinos are massive particles. However, the mass mechanism of neutrinos is unknown. A<br />
minimal solution requires the existence of so-called sterile neutrinos: neutrinos that are even more elusive than ordinary neutrinos. <br />
We will investigate how to parametrize the matrix that describes the mixing between ordinary and sterile neutrinos. We will then use this<br />
to calculate how sterile neutrinos induce rare nuclear decays and determine the sensitivity of ongoing experiments to observe sterile<br />
neutrinos.<br />
<br />
Supervisor: Jordy de Vries (devries.jordy at gmail.com)<br />
<br />
<br />
=== KM3NeT ===<br />
<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
==== Data analysis of the first deployed KM3NeT detection lines ====<br />
<br />
First detection lines of the KM3NeT neutrino telescope have been deployed<br />
in the Mediterranean Sea, and a first data set is available. The lines consist<br />
of light-sensitive detectors that record the time of arrival of photons<br />
produced by relativistic particles in the deep sea, and their number.<br />
In this project we will study the first data to separate various components:<br />
photons from potassium decay, bioluminesence, sparks in the photomultipliers,<br />
downgoing muons from cosmic rays, and first neutrinos.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben (paul.de.jong at nikhef.nl)<br />
<br />
==== Neutrino oscillation measurements with the KM3NeT neutrino telescope ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope currently under construction<br />
will be able to measure the oscillations of neutrinos produced in interactions<br />
of cosmic rays with the earth atmosphere. Fundamental neutrino properties can<br />
be deduced from these oscillations measurements, in particular the so-called<br />
mass hierarchy of neutrinos. In this project we will simulate the ORCA measurements<br />
of neutrino oscillations, and study the dependence of the sensitivity on<br />
experimental uncertainties, such as energy resolution and neutrino flavour<br />
identification, and theoretical uncertainties, such as the atmospheric neutrino<br />
flux and neutrino cross sections. The results will help ORCA to identify<br />
the main sources of uncertainty, and therefore to actively try to reduce these<br />
and improve the final measurement.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
==== Performance Studies of ORCA for Dark Matter Detection ====<br />
<br />
The interactions of neutrinos in KM3NeT-ORCA give different signatures which are categorised as track and shower events. This project involves the studies of muon, electron and tau neutrino interactions for the reconstruction performance of ORCA. Efficient reconstruction of such signals is important for Dark Matter searches in the low-mass regime. We will work on understanding the detector performance, e.g. effective acceptance, energy and angular resolution, with different configurations of the detector setup. The result of this study will be very useful to improve the sensitivity of the experiment for Dark Matter detection and its possible location. The student will have the opportunity to work closely with KM3NeT members at Nikhef and gain skills of analyzing data. <br />
<br />
Supervisors: Suzan Basegmez du Pree, Aart Heijboer (s.basegmez.du.pree at nikhef.nl)<br />
<br />
==== Study of Optical Properties of Sea Water using Hit Coincidences in MC Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
By studying coincidences of L1 hits between neighbouring DOMs, for various Monte Carlo (MC) data sets with different sea water optical properties such as scattering and absorption coefficients, in this project we try to figure out if and how well we can quantify optical sea water properties by studying L1 hit coincidences in real KM3NeT data.<br />
<br />
Supervisor: Daan van Eijk (dveijk at nikhef.nl)<br />
<br />
==== Determination of Inter-DOM Distances using Hit Coincidences in KM3NeT Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
The number of L1 hit coincidences from atmospheric muons between neighbouring DOMs on a DU is expected to decrease exponentially. By fitting the observed number of L1 hit coincidences between neighbouring DOMs in real data to the expected exponential decay, in this project we study how accurately we can determine the distances between DOMs on a single DU. In addition, we try to determine the distances between DUs by looking for L1 hit coincidences between DOMs on neighbouring DUs.<br />
<br />
Supervisor: Daan van Eijk (dveijk at nikhef.nl)<br />
<br />
<br />
=== ATLAS ===<br />
<br />
==== The Higgs boson life-time ====<br />
<br />
The Higgs particle does not have eternal life. The Standard Model (SM) predicts that it decays into other particles and as these couplings are fixed we can predict its life-time with very high precision. Determining this life-time is a crucial test for the Standard Model. If the Higgs boson life-time is shorter that we expect this could mean that the Higgs boson could decay into non-SM particles. In this project we investigate a) how we can identify Higgs particles in the detector and b) how we plan to use quantum-interference to get a handle on the Higgs boson's life-time. <br />
<br />
Supervisor: Wouter Verkerke (verkerke_at_nikhef.nl)<br />
<br />
==== The Higgs boson decaying to photons ====<br />
<br />
One of the main channels used to analyse the properties of the Higgs boson is when the Higgs boson decays into two photons. The crucial building block in this analysis is our ability to reconstruct the energy and the direction of the photons in the ATLAS detector and in this project we will revisit the photon reconstruction. We will start by studying simulations and learning about photon reconstruction in general. Then our goal is to determine the energy and position resolution of photons in the ATLAS detector and see if we can exploit our knowledge on the photon resolution to get an (improved) estimate of the Higgs boson mass. For the analysis we will use the '''real data from the LHC''' - the ATLAS open data project.<br />
<br />
Supervisor: Ashley McDougall and Ivo van Vulpen (Ivo.van.Vulpen_at_nikhef.nl)<br />
<br />
<br />
=== LHCb (1) ===<br />
<br />
One of the most fascinating mysteries in physics today is: how is it possible that universe is filled with matter? If the Big Bang produced equal amounts of matter and antimatter, we still do not understand the mechanism that lead to the excess of matter over antimatter that we observe today.<br />
<br />
One interesting feature of some particles is that they can transform themselves into their antiparticles, then back to particle, and so forth, in an oscillatory way until they finally decay. In particular, beauty mesons (B) can oscillate into their antiparticle (B ̄). The parameters of this oscillation, such as amplitude, frequency and phase, are calculable mathematically: predictions for it are available in the standard model (SM) of particle physics. But the oscillations according to the SM alone would not lead to the imbalance of matter in the universe – we still need to find a new type of physics that may be able to explain it.<br />
<br />
In this context, it is very important to measure B oscillations in the laboratory, and compare these observations with the expectations from the SM. Are the experimental data in good agreement with the SM, as we expect? If the aswer is not, i.e. if there are features of the oscillation that we do not understand well, then we may be observing “new physics”. In other words, the data may reveal a new mechanism that generates a different matter-antimatter balance than predicted by the SM, that may potentially solve the puzzle.<br />
<br />
The LHCb experiment at CERN is dedicated to such studies: LHCb detectors are placed in a region along the LHC collider beamline, where a large number of B mesons are produced, arising from the proton-proton collision data from the LHC collider. Looking at the LHCb data we can obtain large samples of B mesons, and observe their oscillations.<br />
In this project we will learn how to select a sample of B mesons out of the data taken with the LHCb detector, measure the parameters that govern their oscillation and compare them with the SM.<br />
<br />
For more information, please contact Mara Soares (msoares_at_nikhef.nl).<br />
<br />
== Bachelor Projects 2020 ==<br />
<br />
<br />
=== Dark Matter ===<br />
<br />
==== XAMS ====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso.<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source and liquid scintillatorneutron detector we have acquired for the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study of neutron transport in xenon.<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Backgrounds in Radioactive Decay Measurements ====<br />
At Nikhef, the XENON group has a working setup, continuously monitoring the<br />
radioactive decay of Cobalt-60, Caesium-137 and Titanium-44. This beautiful setup is<br />
however not shielded perfectly; it is still vulnerable to background radioactivity. Our<br />
current way of working around this background radiation is to subtract it from our<br />
waveforms. You as a BSc student could help us hands-on and with analyses:<br />
together, we can disassemble the setup, measure background spectra and<br />
implement this in the data analysis. You can use all the data to validate the<br />
lifetime of our isotopes!<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
=== ATLAS ===<br />
<br />
==== Project ATLAS-ITk ====<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
==== The Most Energetic Higgs Boson ====<br />
A common approach to search for physics beyond the standard model is by searching for the direct production of new particles. Alternatively, indirect quantum effects on the production of known particles -such as the Higgs Boson- could reveal the first cracks in the theory. Processes with high energy transfer are of particular potential since possible deviations are expected to increase with the square of the involved energy scale. Using the entire data-set collected by the ATLAS experiment at CERN during the four years of the LHC’s Run 2, a proof-of-principle analysis, targeting transverse momenta of the above 400 GeV, has been developed by Nikhef researchers. The first results of this Higgs boson study are expected to be published this year and this project aims to develop refinements of the analysis techniques. We will investigate the usage of sophisticated machine learning tools such as artificial neural networks, the search for new variables that can help discriminating the signal from its background, revisiting the analysis categorisation and improving the reconstruction techniques at these extreme momenta. Supervisors: Brian Moser and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs: The Next Generation ====<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks has been developed by Nikhef researchers and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays), advanced analysis techiques (using deep learning methods) and expanding the theory interpretation. Another opportunity would be the development of a new statistical combination with various independent searches, which could significantly improve the discovery potential. Supervisors: Marko Stamenkovic and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs interferentie ====<br />
In 2012 hebben het ATLAS en het CMS experiment het Higgs deeltje gevonden. Inmiddels zijn we het Higgs boson aan het bestuderen, hoe gedraagt het zich precies, bestaan er meer soorten Higgs bosonen of is er echt maar eentje van? In dit project leer je hoe we een Higgs boson kunnen herkennen in de detector en gaan we kijken naar hoe de signalen veranderen als er meer Higgs bosonen bestaan of misschien wel andere exotische nieuwe deeltjes. <br />
Dit doen we door gebruik te maken van quantum interferentie wat plaats vindt tussen het Higgs boson en achtergrondprocessen. Hoe dit precies werkt leer je in het project. Supervisor: Hella Snoek (h.snoek_at_nikhef.nl)<br />
<br />
=== B-Physics - LHCb ===<br />
<br />
==== Time dependent CP violation ====<br />
The LHCb experiment studies CP violation withB-meson decays.<br />
The project focusses on the measurement of the unitarity angle gamma using decays of the Bs mesons to Ds K.<br />
Supervisors: Sevda Esen & Michele Veronesi<br />
<br />
==== Machine learning ====<br />
Machine learning has proven to be an indispensable tool in the selection of interesting events in high energy physics. Such technologies will become increasingly important as detector upgrades are introduced and data rates increase by orders of magnitude. HEPDrone is a toolkit to enable the creation of a drone classifier from any machine learning classifier, such that different classifiers may be standardised into a single form and executed in parallel. A detailed evaluation of the performance of different drone models in the real production environment of LHCb will give the collaboration a complete idea of not only the advantages of the drone model, but also the limits of drone complexity given the available computing resources.<br />
Requirements: Advanced python and Advanced C++<br />
Supervisor: Sean Benson<br />
<br />
==== LHCb simulations of physics beyond the Standard Model ====<br />
This project is of relatively theoretical and computing nature and performs simulation studies for physics beyond the Standard Model in the context of long lived particles. It is related to test the sensitivity of the LHCb experiment to detect specific signals of physics beyond the Standard Model.<br />
supervisor: Carlos Vazquez Sierra<br />
<br />
=== Detector R&D ===<br />
<br />
==== Fast timing detectoren ====<br />
Op dit moment maken we veel gebruik van silicon detectoren in onze deeltjes experimenten. Deze zijn gevoelig voor geladen deeltjes en zijn bij uitstek geschikt om de paden vast te leggen die de deeltjes maken die in de botsingen worden gemaakt. Bijvoorbeeld in de Atlas en LHCb experimenten worden tientallen tot honderden deeltjes gemaakt bij elk botsingsgebeurtenis (event) die met 40MHz plaatsvinden. Voor toekomstige deeltjesdetectoren willen we niet alleen het traject vastleggen maar ook met grote precisie een tijdsmeting toevoegen. We hebben hiervoor dus nieuwe detectoren nodig die behalve met een hele hoge snelheid en efficientie de posities van de langsvliegende deeltjes kunnen vastleggen, maar hier ook een zeer nauwkeurige tijdsmeting (in orde van picosecondes) aan kunnen toevoegen. We hebben met verschillende detectoren metingen gedaan, in testbundels op CERN, maar ook in het lab op Nikhef kunnen we metingen doen. In dit project ga je samen met het fast-timing detectoren team op het Nikhef metingen verrichten en de resultaten hiervan bekijken. Contact: Hella Snoek (h.snoek@nikhef.nl)<br />
<br />
==== Muon tomography ====<br />
In this project we are not looking for where cosmic rays come from. We are looking for what we can use them for instead. The muons in cosmic rays can be used to ‘probe’ massive objects. Muons are short lived particles that carry the same charge as electrons, have a high penetrating power and can be detected relatively easy. It is possible to reconstruct a density distribution within an object by measuring muon scattering and absorption. In this context the objects may be freight containers, buildings, melting furnaces, etc… <br />
<br />
Systems that scan objects through the use of muons are often large (objects often need to be enclosed by the system) and complex. The question we want to answer is: Can we develop a smaller, simpler and cheaper system for muon tomography? <br />
<br />
A method to detect muons is by using a material that scintillates (emits light) when hit by an ionising particle. When this light emission is prompt after the passage of the muon, timing information of the light can be used to reconstruct the path of the muon.<br />
In this experiment we make a muon tracker based on two sheets of scintillating material and photo multiplier tubes (PMTs). Photo multiplier tubes are fast responding and very sensitive light detectors (capable of detecting single photons).<br />
<br />
The big question is: How well does this system perform?<br />
<br />
Currently a set-up is being build. You have a lot of freedom to choose a focus in this project (theory, simulation, hardware, or a combination of those).<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Spectral X-ray imaging - Looking at colours the eyes can't see ====<br />
When a conventional X-ray image is made to analyse the composition of a sample, or to perform a medical examination on a patient, one acquires an image that only shows intensities. One obtains a ‘black and white’ image. Most of the information carried by the photon energy is lost. Lacking spectral information can result in an ambiguity between material composition and amount of material in the sample. If the X-ray intensity as a function of the energy can be measured (i.e. a ‘colour’ X-ray image) more information can be obtained from a sample. This translates to less required dose and/or to a better understanding of the sample that is being investigated. For example, two fields that can benefit from spectral X-ray imaging are mammography and real time CT.<br />
<br />
X-ray detectors based on Medipix/Timepix pixel chips have spectral resolving capabilities and can be used to make polychromatic X-ray images. Medipix and Timepix chips have branched from pixel chips developed for detectors for high energy physics collider experiments.<br />
<br />
Some themes that students can work on: <br />
<br />
- Optimising methods to acquire spectral X-ray images.<br />
<br />
- Determining how much existing applications benefit from spectral X-ray imaging and looking for potential new applications.<br />
<br />
- Characterising, calibrating, optimising X-ray imaging detector systems.<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Holographic emitter ====<br />
A difficulty in generating holograms (based on the interference of light) is the required dense spatial light field sampling. One would need pixels of less than 200 nanometer. With larger pixels artefacts occur due to spatial under sampling. A pixel pitch of 200 nm or less is difficult, if not, impossible, to achieve, especially for larger areas. Another challenge is the massive amount of computing power that is required to control such a dense pixel matrix. <br />
<br />
A new holographic projection method has been developed that reduces under sampling artefacts, regardless of spatial sample density. The trick is to create 'pixels' at random but known positions, resulting in an array that lacks any spatial periodicity. As a result a holographic emitter can be built with a significantly lower sample density and less required computing power. This could bring holography in reach for many applications like display, lithography, 3D printing, metrology, etc...<br />
<br />
The big question: How does the performance of the holographic emitter depend on sample density and sample positions?<br />
<br />
The aspects of a holographic image we are interested in are:<br />
<br />
- Noise<br />
<br />
- Contrast<br />
<br />
- Suppression of under sampling artefacts<br />
<br />
- Resolution <br />
<br />
For this project we are building a proof of concept holographic emitter. This set-up will be used to verify simulation results (and to make some cool holograms of course). <br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
=== KM3NeT ===<br />
<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
==== Data analysis of the first deployed KM3NeT detection lines ====<br />
<br />
First detection lines of the KM3NeT neutrino telescope have been deployed<br />
in the Mediterranean Sea, and a first data set is available. The lines consist<br />
of light-sensitive detectors that record the time of arrival of photons<br />
produced by relativistic particles in the deep sea, and their number.<br />
In this project we will study the first data to separate various components:<br />
photons from potassium decay, bioluminesence, sparks in the photomultipliers,<br />
downgoing muons from cosmic rays, and perhaps first neutrinos.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Neutrino oscillation measurements with the KM3NeT neutrino telescope ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope currently under construction<br />
will be able to measure the oscillations of neutrinos produced in interactions<br />
of cosmic rays with the earth atmosphere. Fundamental neutrino properties can<br />
be deduced from these oscillations measurements, in particular the so-called<br />
mass hierarchy of neutrinos. In this project we will simulate the ORCA measurements<br />
of neutrino oscillations, and study the dependence of the sensitivity on<br />
experimental uncertainties, such as energy resolution and neutrino flavour<br />
identification, and theoretical uncertainties, such as the atmospheric neutrino<br />
flux and neutrino cross sections. The results will help ORCA to identify<br />
the main sources of uncertainty, and therefore to actively try to reduce these<br />
and improve the final measurement.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Performance Studies of ORCA for Dark Matter Detection ====<br />
<br />
The interactions of neutrinos in KM3NeT-ORCA give different signatures which are categorised as track and shower events. This project involves the studies of muon, electron and tau neutrino interactions for the reconstruction performance of ORCA. Efficient reconstruction of such signals is important for Dark Matter searches in the low-mass regime. We will work on understanding the detector performance, e.g. effective acceptance, energy and angular resolution, with different configurations of the detector setup. The result of this study will be very useful to improve the sensitivity of the experiment for Dark Matter detection and its possible location. The student will have the opportunity to work closely with KM3NeT members at Nikhef and gain skills of analyzing data. <br />
<br />
Supervisors: Suzan Basegmez du Pree, Aart Heijboer<br />
<br />
==== A search for periodic sources in Antares data ====<br />
<br />
The Antares deep-sea neutrino telescope has been operated for more then ten years. A search for periodic sources is proposed by applying a fast Fourier transformation (FFT) analysis on the available low-level data. This search will be combined with a (literature) study of pulsars which are thought to emit neutrinos.<br />
<br />
Supervisor: Maarten de Jong<br />
<br />
==== Study of Optical Properties of Sea Water using Hit Coincidences in MC Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
By studying coincidences of L1 hits between neighbouring DOMs, for various Monte Carlo (MC) data sets with different sea water optical properties such as scattering and absorption coefficients, in this project we try to figure out if and how well we can quantify optical sea water properties by studying L1 hit coincidences in real KM3NeT data.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
==== Determination of Inter-DOM Distances using Hit Coincidences in KM3NeT Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
The number of L1 hit coincidences from atmospheric muons between neighbouring DOMs on a DU is expected to decrease exponentially. By fitting the observed number of L1 hit coincidences between neighbouring DOMs in real data to the expected exponential decay, in this project we study how accurately we can determine the distances between DOMs on a single DU. In addition, we try to determine the distances between DUs by looking for L1 hit coincidences between DOMs on neighbouring DUs.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
=== VIRGO ===<br />
<br />
The Advanced LIGO and Advanced Virgo interferometers have recently observed gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results.<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Frank Linde (frank.linde_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
<br><br><br><br />
<br />
== Bachelor Projects 2017 ==<br />
<br />
=== Extreme Astronomy – Preparing for CTA, the Next-Generation Gamma-Ray Observatory ===<br />
<br />
The Cherenkov Telescope Array (CTA) is a planned facility for measuring gamma rays from space covering more than four orders of magnitude in energy, up to energies exceeding 100 TeV. CTA employs the imaging atmospheric Cherenkov technique to measure properties of cosmic gamma rays. This technique is based on measuring Cherenkov light emitted during the development of a gamma-ray air shower. CTA will be built at two experimental sites, one in the Northern, one in the Southern hemisphere, and will consist of up to 100 telescopes. It represents a major leap forward in sensitivity and precision for gamma-ray astronomy, and will allow us to explore very-high-energy processes of the extreme Universe at an unprecedented level.<br />
<br />
Two projects for students are available at the CTA group of UvA in the field of optical and photonic R&D contributing to the starting phase of CTA. For the first project the student will conduct measurements to characterise novel kinds of single-photon detectors, referred to as silicon photomultipliers, and evaluate different types of these sensors for their use for CTA. For the second project the student will develop and test an imaging system making use of a liquid crystal display. This flexible light source will be able to mimic images from different light sources of the night sky as seen by cameras of CTA, for instance gamma-ray air showers or stars, and will be used for camera tests and calibration.<br />
<br />
<br />
Supervisors: David Berge, Maurice Stephan (postdoc)<br />
<br />
=== Dark Matter ===<br />
<br />
<!--<br />
==== XENON1T - the world's most sensitive dark matter detector ====<br />
<br />
Finding the mysterious dark matter particles is one of the most challenging enterprises in physics today. Soon we will get first data from the world's most sensitive dark matter detector yet: the XENON1T experiment.<br />
<br />
The first goal of this project is to understand why dak matter is necessary to understand the universe, and how we could detect it with XENON1T. Then, you can contribute to our group's efforts preparing for <br />
and analyzing the XENON1T data by, for example: examining XENON1T's calibration signals to check for problems in the experiment, testing our data analysis software with simulated dark matter signals, or studying the physics behind XENON1T's detection process to learn how to better distinguish dark matter signals from backgrounds. For data analyis, experience with or willingness to learn programming in python is essential.<br />
<br />
<br />
Supervisors: M.P. Decowski & J. Aalbers --><br />
<br />
==== Neutrinoless double beta decay sensitivity study in future dark matter detectors ====<br />
<br />
The discovery of neutrino oscillation (Nobel Physics 2015) means that neutrinos have mass. We already know that their masses are tiny, more than one million times smaller than the next-lightest particle in the standard model, the electron. This raises the question if the mass-generation mechanism is the same for neutrinos as it is for the other subatomic particles. In particular, since neutrinos are electrically neutral, they could be their own anti-particles - we call these types of particles Majorana. The only practical way to discover if neutrinos are Majorana is through the search of an extremely rare radioactive decay called neutrinoless double beta decay (0n2b). A few isotopes are candidates for this process, among them Xe-136. The natural abundance of Xe-136 in natural xenon is about 9%, and this gives the opportunity to look for a 0n2b signal in xenon-based dark matter detectors like XENON1T and the future XENONnT and DARWIN detectors. <br />
<br />
We are looking for a student interested in doing a sensitivity study for 0n2b in XENONnT and the DARWIN experiments. The first goal will be to understand the physics addressed in neutrinoless double beta decay. Then the student will inventory possible backgrounds for the signal, use a (controversial) claim of a 0n2b signal as a benchmark and finally obtain the sensitivity of these future detectors. The work will involve simulations and analysis, building on an existing framework developed in our group. <br />
<br />
Supervisors: M.P. Decowski & A. Tiseni<br />
<br />
==== Shaking Dark Matter detectors ====<br />
<br />
Our XENON1T detector is built in the lab underneath the Gran Sasso mountains in central Italy. The lab is very well suited for low-background experiments due to the 1.5km of rock overburden. <br />
However, as you may know, cental Italy has been plagued by earthqaukes over the past decade, with the most recentones occurring in January 2017. We need a BSc student to investigate the <br />
details of such earthquakes in our underground lab. What are the magnitdues by which stuff is moving underground? What are the accelerations? What is the potential effect on our experimental<br />
setup? What would ahppen if an earthquake happens much closer to our lab? Furthermore we are interested to find out whether Earthquakes can be predicted. Some papers claim that before<br />
an earthquake the radon emanating from rock increases. In our lab we measure the radon concentration as a function of time: can you find a correlation between the measurements and recent <br />
earthquakes?<br />
<br />
If you are interested in finding out more about earthquakes, please contact M.P. Decowski or A.P. Colijn<br />
<br />
==== XAMS - a baby dark matter detector ====<br />
<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso<br />
we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector<br />
are identical to its big sibling in Gran Sasso.<br />
<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source we have acquired<br />
before the start of the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project<br />
will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study<br />
of neutron transport in xenon.<br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
==== Radon is bad for Dark Matter ====<br />
<br />
Radon is the dominant background for xenon based dark matter detectors, like the XENON1T experiment. In our lab at Nikhef we are investigating ways to reduce or eliminate the effect of radon<br />
on our sensitivity. For our lab setup XAMS we have designed and constructed a radon detector, that can be used in xenon systems at high-pressure. This completely new detector<br />
is now waiting for a BSc student to fully chracterize and use it. During this project you will first study the effect that radon contaminations have on dark matter detectors, then you will start working to<br />
understand our new radon detector in detail. You will learn howto use a radioactive source to calibrate the detector: this is something which is not easy and has not been done before in our lab. <br />
If you manage to succesfully calibrate the detector, we then want to incorporate it into our lab xenon system at Nikhef and maybe at some later stage in the real XENON1T detector!<br />
<br />
The profile of the student to work on this project is broad. I expect a good theoretical knowledge in order to quickly get upto speed with understanding dark mater detectors, and in addition I <br />
need 'lab-creativity' in order to develop methods for calibrating the new detector. If a good method is developed, it will be used for many years by the Nikhef dark matter group and beyond. <br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
=== ATLAS ===<br />
<br />
<br />
==== ATLAS (1): Searching for new physics with the Higgs and W bosons ====<br />
<br />
The strength of the Higgs interactions with electroweak bosons are precisely defined in the<br />
Standard Model. Therefore they are sensitive probes of the mechanism of electroweak symmetry<br />
breaking and enable searches for new physics beyond the SM. With the data collected by the ATLAS<br />
experiment in years 2015-2016 we plan to measure separately the Higgs coupling to<br />
longitudinally and transversely polarised W bosons in a process of weak boson fusion. To<br />
maximise experimental sensitivity we are developing techniques to separate the signal from<br />
background processes. You will take part in investigating possible improvements from<br />
reconstructing events in reference frames boosted with respect to the detector. During the<br />
project you will learn modern experimental analysis techniques. This project is a part of Vector<br />
Boson Scattering Coordination and Action Network (VBSCan) which connects researchers studying<br />
this and related topics worldwide.<br />
<br />
Supervisors: Pamela Ferrari, Magdalena Slawinska, Bob van Eijk<br />
<br />
<br />
==== ATLAS (2): Dark-matter-motivated searches for supersymmetric particles at the LHC ====<br />
<br />
Supersymmetry, a symmetry between fermions and bosons in particle physics,<br />
may provide a particle that could be the dark matter in the universe.<br />
The observation of an excess of gamma rays originating from the centre of our<br />
galaxy could be explained in a model where supersymmetric dark matter<br />
particles annihilate each other in the galactic centre, leading to gamma rays.<br />
<br />
Given the model parameters, it should also be possible to produce such<br />
particles at the LHC, at CERN in Geneva. But it is not so easy to observe<br />
them: the signal is small, and the noise (background) is large.<br />
In this project, we will use simulations of signal and background to<br />
optimize experimental searches for such particles with the ATLAS detector,<br />
apply them to the data collected in 2015, and prepare for the new data in<br />
2016 and later.Where possible, we will explore new machine learning techniques.<br />
<br />
Supervisors: Paul de Jong, Broos Vermeulen<br />
<br />
<br />
==== ATLAS (3): Simulations / Quality tests for the ATLAS High-Luminosity LHC Upgrade ====<br />
<br />
One of the key sub-systems of the ATLAS experiment at the Large<br />
Hadron Collider (LHC) is the Inner Detector (ID), designed to provide<br />
excellent charged particles momentum and vertex resolution measurements.<br />
<br />
At Phase-2 of the LHC run, in ~2025, the operating luminosity of<br />
the collider will be increased significantly.<br />
This will imply an upgrade of all ATLAS subsystems. In particular,<br />
the ID will be fully replaced with a tracker completely made of<br />
Silicon, having higher granularity and radiation hardness.<br />
The R&D process for the new ATLAS ID is now ongoing.<br />
Different geometrical layouts are simulated and their performance is<br />
studied under different operating conditions in search for the optimal<br />
detector architecture. Also, the performance of the new<br />
Si-sensors/modules is under investigation with dedicated laboratory tests.<br />
<br />
The focus of the project could be on the simulation of the High-Luminosity LHC<br />
version of the ATLAS Inner Detector. The student will learn how a<br />
high-energy physics experiment is designed and optimized.<br />
Alternatively, if possible at that moment, the student could<br />
work on a project at the Nikhef Silicon laboratory at the test-bench for<br />
new ATLAS Si-strip detectors and participate in the quality<br />
assurance procedure for the new ATLAS Si detectors.<br />
<br />
==== ATLAS (4): Higgs productie in Run-2 van de LHC ====<br />
In de eerste run van de LHC is onder andere bij het ATLAS experiment het Higgs deeltje gevonden. Nu is de tweede run begonnen en kan het Higgs deeltje worden bevestigd. Door de verhoogde energie ziet de achtergrond er echter heel anders uit, dus is de optimalisatie van het wegsnijden van de achtergronden qua fysica anders. Voor je bachelor project kan met behulp van de ATLAS detector het Higgs deeltje in run twee komen vinden. <br />
<br />
Supervisors: Lydia Brenner, Wouter Verkerke<br />
<br />
==== ATLAS (5): De lange staart van het Higgs boson ====<br />
<br />
[[File:HiggsMassa.png |thumb|left|upright=1.25]]<br />
<br />
<br><br />
Na de ontdekking van het Higgs boson in 2012 zijn we druk bezig om te kijken of zijn eigenschappen overeenkomen met de voorspellingen van het Standaard Model. Een van de belangrijkste eigenschappen is de zogenaamde breedte van het Higgs boson. Als het Higgs boson naast de Standaard Model deeltjes ook in exotische nieuwe speeltje uit elkaar kan vallen (bijvoorbeeld donkere materie) dan zal dat ale eerste zichtbaar worden in een afwijking van de breedte tov de verwachting. We gaan in dit project uitzoeken hoe de strategie die nu gebruikt wordt (meten van de hoeveelheid Higgs bosonen met een extreem hoge massa) precies werkt en kijken of we door het toevoegen van nieuwe ideeën een verbetering kunnen aanbrengen. <br />
<br />
<br><br />
Specifiek: We gaan eerst in detail de eigenschappen bekijken van het Higgs signaal en de twee achtergronden die er het meest op lijken. Daarna gaan we op zoek naar de verschillen en een manier waarop we onze kennis daarover kunnen gebruiken om gevoeliger te worden voor het Higgs signaal.<br />
<br />
Supervisors: Hella Snoek, Ivo van Vulpen<br />
<br />
E-mail: H.Snoek_at_nikhef.nl & Ivo.van.Vulpen_at_nikhef.nl<br />
<br><br><br><br><br><br><br />
<br />
=== ATLAS (6): Project ATLAS-ITk ===<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
<br><br />
<br />
=== KM3Net ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierachy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
The first phase of the KM3NeT neutrino telescope is currently under construction, with the first two detection units operational at 3500m depth in the Mediterranean Sea, 100 km off the coast of Sicily.<br />
<br />
<br />
==== KM3NeT (1): Photon counting in KM3NeT ====<br />
<br />
The details of a neutrino interaction, such as its incoming direction and energy, determine the pattern, time and amount, of recorded photons (´hits´) by the photo-multplier tubes. The time of arrival is recorded with nanosecond accuracy and the amount of photons is encoded in the length of the pulse(time-over-threshold, ToT). Currently, only the photon arrival time and the number of photo-multipliers that record a hit are used in reconstructing event properties.<br />
In this project, the distributions of the ToT mainly originating from photons from potassium-40 decays in the sea-water and from atmospheric muons passing through the water will be studied. The goals are to investigate the properties of the ToT distributions obtained from data and simulation, in particular the dependence on the photo-multiplier efficiency and atmospheric muon flux.<br />
In this project we will be extensively using the programming language C++ to analyse the data, so a reasonable proficiency is required.<br />
<br />
Supervisors: Ronald Bruijn & Karel Melis<br />
<br />
Email: rbruijn_at_nikhef.nl<br />
<br />
<br />
<br />
<br><br><br><br />
<br />
=== VIRGO ===<br />
<br />
"It is anticipated that in the next few years, Advanced LIGO and Advanced Virgo will start observing gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results."<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Jo van den Brand (jo_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
=== LHCb ===<br />
<br />
Begeleider: Sean Benson<br />
<br />
Title: <br />
Searching for physics beyond the Standard Model with LHCb<br />
<br />
The LHCb experiment is designed to study the "The Flavour Problem" in particle physics:<br />
Why is the universe dominated by matter over antimatter? Why are there three generations of elementary particles? What is the origin of quark flavour changing interactions.<br />
<br />
To solve these riddles, LHCb performs precision measurements on b-quark particle decays.<br />
An intriguing signal has recently been observed in the decay of a B-meson to a K* and two muons: Bd→K*μμ, which does not seem to behave according to the predictions of the Standard Model<br />
In this project the bachelor student will investigate this further by studying the case where the K* particle decays to a so-called k-short particle and a π0. The observation of such a final state will provide valuable information in the search for physics beyond the Standard Model.<br />
<br />
In this ambitious project the student is expected to study both a theory on the mechanism of CP violation with B mesons, in addition to data analysis with B decays. Programming experience in python is required.<br />
<br />
The LHCb experiment at CERN analyzes the properties of B-hadrons produced in proton-proton collisions at the LHC. For projects in the LHCb group, please contact Marcel Mark (marcel.merk_at_nikhef.nl)<br />
<br />
<br />
=== LHCb (1) ===<br />
<br />
One of the most fascinating mysteries in physics today is: how is it possible that universe is filled with matter? If the Big Bang produced equal amounts of matter and antimatter, we still do not understand the mechanism that lead to the excess of matter over antimatter that we observe today.<br />
<br />
One interesting feature of some particles is that they can transform themselves into their antiparticles, then back to particle, and so forth, in an oscillatory way until they finally decay. In particular, beauty mesons (B) can oscillate into their antiparticle (B ̄). The parameters of this oscillation, such as amplitude, frequency and phase, are calculable mathematically: predictions for it are available in the standard model (SM) of particle physics. But the oscillations according to the SM alone would not lead to the imbalance of matter in the universe – we still need to find a new type of physics that may be able to explain it.<br />
<br />
In this context, it is very important to measure B oscillations in the laboratory, and compare these observations with the expectations from the SM. Are the experimental data in good agreement with the SM, as we expect? If the aswer is not, i.e. if there are features of the oscillation that we do not understand well, then we may be observing “new physics”. In other words, the data may reveal a new mechanism that generates a different matter-antimatter balance than predicted by the SM, that may potentially solve the puzzle.<br />
<br />
The LHCb experiment at CERN is dedicated to such studies: LHCb detectors are placed in a region along the LHC collider beamline, where a large number of B mesons are produced, arising from the proton-proton collision data from the LHC collider. Looking at the LHCb data we can obtain large samples of B mesons, and observe their oscillations.<br />
In this project we will learn how to select a sample of B mesons out of the data taken with the LHCb detector, measure the parameters that govern their oscillation and compare them with the SM.<br />
<br />
For more information, please contact Mara Soares (msoares_at_nikhef.nl).</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Bachelor_Projects&diff=939Bachelor Projects2024-02-09T13:48:50Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>== Bachelor Projects 2024 ==<br />
<br />
=== Detector R&D ===<br />
<br />
=== KM3NeT ===<br />
<br />
=== Dark Matter ===<br />
<br />
=== ATLAS ===<br />
<br />
=== LHCb ===<br />
<br />
=== Gravitational waves ===<br />
<br />
=== Theory ===<br />
'''The Schiff theorem for Electric Dipole Moments (Jordy de Vries)'''<br />
<br />
Electric Dipole Moments (EDMs) of nucleons, atoms and molecules are important experimental observables to look for beyond-the-Standard-Model sources of fundamental symmetry violation. Specifically, the violation of Charge-Parity (CP) symmetry, which is present in the SM but not in sufficient amounts to explain the observed matter-antimatter asymmetry in the universe, can be probed through EDMs. To understand what EDM measurements on larger systems tell us about the fundamental physics at the elemental particle scale, and to assess what systems are most promising for EDM experiments, the Schiff theorem is essential. This theorem describes how, under certain simplifications, the EDMs of atoms and molecules vanish due to screening. In this project, you will investigate the theory behind Schiff screening, including possible violations of the theorem which lead to interesting systems with which to probe EDMs. For this project, the courses Advanced Quantum Physics & Atomic Physics are useful, but not strictly necessary.<br />
<br />
<br />
'''High-energy neutrino-nucleon interactions at the LHC with FASER''' (Juan Rojo, VU Amsterdam & Nikhef Theory)<br />
<br />
High-energy collisions at the Large Hadron Collider (LHC) produce an unprecedented number of light particles along the beam collision axis, outside of the acceptance of existing experiments. The FASER experiment, located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, provides new opportunities to probe Standard Model (SM) processes, in particular high-energy neutrino physics, and search for physics beyond the Standard Model (BSM). In this project, the student(s) will carry out updated theoretical predictions and numerical simulations for relevant physical processes at FASER, in particular concerning neutrino production and scattering, and assess their implications for our current models of proton structure and of QCD, the quantum field theory of the strong nuclear force. The project will also involve studying the implications of these results for ultra-high-energy particle astrophysics such as at the KM3NET and AUGER experiments. For this project, having followed the elective courses "Introduction to (astro-)particle physics" and "Standard Model of Elementary Particles" is required.<br />
<br />
''Contact: [[Mailto:j.rojo@vu.nl Juan Rojo]]''<br />
<br />
'''Probing the proton spin with machine learning at future colliders''' (Juan Rojo, VU Amsterdam & Nikhef Theory)<br />
<br />
An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions in particle physics from the nature of the Higgs boson to the origin of cosmic neutrinos. This effort requires combining an extensive experimental dataset and cutting-edge theory calculations within a machine learning framework where neural networks parametrise the underlying physical laws while minimising ad-hoc model assumptions. The upcoming Electron Ion Collider (EIC), to start taking data in 2030, will be the world's first ever polarised lepton-hadron collider and will offer a plethora of opportunities to address key open questions in our understanding of the strong nuclear force, such as the origin of the mass and the intrinsic angular momentum (spin) of hadrons and whether there exists a state of matter which is entirely dominated by gluons. In this project, the student will carry out a determination of the polarised quark and gluon substructure of the proton by means of the machine learning tools provided by the NNPDF open-source fitting framework and include projections for the impact of future EIC data on the spin content of the proton and on non-perturbative models of hadron structure. For this project, having followed the elective courses "Introduction to (astro-)particle physics" and "Standard Model of Elementary Particles" is required.<br />
<br />
''Contact: [[Mailto:j.rojo@vu.nl Juan Rojo]]''<br />
<br />
== Bachelor Projects 2023 ==<br />
<br />
=== KM3NeT ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along 200-700m long vertical lines, called detection units.<br />
<br />
<br />
==== Search for cosmic neutrinos with the first KM3NeT data ====<br />
<br />
The KM3NeT/ARCA block is tuned for the detection of cosmic neutrinos and search for their sources. The first data of ARCA will be used to search for cosmic neutrino sources, and to search for a neutrino signal in response to external alerts for transients (gamma-ray bursts, IceCube neutrinos, gravitational wave events). Furthermore there is the opportunity to search for a neutrino signal from dark matter annihilation in the galactic halo and in dwarf spheroidal galaxies.<br />
<br />
Supervisors: Thijs van Eeden, Jhilik Majumdar, Clara Gatius, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
<br />
==== Neutrino oscillations with KM3NeT/ORCA ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope is able to measure the oscillations of neutrinos produced in interactions of cosmic rays with the earth atmosphere. Fundamental neutrino properties can be deduced from these oscillations measurements. In this project we will use the first data of ORCA to study neutrino oscillations and fit neutrino mixing parameters and mass differences between neutrino mass states. We will study data selection, event reconstruction, and effects of systematic uncertainties on the results. <br />
<br />
Supervisors: Bouke Jung, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
<br />
==== Multi-messenger astronomy with neutrinos and radio signals ====<br />
The main goal of neutrino telescopes, such as ANTARES, KM3NeT and IceCube, is to detect cosmic neutrinos from astrophysical sources. When an interesting neutrino candidate is detected they send out a message to alert the scientific community. Other scientific instruments, like the Murchison Widefield Array (MWA) radio telescope, can then do a follow-up observation, to see if there are other messengers coming from the same source as the neutrinos. In this project you will analyse MWA data that were taken after the reception of neutrino alerts, to search for a radio source that can be associated with a neutrino source.<br />
<br />
Supervisor: Mieke Bouwhuis (mieke.bouwhuis at nikhef.nl)<br />
<br />
<br />
<br />
=== Dark Matter ===<br />
<br />
==== Investigating muon spallation backgrounds in KamLAND neutrino detector ====<br />
The KamLAND neutrino detector in Japan is designed to measure among other things neutrinoless double beta decay, an important process in particle physics that, should it be observed, would confirm that neutrinos might be their own antiparticles. However, the lack of detection of this process can be blamed on various backgrounds, one of which is muon spallation. Only recently did we start studying these spallation backgrounds in detail and we are looking for a student that has a strong interest in programming, simulations and data analysis to help the progression. The goal of this project is to allow for a better understanding of the behaviour of spallation events and to contribute to the simulation of the background that will be used in KamLAND, as well as future neutrino and dark matter experiments.<br />
<br />
Supervisors: Kelly Weerman and Patrick Decowski (decowski@nikhef.nl)<br />
<br />
==== First measurements with new VULCAN detectors ====<br />
At Nikhef we have a brand new experiment designed to measure the reflectance, transmission, and fluorescence properties of materials at vacuum ultraviolet (VUV) wavelengths. The materials to be studied are used to construct the XENONnT dark matter and the DUNE neutrino detectors. <br />
<br />
In this project, you will calibrate the characteristics of the VUV lamp and of the SiPM photon sensors used in VULCAN. Lab work at the Nikhef building will be a main part of the project, but you will also analyse the data you collect using modern analysis tools.<br />
<br />
You will gain experience with VUV optics, vacuum systems, single-photon sensors, and data analysis using Python and/or C++ tools.<br />
<br />
Supervisors: Marjolein van Nuland and Tina Pollmann (t.pollmann@nikhef.nl)<br />
<br />
==== The XAMS dark matter R&D setup at Nikhef ====<br />
The Nikhef dark matter group has a small version of the XENONnT dark matter detector in our Nikhef lab. With this detector we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENONnT experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso. We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with recently upgraded hardware to test a novel concept for UV light detection. The goal of this project will be to do the first measurements and analyze the data. Depending on the progress with the hardware we intend to complete the first measurements with our upgraded setup.<br />
<br />
Supervisors: Patrick Decowski (decowski@nikhef.nl) and A.P. Colijn (colijn@nikhef.nl)<br />
<br />
==== Reconstruction software for the XENONnT dark matter experiment ====<br />
The XENONnT dark matter experiment became operational in 2021. The experiment is in the Gran Sasso underground laboratory in Italy and the hardware is not being touched. However, we keep on developing and perfecting our reconstruction software. For this project we are looking for a student with a keen interest in and talent for writing physics-based event reconstruction software (we use python). Specifically we have an idea to improve the localization of events inside the XENONnT for which proto-type software exists. The proto-type software needs to be implemented in the XENONnT reconstruction framework and subsequently it needs to be validated on the first data from the experiment. The final goal of the project is to deliver the reconstruction software to the collaboration to be used during the lifetime of the experiment.<br />
<br />
Supervisors: Patrick Decowski and A.P. Colijn (colijn@nikhef.nl)<br />
<br />
=== ATLAS ===<br />
<br />
==== Machine-Learning in Top-Quark physics ====<br />
As the heaviest elementary particle the top quarks plays a key role in the Standard Model. Discovered in 1995 at the Tevatron accelerator, top quarks are now abundantly produced at the Large Hadron Collider (LHC) located at the European Organization for Nuclear Research (CERN) . But do these produced top quarks behave as predicted by the Standard Model or are there signs of new physics? To describe possible deviations, we use calculations from Effective Field Theory (EFT) that allows to add new interactions. For this project simulated data samples with deviations predicted by EFT are available.<br />
<br />
The candidate applies new techniques involving machine-learning to separate backgrounds from top quark production, aware for signs of new physics. Existing tools can be used to quantify the improvements on finding new interactions involving top quarks. Depending on the candidates interest, the focus of the project can be put more on machine-learning or top quark physics. For this project, we use the Python computing language and the ROOT package. Therefore, some proficiency with Python is required. Knowledge of C++ and root is advantageous but not required. <br />
<br />
Supervisors: Jordy Degens (PhD candidate) and Marcel Vreeswijk (h73@nikhef.nl).<br />
<br />
==== '''New machine learning approaches to target Higgs interference signatures in LHC data''' ====<br />
In this project we aim to improve an ongoing analysis to determine the lifetime of the Higgs Boson through state-of-the-art machine learning techniques, in particular by addressing a novel solution to an as of yet unsolved fundamental problem in modeling quantum interference. While the Higgs is an elusive particle that generally only appears in physics processes with small cross sections, its signature can be amplified in the Large Hadron Collider (LHC) through quantum interference with larger background (non-Higgs) processes. This is the effect that the Higgs’ lifetime analysis relies on to be able to measure the relevant Higgs signature. A fundamental physics modelling problem arises though in the simulation of individual events for this interference due to the fact that these events are in reality described by a superposition of underlying Higgs and non-Higgs processes.<br />
<br />
Since machine learning models in particle physics are typically trained to characterise individual physics events, the fact that interference events cannot currently be generated is a significant problem when interference is the target. In the currently existing Higgs lifetime analysis, a machine learning model was trained which instead focuses only on the explicit Higgs-mediated processes as a proxy, which is suboptimal. The aim of this project is to improve upon this current machine learning strategy used in this analysis by implementing either of the inference-aware approaches suggested in [1] and [2]. The idea behind these inference-aware machine learning algorithms is that they do not optimise for a simplified goal such as the loss function which is common in traditional machine learning, but rather for the end-goal of the analysis. In this case, this would omit the need for interference event generation altogether and allow the machine learning models to be trained optimally regardless.<br />
<br />
The goal of this project is to use either of the frameworks used in [1] and [2] (which are both publicly available) and run them with a simplified dataset from the aforementioned analysis as a proof-of-principle. In case this goal is achieved, the next goal would be to actually implement the newly developed machine learning models in the full analysis and to determine the improvement upon the existing result. Successful completion of these tasks would not only benefit the Higgs lifetime analysis, but would be an important stepping stone to future developments to make machine learning approaches deal better with other hard to model effects such as systematic uncertainties.<br />
<br />
Supervisors: Zef Wolffs, Ivo van Vulpen and Matous Vozak (matous.vozak@cern.ch)<br />
<br />
==== '''Reconstructing tracks from particle physics detector hits with state-of-the-art machine learning techniques''' ====<br />
This project concerns the application of new machine learning techniques to tackle the problem of track reconstruction at the ATLAS detector in CERN. While algorithms to construct particle tracks from low-level detector information such as particle hits and timestamps have been around for decades, recent developments in the field of machine learning open up new opportunities to improve these algorithms significantly. In particular graph-based neural networks and attention architectures prove promising candidates for solving these problems based on preliminary studies. <br />
<br />
In this project the student will develop machine learning models to initially reconstruct tracks from simplified test data. If time allows, real data from the ATLAS detector can be analyzed as well in the scope of this project. The student will need some familiarity with programming in python and an interest in machine learning, but a physics background is not required. In this project the student will be able to contribute to fundamental physics research and will familiarize themselves with state-of-the-art machine learning models.<br />
<br />
Supervisors: Zef Wolffs, Ivo van Vulpen and Matous Vozak (matous.vozak@cern.ch)<br />
<br />
=== LHCb ===<br />
<br />
=== Gravitational Waves ===<br />
<br />
====Staying in shape====<br />
Nikhef is co-leading the current effort to realise the Einstein Telescope (ET), a future 10km-scale underground observatory for gravitational waves. Numerical modelling software forms a crucial subsystem for the design and operation of the GW detectors. Our interferometer simulation software Finesse was developed for the design and commissioning of gravitational wave detectors and has become the main interferometer software tool in the community world wide. In our group we use Finesse to predict the shape of the laser beam and how this affects the GW data. You will join our group using Python-based scripts to model mis-shaped lasers and see how the interferometer reacts.<br />
<br />
Required knowledge:<br />
<br />
Good knowledge of Python is required.<br />
<br />
Knowledge of optics will be useful but is not required.<br />
<br />
Supervisors: Anna Green (agreen@nikhef.nl) and Andreas Freise (a.freise@nikhef.nl)<br />
<br />
====Riding the wave====<br />
Theoretical predictions of gravitational-wave (GW) signals provide essential tools to detect and analyse transient GW events in the data of GW instruments like LIGO and Virgo. Over the last few years, there has been significant effort to develop signal models that accurately describe the complex morphology of GWs from merging neutron-star and black-hole binaries. Our work focusses on a particular class of GW binary sources: those that come from two black holes meeting at close separation in dense stellar environments. Here, we expect the merging binary to be in a non-circular orbit and to have arbitrary spin orientations, which significantly complicates the prediction of its GW signal.<br />
<br />
We are looking for '''two''' students who are interested in the development of accurate and efficient GW models and their application in GW data analysis. We are offering '''two separate projects''' that aim to improve signal modeling at the interface of perturbation theory, numerical relativity simulations and fast phenomenological descriptions. Some proficiency in computing is required (Mathematica, Python or C++).<br />
<br />
Supervisor: Maria Haney (mhaney@nikhef.nl)<br />
<br />
=== Detector R&D ===<br />
<br />
====Charge collection study of fast monolithic detectors====<br />
In view of the upgrade of the ALICE tracking detector, innovative ultrathin monolithic silicon sensors are developed for testing. These devices are provided with analogue outputs to study in detail the charge collection and the timing properties of the sensor.<br />
The goal of the project is to contribute to the study of the charge collection features of the samples by measuring the response of the sensor to Fe55 X-rays.<br />
We are looking for a student with a focus on lab work and interested in contributing to the python-based data analysis.<br />
Depending on the progress with the intended measurement and the availability of the hardware, further studies with Sr90 electrons and a laser setup could be possible.<br />
<br />
Contacts: Jory Sonneveld (jory.sonneveld@nikhef.nl), Roberto Russo (rrusso@nikhef.nl)<br />
<br />
====Laser setup for silicon sensor studies====<br />
The Detector R&D group at Nikhef develops and tests detector concepts before they are used in scientific programs at Nikhef. To achieve such a goal, advanced instrumentation and setups are required.<br />
The goal of the project is to contribute to the design and construction of a fast infrared laser setup aimed at the characterization of silicon sensors for high energy physics experiments.<br />
We are looking for a student with a focus on lab work and interest in instrumentation and optics. Besides contributing to the setup construction, measurements finalised at the characterization of the laser beam (e.g. spot size, intensity) are foreseen.<br />
<br />
Contacts: Jory Sonneveld (jory.sonneveld@nikhef.nl), Roberto Russo (rrusso@nikhef.nl)<br />
<br />
==== Characterization of monolithic silicon sensors ====<br />
As part of the ongoing efforts for the design of ultimate tracking detectors, an excellent understanding of the basic performance of the detectors is required. To do so, the silicon detectors can be tested by making an electrical contact with the sensor using a probe station, a device for micrometer precision placement of temporary electrical contacts to acquire signals from internal nodes of semiconductor devices, to investigate aspects such as it's depletion voltage, depletion depth, the dark current and more which are essential for understanding the results gathered by the sensors later in the laboratory and allow the investigation of aspects that can be improved in further chip iterations. The goal of the project is to investigate the performance of monolithic sensors, where electronics is integrated into the sensor, developed for collider experiments like those at the large hadron collider at CERN and beyond. Depending on the progress with the planned measurements, further tests with the electronics and readout of the chip, as well as measurements with advanced laster instrumentation are also possible.<br />
<br />
Contacts: Jory Sonneveld (jory.sonneveld@nikhef.nl), Uwe Kraemer (uwe.kraemer@nikhef.nl)<br />
<br />
=== Theory ===<br />
'''Axion-Electrodynamics (Jordy de Vries and Arghavan Safavi-Nani)'''<br />
<br />
Axions are hypothetical particles that are introduced to solve the so-called strong CP problem. Being very light, axion can be described as a coherent classical field similar to electromagnetic fields. In this project, you will develop the modifications of Maxwell’s equations to include axion fields. Reference: arXiv:1401.0709 . <br />
<br />
'''Axions in a Paul-trap (Jordy de Vries and Arghavan Safavi-Nani)'''<br />
<br />
Axions are hypothetical particles that are introduced to solve the so-called strong CP problem. If axions form the dark matter in our universe, they can be described by a coherent oscillating background field. This oscillating field interacts with charged particles and it possible to detect axions by the motion of ions in a Paul trap. In this project, you will investigate how these interactions work and what are the observables associated to the detection of axions in ion traps.<br />
<br />
'''Phase space integrals for double-weak processes (Jordy de Vries)'''<br />
<br />
The rarest processes ever measured are so-called double weak processes in which two neutrons undergo beta decay at the same time in a nucleus. Lifetimes of these processes are in the 10^22 years range. Theoretical computations of these rates involve so-called phase space integrals that take into account the possible momentum configurations of the outgoing electrons and neutrinos. In this project you will investigate these phase space integrals and develop a method to compute them. <br />
<br />
<br />
<br />
<br />
<br />
<br />
== Bachelor Projects 2022 ==<br />
<br />
=== Dark Matter ===<br />
<br />
==== Response of materials to scintillation light from liquid noble gasses ====<br />
<br />
The liquid form of the noble gases argon and xenon is a popular target material for neutrino and dark matter detectors. The scintillation light from noble gases is in the vacuum UV spectral region. Air and many materials used for optical studies are not transparent to these photons. Measurements of the optical properties of detector materials, such as their reflectivity for example, thus have to be performed with dedicated VUV optics and in vacuum. Additionally, to reproduce the conditions in the detectors, the samples must be cooled to cryogenic temperatures. In this BSc project, you will calibrate the photon detectors in an experimental setup designed to study the optical response of materials excited with VUV photons. You will learn about material requirements for rare event search detectors, vacuum instrumentation, vacuum UV optics including monochromators and spectrometers, and single-photon sensors.<br />
<br />
Supervisors: T. Pollmann (t.pollmann_at_nikhef.nl)<br />
====XAMS====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENONnT detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENONnT experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso. We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with recently upgraded hardware to test a novel concept for UV light detection. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complete the first measurements with our upgraded setup.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
==== XENONnT reconstruction software ====<br />
The XENONnT experiment becomes operational during 2021. While the hwardware is finished we keep on developing and perfecting our reconstruction software. For this project we are looking for a student with a keen interest in and talent for writing physics based event reconstruction software (we use python). Specifically we have an idea to improve the localization of events inside the XENONnT for which proto-type software exists. The proto-type software needs to be implemented in the XENONnT reconstruction framework and subsequently it needs to be validated on the first data from the experiment. The final goal of the project is to deliver the reconstruction software to the collaboration that will be used during teh full lifetime of the experiment.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
=== ATLAS ===<br />
<br />
==== The Higgs boson - did we miss anything and can we do better? ====<br />
<br />
The Higgs boson is a key element of the Standard Model (SM) of particle physics, however, it can also represent a link between yet unexplored 'new' physics beyond the SM. What is the Higgs boson life-time? How precisely can we measure its mass? Is there an additional heavy Higgs boson? Do other particles, not contained in the SM, couple to the Higgs? All these questions can be studied by measuring Higgs properties using one of the Higgs decay modes to photons, vector bosons, quarks and leptons and comparing them with the (beyond) SM predictions. <br />
<br />
As the restart of the Large Hadron Collider (LHC) is imminent, it is essential to develop and test new physics ideas and strategies. '''The ATLAS open data project''' will allow students to work on a real analysis digging through the LHC data collected during Run2. Students will go through all the key aspects of a Higgs analysis performed also by ATLAS physicists. They will learn about Higgs boson theory and its simulation, what objects are reconstructed in the ATLAS experiment, how well do we understand them and finally how does this project into our understanding of the Higgs boson and its properties. <br />
<br />
The exact focus of the topic is flexible depending on the interest of a student. For instance, a student can delve into how precisely can we determine objects' energy and their positions and see whether we can '''improve our estimate of the Higgs mass (project 1)'''. Another possibility is to focus on trying to find out whether there is '''an additional (heavier) Higgs (project 2)''' in the data and how confident we can be of that. Each of these projects will most likely yield new questions, so feel free to take a tangent and walk into yet unexplored territory and see what the data tells you.<br />
<br />
Supervisor: Matouš Vozak (m.vozak_at_nikhef.nl) & Ivo van Vulpen (Ivo.van.Vulpen_at_nikhef.nl)<br />
<br />
==== The Higgs boson life-time ====<br />
<br />
The Higgs particle does not have eternal life. The Standard Model (SM) predicts that it decays into other particles and as these couplings are fixed we can predict its life-time with very high precision. Determining this life-time is a crucial test for the Standard Model. If the Higgs boson life-time is shorter that we expect this could mean that the Higgs boson could decay into non-SM particles. In this project we investigate a) how we can identify Higgs particles in the detector and b) how we plan to use quantum-interference to get a handle on the Higgs boson's life-time. <br />
<br />
Supervisor: Wouter Verkerke (verkerke_at_nikhef.nl)<br />
<br />
==== Higgs interferentie ====<br />
In 2012 hebben het ATLAS en het CMS experiment het Higgs deeltje gevonden. Inmiddels zijn we het Higgs boson aan het bestuderen, hoe gedraagt het zich precies, bestaan er meer soorten Higgs bosonen of is er echt maar eentje van? In dit project leer je hoe we een Higgs boson kunnen herkennen in de detector en gaan we kijken naar hoe de signalen veranderen als er meer Higgs bosonen bestaan of misschien wel andere exotische nieuwe deeltjes. <br />
Dit doen we door gebruik te maken van quantum interferentie wat plaats vindt tussen het Higgs boson en achtergrondprocessen. Hoe dit precies werkt leer je in het project. Supervisor: Hella Snoek (h.snoek_at_nikhef.nl)<br />
<br />
<br />
=== LHCb ===<br />
<br />
<br />
==== Exotic neutrinos in B decays====<br />
<br />
Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, heavier, neutral leptons. In the LHCb group at Nikhef we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undisovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The bachelor project will contribute with the optimization of the selection using state-of-the-art tools for the multi-variate analysis.<br />
<br />
Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
<br />
<br />
=== Gravitational Waves ===<br />
<br />
=== Detector R&D ===<br />
Answering big elementary particle physics questions requires pioneering experiments. The Detector R&D program at Nikhef is aimed at conceptualizing and testing of instrumentation concepts before they are implemented in scientific programs at Nikhef. <br />
<br />
==== Time resolution of monolithic timing detectors ====<br />
For the upgrade of the vertex detectors of the large LHC experiments like LHCb and ALICE, new silicon pixel detectors will developed now that can register the passing particles with a time precision of tens of picoseconds. ALICE is the first experiment at the LHC to have installed monolithic sensors where electronics is integrated into the sensor resulting in ultrathin, low-material detectors, that will soon see it's first particles from LHC collisions. In this project you will measure the time resolution of these promising integrated sensors with a laser setup in our laboratory.<br />
<br />
Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
==== Modeling radiation damage in silicon sensors ====<br />
In the coming years, the ATLAS experiment at the LHC works on upgrades to prepare for the high-luminosity LHC, where many more collisions will take place than today. Analyses of LHC data rely heavily on simulations of the detector. It may sound counterintuitive, but particle detectors do not actually like particles: after many collisions at the LHC, a silicon pixel detector has seen so many particles that its bulk gathers defects. Charge generated by traversing particles can get trapped in defects resulting in less charge induced in the readout electrodes, reducing detector performance in resolution and efficiency. In this project, you will be part of the international ATLAS collaboration and compare different models of radiation damage with measured data and you will contribute to the open source program Allpix Squared that is widely used for simulations in many areas of particle physics.<br />
<br />
Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
==== Time resolution of a new digital pixel test structure from test beam data ====<br />
For the upgrade of the ALICE detector, ultrathin picosecond timing integrated sensors are developed. To reduce power consumption, asynchronous readout is implemented in this prototype sensor in a digital pixel test structure. This structure was studied in test beams with an ALPIDE (ALICE PIxel DEtector) telescope at CERN. You will measure the efficiency and time resolution of this new sensor with the latest data from test beams at CERN.<br />
<br />
Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
<br />
==== Fast timing detectoren ====<br />
Op dit moment maken we veel gebruik van silicon detectoren in onze deeltjes experimenten. Deze zijn gevoelig voor geladen deeltjes en zijn bij uitstek geschikt om de paden vast te leggen die de deeltjes maken die in de botsingen worden gemaakt. Bijvoorbeeld in de Atlas en LHCb experimenten worden tientallen tot honderden deeltjes gemaakt bij elk botsingsgebeurtenis (event) die met 40MHz plaatsvinden. Voor toekomstige deeltjesdetectoren willen we niet alleen het traject vastleggen maar ook met grote precisie een tijdsmeting toevoegen. We hebben hiervoor dus nieuwe detectoren nodig die behalve met een hele hoge snelheid en efficientie de posities van de langsvliegende deeltjes kunnen vastleggen, maar hier ook een zeer nauwkeurige tijdsmeting (in orde van picosecondes) aan kunnen toevoegen. We hebben met verschillende detectoren metingen gedaan, in testbundels op CERN, maar ook in het lab op Nikhef kunnen we metingen doen. In dit project ga je samen met het fast-timing detectoren team op het Nikhef metingen verrichten en de resultaten hiervan bekijken. Contact: Hella Snoek (h.snoek@nikhef.nl)<br />
<br />
<br />
=== KM3NeT ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along 200-700m long vertical lines, called detection units.<br />
<br />
==== Neutrino oscillation measurements with the first KM3NeT data ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope is able to measure the oscillations of neutrinos produced in interactions of cosmic rays with the earth atmosphere. Fundamental neutrino properties can be deduced from these oscillations measurements. In this project we will use the first data of ORCA (more than one year with six detection units) to study neutrino oscillations and fit neutrino mixing parameters and mass differences between neutrino mass states. We will study data selection, event reconstruction, and effects of systematic uncertainties on the results. <br />
<br />
Supervisors: Brian O'Fearraigh, Ronald Bruijn, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
==== Search for sterile neutrinos with KM3NeT. ====<br />
A detailed study of neutrino oscillations in the KM3NeT detector is sensitive to the existence of so-called sterile neutrinos: neutrinos that are not part of the Standard Model of particle physics, and have no ordinary interactions with matter. We will use a mixture of data and simulations to estimate KM3NeT sensitivity.<br />
<br />
Supervisors: Alba Domi, Paul de Jong<br />
<br />
==== Machine learning for event classification in KM3NeT ====<br />
The classification of neutrino events recorded in the KM3NeT detector in terms of originating from electron neutrinos, muon neutrinos, or tau neutrinos, is very well suited for machine learning techniques. We will study the performance of a few advanced machine learning techniques on simulated high-energy neutrino events.<br />
<br />
Supervisors: Alba Domi, Paul de Jong<br />
<br />
==== Multi-messenger astronomy with neutrinos and radio signals ====<br />
The main goal of neutrino telescopes, such as ANTARES, KM3NeT and IceCube, is to detect cosmic neutrinos from astrophysical sources. When an interesting neutrino candidate is detected they send out a message to alert the scientific community. Other scientific instruments, like the Murchison Widefield Array (MWA) radio telescope, can then do a follow-up observation, to see if there are other messengers coming from the same source as the neutrinos. In this project you will analyse MWA data that were taken after the reception of neutrino alerts, to search for a radio source that can be associated with a neutrino source.<br />
<br />
Supervisor: Mieke Bouwhuis (mieke.bouwhuis at nikhef.nl)<br />
<br />
=== Theory ===<br />
<br />
==== Effective Field Theories of Particle Physics from low- to high-energies (2022 not yet determined if available in 2023) ====<br />
<br />
Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations<nowiki>''</nowiki> seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature.<br />
<br />
Until recently, it was widely assumed that matter particles from each of the three generations interact with the same (“universal”) strength. This hypothesis is being challenged by new measurements at the Large Hadron Collider (LHC) at CERN, which hint towards non-universal interactions. If confirmed, these measurements will be the first signs of new particles and interactions in high-energy colliders. These exciting findings indicate the urgent need to explore such phenomena in depth.<br />
<br />
The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Effective Field Theory (EFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes. Specifically, the goal is to connect measurements from ATLAS and LHCb among them and to jointly interpret this information with that provided by other experiments, from CMS and Belle-II to very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
<br />
''Methodology and workplan''<br />
<br />
This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories.<br />
<br />
This project accommodates several students, who would work together in developing the main formalism while each of them focuses on a specific sub-project. The maximum capacity of this project is 5 students. <br />
<br />
Depending on the student profile, sub-projects with a strong computational / machine learning component are also possible.<br />
<br />
During the first four weeks of the project, students will learn the required background material on effective field theories, following the guidelines from the supervisors. Afterwards, they will focus on different sub-projects, each covering a different aspect of the same global EFT program.<br />
<br />
Required knowledge<br />
<br />
Quantum Mechanics 2, Particle Physics 1 (required)<br />
<br />
Advanced Quantum Mechanics, Particle Physics 2, Machine Learning (optional)<br />
<br />
Available subprojects<br />
<br />
Here we list the available subprojects, including the corresponding daily supervisor(s) in each case.<br />
<br />
''Subproject #1: SMEFT & Flavour symmetries'' <br />
<br />
Daily supervisors: Jordy de Vries (UvA), Keri Vos (Maastricht University), Jaco ter Hoeve (VU), Giacomo Magni (VU)<br />
<br />
While the power of the Standard Model EFT (named SMEFT) framework is its generality and lack of assumptions, the number of operators is somewhat daunting. A popular way to trim the number of operators is to assume flavour symmetries that relate operators with different quark and lepton flavours. In this project you will investigate the theoretical basis for commonly-used flavour symmetries and what they imply for the connection between high-energy observables involving third-generation particles (top and bottom quarks and tau leptons) and low-energy precision tests involving first- and second-generation particles. The investigations of this project are connected with Subproject #2.<br />
<br />
''Subproject #2: SMEFT & magnetic moment of the muon''<br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU)<br />
<br />
The magnetic moment of the muon appears to differ from the Standard Model expectations by a large amount, well beyond the known experimental and theoretical uncertainties. Recent experiments have only strengthened the significance of this anomaly. In this project, the students will investigate the feasibility of implementing the measurement of the magnetic moment of the muon into a global SMEFT analysis, by exploiting recently provided calculations. Special attention will be devoted to the flavour assumptions required to consistently match this measurement with the LHC data, also at the light of the connection with Subproject #1. The SMEFiT analysis framework will be used to connect the g-2 data with high-energy LHC measurements.<br />
<br />
''Subproject #3: CP Violation and low-energy precision experiments''<br />
<br />
Most analyses of LHC data are performed under the assumption that CP symmetry (charge conjugation + parity, essentially the symmetry between particles and anti-particles) is conserved. More recent analyses attempt to also measure possible new sources of CP violation in SMEFT operators in the Higgs and top sector. <br />
<br />
''Subproject #3a: CP Violation and low-energy precision experiments''<br />
<br />
Daily supervisors: Jordy de Vries (UvA), Juan Rojo (VU)<br />
<br />
Low-energy precision experiments can also set stringent constraints on new mechanisms of CP violation. In this project you will try to combine high- and low-energy data to put CP symmetry to the test. <br />
<br />
''Subproject #3b: CP Violation and flavour physics experiments''<br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU)<br />
<br />
Besides low-energy precision experiments, also B-meson decays are excellent probes of CP violation. Unlike most low-energy experiments, this allows us to probe CP violation in the third generation. In this project you will link constraints on CP violation at high-energy to those from B meson decays. <br />
<br />
''Subproject #4: SMEFT & optimal observables'' <br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU), Tommaso Giani (VU & Nikhef)<br />
<br />
In full generality, the number of operators in SMEFT spans a very large parameter space. These parameters are constrained by experimental inputs from ATLAS and CMS, depending on the precise parameters these constraints may be more or less stringent. In order to fully exploit the whole parameters space in SMEFT, it is necessary to devise statistically optimal observables that have a large constraining power. In this project, we will define such observables. This project has a strong computational / machine learning component and may involve simulations based on tools such as MadGraph and Pythia8.<br />
<br />
Contacts:<br />
<br />
Juan Rojo (VU Amsterdam & Nikhef): j.rojo at vu.nl<br />
<br />
Keri Vos (UM & Nikhef): k.vos at maastrichtuniversity.nl <br />
<br />
Jordy de Vries (UvA & Nikhef): j.devries4 at uva.nl<br />
<br />
== Bachelor Projects 2021 ==<br />
=== Dark Matter ===<br />
<br />
==== XAMS ====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso.<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with recently upgraded hardware to test a novel concept for UV light detection. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complete the first measurements with our upgraded setup.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== XENONnT reconstruction software ====<br />
The XENONnT experiment becomes operational during 2021. While the hwardware is finished we keep on developing and perfecting our reconstruction software. For this project we are looking for a student with a keen interest in and talent for writing physics based event reconstruction software (we use python). Specifically we have an idea to improve the localization of events inside the XENONnT for which proto-type software exists. The proto-type software needs to be implemented in the XENONnT reconstruction framework and subsequently it needs to be validated on the first data from the experiment. The final goal of the project is to deliver the reconstruction software to the collaboration that will be used during teh full lifetime of the experiment.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Backgrounds in Radioactive Decay Measurements ====<br />
At Nikhef, the XENON group has a working setup, continuously monitoring the<br />
radioactive decay of Cobalt-60, Caesium-137 and Titanium-44. This beautiful setup is<br />
however not shielded perfectly; it is still vulnerable to background radioactivity. Our<br />
current way of working around this background radiation is to subtract it from our<br />
waveforms. You as a BSc student could help us hands-on and with analyses:<br />
together, we can disassemble the setup, measure background spectra and<br />
implement this in the data analysis. You can use all the data to validate the<br />
lifetime of our isotopes!<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Detection of scintillation light from liquid noble gasses ====<br />
<br />
The liquid form of the noble gases argon and xenon is a popular target material for neutrino and dark matter detectors. The scintillation light from noble gases is in the vacuum UV spectral region. Air and many materials used for optics studies are not transparent to these photons. Measurements of the optical properties of detector materials, such as their reflectivity for example, thus have to be performed with dedicated VUV optics and in vacuum. Additionally, to reproduce the conditions in the detectors, the samples must be cooled to cryogenic temperatures. In this BSc project, you will design, using professional hardware design software, a vacuum chamber to hold the detector materials whose optical properties are to be investigated, as well as the cooling system and photon detectors. You will learn about material requirements for rare event search detectors, vacuum instrumentation, vacuum UV optics including monochromators and spectrometers, and single-photon sensors.<br />
<br />
Supervisors: T. Pollmann (t.pollmann_at_nikhef.nl)<br />
<br />
=== Detector R&D ===<br />
<br />
==== Characterization of the new ultrathin ALPIDE monolithic active pixel sensor ====<br />
At the Large Hadron Collider at CERN, major upgrades of experiments take place in the long shutdown years where particle collisions are paused. The ALICE inner tracking system (ITS) 2, the part of the ALICE experiment closest to the beam pipe, is currently being installed at CERN. This detector makes use of ultra-lightweight monolithic active pixel sensors, the first to use this technology at particle colliders after the STAR experiment at RHIC in Brookhaven. These very thin pixel detectors have a low power consumption, result in very little material in the detector, and still have optimal timing and resolution -- and are a promising technology for future experiments. To characterize the performance of these sensors, you will learn to set up experiments, carry out measurements, and analyze data using various instruments available in the detector R&D lab at Nikhef. This could lead to novel insights of monolithic active pixel sensors. It is also possible to do measurements from home using data from the first test beams with bent (yes, with a curvature!) ALPIDE sensors. You will work in an international, stimulating research environment in the detector R&D group at Nikhef at the forefront of silicon detector technologies for high energy physics. ''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
==== Simulation of 3D silicon sensors ====<br />
<br />
For the upgrade of the vertex detector of the LHCb experiment novel silicon pixel detectors have to be developed that can register the passing particles with a time precision of tens of picoseconds. Given the harsh radiation environment very close to the LHCb interaction point only a limited number of technologies can be applied. One of the most promising technologies are the so-called 3D sensors whose readout electrodes are pillars that are placed into the sensor perpendicular to the surface; this in contrast to ’standard’ planar silicon sensors where the pixel electrodes are at the surface, similar to the camera in your smartphone. To understand the time response of these 3D sensors, simulations with TCAD software have to be performed and the results will be compared to measured data. These simulations involve the creation/adaptation of the 3D structures of the model, optimising the simulation speed, and analysing the signals as function voltage, track impact point and deposited charge. If time and Covid regulations permit, gaining some hands-on experience with such 3D sensors in the R&D labs at Nikhef is possible. ''Contacts: [mailto:martinb@nikhef.nl Martin van Beuzekom] [mailto:k.heijhoff@cern.ch Kevin Heijhoff] ''<br />
<br />
<br />
=== Theory ===<br />
<br />
==== Standard Model Effective Field Theory analysis of Z+dijet production ====<br />
The goal of this project is to study the effect of higher dimensional operators from the Standard Model Effective Field Theory in Z-boson production measured at LHC. The ATLAS collaboration has just reported in 2020 the measurement of Z production alongside with a pair of jets, based on the full Run II luminosity. In this project we aim to study the effect of dimension six SMEFT operators on the signal (EW-induced) and/or background (QCD-induced), finding which is the kinematic variable that maximises the possible effect of beyond the SM operators and thus may provide the best constraint on New Physics. The outcome of this project may be the first step of the inclusion of Vector production in a global SMEFT fit. <br />
<br />
References: https://arxiv.org/pdf/2006.15458.pdf, https://www.hepdata.net/record/ins1803608<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Maximum precision on new physics through information theory ====<br />
One way to look for physics beyond the standard model is through the framework of effective field theory. In this framework, deviations from the standard model are described by a set of continuous parameters. Finding constraints on these parameters might point to the discovery of new physics. With the large number of LHC experiments we currently face, we want to be able to quantify the maximum knowledge that (future) experiments can provide on new physics parameters. In this project, the student will study and quantify the maximum information that is contained in particle physics experiments through information theory. The central object of study will be the Fisher information matrix. The idea is to work with a simple toy experiment that describes Higgs physics and compute its associated Fisher information matrix to quantify the optimal bounds on new physics. The project will start with studying central objects from statistics and information theory. Later, we will apply these to open problems in particle physics.<br />
<br />
Reference: https://arxiv.org/pdf/1612.05261.pdf<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Seesaw mechanism and neutrino mass ==== <br />
Many unsolved questions in particle physics are related to the nature of the neutrino and its mass generation. The goal of this theoretical project is to understand and review one of the possible candidate theories that describe how neutrinos mix and get massive, namely the Seesaw mechanism. Among the many possible Seesaw mechanisms that can generate new phenomenology including lepton number non-conservation, the student will focus on one minimal model to understand the key processes that are currently used to probe the validity of the given theory. <br />
<br />
References: https://cds.cern.ch/record/408119/files/9911364.pdf, https://arxiv.org/pdf/1711.02180.pdf<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Mixing of sterile neutrinos ====<br />
<br />
Neutrino oscillation experiments demonstrate that neutrinos are massive particles. However, the mass mechanism of neutrinos is unknown. A<br />
minimal solution requires the existence of so-called sterile neutrinos: neutrinos that are even more elusive than ordinary neutrinos. <br />
We will investigate how to parametrize the matrix that describes the mixing between ordinary and sterile neutrinos. We will then use this<br />
to calculate how sterile neutrinos induce rare nuclear decays and determine the sensitivity of ongoing experiments to observe sterile<br />
neutrinos.<br />
<br />
Supervisor: Jordy de Vries (devries.jordy at gmail.com)<br />
<br />
<br />
=== KM3NeT ===<br />
<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
==== Data analysis of the first deployed KM3NeT detection lines ====<br />
<br />
First detection lines of the KM3NeT neutrino telescope have been deployed<br />
in the Mediterranean Sea, and a first data set is available. The lines consist<br />
of light-sensitive detectors that record the time of arrival of photons<br />
produced by relativistic particles in the deep sea, and their number.<br />
In this project we will study the first data to separate various components:<br />
photons from potassium decay, bioluminesence, sparks in the photomultipliers,<br />
downgoing muons from cosmic rays, and first neutrinos.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben (paul.de.jong at nikhef.nl)<br />
<br />
==== Neutrino oscillation measurements with the KM3NeT neutrino telescope ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope currently under construction<br />
will be able to measure the oscillations of neutrinos produced in interactions<br />
of cosmic rays with the earth atmosphere. Fundamental neutrino properties can<br />
be deduced from these oscillations measurements, in particular the so-called<br />
mass hierarchy of neutrinos. In this project we will simulate the ORCA measurements<br />
of neutrino oscillations, and study the dependence of the sensitivity on<br />
experimental uncertainties, such as energy resolution and neutrino flavour<br />
identification, and theoretical uncertainties, such as the atmospheric neutrino<br />
flux and neutrino cross sections. The results will help ORCA to identify<br />
the main sources of uncertainty, and therefore to actively try to reduce these<br />
and improve the final measurement.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
==== Performance Studies of ORCA for Dark Matter Detection ====<br />
<br />
The interactions of neutrinos in KM3NeT-ORCA give different signatures which are categorised as track and shower events. This project involves the studies of muon, electron and tau neutrino interactions for the reconstruction performance of ORCA. Efficient reconstruction of such signals is important for Dark Matter searches in the low-mass regime. We will work on understanding the detector performance, e.g. effective acceptance, energy and angular resolution, with different configurations of the detector setup. The result of this study will be very useful to improve the sensitivity of the experiment for Dark Matter detection and its possible location. The student will have the opportunity to work closely with KM3NeT members at Nikhef and gain skills of analyzing data. <br />
<br />
Supervisors: Suzan Basegmez du Pree, Aart Heijboer (s.basegmez.du.pree at nikhef.nl)<br />
<br />
==== Study of Optical Properties of Sea Water using Hit Coincidences in MC Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
By studying coincidences of L1 hits between neighbouring DOMs, for various Monte Carlo (MC) data sets with different sea water optical properties such as scattering and absorption coefficients, in this project we try to figure out if and how well we can quantify optical sea water properties by studying L1 hit coincidences in real KM3NeT data.<br />
<br />
Supervisor: Daan van Eijk (dveijk at nikhef.nl)<br />
<br />
==== Determination of Inter-DOM Distances using Hit Coincidences in KM3NeT Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
The number of L1 hit coincidences from atmospheric muons between neighbouring DOMs on a DU is expected to decrease exponentially. By fitting the observed number of L1 hit coincidences between neighbouring DOMs in real data to the expected exponential decay, in this project we study how accurately we can determine the distances between DOMs on a single DU. In addition, we try to determine the distances between DUs by looking for L1 hit coincidences between DOMs on neighbouring DUs.<br />
<br />
Supervisor: Daan van Eijk (dveijk at nikhef.nl)<br />
<br />
<br />
=== ATLAS ===<br />
<br />
==== The Higgs boson life-time ====<br />
<br />
The Higgs particle does not have eternal life. The Standard Model (SM) predicts that it decays into other particles and as these couplings are fixed we can predict its life-time with very high precision. Determining this life-time is a crucial test for the Standard Model. If the Higgs boson life-time is shorter that we expect this could mean that the Higgs boson could decay into non-SM particles. In this project we investigate a) how we can identify Higgs particles in the detector and b) how we plan to use quantum-interference to get a handle on the Higgs boson's life-time. <br />
<br />
Supervisor: Wouter Verkerke (verkerke_at_nikhef.nl)<br />
<br />
==== The Higgs boson decaying to photons ====<br />
<br />
One of the main channels used to analyse the properties of the Higgs boson is when the Higgs boson decays into two photons. The crucial building block in this analysis is our ability to reconstruct the energy and the direction of the photons in the ATLAS detector and in this project we will revisit the photon reconstruction. We will start by studying simulations and learning about photon reconstruction in general. Then our goal is to determine the energy and position resolution of photons in the ATLAS detector and see if we can exploit our knowledge on the photon resolution to get an (improved) estimate of the Higgs boson mass. For the analysis we will use the '''real data from the LHC''' - the ATLAS open data project.<br />
<br />
Supervisor: Ashley McDougall and Ivo van Vulpen (Ivo.van.Vulpen_at_nikhef.nl)<br />
<br />
<br />
=== LHCb (1) ===<br />
<br />
One of the most fascinating mysteries in physics today is: how is it possible that universe is filled with matter? If the Big Bang produced equal amounts of matter and antimatter, we still do not understand the mechanism that lead to the excess of matter over antimatter that we observe today.<br />
<br />
One interesting feature of some particles is that they can transform themselves into their antiparticles, then back to particle, and so forth, in an oscillatory way until they finally decay. In particular, beauty mesons (B) can oscillate into their antiparticle (B ̄). The parameters of this oscillation, such as amplitude, frequency and phase, are calculable mathematically: predictions for it are available in the standard model (SM) of particle physics. But the oscillations according to the SM alone would not lead to the imbalance of matter in the universe – we still need to find a new type of physics that may be able to explain it.<br />
<br />
In this context, it is very important to measure B oscillations in the laboratory, and compare these observations with the expectations from the SM. Are the experimental data in good agreement with the SM, as we expect? If the aswer is not, i.e. if there are features of the oscillation that we do not understand well, then we may be observing “new physics”. In other words, the data may reveal a new mechanism that generates a different matter-antimatter balance than predicted by the SM, that may potentially solve the puzzle.<br />
<br />
The LHCb experiment at CERN is dedicated to such studies: LHCb detectors are placed in a region along the LHC collider beamline, where a large number of B mesons are produced, arising from the proton-proton collision data from the LHC collider. Looking at the LHCb data we can obtain large samples of B mesons, and observe their oscillations.<br />
In this project we will learn how to select a sample of B mesons out of the data taken with the LHCb detector, measure the parameters that govern their oscillation and compare them with the SM.<br />
<br />
For more information, please contact Mara Soares (msoares_at_nikhef.nl).<br />
<br />
== Bachelor Projects 2020 ==<br />
<br />
<br />
=== Dark Matter ===<br />
<br />
==== XAMS ====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso.<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source and liquid scintillatorneutron detector we have acquired for the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study of neutron transport in xenon.<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Backgrounds in Radioactive Decay Measurements ====<br />
At Nikhef, the XENON group has a working setup, continuously monitoring the<br />
radioactive decay of Cobalt-60, Caesium-137 and Titanium-44. This beautiful setup is<br />
however not shielded perfectly; it is still vulnerable to background radioactivity. Our<br />
current way of working around this background radiation is to subtract it from our<br />
waveforms. You as a BSc student could help us hands-on and with analyses:<br />
together, we can disassemble the setup, measure background spectra and<br />
implement this in the data analysis. You can use all the data to validate the<br />
lifetime of our isotopes!<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
=== ATLAS ===<br />
<br />
==== Project ATLAS-ITk ====<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
==== The Most Energetic Higgs Boson ====<br />
A common approach to search for physics beyond the standard model is by searching for the direct production of new particles. Alternatively, indirect quantum effects on the production of known particles -such as the Higgs Boson- could reveal the first cracks in the theory. Processes with high energy transfer are of particular potential since possible deviations are expected to increase with the square of the involved energy scale. Using the entire data-set collected by the ATLAS experiment at CERN during the four years of the LHC’s Run 2, a proof-of-principle analysis, targeting transverse momenta of the above 400 GeV, has been developed by Nikhef researchers. The first results of this Higgs boson study are expected to be published this year and this project aims to develop refinements of the analysis techniques. We will investigate the usage of sophisticated machine learning tools such as artificial neural networks, the search for new variables that can help discriminating the signal from its background, revisiting the analysis categorisation and improving the reconstruction techniques at these extreme momenta. Supervisors: Brian Moser and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs: The Next Generation ====<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks has been developed by Nikhef researchers and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays), advanced analysis techiques (using deep learning methods) and expanding the theory interpretation. Another opportunity would be the development of a new statistical combination with various independent searches, which could significantly improve the discovery potential. Supervisors: Marko Stamenkovic and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs interferentie ====<br />
In 2012 hebben het ATLAS en het CMS experiment het Higgs deeltje gevonden. Inmiddels zijn we het Higgs boson aan het bestuderen, hoe gedraagt het zich precies, bestaan er meer soorten Higgs bosonen of is er echt maar eentje van? In dit project leer je hoe we een Higgs boson kunnen herkennen in de detector en gaan we kijken naar hoe de signalen veranderen als er meer Higgs bosonen bestaan of misschien wel andere exotische nieuwe deeltjes. <br />
Dit doen we door gebruik te maken van quantum interferentie wat plaats vindt tussen het Higgs boson en achtergrondprocessen. Hoe dit precies werkt leer je in het project. Supervisor: Hella Snoek (h.snoek_at_nikhef.nl)<br />
<br />
=== B-Physics - LHCb ===<br />
<br />
==== Time dependent CP violation ====<br />
The LHCb experiment studies CP violation withB-meson decays.<br />
The project focusses on the measurement of the unitarity angle gamma using decays of the Bs mesons to Ds K.<br />
Supervisors: Sevda Esen & Michele Veronesi<br />
<br />
==== Machine learning ====<br />
Machine learning has proven to be an indispensable tool in the selection of interesting events in high energy physics. Such technologies will become increasingly important as detector upgrades are introduced and data rates increase by orders of magnitude. HEPDrone is a toolkit to enable the creation of a drone classifier from any machine learning classifier, such that different classifiers may be standardised into a single form and executed in parallel. A detailed evaluation of the performance of different drone models in the real production environment of LHCb will give the collaboration a complete idea of not only the advantages of the drone model, but also the limits of drone complexity given the available computing resources.<br />
Requirements: Advanced python and Advanced C++<br />
Supervisor: Sean Benson<br />
<br />
==== LHCb simulations of physics beyond the Standard Model ====<br />
This project is of relatively theoretical and computing nature and performs simulation studies for physics beyond the Standard Model in the context of long lived particles. It is related to test the sensitivity of the LHCb experiment to detect specific signals of physics beyond the Standard Model.<br />
supervisor: Carlos Vazquez Sierra<br />
<br />
=== Detector R&D ===<br />
<br />
==== Fast timing detectoren ====<br />
Op dit moment maken we veel gebruik van silicon detectoren in onze deeltjes experimenten. Deze zijn gevoelig voor geladen deeltjes en zijn bij uitstek geschikt om de paden vast te leggen die de deeltjes maken die in de botsingen worden gemaakt. Bijvoorbeeld in de Atlas en LHCb experimenten worden tientallen tot honderden deeltjes gemaakt bij elk botsingsgebeurtenis (event) die met 40MHz plaatsvinden. Voor toekomstige deeltjesdetectoren willen we niet alleen het traject vastleggen maar ook met grote precisie een tijdsmeting toevoegen. We hebben hiervoor dus nieuwe detectoren nodig die behalve met een hele hoge snelheid en efficientie de posities van de langsvliegende deeltjes kunnen vastleggen, maar hier ook een zeer nauwkeurige tijdsmeting (in orde van picosecondes) aan kunnen toevoegen. We hebben met verschillende detectoren metingen gedaan, in testbundels op CERN, maar ook in het lab op Nikhef kunnen we metingen doen. In dit project ga je samen met het fast-timing detectoren team op het Nikhef metingen verrichten en de resultaten hiervan bekijken. Contact: Hella Snoek (h.snoek@nikhef.nl)<br />
<br />
==== Muon tomography ====<br />
In this project we are not looking for where cosmic rays come from. We are looking for what we can use them for instead. The muons in cosmic rays can be used to ‘probe’ massive objects. Muons are short lived particles that carry the same charge as electrons, have a high penetrating power and can be detected relatively easy. It is possible to reconstruct a density distribution within an object by measuring muon scattering and absorption. In this context the objects may be freight containers, buildings, melting furnaces, etc… <br />
<br />
Systems that scan objects through the use of muons are often large (objects often need to be enclosed by the system) and complex. The question we want to answer is: Can we develop a smaller, simpler and cheaper system for muon tomography? <br />
<br />
A method to detect muons is by using a material that scintillates (emits light) when hit by an ionising particle. When this light emission is prompt after the passage of the muon, timing information of the light can be used to reconstruct the path of the muon.<br />
In this experiment we make a muon tracker based on two sheets of scintillating material and photo multiplier tubes (PMTs). Photo multiplier tubes are fast responding and very sensitive light detectors (capable of detecting single photons).<br />
<br />
The big question is: How well does this system perform?<br />
<br />
Currently a set-up is being build. You have a lot of freedom to choose a focus in this project (theory, simulation, hardware, or a combination of those).<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Spectral X-ray imaging - Looking at colours the eyes can't see ====<br />
When a conventional X-ray image is made to analyse the composition of a sample, or to perform a medical examination on a patient, one acquires an image that only shows intensities. One obtains a ‘black and white’ image. Most of the information carried by the photon energy is lost. Lacking spectral information can result in an ambiguity between material composition and amount of material in the sample. If the X-ray intensity as a function of the energy can be measured (i.e. a ‘colour’ X-ray image) more information can be obtained from a sample. This translates to less required dose and/or to a better understanding of the sample that is being investigated. For example, two fields that can benefit from spectral X-ray imaging are mammography and real time CT.<br />
<br />
X-ray detectors based on Medipix/Timepix pixel chips have spectral resolving capabilities and can be used to make polychromatic X-ray images. Medipix and Timepix chips have branched from pixel chips developed for detectors for high energy physics collider experiments.<br />
<br />
Some themes that students can work on: <br />
<br />
- Optimising methods to acquire spectral X-ray images.<br />
<br />
- Determining how much existing applications benefit from spectral X-ray imaging and looking for potential new applications.<br />
<br />
- Characterising, calibrating, optimising X-ray imaging detector systems.<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Holographic emitter ====<br />
A difficulty in generating holograms (based on the interference of light) is the required dense spatial light field sampling. One would need pixels of less than 200 nanometer. With larger pixels artefacts occur due to spatial under sampling. A pixel pitch of 200 nm or less is difficult, if not, impossible, to achieve, especially for larger areas. Another challenge is the massive amount of computing power that is required to control such a dense pixel matrix. <br />
<br />
A new holographic projection method has been developed that reduces under sampling artefacts, regardless of spatial sample density. The trick is to create 'pixels' at random but known positions, resulting in an array that lacks any spatial periodicity. As a result a holographic emitter can be built with a significantly lower sample density and less required computing power. This could bring holography in reach for many applications like display, lithography, 3D printing, metrology, etc...<br />
<br />
The big question: How does the performance of the holographic emitter depend on sample density and sample positions?<br />
<br />
The aspects of a holographic image we are interested in are:<br />
<br />
- Noise<br />
<br />
- Contrast<br />
<br />
- Suppression of under sampling artefacts<br />
<br />
- Resolution <br />
<br />
For this project we are building a proof of concept holographic emitter. This set-up will be used to verify simulation results (and to make some cool holograms of course). <br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
=== KM3NeT ===<br />
<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
==== Data analysis of the first deployed KM3NeT detection lines ====<br />
<br />
First detection lines of the KM3NeT neutrino telescope have been deployed<br />
in the Mediterranean Sea, and a first data set is available. The lines consist<br />
of light-sensitive detectors that record the time of arrival of photons<br />
produced by relativistic particles in the deep sea, and their number.<br />
In this project we will study the first data to separate various components:<br />
photons from potassium decay, bioluminesence, sparks in the photomultipliers,<br />
downgoing muons from cosmic rays, and perhaps first neutrinos.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Neutrino oscillation measurements with the KM3NeT neutrino telescope ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope currently under construction<br />
will be able to measure the oscillations of neutrinos produced in interactions<br />
of cosmic rays with the earth atmosphere. Fundamental neutrino properties can<br />
be deduced from these oscillations measurements, in particular the so-called<br />
mass hierarchy of neutrinos. In this project we will simulate the ORCA measurements<br />
of neutrino oscillations, and study the dependence of the sensitivity on<br />
experimental uncertainties, such as energy resolution and neutrino flavour<br />
identification, and theoretical uncertainties, such as the atmospheric neutrino<br />
flux and neutrino cross sections. The results will help ORCA to identify<br />
the main sources of uncertainty, and therefore to actively try to reduce these<br />
and improve the final measurement.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Performance Studies of ORCA for Dark Matter Detection ====<br />
<br />
The interactions of neutrinos in KM3NeT-ORCA give different signatures which are categorised as track and shower events. This project involves the studies of muon, electron and tau neutrino interactions for the reconstruction performance of ORCA. Efficient reconstruction of such signals is important for Dark Matter searches in the low-mass regime. We will work on understanding the detector performance, e.g. effective acceptance, energy and angular resolution, with different configurations of the detector setup. The result of this study will be very useful to improve the sensitivity of the experiment for Dark Matter detection and its possible location. The student will have the opportunity to work closely with KM3NeT members at Nikhef and gain skills of analyzing data. <br />
<br />
Supervisors: Suzan Basegmez du Pree, Aart Heijboer<br />
<br />
==== A search for periodic sources in Antares data ====<br />
<br />
The Antares deep-sea neutrino telescope has been operated for more then ten years. A search for periodic sources is proposed by applying a fast Fourier transformation (FFT) analysis on the available low-level data. This search will be combined with a (literature) study of pulsars which are thought to emit neutrinos.<br />
<br />
Supervisor: Maarten de Jong<br />
<br />
==== Study of Optical Properties of Sea Water using Hit Coincidences in MC Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
By studying coincidences of L1 hits between neighbouring DOMs, for various Monte Carlo (MC) data sets with different sea water optical properties such as scattering and absorption coefficients, in this project we try to figure out if and how well we can quantify optical sea water properties by studying L1 hit coincidences in real KM3NeT data.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
==== Determination of Inter-DOM Distances using Hit Coincidences in KM3NeT Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
The number of L1 hit coincidences from atmospheric muons between neighbouring DOMs on a DU is expected to decrease exponentially. By fitting the observed number of L1 hit coincidences between neighbouring DOMs in real data to the expected exponential decay, in this project we study how accurately we can determine the distances between DOMs on a single DU. In addition, we try to determine the distances between DUs by looking for L1 hit coincidences between DOMs on neighbouring DUs.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
=== VIRGO ===<br />
<br />
The Advanced LIGO and Advanced Virgo interferometers have recently observed gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results.<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Frank Linde (frank.linde_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
<br><br><br><br />
<br />
== Bachelor Projects 2017 ==<br />
<br />
=== Extreme Astronomy – Preparing for CTA, the Next-Generation Gamma-Ray Observatory ===<br />
<br />
The Cherenkov Telescope Array (CTA) is a planned facility for measuring gamma rays from space covering more than four orders of magnitude in energy, up to energies exceeding 100 TeV. CTA employs the imaging atmospheric Cherenkov technique to measure properties of cosmic gamma rays. This technique is based on measuring Cherenkov light emitted during the development of a gamma-ray air shower. CTA will be built at two experimental sites, one in the Northern, one in the Southern hemisphere, and will consist of up to 100 telescopes. It represents a major leap forward in sensitivity and precision for gamma-ray astronomy, and will allow us to explore very-high-energy processes of the extreme Universe at an unprecedented level.<br />
<br />
Two projects for students are available at the CTA group of UvA in the field of optical and photonic R&D contributing to the starting phase of CTA. For the first project the student will conduct measurements to characterise novel kinds of single-photon detectors, referred to as silicon photomultipliers, and evaluate different types of these sensors for their use for CTA. For the second project the student will develop and test an imaging system making use of a liquid crystal display. This flexible light source will be able to mimic images from different light sources of the night sky as seen by cameras of CTA, for instance gamma-ray air showers or stars, and will be used for camera tests and calibration.<br />
<br />
<br />
Supervisors: David Berge, Maurice Stephan (postdoc)<br />
<br />
=== Dark Matter ===<br />
<br />
<!--<br />
==== XENON1T - the world's most sensitive dark matter detector ====<br />
<br />
Finding the mysterious dark matter particles is one of the most challenging enterprises in physics today. Soon we will get first data from the world's most sensitive dark matter detector yet: the XENON1T experiment.<br />
<br />
The first goal of this project is to understand why dak matter is necessary to understand the universe, and how we could detect it with XENON1T. Then, you can contribute to our group's efforts preparing for <br />
and analyzing the XENON1T data by, for example: examining XENON1T's calibration signals to check for problems in the experiment, testing our data analysis software with simulated dark matter signals, or studying the physics behind XENON1T's detection process to learn how to better distinguish dark matter signals from backgrounds. For data analyis, experience with or willingness to learn programming in python is essential.<br />
<br />
<br />
Supervisors: M.P. Decowski & J. Aalbers --><br />
<br />
==== Neutrinoless double beta decay sensitivity study in future dark matter detectors ====<br />
<br />
The discovery of neutrino oscillation (Nobel Physics 2015) means that neutrinos have mass. We already know that their masses are tiny, more than one million times smaller than the next-lightest particle in the standard model, the electron. This raises the question if the mass-generation mechanism is the same for neutrinos as it is for the other subatomic particles. In particular, since neutrinos are electrically neutral, they could be their own anti-particles - we call these types of particles Majorana. The only practical way to discover if neutrinos are Majorana is through the search of an extremely rare radioactive decay called neutrinoless double beta decay (0n2b). A few isotopes are candidates for this process, among them Xe-136. The natural abundance of Xe-136 in natural xenon is about 9%, and this gives the opportunity to look for a 0n2b signal in xenon-based dark matter detectors like XENON1T and the future XENONnT and DARWIN detectors. <br />
<br />
We are looking for a student interested in doing a sensitivity study for 0n2b in XENONnT and the DARWIN experiments. The first goal will be to understand the physics addressed in neutrinoless double beta decay. Then the student will inventory possible backgrounds for the signal, use a (controversial) claim of a 0n2b signal as a benchmark and finally obtain the sensitivity of these future detectors. The work will involve simulations and analysis, building on an existing framework developed in our group. <br />
<br />
Supervisors: M.P. Decowski & A. Tiseni<br />
<br />
==== Shaking Dark Matter detectors ====<br />
<br />
Our XENON1T detector is built in the lab underneath the Gran Sasso mountains in central Italy. The lab is very well suited for low-background experiments due to the 1.5km of rock overburden. <br />
However, as you may know, cental Italy has been plagued by earthqaukes over the past decade, with the most recentones occurring in January 2017. We need a BSc student to investigate the <br />
details of such earthquakes in our underground lab. What are the magnitdues by which stuff is moving underground? What are the accelerations? What is the potential effect on our experimental<br />
setup? What would ahppen if an earthquake happens much closer to our lab? Furthermore we are interested to find out whether Earthquakes can be predicted. Some papers claim that before<br />
an earthquake the radon emanating from rock increases. In our lab we measure the radon concentration as a function of time: can you find a correlation between the measurements and recent <br />
earthquakes?<br />
<br />
If you are interested in finding out more about earthquakes, please contact M.P. Decowski or A.P. Colijn<br />
<br />
==== XAMS - a baby dark matter detector ====<br />
<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso<br />
we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector<br />
are identical to its big sibling in Gran Sasso.<br />
<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source we have acquired<br />
before the start of the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project<br />
will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study<br />
of neutron transport in xenon.<br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
==== Radon is bad for Dark Matter ====<br />
<br />
Radon is the dominant background for xenon based dark matter detectors, like the XENON1T experiment. In our lab at Nikhef we are investigating ways to reduce or eliminate the effect of radon<br />
on our sensitivity. For our lab setup XAMS we have designed and constructed a radon detector, that can be used in xenon systems at high-pressure. This completely new detector<br />
is now waiting for a BSc student to fully chracterize and use it. During this project you will first study the effect that radon contaminations have on dark matter detectors, then you will start working to<br />
understand our new radon detector in detail. You will learn howto use a radioactive source to calibrate the detector: this is something which is not easy and has not been done before in our lab. <br />
If you manage to succesfully calibrate the detector, we then want to incorporate it into our lab xenon system at Nikhef and maybe at some later stage in the real XENON1T detector!<br />
<br />
The profile of the student to work on this project is broad. I expect a good theoretical knowledge in order to quickly get upto speed with understanding dark mater detectors, and in addition I <br />
need 'lab-creativity' in order to develop methods for calibrating the new detector. If a good method is developed, it will be used for many years by the Nikhef dark matter group and beyond. <br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
=== ATLAS ===<br />
<br />
<br />
==== ATLAS (1): Searching for new physics with the Higgs and W bosons ====<br />
<br />
The strength of the Higgs interactions with electroweak bosons are precisely defined in the<br />
Standard Model. Therefore they are sensitive probes of the mechanism of electroweak symmetry<br />
breaking and enable searches for new physics beyond the SM. With the data collected by the ATLAS<br />
experiment in years 2015-2016 we plan to measure separately the Higgs coupling to<br />
longitudinally and transversely polarised W bosons in a process of weak boson fusion. To<br />
maximise experimental sensitivity we are developing techniques to separate the signal from<br />
background processes. You will take part in investigating possible improvements from<br />
reconstructing events in reference frames boosted with respect to the detector. During the<br />
project you will learn modern experimental analysis techniques. This project is a part of Vector<br />
Boson Scattering Coordination and Action Network (VBSCan) which connects researchers studying<br />
this and related topics worldwide.<br />
<br />
Supervisors: Pamela Ferrari, Magdalena Slawinska, Bob van Eijk<br />
<br />
<br />
==== ATLAS (2): Dark-matter-motivated searches for supersymmetric particles at the LHC ====<br />
<br />
Supersymmetry, a symmetry between fermions and bosons in particle physics,<br />
may provide a particle that could be the dark matter in the universe.<br />
The observation of an excess of gamma rays originating from the centre of our<br />
galaxy could be explained in a model where supersymmetric dark matter<br />
particles annihilate each other in the galactic centre, leading to gamma rays.<br />
<br />
Given the model parameters, it should also be possible to produce such<br />
particles at the LHC, at CERN in Geneva. But it is not so easy to observe<br />
them: the signal is small, and the noise (background) is large.<br />
In this project, we will use simulations of signal and background to<br />
optimize experimental searches for such particles with the ATLAS detector,<br />
apply them to the data collected in 2015, and prepare for the new data in<br />
2016 and later.Where possible, we will explore new machine learning techniques.<br />
<br />
Supervisors: Paul de Jong, Broos Vermeulen<br />
<br />
<br />
==== ATLAS (3): Simulations / Quality tests for the ATLAS High-Luminosity LHC Upgrade ====<br />
<br />
One of the key sub-systems of the ATLAS experiment at the Large<br />
Hadron Collider (LHC) is the Inner Detector (ID), designed to provide<br />
excellent charged particles momentum and vertex resolution measurements.<br />
<br />
At Phase-2 of the LHC run, in ~2025, the operating luminosity of<br />
the collider will be increased significantly.<br />
This will imply an upgrade of all ATLAS subsystems. In particular,<br />
the ID will be fully replaced with a tracker completely made of<br />
Silicon, having higher granularity and radiation hardness.<br />
The R&D process for the new ATLAS ID is now ongoing.<br />
Different geometrical layouts are simulated and their performance is<br />
studied under different operating conditions in search for the optimal<br />
detector architecture. Also, the performance of the new<br />
Si-sensors/modules is under investigation with dedicated laboratory tests.<br />
<br />
The focus of the project could be on the simulation of the High-Luminosity LHC<br />
version of the ATLAS Inner Detector. The student will learn how a<br />
high-energy physics experiment is designed and optimized.<br />
Alternatively, if possible at that moment, the student could<br />
work on a project at the Nikhef Silicon laboratory at the test-bench for<br />
new ATLAS Si-strip detectors and participate in the quality<br />
assurance procedure for the new ATLAS Si detectors.<br />
<br />
==== ATLAS (4): Higgs productie in Run-2 van de LHC ====<br />
In de eerste run van de LHC is onder andere bij het ATLAS experiment het Higgs deeltje gevonden. Nu is de tweede run begonnen en kan het Higgs deeltje worden bevestigd. Door de verhoogde energie ziet de achtergrond er echter heel anders uit, dus is de optimalisatie van het wegsnijden van de achtergronden qua fysica anders. Voor je bachelor project kan met behulp van de ATLAS detector het Higgs deeltje in run twee komen vinden. <br />
<br />
Supervisors: Lydia Brenner, Wouter Verkerke<br />
<br />
==== ATLAS (5): De lange staart van het Higgs boson ====<br />
<br />
[[File:HiggsMassa.png |thumb|left|upright=1.25]]<br />
<br />
<br><br />
Na de ontdekking van het Higgs boson in 2012 zijn we druk bezig om te kijken of zijn eigenschappen overeenkomen met de voorspellingen van het Standaard Model. Een van de belangrijkste eigenschappen is de zogenaamde breedte van het Higgs boson. Als het Higgs boson naast de Standaard Model deeltjes ook in exotische nieuwe speeltje uit elkaar kan vallen (bijvoorbeeld donkere materie) dan zal dat ale eerste zichtbaar worden in een afwijking van de breedte tov de verwachting. We gaan in dit project uitzoeken hoe de strategie die nu gebruikt wordt (meten van de hoeveelheid Higgs bosonen met een extreem hoge massa) precies werkt en kijken of we door het toevoegen van nieuwe ideeën een verbetering kunnen aanbrengen. <br />
<br />
<br><br />
Specifiek: We gaan eerst in detail de eigenschappen bekijken van het Higgs signaal en de twee achtergronden die er het meest op lijken. Daarna gaan we op zoek naar de verschillen en een manier waarop we onze kennis daarover kunnen gebruiken om gevoeliger te worden voor het Higgs signaal.<br />
<br />
Supervisors: Hella Snoek, Ivo van Vulpen<br />
<br />
E-mail: H.Snoek_at_nikhef.nl & Ivo.van.Vulpen_at_nikhef.nl<br />
<br><br><br><br><br><br><br />
<br />
=== ATLAS (6): Project ATLAS-ITk ===<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
<br><br />
<br />
=== KM3Net ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierachy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
The first phase of the KM3NeT neutrino telescope is currently under construction, with the first two detection units operational at 3500m depth in the Mediterranean Sea, 100 km off the coast of Sicily.<br />
<br />
<br />
==== KM3NeT (1): Photon counting in KM3NeT ====<br />
<br />
The details of a neutrino interaction, such as its incoming direction and energy, determine the pattern, time and amount, of recorded photons (´hits´) by the photo-multplier tubes. The time of arrival is recorded with nanosecond accuracy and the amount of photons is encoded in the length of the pulse(time-over-threshold, ToT). Currently, only the photon arrival time and the number of photo-multipliers that record a hit are used in reconstructing event properties.<br />
In this project, the distributions of the ToT mainly originating from photons from potassium-40 decays in the sea-water and from atmospheric muons passing through the water will be studied. The goals are to investigate the properties of the ToT distributions obtained from data and simulation, in particular the dependence on the photo-multiplier efficiency and atmospheric muon flux.<br />
In this project we will be extensively using the programming language C++ to analyse the data, so a reasonable proficiency is required.<br />
<br />
Supervisors: Ronald Bruijn & Karel Melis<br />
<br />
Email: rbruijn_at_nikhef.nl<br />
<br />
<br />
<br />
<br><br><br><br />
<br />
=== VIRGO ===<br />
<br />
"It is anticipated that in the next few years, Advanced LIGO and Advanced Virgo will start observing gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results."<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Jo van den Brand (jo_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
=== LHCb ===<br />
<br />
Begeleider: Sean Benson<br />
<br />
Title: <br />
Searching for physics beyond the Standard Model with LHCb<br />
<br />
The LHCb experiment is designed to study the "The Flavour Problem" in particle physics:<br />
Why is the universe dominated by matter over antimatter? Why are there three generations of elementary particles? What is the origin of quark flavour changing interactions.<br />
<br />
To solve these riddles, LHCb performs precision measurements on b-quark particle decays.<br />
An intriguing signal has recently been observed in the decay of a B-meson to a K* and two muons: Bd→K*μμ, which does not seem to behave according to the predictions of the Standard Model<br />
In this project the bachelor student will investigate this further by studying the case where the K* particle decays to a so-called k-short particle and a π0. The observation of such a final state will provide valuable information in the search for physics beyond the Standard Model.<br />
<br />
In this ambitious project the student is expected to study both a theory on the mechanism of CP violation with B mesons, in addition to data analysis with B decays. Programming experience in python is required.<br />
<br />
The LHCb experiment at CERN analyzes the properties of B-hadrons produced in proton-proton collisions at the LHC. For projects in the LHCb group, please contact Marcel Mark (marcel.merk_at_nikhef.nl)<br />
<br />
<br />
=== LHCb (1) ===<br />
<br />
One of the most fascinating mysteries in physics today is: how is it possible that universe is filled with matter? If the Big Bang produced equal amounts of matter and antimatter, we still do not understand the mechanism that lead to the excess of matter over antimatter that we observe today.<br />
<br />
One interesting feature of some particles is that they can transform themselves into their antiparticles, then back to particle, and so forth, in an oscillatory way until they finally decay. In particular, beauty mesons (B) can oscillate into their antiparticle (B ̄). The parameters of this oscillation, such as amplitude, frequency and phase, are calculable mathematically: predictions for it are available in the standard model (SM) of particle physics. But the oscillations according to the SM alone would not lead to the imbalance of matter in the universe – we still need to find a new type of physics that may be able to explain it.<br />
<br />
In this context, it is very important to measure B oscillations in the laboratory, and compare these observations with the expectations from the SM. Are the experimental data in good agreement with the SM, as we expect? If the aswer is not, i.e. if there are features of the oscillation that we do not understand well, then we may be observing “new physics”. In other words, the data may reveal a new mechanism that generates a different matter-antimatter balance than predicted by the SM, that may potentially solve the puzzle.<br />
<br />
The LHCb experiment at CERN is dedicated to such studies: LHCb detectors are placed in a region along the LHC collider beamline, where a large number of B mesons are produced, arising from the proton-proton collision data from the LHC collider. Looking at the LHCb data we can obtain large samples of B mesons, and observe their oscillations.<br />
In this project we will learn how to select a sample of B mesons out of the data taken with the LHCb detector, measure the parameters that govern their oscillation and compare them with the SM.<br />
<br />
For more information, please contact Mara Soares (msoares_at_nikhef.nl).</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Bachelor_Projects&diff=938Bachelor Projects2024-02-09T13:45:17Z<p>Rojo@nikhef.nl: /* Theory */</p>
<hr />
<div>== Bachelor Projects 2024 ==<br />
<br />
=== Detector R&D ===<br />
<br />
=== KM3NeT ===<br />
<br />
=== Dark Matter ===<br />
<br />
=== ATLAS ===<br />
<br />
=== LHCb ===<br />
<br />
=== Gravitational waves ===<br />
<br />
=== Theory ===<br />
'''The Schiff theorem for Electric Dipole Moments (Jordy de Vries)'''<br />
<br />
Electric Dipole Moments (EDMs) of nucleons, atoms and molecules are important experimental observables to look for beyond-the-Standard-Model sources of fundamental symmetry violation. Specifically, the violation of Charge-Parity (CP) symmetry, which is present in the SM but not in sufficient amounts to explain the observed matter-antimatter asymmetry in the universe, can be probed through EDMs. To understand what EDM measurements on larger systems tell us about the fundamental physics at the elemental particle scale, and to assess what systems are most promising for EDM experiments, the Schiff theorem is essential. This theorem describes how, under certain simplifications, the EDMs of atoms and molecules vanish due to screening. In this project, you will investigate the theory behind Schiff screening, including possible violations of the theorem which lead to interesting systems with which to probe EDMs. For this project, the courses Advanced Quantum Physics & Atomic Physics are useful, but not strictly necessary.<br />
<br />
<br />
'''High-energy neutrino-nucleon interactions at the LHC with FASER''' (Juan Rojo, VU Amsterdam & Nikhef Theory)<br />
<br />
High-energy collisions at the Large Hadron Collider (LHC) produce an unprecedented number of light particles along the beam collision axis, outside of the acceptance of existing experiments. The FASER experiment, located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, provides new opportunities to probe Standard Model (SM) processes, in particular high-energy neutrino physics, and search for physics beyond the Standard Model (BSM). In this project, the student(s) will carry out updated theoretical predictions and numerical simulations for relevant physical processes at FASER, in particular concerning neutrino production and scattering, and assess their implications for our current models of proton structure and of QCD, the quantum field theory of the strong nuclear force. The project will also involve studying the implications of these results for ultra-high-energy particle astrophysics such as at the KM3NET and AUGER experiments. For this project, having followed the elective courses "Introduction to (astro-)particle physics" and "Standard Model of Elementary Particles" is required.<br />
<br />
''Contact: [[Mailto:j.rojo@vu.nl|Juan Rojo]]''<br />
<br />
'''Probing the proton spin with machine learning at future colliders''' (Juan Rojo, VU Amsterdam & Nikhef Theory)<br />
<br />
At energy-frontier facilities such as the Large Hadron Collider (LHC), scientists study the laws of nature in their quest for novel phenomena both within and beyond the Standard Model of particle physics. An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions from the nature of the Higgs boson to the origin of cosmic neutrinos. The key to address some of these questions is by carrying out an universal analysis of nucleon structure from the simultaneous determination of the momentum and spin distributions of quarks and gluons and their fragmentation into hadrons. This effort requires combining an extensive experimental dataset and cutting-edge theory calculations within a machine learning framework where neural networks parametrise the underlying physical laws while minimising ad-hoc model assumptions. The upcoming Electron Ion Collider (EIC), to start taking data in 2029, will be the world's first ever polarised lepton-hadron collider and will offer a plethora of opportunities to address key open questions in our understanding of the strong nuclear force, such as the origin of the mass and the intrinsic angular momentum (spin) of hadrons and whether there exists a state of matter which is entirely dominated by gluons. To fully exploit this scientific potential, novel analysis methodologies need to be develop that make it possible to carry out large-scale, coherent interpretations of measurements from the EIC and other high-energy colliders. In this project, the student will carry out a new global analysis of the spin structure of the proton by means of the machine learning tools provided by the NNPDF open-source fitting framework and state-of-the-art calculations in perturbative Quantum Chromodynamics, and integrate it within the corresponding global NNPDF analyses of unpolarised proton and nuclear structure in the framework of a combined integrated global analysis of non-perturbative QCD. Specifically, the project aims to realise a NNLO global fit of polarised quark and gluon PDFs that combines all available data and state-of-the-art perturbative QCD calculations, and study the phenomenological implications for other experiments, including the EIC, for the spin content of the proton, for comparisons with lattice QCD calculations, and for nonpperturbative models of hadron structure.<br />
<br />
''Contact: [[Mailto:j.rojo@vu.nl|Juan Rojo]]''<br />
<br />
== Bachelor Projects 2023 ==<br />
<br />
=== KM3NeT ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along 200-700m long vertical lines, called detection units.<br />
<br />
<br />
==== Search for cosmic neutrinos with the first KM3NeT data ====<br />
<br />
The KM3NeT/ARCA block is tuned for the detection of cosmic neutrinos and search for their sources. The first data of ARCA will be used to search for cosmic neutrino sources, and to search for a neutrino signal in response to external alerts for transients (gamma-ray bursts, IceCube neutrinos, gravitational wave events). Furthermore there is the opportunity to search for a neutrino signal from dark matter annihilation in the galactic halo and in dwarf spheroidal galaxies.<br />
<br />
Supervisors: Thijs van Eeden, Jhilik Majumdar, Clara Gatius, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
<br />
==== Neutrino oscillations with KM3NeT/ORCA ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope is able to measure the oscillations of neutrinos produced in interactions of cosmic rays with the earth atmosphere. Fundamental neutrino properties can be deduced from these oscillations measurements. In this project we will use the first data of ORCA to study neutrino oscillations and fit neutrino mixing parameters and mass differences between neutrino mass states. We will study data selection, event reconstruction, and effects of systematic uncertainties on the results. <br />
<br />
Supervisors: Bouke Jung, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
<br />
==== Multi-messenger astronomy with neutrinos and radio signals ====<br />
The main goal of neutrino telescopes, such as ANTARES, KM3NeT and IceCube, is to detect cosmic neutrinos from astrophysical sources. When an interesting neutrino candidate is detected they send out a message to alert the scientific community. Other scientific instruments, like the Murchison Widefield Array (MWA) radio telescope, can then do a follow-up observation, to see if there are other messengers coming from the same source as the neutrinos. In this project you will analyse MWA data that were taken after the reception of neutrino alerts, to search for a radio source that can be associated with a neutrino source.<br />
<br />
Supervisor: Mieke Bouwhuis (mieke.bouwhuis at nikhef.nl)<br />
<br />
<br />
<br />
=== Dark Matter ===<br />
<br />
==== Investigating muon spallation backgrounds in KamLAND neutrino detector ====<br />
The KamLAND neutrino detector in Japan is designed to measure among other things neutrinoless double beta decay, an important process in particle physics that, should it be observed, would confirm that neutrinos might be their own antiparticles. However, the lack of detection of this process can be blamed on various backgrounds, one of which is muon spallation. Only recently did we start studying these spallation backgrounds in detail and we are looking for a student that has a strong interest in programming, simulations and data analysis to help the progression. The goal of this project is to allow for a better understanding of the behaviour of spallation events and to contribute to the simulation of the background that will be used in KamLAND, as well as future neutrino and dark matter experiments.<br />
<br />
Supervisors: Kelly Weerman and Patrick Decowski (decowski@nikhef.nl)<br />
<br />
==== First measurements with new VULCAN detectors ====<br />
At Nikhef we have a brand new experiment designed to measure the reflectance, transmission, and fluorescence properties of materials at vacuum ultraviolet (VUV) wavelengths. The materials to be studied are used to construct the XENONnT dark matter and the DUNE neutrino detectors. <br />
<br />
In this project, you will calibrate the characteristics of the VUV lamp and of the SiPM photon sensors used in VULCAN. Lab work at the Nikhef building will be a main part of the project, but you will also analyse the data you collect using modern analysis tools.<br />
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You will gain experience with VUV optics, vacuum systems, single-photon sensors, and data analysis using Python and/or C++ tools.<br />
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Supervisors: Marjolein van Nuland and Tina Pollmann (t.pollmann@nikhef.nl)<br />
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==== The XAMS dark matter R&D setup at Nikhef ====<br />
The Nikhef dark matter group has a small version of the XENONnT dark matter detector in our Nikhef lab. With this detector we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENONnT experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso. We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with recently upgraded hardware to test a novel concept for UV light detection. The goal of this project will be to do the first measurements and analyze the data. Depending on the progress with the hardware we intend to complete the first measurements with our upgraded setup.<br />
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Supervisors: Patrick Decowski (decowski@nikhef.nl) and A.P. Colijn (colijn@nikhef.nl)<br />
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==== Reconstruction software for the XENONnT dark matter experiment ====<br />
The XENONnT dark matter experiment became operational in 2021. The experiment is in the Gran Sasso underground laboratory in Italy and the hardware is not being touched. However, we keep on developing and perfecting our reconstruction software. For this project we are looking for a student with a keen interest in and talent for writing physics-based event reconstruction software (we use python). Specifically we have an idea to improve the localization of events inside the XENONnT for which proto-type software exists. The proto-type software needs to be implemented in the XENONnT reconstruction framework and subsequently it needs to be validated on the first data from the experiment. The final goal of the project is to deliver the reconstruction software to the collaboration to be used during the lifetime of the experiment.<br />
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Supervisors: Patrick Decowski and A.P. Colijn (colijn@nikhef.nl)<br />
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=== ATLAS ===<br />
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==== Machine-Learning in Top-Quark physics ====<br />
As the heaviest elementary particle the top quarks plays a key role in the Standard Model. Discovered in 1995 at the Tevatron accelerator, top quarks are now abundantly produced at the Large Hadron Collider (LHC) located at the European Organization for Nuclear Research (CERN) . But do these produced top quarks behave as predicted by the Standard Model or are there signs of new physics? To describe possible deviations, we use calculations from Effective Field Theory (EFT) that allows to add new interactions. For this project simulated data samples with deviations predicted by EFT are available.<br />
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The candidate applies new techniques involving machine-learning to separate backgrounds from top quark production, aware for signs of new physics. Existing tools can be used to quantify the improvements on finding new interactions involving top quarks. Depending on the candidates interest, the focus of the project can be put more on machine-learning or top quark physics. For this project, we use the Python computing language and the ROOT package. Therefore, some proficiency with Python is required. Knowledge of C++ and root is advantageous but not required. <br />
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Supervisors: Jordy Degens (PhD candidate) and Marcel Vreeswijk (h73@nikhef.nl).<br />
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==== '''New machine learning approaches to target Higgs interference signatures in LHC data''' ====<br />
In this project we aim to improve an ongoing analysis to determine the lifetime of the Higgs Boson through state-of-the-art machine learning techniques, in particular by addressing a novel solution to an as of yet unsolved fundamental problem in modeling quantum interference. While the Higgs is an elusive particle that generally only appears in physics processes with small cross sections, its signature can be amplified in the Large Hadron Collider (LHC) through quantum interference with larger background (non-Higgs) processes. This is the effect that the Higgs’ lifetime analysis relies on to be able to measure the relevant Higgs signature. A fundamental physics modelling problem arises though in the simulation of individual events for this interference due to the fact that these events are in reality described by a superposition of underlying Higgs and non-Higgs processes.<br />
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Since machine learning models in particle physics are typically trained to characterise individual physics events, the fact that interference events cannot currently be generated is a significant problem when interference is the target. In the currently existing Higgs lifetime analysis, a machine learning model was trained which instead focuses only on the explicit Higgs-mediated processes as a proxy, which is suboptimal. The aim of this project is to improve upon this current machine learning strategy used in this analysis by implementing either of the inference-aware approaches suggested in [1] and [2]. The idea behind these inference-aware machine learning algorithms is that they do not optimise for a simplified goal such as the loss function which is common in traditional machine learning, but rather for the end-goal of the analysis. In this case, this would omit the need for interference event generation altogether and allow the machine learning models to be trained optimally regardless.<br />
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The goal of this project is to use either of the frameworks used in [1] and [2] (which are both publicly available) and run them with a simplified dataset from the aforementioned analysis as a proof-of-principle. In case this goal is achieved, the next goal would be to actually implement the newly developed machine learning models in the full analysis and to determine the improvement upon the existing result. Successful completion of these tasks would not only benefit the Higgs lifetime analysis, but would be an important stepping stone to future developments to make machine learning approaches deal better with other hard to model effects such as systematic uncertainties.<br />
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Supervisors: Zef Wolffs, Ivo van Vulpen and Matous Vozak (matous.vozak@cern.ch)<br />
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==== '''Reconstructing tracks from particle physics detector hits with state-of-the-art machine learning techniques''' ====<br />
This project concerns the application of new machine learning techniques to tackle the problem of track reconstruction at the ATLAS detector in CERN. While algorithms to construct particle tracks from low-level detector information such as particle hits and timestamps have been around for decades, recent developments in the field of machine learning open up new opportunities to improve these algorithms significantly. In particular graph-based neural networks and attention architectures prove promising candidates for solving these problems based on preliminary studies. <br />
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In this project the student will develop machine learning models to initially reconstruct tracks from simplified test data. If time allows, real data from the ATLAS detector can be analyzed as well in the scope of this project. The student will need some familiarity with programming in python and an interest in machine learning, but a physics background is not required. In this project the student will be able to contribute to fundamental physics research and will familiarize themselves with state-of-the-art machine learning models.<br />
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Supervisors: Zef Wolffs, Ivo van Vulpen and Matous Vozak (matous.vozak@cern.ch)<br />
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=== LHCb ===<br />
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=== Gravitational Waves ===<br />
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====Staying in shape====<br />
Nikhef is co-leading the current effort to realise the Einstein Telescope (ET), a future 10km-scale underground observatory for gravitational waves. Numerical modelling software forms a crucial subsystem for the design and operation of the GW detectors. Our interferometer simulation software Finesse was developed for the design and commissioning of gravitational wave detectors and has become the main interferometer software tool in the community world wide. In our group we use Finesse to predict the shape of the laser beam and how this affects the GW data. You will join our group using Python-based scripts to model mis-shaped lasers and see how the interferometer reacts.<br />
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Required knowledge:<br />
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Good knowledge of Python is required.<br />
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Knowledge of optics will be useful but is not required.<br />
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Supervisors: Anna Green (agreen@nikhef.nl) and Andreas Freise (a.freise@nikhef.nl)<br />
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====Riding the wave====<br />
Theoretical predictions of gravitational-wave (GW) signals provide essential tools to detect and analyse transient GW events in the data of GW instruments like LIGO and Virgo. Over the last few years, there has been significant effort to develop signal models that accurately describe the complex morphology of GWs from merging neutron-star and black-hole binaries. Our work focusses on a particular class of GW binary sources: those that come from two black holes meeting at close separation in dense stellar environments. Here, we expect the merging binary to be in a non-circular orbit and to have arbitrary spin orientations, which significantly complicates the prediction of its GW signal.<br />
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We are looking for '''two''' students who are interested in the development of accurate and efficient GW models and their application in GW data analysis. We are offering '''two separate projects''' that aim to improve signal modeling at the interface of perturbation theory, numerical relativity simulations and fast phenomenological descriptions. Some proficiency in computing is required (Mathematica, Python or C++).<br />
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Supervisor: Maria Haney (mhaney@nikhef.nl)<br />
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=== Detector R&D ===<br />
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====Charge collection study of fast monolithic detectors====<br />
In view of the upgrade of the ALICE tracking detector, innovative ultrathin monolithic silicon sensors are developed for testing. These devices are provided with analogue outputs to study in detail the charge collection and the timing properties of the sensor.<br />
The goal of the project is to contribute to the study of the charge collection features of the samples by measuring the response of the sensor to Fe55 X-rays.<br />
We are looking for a student with a focus on lab work and interested in contributing to the python-based data analysis.<br />
Depending on the progress with the intended measurement and the availability of the hardware, further studies with Sr90 electrons and a laser setup could be possible.<br />
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Contacts: Jory Sonneveld (jory.sonneveld@nikhef.nl), Roberto Russo (rrusso@nikhef.nl)<br />
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====Laser setup for silicon sensor studies====<br />
The Detector R&D group at Nikhef develops and tests detector concepts before they are used in scientific programs at Nikhef. To achieve such a goal, advanced instrumentation and setups are required.<br />
The goal of the project is to contribute to the design and construction of a fast infrared laser setup aimed at the characterization of silicon sensors for high energy physics experiments.<br />
We are looking for a student with a focus on lab work and interest in instrumentation and optics. Besides contributing to the setup construction, measurements finalised at the characterization of the laser beam (e.g. spot size, intensity) are foreseen.<br />
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Contacts: Jory Sonneveld (jory.sonneveld@nikhef.nl), Roberto Russo (rrusso@nikhef.nl)<br />
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==== Characterization of monolithic silicon sensors ====<br />
As part of the ongoing efforts for the design of ultimate tracking detectors, an excellent understanding of the basic performance of the detectors is required. To do so, the silicon detectors can be tested by making an electrical contact with the sensor using a probe station, a device for micrometer precision placement of temporary electrical contacts to acquire signals from internal nodes of semiconductor devices, to investigate aspects such as it's depletion voltage, depletion depth, the dark current and more which are essential for understanding the results gathered by the sensors later in the laboratory and allow the investigation of aspects that can be improved in further chip iterations. The goal of the project is to investigate the performance of monolithic sensors, where electronics is integrated into the sensor, developed for collider experiments like those at the large hadron collider at CERN and beyond. Depending on the progress with the planned measurements, further tests with the electronics and readout of the chip, as well as measurements with advanced laster instrumentation are also possible.<br />
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Contacts: Jory Sonneveld (jory.sonneveld@nikhef.nl), Uwe Kraemer (uwe.kraemer@nikhef.nl)<br />
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=== Theory ===<br />
'''Axion-Electrodynamics (Jordy de Vries and Arghavan Safavi-Nani)'''<br />
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Axions are hypothetical particles that are introduced to solve the so-called strong CP problem. Being very light, axion can be described as a coherent classical field similar to electromagnetic fields. In this project, you will develop the modifications of Maxwell’s equations to include axion fields. Reference: arXiv:1401.0709 . <br />
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'''Axions in a Paul-trap (Jordy de Vries and Arghavan Safavi-Nani)'''<br />
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Axions are hypothetical particles that are introduced to solve the so-called strong CP problem. If axions form the dark matter in our universe, they can be described by a coherent oscillating background field. This oscillating field interacts with charged particles and it possible to detect axions by the motion of ions in a Paul trap. In this project, you will investigate how these interactions work and what are the observables associated to the detection of axions in ion traps.<br />
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'''Phase space integrals for double-weak processes (Jordy de Vries)'''<br />
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The rarest processes ever measured are so-called double weak processes in which two neutrons undergo beta decay at the same time in a nucleus. Lifetimes of these processes are in the 10^22 years range. Theoretical computations of these rates involve so-called phase space integrals that take into account the possible momentum configurations of the outgoing electrons and neutrinos. In this project you will investigate these phase space integrals and develop a method to compute them. <br />
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== Bachelor Projects 2022 ==<br />
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=== Dark Matter ===<br />
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==== Response of materials to scintillation light from liquid noble gasses ====<br />
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The liquid form of the noble gases argon and xenon is a popular target material for neutrino and dark matter detectors. The scintillation light from noble gases is in the vacuum UV spectral region. Air and many materials used for optical studies are not transparent to these photons. Measurements of the optical properties of detector materials, such as their reflectivity for example, thus have to be performed with dedicated VUV optics and in vacuum. Additionally, to reproduce the conditions in the detectors, the samples must be cooled to cryogenic temperatures. In this BSc project, you will calibrate the photon detectors in an experimental setup designed to study the optical response of materials excited with VUV photons. You will learn about material requirements for rare event search detectors, vacuum instrumentation, vacuum UV optics including monochromators and spectrometers, and single-photon sensors.<br />
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Supervisors: T. Pollmann (t.pollmann_at_nikhef.nl)<br />
====XAMS====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENONnT detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENONnT experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso. We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with recently upgraded hardware to test a novel concept for UV light detection. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complete the first measurements with our upgraded setup.<br />
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Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
==== XENONnT reconstruction software ====<br />
The XENONnT experiment becomes operational during 2021. While the hwardware is finished we keep on developing and perfecting our reconstruction software. For this project we are looking for a student with a keen interest in and talent for writing physics based event reconstruction software (we use python). Specifically we have an idea to improve the localization of events inside the XENONnT for which proto-type software exists. The proto-type software needs to be implemented in the XENONnT reconstruction framework and subsequently it needs to be validated on the first data from the experiment. The final goal of the project is to deliver the reconstruction software to the collaboration that will be used during teh full lifetime of the experiment.<br />
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Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
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=== ATLAS ===<br />
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==== The Higgs boson - did we miss anything and can we do better? ====<br />
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The Higgs boson is a key element of the Standard Model (SM) of particle physics, however, it can also represent a link between yet unexplored 'new' physics beyond the SM. What is the Higgs boson life-time? How precisely can we measure its mass? Is there an additional heavy Higgs boson? Do other particles, not contained in the SM, couple to the Higgs? All these questions can be studied by measuring Higgs properties using one of the Higgs decay modes to photons, vector bosons, quarks and leptons and comparing them with the (beyond) SM predictions. <br />
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As the restart of the Large Hadron Collider (LHC) is imminent, it is essential to develop and test new physics ideas and strategies. '''The ATLAS open data project''' will allow students to work on a real analysis digging through the LHC data collected during Run2. Students will go through all the key aspects of a Higgs analysis performed also by ATLAS physicists. They will learn about Higgs boson theory and its simulation, what objects are reconstructed in the ATLAS experiment, how well do we understand them and finally how does this project into our understanding of the Higgs boson and its properties. <br />
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The exact focus of the topic is flexible depending on the interest of a student. For instance, a student can delve into how precisely can we determine objects' energy and their positions and see whether we can '''improve our estimate of the Higgs mass (project 1)'''. Another possibility is to focus on trying to find out whether there is '''an additional (heavier) Higgs (project 2)''' in the data and how confident we can be of that. Each of these projects will most likely yield new questions, so feel free to take a tangent and walk into yet unexplored territory and see what the data tells you.<br />
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Supervisor: Matouš Vozak (m.vozak_at_nikhef.nl) & Ivo van Vulpen (Ivo.van.Vulpen_at_nikhef.nl)<br />
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==== The Higgs boson life-time ====<br />
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The Higgs particle does not have eternal life. The Standard Model (SM) predicts that it decays into other particles and as these couplings are fixed we can predict its life-time with very high precision. Determining this life-time is a crucial test for the Standard Model. If the Higgs boson life-time is shorter that we expect this could mean that the Higgs boson could decay into non-SM particles. In this project we investigate a) how we can identify Higgs particles in the detector and b) how we plan to use quantum-interference to get a handle on the Higgs boson's life-time. <br />
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Supervisor: Wouter Verkerke (verkerke_at_nikhef.nl)<br />
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==== Higgs interferentie ====<br />
In 2012 hebben het ATLAS en het CMS experiment het Higgs deeltje gevonden. Inmiddels zijn we het Higgs boson aan het bestuderen, hoe gedraagt het zich precies, bestaan er meer soorten Higgs bosonen of is er echt maar eentje van? In dit project leer je hoe we een Higgs boson kunnen herkennen in de detector en gaan we kijken naar hoe de signalen veranderen als er meer Higgs bosonen bestaan of misschien wel andere exotische nieuwe deeltjes. <br />
Dit doen we door gebruik te maken van quantum interferentie wat plaats vindt tussen het Higgs boson en achtergrondprocessen. Hoe dit precies werkt leer je in het project. Supervisor: Hella Snoek (h.snoek_at_nikhef.nl)<br />
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=== LHCb ===<br />
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==== Exotic neutrinos in B decays====<br />
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Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, heavier, neutral leptons. In the LHCb group at Nikhef we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undisovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The bachelor project will contribute with the optimization of the selection using state-of-the-art tools for the multi-variate analysis.<br />
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Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
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=== Gravitational Waves ===<br />
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=== Detector R&D ===<br />
Answering big elementary particle physics questions requires pioneering experiments. The Detector R&D program at Nikhef is aimed at conceptualizing and testing of instrumentation concepts before they are implemented in scientific programs at Nikhef. <br />
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==== Time resolution of monolithic timing detectors ====<br />
For the upgrade of the vertex detectors of the large LHC experiments like LHCb and ALICE, new silicon pixel detectors will developed now that can register the passing particles with a time precision of tens of picoseconds. ALICE is the first experiment at the LHC to have installed monolithic sensors where electronics is integrated into the sensor resulting in ultrathin, low-material detectors, that will soon see it's first particles from LHC collisions. In this project you will measure the time resolution of these promising integrated sensors with a laser setup in our laboratory.<br />
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Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
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==== Modeling radiation damage in silicon sensors ====<br />
In the coming years, the ATLAS experiment at the LHC works on upgrades to prepare for the high-luminosity LHC, where many more collisions will take place than today. Analyses of LHC data rely heavily on simulations of the detector. It may sound counterintuitive, but particle detectors do not actually like particles: after many collisions at the LHC, a silicon pixel detector has seen so many particles that its bulk gathers defects. Charge generated by traversing particles can get trapped in defects resulting in less charge induced in the readout electrodes, reducing detector performance in resolution and efficiency. In this project, you will be part of the international ATLAS collaboration and compare different models of radiation damage with measured data and you will contribute to the open source program Allpix Squared that is widely used for simulations in many areas of particle physics.<br />
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Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
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==== Time resolution of a new digital pixel test structure from test beam data ====<br />
For the upgrade of the ALICE detector, ultrathin picosecond timing integrated sensors are developed. To reduce power consumption, asynchronous readout is implemented in this prototype sensor in a digital pixel test structure. This structure was studied in test beams with an ALPIDE (ALICE PIxel DEtector) telescope at CERN. You will measure the efficiency and time resolution of this new sensor with the latest data from test beams at CERN.<br />
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Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
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==== Fast timing detectoren ====<br />
Op dit moment maken we veel gebruik van silicon detectoren in onze deeltjes experimenten. Deze zijn gevoelig voor geladen deeltjes en zijn bij uitstek geschikt om de paden vast te leggen die de deeltjes maken die in de botsingen worden gemaakt. Bijvoorbeeld in de Atlas en LHCb experimenten worden tientallen tot honderden deeltjes gemaakt bij elk botsingsgebeurtenis (event) die met 40MHz plaatsvinden. Voor toekomstige deeltjesdetectoren willen we niet alleen het traject vastleggen maar ook met grote precisie een tijdsmeting toevoegen. We hebben hiervoor dus nieuwe detectoren nodig die behalve met een hele hoge snelheid en efficientie de posities van de langsvliegende deeltjes kunnen vastleggen, maar hier ook een zeer nauwkeurige tijdsmeting (in orde van picosecondes) aan kunnen toevoegen. We hebben met verschillende detectoren metingen gedaan, in testbundels op CERN, maar ook in het lab op Nikhef kunnen we metingen doen. In dit project ga je samen met het fast-timing detectoren team op het Nikhef metingen verrichten en de resultaten hiervan bekijken. Contact: Hella Snoek (h.snoek@nikhef.nl)<br />
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=== KM3NeT ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown neutrino mass hierarchy.<br />
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The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along 200-700m long vertical lines, called detection units.<br />
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==== Neutrino oscillation measurements with the first KM3NeT data ====<br />
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The ORCA block of the KM3NeT neutrino telescope is able to measure the oscillations of neutrinos produced in interactions of cosmic rays with the earth atmosphere. Fundamental neutrino properties can be deduced from these oscillations measurements. In this project we will use the first data of ORCA (more than one year with six detection units) to study neutrino oscillations and fit neutrino mixing parameters and mass differences between neutrino mass states. We will study data selection, event reconstruction, and effects of systematic uncertainties on the results. <br />
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Supervisors: Brian O'Fearraigh, Ronald Bruijn, Paul de Jong (paul.de.jong at nikhef.nl)<br />
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==== Search for sterile neutrinos with KM3NeT. ====<br />
A detailed study of neutrino oscillations in the KM3NeT detector is sensitive to the existence of so-called sterile neutrinos: neutrinos that are not part of the Standard Model of particle physics, and have no ordinary interactions with matter. We will use a mixture of data and simulations to estimate KM3NeT sensitivity.<br />
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Supervisors: Alba Domi, Paul de Jong<br />
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==== Machine learning for event classification in KM3NeT ====<br />
The classification of neutrino events recorded in the KM3NeT detector in terms of originating from electron neutrinos, muon neutrinos, or tau neutrinos, is very well suited for machine learning techniques. We will study the performance of a few advanced machine learning techniques on simulated high-energy neutrino events.<br />
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Supervisors: Alba Domi, Paul de Jong<br />
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==== Multi-messenger astronomy with neutrinos and radio signals ====<br />
The main goal of neutrino telescopes, such as ANTARES, KM3NeT and IceCube, is to detect cosmic neutrinos from astrophysical sources. When an interesting neutrino candidate is detected they send out a message to alert the scientific community. Other scientific instruments, like the Murchison Widefield Array (MWA) radio telescope, can then do a follow-up observation, to see if there are other messengers coming from the same source as the neutrinos. In this project you will analyse MWA data that were taken after the reception of neutrino alerts, to search for a radio source that can be associated with a neutrino source.<br />
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Supervisor: Mieke Bouwhuis (mieke.bouwhuis at nikhef.nl)<br />
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=== Theory ===<br />
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==== Effective Field Theories of Particle Physics from low- to high-energies (2022 not yet determined if available in 2023) ====<br />
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Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations<nowiki>''</nowiki> seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature.<br />
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Until recently, it was widely assumed that matter particles from each of the three generations interact with the same (“universal”) strength. This hypothesis is being challenged by new measurements at the Large Hadron Collider (LHC) at CERN, which hint towards non-universal interactions. If confirmed, these measurements will be the first signs of new particles and interactions in high-energy colliders. These exciting findings indicate the urgent need to explore such phenomena in depth.<br />
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The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Effective Field Theory (EFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes. Specifically, the goal is to connect measurements from ATLAS and LHCb among them and to jointly interpret this information with that provided by other experiments, from CMS and Belle-II to very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
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''Methodology and workplan''<br />
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This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories.<br />
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This project accommodates several students, who would work together in developing the main formalism while each of them focuses on a specific sub-project. The maximum capacity of this project is 5 students. <br />
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Depending on the student profile, sub-projects with a strong computational / machine learning component are also possible.<br />
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During the first four weeks of the project, students will learn the required background material on effective field theories, following the guidelines from the supervisors. Afterwards, they will focus on different sub-projects, each covering a different aspect of the same global EFT program.<br />
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Required knowledge<br />
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Quantum Mechanics 2, Particle Physics 1 (required)<br />
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Advanced Quantum Mechanics, Particle Physics 2, Machine Learning (optional)<br />
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Available subprojects<br />
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Here we list the available subprojects, including the corresponding daily supervisor(s) in each case.<br />
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''Subproject #1: SMEFT & Flavour symmetries'' <br />
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Daily supervisors: Jordy de Vries (UvA), Keri Vos (Maastricht University), Jaco ter Hoeve (VU), Giacomo Magni (VU)<br />
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While the power of the Standard Model EFT (named SMEFT) framework is its generality and lack of assumptions, the number of operators is somewhat daunting. A popular way to trim the number of operators is to assume flavour symmetries that relate operators with different quark and lepton flavours. In this project you will investigate the theoretical basis for commonly-used flavour symmetries and what they imply for the connection between high-energy observables involving third-generation particles (top and bottom quarks and tau leptons) and low-energy precision tests involving first- and second-generation particles. The investigations of this project are connected with Subproject #2.<br />
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''Subproject #2: SMEFT & magnetic moment of the muon''<br />
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Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU)<br />
<br />
The magnetic moment of the muon appears to differ from the Standard Model expectations by a large amount, well beyond the known experimental and theoretical uncertainties. Recent experiments have only strengthened the significance of this anomaly. In this project, the students will investigate the feasibility of implementing the measurement of the magnetic moment of the muon into a global SMEFT analysis, by exploiting recently provided calculations. Special attention will be devoted to the flavour assumptions required to consistently match this measurement with the LHC data, also at the light of the connection with Subproject #1. The SMEFiT analysis framework will be used to connect the g-2 data with high-energy LHC measurements.<br />
<br />
''Subproject #3: CP Violation and low-energy precision experiments''<br />
<br />
Most analyses of LHC data are performed under the assumption that CP symmetry (charge conjugation + parity, essentially the symmetry between particles and anti-particles) is conserved. More recent analyses attempt to also measure possible new sources of CP violation in SMEFT operators in the Higgs and top sector. <br />
<br />
''Subproject #3a: CP Violation and low-energy precision experiments''<br />
<br />
Daily supervisors: Jordy de Vries (UvA), Juan Rojo (VU)<br />
<br />
Low-energy precision experiments can also set stringent constraints on new mechanisms of CP violation. In this project you will try to combine high- and low-energy data to put CP symmetry to the test. <br />
<br />
''Subproject #3b: CP Violation and flavour physics experiments''<br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU)<br />
<br />
Besides low-energy precision experiments, also B-meson decays are excellent probes of CP violation. Unlike most low-energy experiments, this allows us to probe CP violation in the third generation. In this project you will link constraints on CP violation at high-energy to those from B meson decays. <br />
<br />
''Subproject #4: SMEFT & optimal observables'' <br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU), Tommaso Giani (VU & Nikhef)<br />
<br />
In full generality, the number of operators in SMEFT spans a very large parameter space. These parameters are constrained by experimental inputs from ATLAS and CMS, depending on the precise parameters these constraints may be more or less stringent. In order to fully exploit the whole parameters space in SMEFT, it is necessary to devise statistically optimal observables that have a large constraining power. In this project, we will define such observables. This project has a strong computational / machine learning component and may involve simulations based on tools such as MadGraph and Pythia8.<br />
<br />
Contacts:<br />
<br />
Juan Rojo (VU Amsterdam & Nikhef): j.rojo at vu.nl<br />
<br />
Keri Vos (UM & Nikhef): k.vos at maastrichtuniversity.nl <br />
<br />
Jordy de Vries (UvA & Nikhef): j.devries4 at uva.nl<br />
<br />
== Bachelor Projects 2021 ==<br />
=== Dark Matter ===<br />
<br />
==== XAMS ====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso.<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with recently upgraded hardware to test a novel concept for UV light detection. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complete the first measurements with our upgraded setup.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== XENONnT reconstruction software ====<br />
The XENONnT experiment becomes operational during 2021. While the hwardware is finished we keep on developing and perfecting our reconstruction software. For this project we are looking for a student with a keen interest in and talent for writing physics based event reconstruction software (we use python). Specifically we have an idea to improve the localization of events inside the XENONnT for which proto-type software exists. The proto-type software needs to be implemented in the XENONnT reconstruction framework and subsequently it needs to be validated on the first data from the experiment. The final goal of the project is to deliver the reconstruction software to the collaboration that will be used during teh full lifetime of the experiment.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Backgrounds in Radioactive Decay Measurements ====<br />
At Nikhef, the XENON group has a working setup, continuously monitoring the<br />
radioactive decay of Cobalt-60, Caesium-137 and Titanium-44. This beautiful setup is<br />
however not shielded perfectly; it is still vulnerable to background radioactivity. Our<br />
current way of working around this background radiation is to subtract it from our<br />
waveforms. You as a BSc student could help us hands-on and with analyses:<br />
together, we can disassemble the setup, measure background spectra and<br />
implement this in the data analysis. You can use all the data to validate the<br />
lifetime of our isotopes!<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Detection of scintillation light from liquid noble gasses ====<br />
<br />
The liquid form of the noble gases argon and xenon is a popular target material for neutrino and dark matter detectors. The scintillation light from noble gases is in the vacuum UV spectral region. Air and many materials used for optics studies are not transparent to these photons. Measurements of the optical properties of detector materials, such as their reflectivity for example, thus have to be performed with dedicated VUV optics and in vacuum. Additionally, to reproduce the conditions in the detectors, the samples must be cooled to cryogenic temperatures. In this BSc project, you will design, using professional hardware design software, a vacuum chamber to hold the detector materials whose optical properties are to be investigated, as well as the cooling system and photon detectors. You will learn about material requirements for rare event search detectors, vacuum instrumentation, vacuum UV optics including monochromators and spectrometers, and single-photon sensors.<br />
<br />
Supervisors: T. Pollmann (t.pollmann_at_nikhef.nl)<br />
<br />
=== Detector R&D ===<br />
<br />
==== Characterization of the new ultrathin ALPIDE monolithic active pixel sensor ====<br />
At the Large Hadron Collider at CERN, major upgrades of experiments take place in the long shutdown years where particle collisions are paused. The ALICE inner tracking system (ITS) 2, the part of the ALICE experiment closest to the beam pipe, is currently being installed at CERN. This detector makes use of ultra-lightweight monolithic active pixel sensors, the first to use this technology at particle colliders after the STAR experiment at RHIC in Brookhaven. These very thin pixel detectors have a low power consumption, result in very little material in the detector, and still have optimal timing and resolution -- and are a promising technology for future experiments. To characterize the performance of these sensors, you will learn to set up experiments, carry out measurements, and analyze data using various instruments available in the detector R&D lab at Nikhef. This could lead to novel insights of monolithic active pixel sensors. It is also possible to do measurements from home using data from the first test beams with bent (yes, with a curvature!) ALPIDE sensors. You will work in an international, stimulating research environment in the detector R&D group at Nikhef at the forefront of silicon detector technologies for high energy physics. ''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
==== Simulation of 3D silicon sensors ====<br />
<br />
For the upgrade of the vertex detector of the LHCb experiment novel silicon pixel detectors have to be developed that can register the passing particles with a time precision of tens of picoseconds. Given the harsh radiation environment very close to the LHCb interaction point only a limited number of technologies can be applied. One of the most promising technologies are the so-called 3D sensors whose readout electrodes are pillars that are placed into the sensor perpendicular to the surface; this in contrast to ’standard’ planar silicon sensors where the pixel electrodes are at the surface, similar to the camera in your smartphone. To understand the time response of these 3D sensors, simulations with TCAD software have to be performed and the results will be compared to measured data. These simulations involve the creation/adaptation of the 3D structures of the model, optimising the simulation speed, and analysing the signals as function voltage, track impact point and deposited charge. If time and Covid regulations permit, gaining some hands-on experience with such 3D sensors in the R&D labs at Nikhef is possible. ''Contacts: [mailto:martinb@nikhef.nl Martin van Beuzekom] [mailto:k.heijhoff@cern.ch Kevin Heijhoff] ''<br />
<br />
<br />
=== Theory ===<br />
<br />
==== Standard Model Effective Field Theory analysis of Z+dijet production ====<br />
The goal of this project is to study the effect of higher dimensional operators from the Standard Model Effective Field Theory in Z-boson production measured at LHC. The ATLAS collaboration has just reported in 2020 the measurement of Z production alongside with a pair of jets, based on the full Run II luminosity. In this project we aim to study the effect of dimension six SMEFT operators on the signal (EW-induced) and/or background (QCD-induced), finding which is the kinematic variable that maximises the possible effect of beyond the SM operators and thus may provide the best constraint on New Physics. The outcome of this project may be the first step of the inclusion of Vector production in a global SMEFT fit. <br />
<br />
References: https://arxiv.org/pdf/2006.15458.pdf, https://www.hepdata.net/record/ins1803608<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Maximum precision on new physics through information theory ====<br />
One way to look for physics beyond the standard model is through the framework of effective field theory. In this framework, deviations from the standard model are described by a set of continuous parameters. Finding constraints on these parameters might point to the discovery of new physics. With the large number of LHC experiments we currently face, we want to be able to quantify the maximum knowledge that (future) experiments can provide on new physics parameters. In this project, the student will study and quantify the maximum information that is contained in particle physics experiments through information theory. The central object of study will be the Fisher information matrix. The idea is to work with a simple toy experiment that describes Higgs physics and compute its associated Fisher information matrix to quantify the optimal bounds on new physics. The project will start with studying central objects from statistics and information theory. Later, we will apply these to open problems in particle physics.<br />
<br />
Reference: https://arxiv.org/pdf/1612.05261.pdf<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Seesaw mechanism and neutrino mass ==== <br />
Many unsolved questions in particle physics are related to the nature of the neutrino and its mass generation. The goal of this theoretical project is to understand and review one of the possible candidate theories that describe how neutrinos mix and get massive, namely the Seesaw mechanism. Among the many possible Seesaw mechanisms that can generate new phenomenology including lepton number non-conservation, the student will focus on one minimal model to understand the key processes that are currently used to probe the validity of the given theory. <br />
<br />
References: https://cds.cern.ch/record/408119/files/9911364.pdf, https://arxiv.org/pdf/1711.02180.pdf<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Mixing of sterile neutrinos ====<br />
<br />
Neutrino oscillation experiments demonstrate that neutrinos are massive particles. However, the mass mechanism of neutrinos is unknown. A<br />
minimal solution requires the existence of so-called sterile neutrinos: neutrinos that are even more elusive than ordinary neutrinos. <br />
We will investigate how to parametrize the matrix that describes the mixing between ordinary and sterile neutrinos. We will then use this<br />
to calculate how sterile neutrinos induce rare nuclear decays and determine the sensitivity of ongoing experiments to observe sterile<br />
neutrinos.<br />
<br />
Supervisor: Jordy de Vries (devries.jordy at gmail.com)<br />
<br />
<br />
=== KM3NeT ===<br />
<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
==== Data analysis of the first deployed KM3NeT detection lines ====<br />
<br />
First detection lines of the KM3NeT neutrino telescope have been deployed<br />
in the Mediterranean Sea, and a first data set is available. The lines consist<br />
of light-sensitive detectors that record the time of arrival of photons<br />
produced by relativistic particles in the deep sea, and their number.<br />
In this project we will study the first data to separate various components:<br />
photons from potassium decay, bioluminesence, sparks in the photomultipliers,<br />
downgoing muons from cosmic rays, and first neutrinos.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben (paul.de.jong at nikhef.nl)<br />
<br />
==== Neutrino oscillation measurements with the KM3NeT neutrino telescope ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope currently under construction<br />
will be able to measure the oscillations of neutrinos produced in interactions<br />
of cosmic rays with the earth atmosphere. Fundamental neutrino properties can<br />
be deduced from these oscillations measurements, in particular the so-called<br />
mass hierarchy of neutrinos. In this project we will simulate the ORCA measurements<br />
of neutrino oscillations, and study the dependence of the sensitivity on<br />
experimental uncertainties, such as energy resolution and neutrino flavour<br />
identification, and theoretical uncertainties, such as the atmospheric neutrino<br />
flux and neutrino cross sections. The results will help ORCA to identify<br />
the main sources of uncertainty, and therefore to actively try to reduce these<br />
and improve the final measurement.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
==== Performance Studies of ORCA for Dark Matter Detection ====<br />
<br />
The interactions of neutrinos in KM3NeT-ORCA give different signatures which are categorised as track and shower events. This project involves the studies of muon, electron and tau neutrino interactions for the reconstruction performance of ORCA. Efficient reconstruction of such signals is important for Dark Matter searches in the low-mass regime. We will work on understanding the detector performance, e.g. effective acceptance, energy and angular resolution, with different configurations of the detector setup. The result of this study will be very useful to improve the sensitivity of the experiment for Dark Matter detection and its possible location. The student will have the opportunity to work closely with KM3NeT members at Nikhef and gain skills of analyzing data. <br />
<br />
Supervisors: Suzan Basegmez du Pree, Aart Heijboer (s.basegmez.du.pree at nikhef.nl)<br />
<br />
==== Study of Optical Properties of Sea Water using Hit Coincidences in MC Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
By studying coincidences of L1 hits between neighbouring DOMs, for various Monte Carlo (MC) data sets with different sea water optical properties such as scattering and absorption coefficients, in this project we try to figure out if and how well we can quantify optical sea water properties by studying L1 hit coincidences in real KM3NeT data.<br />
<br />
Supervisor: Daan van Eijk (dveijk at nikhef.nl)<br />
<br />
==== Determination of Inter-DOM Distances using Hit Coincidences in KM3NeT Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
The number of L1 hit coincidences from atmospheric muons between neighbouring DOMs on a DU is expected to decrease exponentially. By fitting the observed number of L1 hit coincidences between neighbouring DOMs in real data to the expected exponential decay, in this project we study how accurately we can determine the distances between DOMs on a single DU. In addition, we try to determine the distances between DUs by looking for L1 hit coincidences between DOMs on neighbouring DUs.<br />
<br />
Supervisor: Daan van Eijk (dveijk at nikhef.nl)<br />
<br />
<br />
=== ATLAS ===<br />
<br />
==== The Higgs boson life-time ====<br />
<br />
The Higgs particle does not have eternal life. The Standard Model (SM) predicts that it decays into other particles and as these couplings are fixed we can predict its life-time with very high precision. Determining this life-time is a crucial test for the Standard Model. If the Higgs boson life-time is shorter that we expect this could mean that the Higgs boson could decay into non-SM particles. In this project we investigate a) how we can identify Higgs particles in the detector and b) how we plan to use quantum-interference to get a handle on the Higgs boson's life-time. <br />
<br />
Supervisor: Wouter Verkerke (verkerke_at_nikhef.nl)<br />
<br />
==== The Higgs boson decaying to photons ====<br />
<br />
One of the main channels used to analyse the properties of the Higgs boson is when the Higgs boson decays into two photons. The crucial building block in this analysis is our ability to reconstruct the energy and the direction of the photons in the ATLAS detector and in this project we will revisit the photon reconstruction. We will start by studying simulations and learning about photon reconstruction in general. Then our goal is to determine the energy and position resolution of photons in the ATLAS detector and see if we can exploit our knowledge on the photon resolution to get an (improved) estimate of the Higgs boson mass. For the analysis we will use the '''real data from the LHC''' - the ATLAS open data project.<br />
<br />
Supervisor: Ashley McDougall and Ivo van Vulpen (Ivo.van.Vulpen_at_nikhef.nl)<br />
<br />
<br />
=== LHCb (1) ===<br />
<br />
One of the most fascinating mysteries in physics today is: how is it possible that universe is filled with matter? If the Big Bang produced equal amounts of matter and antimatter, we still do not understand the mechanism that lead to the excess of matter over antimatter that we observe today.<br />
<br />
One interesting feature of some particles is that they can transform themselves into their antiparticles, then back to particle, and so forth, in an oscillatory way until they finally decay. In particular, beauty mesons (B) can oscillate into their antiparticle (B ̄). The parameters of this oscillation, such as amplitude, frequency and phase, are calculable mathematically: predictions for it are available in the standard model (SM) of particle physics. But the oscillations according to the SM alone would not lead to the imbalance of matter in the universe – we still need to find a new type of physics that may be able to explain it.<br />
<br />
In this context, it is very important to measure B oscillations in the laboratory, and compare these observations with the expectations from the SM. Are the experimental data in good agreement with the SM, as we expect? If the aswer is not, i.e. if there are features of the oscillation that we do not understand well, then we may be observing “new physics”. In other words, the data may reveal a new mechanism that generates a different matter-antimatter balance than predicted by the SM, that may potentially solve the puzzle.<br />
<br />
The LHCb experiment at CERN is dedicated to such studies: LHCb detectors are placed in a region along the LHC collider beamline, where a large number of B mesons are produced, arising from the proton-proton collision data from the LHC collider. Looking at the LHCb data we can obtain large samples of B mesons, and observe their oscillations.<br />
In this project we will learn how to select a sample of B mesons out of the data taken with the LHCb detector, measure the parameters that govern their oscillation and compare them with the SM.<br />
<br />
For more information, please contact Mara Soares (msoares_at_nikhef.nl).<br />
<br />
== Bachelor Projects 2020 ==<br />
<br />
<br />
=== Dark Matter ===<br />
<br />
==== XAMS ====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso.<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source and liquid scintillatorneutron detector we have acquired for the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study of neutron transport in xenon.<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Backgrounds in Radioactive Decay Measurements ====<br />
At Nikhef, the XENON group has a working setup, continuously monitoring the<br />
radioactive decay of Cobalt-60, Caesium-137 and Titanium-44. This beautiful setup is<br />
however not shielded perfectly; it is still vulnerable to background radioactivity. Our<br />
current way of working around this background radiation is to subtract it from our<br />
waveforms. You as a BSc student could help us hands-on and with analyses:<br />
together, we can disassemble the setup, measure background spectra and<br />
implement this in the data analysis. You can use all the data to validate the<br />
lifetime of our isotopes!<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
=== ATLAS ===<br />
<br />
==== Project ATLAS-ITk ====<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
==== The Most Energetic Higgs Boson ====<br />
A common approach to search for physics beyond the standard model is by searching for the direct production of new particles. Alternatively, indirect quantum effects on the production of known particles -such as the Higgs Boson- could reveal the first cracks in the theory. Processes with high energy transfer are of particular potential since possible deviations are expected to increase with the square of the involved energy scale. Using the entire data-set collected by the ATLAS experiment at CERN during the four years of the LHC’s Run 2, a proof-of-principle analysis, targeting transverse momenta of the above 400 GeV, has been developed by Nikhef researchers. The first results of this Higgs boson study are expected to be published this year and this project aims to develop refinements of the analysis techniques. We will investigate the usage of sophisticated machine learning tools such as artificial neural networks, the search for new variables that can help discriminating the signal from its background, revisiting the analysis categorisation and improving the reconstruction techniques at these extreme momenta. Supervisors: Brian Moser and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs: The Next Generation ====<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks has been developed by Nikhef researchers and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays), advanced analysis techiques (using deep learning methods) and expanding the theory interpretation. Another opportunity would be the development of a new statistical combination with various independent searches, which could significantly improve the discovery potential. Supervisors: Marko Stamenkovic and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs interferentie ====<br />
In 2012 hebben het ATLAS en het CMS experiment het Higgs deeltje gevonden. Inmiddels zijn we het Higgs boson aan het bestuderen, hoe gedraagt het zich precies, bestaan er meer soorten Higgs bosonen of is er echt maar eentje van? In dit project leer je hoe we een Higgs boson kunnen herkennen in de detector en gaan we kijken naar hoe de signalen veranderen als er meer Higgs bosonen bestaan of misschien wel andere exotische nieuwe deeltjes. <br />
Dit doen we door gebruik te maken van quantum interferentie wat plaats vindt tussen het Higgs boson en achtergrondprocessen. Hoe dit precies werkt leer je in het project. Supervisor: Hella Snoek (h.snoek_at_nikhef.nl)<br />
<br />
=== B-Physics - LHCb ===<br />
<br />
==== Time dependent CP violation ====<br />
The LHCb experiment studies CP violation withB-meson decays.<br />
The project focusses on the measurement of the unitarity angle gamma using decays of the Bs mesons to Ds K.<br />
Supervisors: Sevda Esen & Michele Veronesi<br />
<br />
==== Machine learning ====<br />
Machine learning has proven to be an indispensable tool in the selection of interesting events in high energy physics. Such technologies will become increasingly important as detector upgrades are introduced and data rates increase by orders of magnitude. HEPDrone is a toolkit to enable the creation of a drone classifier from any machine learning classifier, such that different classifiers may be standardised into a single form and executed in parallel. A detailed evaluation of the performance of different drone models in the real production environment of LHCb will give the collaboration a complete idea of not only the advantages of the drone model, but also the limits of drone complexity given the available computing resources.<br />
Requirements: Advanced python and Advanced C++<br />
Supervisor: Sean Benson<br />
<br />
==== LHCb simulations of physics beyond the Standard Model ====<br />
This project is of relatively theoretical and computing nature and performs simulation studies for physics beyond the Standard Model in the context of long lived particles. It is related to test the sensitivity of the LHCb experiment to detect specific signals of physics beyond the Standard Model.<br />
supervisor: Carlos Vazquez Sierra<br />
<br />
=== Detector R&D ===<br />
<br />
==== Fast timing detectoren ====<br />
Op dit moment maken we veel gebruik van silicon detectoren in onze deeltjes experimenten. Deze zijn gevoelig voor geladen deeltjes en zijn bij uitstek geschikt om de paden vast te leggen die de deeltjes maken die in de botsingen worden gemaakt. Bijvoorbeeld in de Atlas en LHCb experimenten worden tientallen tot honderden deeltjes gemaakt bij elk botsingsgebeurtenis (event) die met 40MHz plaatsvinden. Voor toekomstige deeltjesdetectoren willen we niet alleen het traject vastleggen maar ook met grote precisie een tijdsmeting toevoegen. We hebben hiervoor dus nieuwe detectoren nodig die behalve met een hele hoge snelheid en efficientie de posities van de langsvliegende deeltjes kunnen vastleggen, maar hier ook een zeer nauwkeurige tijdsmeting (in orde van picosecondes) aan kunnen toevoegen. We hebben met verschillende detectoren metingen gedaan, in testbundels op CERN, maar ook in het lab op Nikhef kunnen we metingen doen. In dit project ga je samen met het fast-timing detectoren team op het Nikhef metingen verrichten en de resultaten hiervan bekijken. Contact: Hella Snoek (h.snoek@nikhef.nl)<br />
<br />
==== Muon tomography ====<br />
In this project we are not looking for where cosmic rays come from. We are looking for what we can use them for instead. The muons in cosmic rays can be used to ‘probe’ massive objects. Muons are short lived particles that carry the same charge as electrons, have a high penetrating power and can be detected relatively easy. It is possible to reconstruct a density distribution within an object by measuring muon scattering and absorption. In this context the objects may be freight containers, buildings, melting furnaces, etc… <br />
<br />
Systems that scan objects through the use of muons are often large (objects often need to be enclosed by the system) and complex. The question we want to answer is: Can we develop a smaller, simpler and cheaper system for muon tomography? <br />
<br />
A method to detect muons is by using a material that scintillates (emits light) when hit by an ionising particle. When this light emission is prompt after the passage of the muon, timing information of the light can be used to reconstruct the path of the muon.<br />
In this experiment we make a muon tracker based on two sheets of scintillating material and photo multiplier tubes (PMTs). Photo multiplier tubes are fast responding and very sensitive light detectors (capable of detecting single photons).<br />
<br />
The big question is: How well does this system perform?<br />
<br />
Currently a set-up is being build. You have a lot of freedom to choose a focus in this project (theory, simulation, hardware, or a combination of those).<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Spectral X-ray imaging - Looking at colours the eyes can't see ====<br />
When a conventional X-ray image is made to analyse the composition of a sample, or to perform a medical examination on a patient, one acquires an image that only shows intensities. One obtains a ‘black and white’ image. Most of the information carried by the photon energy is lost. Lacking spectral information can result in an ambiguity between material composition and amount of material in the sample. If the X-ray intensity as a function of the energy can be measured (i.e. a ‘colour’ X-ray image) more information can be obtained from a sample. This translates to less required dose and/or to a better understanding of the sample that is being investigated. For example, two fields that can benefit from spectral X-ray imaging are mammography and real time CT.<br />
<br />
X-ray detectors based on Medipix/Timepix pixel chips have spectral resolving capabilities and can be used to make polychromatic X-ray images. Medipix and Timepix chips have branched from pixel chips developed for detectors for high energy physics collider experiments.<br />
<br />
Some themes that students can work on: <br />
<br />
- Optimising methods to acquire spectral X-ray images.<br />
<br />
- Determining how much existing applications benefit from spectral X-ray imaging and looking for potential new applications.<br />
<br />
- Characterising, calibrating, optimising X-ray imaging detector systems.<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Holographic emitter ====<br />
A difficulty in generating holograms (based on the interference of light) is the required dense spatial light field sampling. One would need pixels of less than 200 nanometer. With larger pixels artefacts occur due to spatial under sampling. A pixel pitch of 200 nm or less is difficult, if not, impossible, to achieve, especially for larger areas. Another challenge is the massive amount of computing power that is required to control such a dense pixel matrix. <br />
<br />
A new holographic projection method has been developed that reduces under sampling artefacts, regardless of spatial sample density. The trick is to create 'pixels' at random but known positions, resulting in an array that lacks any spatial periodicity. As a result a holographic emitter can be built with a significantly lower sample density and less required computing power. This could bring holography in reach for many applications like display, lithography, 3D printing, metrology, etc...<br />
<br />
The big question: How does the performance of the holographic emitter depend on sample density and sample positions?<br />
<br />
The aspects of a holographic image we are interested in are:<br />
<br />
- Noise<br />
<br />
- Contrast<br />
<br />
- Suppression of under sampling artefacts<br />
<br />
- Resolution <br />
<br />
For this project we are building a proof of concept holographic emitter. This set-up will be used to verify simulation results (and to make some cool holograms of course). <br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
=== KM3NeT ===<br />
<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
==== Data analysis of the first deployed KM3NeT detection lines ====<br />
<br />
First detection lines of the KM3NeT neutrino telescope have been deployed<br />
in the Mediterranean Sea, and a first data set is available. The lines consist<br />
of light-sensitive detectors that record the time of arrival of photons<br />
produced by relativistic particles in the deep sea, and their number.<br />
In this project we will study the first data to separate various components:<br />
photons from potassium decay, bioluminesence, sparks in the photomultipliers,<br />
downgoing muons from cosmic rays, and perhaps first neutrinos.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Neutrino oscillation measurements with the KM3NeT neutrino telescope ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope currently under construction<br />
will be able to measure the oscillations of neutrinos produced in interactions<br />
of cosmic rays with the earth atmosphere. Fundamental neutrino properties can<br />
be deduced from these oscillations measurements, in particular the so-called<br />
mass hierarchy of neutrinos. In this project we will simulate the ORCA measurements<br />
of neutrino oscillations, and study the dependence of the sensitivity on<br />
experimental uncertainties, such as energy resolution and neutrino flavour<br />
identification, and theoretical uncertainties, such as the atmospheric neutrino<br />
flux and neutrino cross sections. The results will help ORCA to identify<br />
the main sources of uncertainty, and therefore to actively try to reduce these<br />
and improve the final measurement.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Performance Studies of ORCA for Dark Matter Detection ====<br />
<br />
The interactions of neutrinos in KM3NeT-ORCA give different signatures which are categorised as track and shower events. This project involves the studies of muon, electron and tau neutrino interactions for the reconstruction performance of ORCA. Efficient reconstruction of such signals is important for Dark Matter searches in the low-mass regime. We will work on understanding the detector performance, e.g. effective acceptance, energy and angular resolution, with different configurations of the detector setup. The result of this study will be very useful to improve the sensitivity of the experiment for Dark Matter detection and its possible location. The student will have the opportunity to work closely with KM3NeT members at Nikhef and gain skills of analyzing data. <br />
<br />
Supervisors: Suzan Basegmez du Pree, Aart Heijboer<br />
<br />
==== A search for periodic sources in Antares data ====<br />
<br />
The Antares deep-sea neutrino telescope has been operated for more then ten years. A search for periodic sources is proposed by applying a fast Fourier transformation (FFT) analysis on the available low-level data. This search will be combined with a (literature) study of pulsars which are thought to emit neutrinos.<br />
<br />
Supervisor: Maarten de Jong<br />
<br />
==== Study of Optical Properties of Sea Water using Hit Coincidences in MC Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
By studying coincidences of L1 hits between neighbouring DOMs, for various Monte Carlo (MC) data sets with different sea water optical properties such as scattering and absorption coefficients, in this project we try to figure out if and how well we can quantify optical sea water properties by studying L1 hit coincidences in real KM3NeT data.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
==== Determination of Inter-DOM Distances using Hit Coincidences in KM3NeT Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
The number of L1 hit coincidences from atmospheric muons between neighbouring DOMs on a DU is expected to decrease exponentially. By fitting the observed number of L1 hit coincidences between neighbouring DOMs in real data to the expected exponential decay, in this project we study how accurately we can determine the distances between DOMs on a single DU. In addition, we try to determine the distances between DUs by looking for L1 hit coincidences between DOMs on neighbouring DUs.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
=== VIRGO ===<br />
<br />
The Advanced LIGO and Advanced Virgo interferometers have recently observed gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results.<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Frank Linde (frank.linde_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
<br><br><br><br />
<br />
== Bachelor Projects 2017 ==<br />
<br />
=== Extreme Astronomy – Preparing for CTA, the Next-Generation Gamma-Ray Observatory ===<br />
<br />
The Cherenkov Telescope Array (CTA) is a planned facility for measuring gamma rays from space covering more than four orders of magnitude in energy, up to energies exceeding 100 TeV. CTA employs the imaging atmospheric Cherenkov technique to measure properties of cosmic gamma rays. This technique is based on measuring Cherenkov light emitted during the development of a gamma-ray air shower. CTA will be built at two experimental sites, one in the Northern, one in the Southern hemisphere, and will consist of up to 100 telescopes. It represents a major leap forward in sensitivity and precision for gamma-ray astronomy, and will allow us to explore very-high-energy processes of the extreme Universe at an unprecedented level.<br />
<br />
Two projects for students are available at the CTA group of UvA in the field of optical and photonic R&D contributing to the starting phase of CTA. For the first project the student will conduct measurements to characterise novel kinds of single-photon detectors, referred to as silicon photomultipliers, and evaluate different types of these sensors for their use for CTA. For the second project the student will develop and test an imaging system making use of a liquid crystal display. This flexible light source will be able to mimic images from different light sources of the night sky as seen by cameras of CTA, for instance gamma-ray air showers or stars, and will be used for camera tests and calibration.<br />
<br />
<br />
Supervisors: David Berge, Maurice Stephan (postdoc)<br />
<br />
=== Dark Matter ===<br />
<br />
<!--<br />
==== XENON1T - the world's most sensitive dark matter detector ====<br />
<br />
Finding the mysterious dark matter particles is one of the most challenging enterprises in physics today. Soon we will get first data from the world's most sensitive dark matter detector yet: the XENON1T experiment.<br />
<br />
The first goal of this project is to understand why dak matter is necessary to understand the universe, and how we could detect it with XENON1T. Then, you can contribute to our group's efforts preparing for <br />
and analyzing the XENON1T data by, for example: examining XENON1T's calibration signals to check for problems in the experiment, testing our data analysis software with simulated dark matter signals, or studying the physics behind XENON1T's detection process to learn how to better distinguish dark matter signals from backgrounds. For data analyis, experience with or willingness to learn programming in python is essential.<br />
<br />
<br />
Supervisors: M.P. Decowski & J. Aalbers --><br />
<br />
==== Neutrinoless double beta decay sensitivity study in future dark matter detectors ====<br />
<br />
The discovery of neutrino oscillation (Nobel Physics 2015) means that neutrinos have mass. We already know that their masses are tiny, more than one million times smaller than the next-lightest particle in the standard model, the electron. This raises the question if the mass-generation mechanism is the same for neutrinos as it is for the other subatomic particles. In particular, since neutrinos are electrically neutral, they could be their own anti-particles - we call these types of particles Majorana. The only practical way to discover if neutrinos are Majorana is through the search of an extremely rare radioactive decay called neutrinoless double beta decay (0n2b). A few isotopes are candidates for this process, among them Xe-136. The natural abundance of Xe-136 in natural xenon is about 9%, and this gives the opportunity to look for a 0n2b signal in xenon-based dark matter detectors like XENON1T and the future XENONnT and DARWIN detectors. <br />
<br />
We are looking for a student interested in doing a sensitivity study for 0n2b in XENONnT and the DARWIN experiments. The first goal will be to understand the physics addressed in neutrinoless double beta decay. Then the student will inventory possible backgrounds for the signal, use a (controversial) claim of a 0n2b signal as a benchmark and finally obtain the sensitivity of these future detectors. The work will involve simulations and analysis, building on an existing framework developed in our group. <br />
<br />
Supervisors: M.P. Decowski & A. Tiseni<br />
<br />
==== Shaking Dark Matter detectors ====<br />
<br />
Our XENON1T detector is built in the lab underneath the Gran Sasso mountains in central Italy. The lab is very well suited for low-background experiments due to the 1.5km of rock overburden. <br />
However, as you may know, cental Italy has been plagued by earthqaukes over the past decade, with the most recentones occurring in January 2017. We need a BSc student to investigate the <br />
details of such earthquakes in our underground lab. What are the magnitdues by which stuff is moving underground? What are the accelerations? What is the potential effect on our experimental<br />
setup? What would ahppen if an earthquake happens much closer to our lab? Furthermore we are interested to find out whether Earthquakes can be predicted. Some papers claim that before<br />
an earthquake the radon emanating from rock increases. In our lab we measure the radon concentration as a function of time: can you find a correlation between the measurements and recent <br />
earthquakes?<br />
<br />
If you are interested in finding out more about earthquakes, please contact M.P. Decowski or A.P. Colijn<br />
<br />
==== XAMS - a baby dark matter detector ====<br />
<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso<br />
we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector<br />
are identical to its big sibling in Gran Sasso.<br />
<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source we have acquired<br />
before the start of the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project<br />
will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study<br />
of neutron transport in xenon.<br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
==== Radon is bad for Dark Matter ====<br />
<br />
Radon is the dominant background for xenon based dark matter detectors, like the XENON1T experiment. In our lab at Nikhef we are investigating ways to reduce or eliminate the effect of radon<br />
on our sensitivity. For our lab setup XAMS we have designed and constructed a radon detector, that can be used in xenon systems at high-pressure. This completely new detector<br />
is now waiting for a BSc student to fully chracterize and use it. During this project you will first study the effect that radon contaminations have on dark matter detectors, then you will start working to<br />
understand our new radon detector in detail. You will learn howto use a radioactive source to calibrate the detector: this is something which is not easy and has not been done before in our lab. <br />
If you manage to succesfully calibrate the detector, we then want to incorporate it into our lab xenon system at Nikhef and maybe at some later stage in the real XENON1T detector!<br />
<br />
The profile of the student to work on this project is broad. I expect a good theoretical knowledge in order to quickly get upto speed with understanding dark mater detectors, and in addition I <br />
need 'lab-creativity' in order to develop methods for calibrating the new detector. If a good method is developed, it will be used for many years by the Nikhef dark matter group and beyond. <br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
=== ATLAS ===<br />
<br />
<br />
==== ATLAS (1): Searching for new physics with the Higgs and W bosons ====<br />
<br />
The strength of the Higgs interactions with electroweak bosons are precisely defined in the<br />
Standard Model. Therefore they are sensitive probes of the mechanism of electroweak symmetry<br />
breaking and enable searches for new physics beyond the SM. With the data collected by the ATLAS<br />
experiment in years 2015-2016 we plan to measure separately the Higgs coupling to<br />
longitudinally and transversely polarised W bosons in a process of weak boson fusion. To<br />
maximise experimental sensitivity we are developing techniques to separate the signal from<br />
background processes. You will take part in investigating possible improvements from<br />
reconstructing events in reference frames boosted with respect to the detector. During the<br />
project you will learn modern experimental analysis techniques. This project is a part of Vector<br />
Boson Scattering Coordination and Action Network (VBSCan) which connects researchers studying<br />
this and related topics worldwide.<br />
<br />
Supervisors: Pamela Ferrari, Magdalena Slawinska, Bob van Eijk<br />
<br />
<br />
==== ATLAS (2): Dark-matter-motivated searches for supersymmetric particles at the LHC ====<br />
<br />
Supersymmetry, a symmetry between fermions and bosons in particle physics,<br />
may provide a particle that could be the dark matter in the universe.<br />
The observation of an excess of gamma rays originating from the centre of our<br />
galaxy could be explained in a model where supersymmetric dark matter<br />
particles annihilate each other in the galactic centre, leading to gamma rays.<br />
<br />
Given the model parameters, it should also be possible to produce such<br />
particles at the LHC, at CERN in Geneva. But it is not so easy to observe<br />
them: the signal is small, and the noise (background) is large.<br />
In this project, we will use simulations of signal and background to<br />
optimize experimental searches for such particles with the ATLAS detector,<br />
apply them to the data collected in 2015, and prepare for the new data in<br />
2016 and later.Where possible, we will explore new machine learning techniques.<br />
<br />
Supervisors: Paul de Jong, Broos Vermeulen<br />
<br />
<br />
==== ATLAS (3): Simulations / Quality tests for the ATLAS High-Luminosity LHC Upgrade ====<br />
<br />
One of the key sub-systems of the ATLAS experiment at the Large<br />
Hadron Collider (LHC) is the Inner Detector (ID), designed to provide<br />
excellent charged particles momentum and vertex resolution measurements.<br />
<br />
At Phase-2 of the LHC run, in ~2025, the operating luminosity of<br />
the collider will be increased significantly.<br />
This will imply an upgrade of all ATLAS subsystems. In particular,<br />
the ID will be fully replaced with a tracker completely made of<br />
Silicon, having higher granularity and radiation hardness.<br />
The R&D process for the new ATLAS ID is now ongoing.<br />
Different geometrical layouts are simulated and their performance is<br />
studied under different operating conditions in search for the optimal<br />
detector architecture. Also, the performance of the new<br />
Si-sensors/modules is under investigation with dedicated laboratory tests.<br />
<br />
The focus of the project could be on the simulation of the High-Luminosity LHC<br />
version of the ATLAS Inner Detector. The student will learn how a<br />
high-energy physics experiment is designed and optimized.<br />
Alternatively, if possible at that moment, the student could<br />
work on a project at the Nikhef Silicon laboratory at the test-bench for<br />
new ATLAS Si-strip detectors and participate in the quality<br />
assurance procedure for the new ATLAS Si detectors.<br />
<br />
==== ATLAS (4): Higgs productie in Run-2 van de LHC ====<br />
In de eerste run van de LHC is onder andere bij het ATLAS experiment het Higgs deeltje gevonden. Nu is de tweede run begonnen en kan het Higgs deeltje worden bevestigd. Door de verhoogde energie ziet de achtergrond er echter heel anders uit, dus is de optimalisatie van het wegsnijden van de achtergronden qua fysica anders. Voor je bachelor project kan met behulp van de ATLAS detector het Higgs deeltje in run twee komen vinden. <br />
<br />
Supervisors: Lydia Brenner, Wouter Verkerke<br />
<br />
==== ATLAS (5): De lange staart van het Higgs boson ====<br />
<br />
[[File:HiggsMassa.png |thumb|left|upright=1.25]]<br />
<br />
<br><br />
Na de ontdekking van het Higgs boson in 2012 zijn we druk bezig om te kijken of zijn eigenschappen overeenkomen met de voorspellingen van het Standaard Model. Een van de belangrijkste eigenschappen is de zogenaamde breedte van het Higgs boson. Als het Higgs boson naast de Standaard Model deeltjes ook in exotische nieuwe speeltje uit elkaar kan vallen (bijvoorbeeld donkere materie) dan zal dat ale eerste zichtbaar worden in een afwijking van de breedte tov de verwachting. We gaan in dit project uitzoeken hoe de strategie die nu gebruikt wordt (meten van de hoeveelheid Higgs bosonen met een extreem hoge massa) precies werkt en kijken of we door het toevoegen van nieuwe ideeën een verbetering kunnen aanbrengen. <br />
<br />
<br><br />
Specifiek: We gaan eerst in detail de eigenschappen bekijken van het Higgs signaal en de twee achtergronden die er het meest op lijken. Daarna gaan we op zoek naar de verschillen en een manier waarop we onze kennis daarover kunnen gebruiken om gevoeliger te worden voor het Higgs signaal.<br />
<br />
Supervisors: Hella Snoek, Ivo van Vulpen<br />
<br />
E-mail: H.Snoek_at_nikhef.nl & Ivo.van.Vulpen_at_nikhef.nl<br />
<br><br><br><br><br><br><br />
<br />
=== ATLAS (6): Project ATLAS-ITk ===<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
<br><br />
<br />
=== KM3Net ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierachy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
The first phase of the KM3NeT neutrino telescope is currently under construction, with the first two detection units operational at 3500m depth in the Mediterranean Sea, 100 km off the coast of Sicily.<br />
<br />
<br />
==== KM3NeT (1): Photon counting in KM3NeT ====<br />
<br />
The details of a neutrino interaction, such as its incoming direction and energy, determine the pattern, time and amount, of recorded photons (´hits´) by the photo-multplier tubes. The time of arrival is recorded with nanosecond accuracy and the amount of photons is encoded in the length of the pulse(time-over-threshold, ToT). Currently, only the photon arrival time and the number of photo-multipliers that record a hit are used in reconstructing event properties.<br />
In this project, the distributions of the ToT mainly originating from photons from potassium-40 decays in the sea-water and from atmospheric muons passing through the water will be studied. The goals are to investigate the properties of the ToT distributions obtained from data and simulation, in particular the dependence on the photo-multiplier efficiency and atmospheric muon flux.<br />
In this project we will be extensively using the programming language C++ to analyse the data, so a reasonable proficiency is required.<br />
<br />
Supervisors: Ronald Bruijn & Karel Melis<br />
<br />
Email: rbruijn_at_nikhef.nl<br />
<br />
<br />
<br />
<br><br><br><br />
<br />
=== VIRGO ===<br />
<br />
"It is anticipated that in the next few years, Advanced LIGO and Advanced Virgo will start observing gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results."<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Jo van den Brand (jo_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
=== LHCb ===<br />
<br />
Begeleider: Sean Benson<br />
<br />
Title: <br />
Searching for physics beyond the Standard Model with LHCb<br />
<br />
The LHCb experiment is designed to study the "The Flavour Problem" in particle physics:<br />
Why is the universe dominated by matter over antimatter? Why are there three generations of elementary particles? What is the origin of quark flavour changing interactions.<br />
<br />
To solve these riddles, LHCb performs precision measurements on b-quark particle decays.<br />
An intriguing signal has recently been observed in the decay of a B-meson to a K* and two muons: Bd→K*μμ, which does not seem to behave according to the predictions of the Standard Model<br />
In this project the bachelor student will investigate this further by studying the case where the K* particle decays to a so-called k-short particle and a π0. The observation of such a final state will provide valuable information in the search for physics beyond the Standard Model.<br />
<br />
In this ambitious project the student is expected to study both a theory on the mechanism of CP violation with B mesons, in addition to data analysis with B decays. Programming experience in python is required.<br />
<br />
The LHCb experiment at CERN analyzes the properties of B-hadrons produced in proton-proton collisions at the LHC. For projects in the LHCb group, please contact Marcel Mark (marcel.merk_at_nikhef.nl)<br />
<br />
<br />
=== LHCb (1) ===<br />
<br />
One of the most fascinating mysteries in physics today is: how is it possible that universe is filled with matter? If the Big Bang produced equal amounts of matter and antimatter, we still do not understand the mechanism that lead to the excess of matter over antimatter that we observe today.<br />
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One interesting feature of some particles is that they can transform themselves into their antiparticles, then back to particle, and so forth, in an oscillatory way until they finally decay. In particular, beauty mesons (B) can oscillate into their antiparticle (B ̄). The parameters of this oscillation, such as amplitude, frequency and phase, are calculable mathematically: predictions for it are available in the standard model (SM) of particle physics. But the oscillations according to the SM alone would not lead to the imbalance of matter in the universe – we still need to find a new type of physics that may be able to explain it.<br />
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In this context, it is very important to measure B oscillations in the laboratory, and compare these observations with the expectations from the SM. Are the experimental data in good agreement with the SM, as we expect? If the aswer is not, i.e. if there are features of the oscillation that we do not understand well, then we may be observing “new physics”. In other words, the data may reveal a new mechanism that generates a different matter-antimatter balance than predicted by the SM, that may potentially solve the puzzle.<br />
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The LHCb experiment at CERN is dedicated to such studies: LHCb detectors are placed in a region along the LHC collider beamline, where a large number of B mesons are produced, arising from the proton-proton collision data from the LHC collider. Looking at the LHCb data we can obtain large samples of B mesons, and observe their oscillations.<br />
In this project we will learn how to select a sample of B mesons out of the data taken with the LHCb detector, measure the parameters that govern their oscillation and compare them with the SM.<br />
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For more information, please contact Mara Soares (msoares_at_nikhef.nl).</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=918Master Projects2023-03-29T06:54:18Z<p>Rojo@nikhef.nl: /* Theoretical Particle Physics: Probing the origin of the proton spin with machine learning */</p>
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<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
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== Projects with a 2023 start ==<br />
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=== ALICE: The next-generation multi-purpose detector at the LHC ===<br />
This main goal of this project is to focus on the next-generation multi-purpose detector planned to be built at the LHC. Its core will be a nearly massless barrel detector consisting of truly cylindrical layers based on curved wafer-scale ultra-thin silicon sensors with MAPS technology, featuring an unprecedented low material budget of 0.05% X0 per layer, with the innermost layers possibly positioned inside the beam pipe. The proposed detector is conceived for studies of pp, pA and AA collisions at luminosities a factor of 20 to 50 times higher than possible with the upgraded ALICE detector, enabling a rich physics program ranging from measurements with electromagnetic probes at ultra-low transverse momenta to precision physics in the charm and beauty sector. <br />
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''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli] and [mailto:marco.van.leeuwen@cern.ch Marco van Leeuwen]''<br />
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=== ALICE: Searching for the strongest magnetic field in nature ===<br />
In a non-central collision between two Pb ions, with a large value of impact parameter, the charged nucleons that do not participate in the interaction (called spectators) create strong magnetic fields. A back of the envelope calculation using the Biot-Savart law brings the magnitude of this filed close to 10^19Gauss in agreement with state of the art theoretical calculation, making it the strongest magnetic field in nature. The presence of this field could have direct implications in the motion of final state particles. The magnetic field, however, decays rapidly. The decay rate depends on the electric conductivity of the medium which is experimentally poorly constrained. Overall, the presence of the magnetic field, the main goal of this project, is so far not confirmed experimentally.<br />
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''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
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=== ALICE: Looking for parity violating effects in strong interactions ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions, in the presence of a deconfined state, gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, what is called the Chiral Magnetic Effect (CME).<br />
The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, however further studies are needed to constrain background effects. These highly anticipated results have the potential to reveal exiting, new physics.<br />
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''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
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=== ALICE: Machine learning techniques as a tool to study the production of heavy flavour particles ===<br />
There was recently a shift in the field of heavy-ion physics triggered by experimental results obtained in collisions between small systems (e.g. protons on protons). These results resemble the ones obtained in collisions between heavy ions. This consequently raises the question of whether we create the smallest QGP droplet in collisions between small systems. The main objective of this project will be to study the production of charm particles such as D-mesons and Λc-baryons in pp collisions at the LHC. This will be done with the help of a new and innovative technique which is based on machine learning (ML). The student will also extend the studies to investigate how this production rate depends on the event activity e.g. on how many particles are created after every collision.<br />
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''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli]''<br />
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=== ALICE: Search for new physics with 4D tracking at the most sensitive vertex detector at the LHC ===<br />
<br />
With the newly installed Inner Tracking System consisting fully of monolithic detectors, ALICE is very sensitive to particles with low transverse momenta, more so than ATLAS and CMS. This will be even more so for the ALICE upgrade detector in 2033. This detector could potentially be even more sensitive to longlived particles that leave peculiar tracks such as disappearing or kinked tracks in the tracker by using timing information along a track. In this project you will investigate how timing information in the different tracking layers can improve or even enable a search for new physics beyond the Standard Model in ALICE. If you show a possibility for major improvements, this can have real consequences for the choice of sensors for this ALICE inner tracker upgrade.<br />
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''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld] and [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
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=== ATLAS: The Higgs boson's self-coupling ===<br />
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The coupling of the Higgs boson to itself is one of the main unobserved interactions of the Standard Model and its observation is crucial to understand the shape of the Higgs potential. Here we propose to study the 'ttHH' final state: two top quarks and two Higgs bosons produced in a single collision. This topology is yet unexplored at the ATLAS experiment and the project consists of setting up the new analysis (including multivariate analysis techniques to recognise the complicated final state), optimising the sensitivity and including the result in the full ATLAS study of the Higgs boson's coupling to itself. With the LHC data from the upcoming Run-3, we might be able to see its first glimpses! <br />
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''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree] and [mailto:cpandini@nikhef.nl Carlo Pandini]'' <br />
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=== ATLAS: Triple-Higgs production as a probe of the Higgs potential ===<br />
So far, the investigation of Higgs self-couplings (the coupling of the Higgs boson to itself) at the LHC has focused on the measurement of the Higgs tri-linear coupling λ3 mainly through direct double-Higgs production searches. In this research project we propose the investigation of Higgs tri-linear and quartic coupling parameters λ3 and λ4, via a novel measurement of triple-Higgs production at the LHC (HHH) with the ATLAS experiment. While in the SM these parameters are expected to be identical, only a combined measurement can provide an answer regarding how the Higgs potential is realised in Nature. Processes in which three Higgs bosons are produced simultaneously are extremely rare, and very difficult to measure and disentangle from background. In this project we plan to investigate different decay channels (to bottom quarks and tau leptons), and to study advanced machine learning techniques to reconstruct such a complex hadronic final state. This kind of processes is still quite unexplored in ATLAS, and the goal of this project is to put the basis for the first measurement of HHH production at the LHC.<br />
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Furthermore, we'd like to study the possible implication of a precise measurement of the self-coupling parameters from HHH production from a phenomenological point of view: what could be the impact of a deviation in the HHH measurements on the big open questions in physics (for instance, the mechanisms at the root of baryogenesis)?<br />
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Contact: ''[mailto:tdupree@nikhef.nl Tristan du Pree] and [mailto:cpandini@nikhef.nl Carlo Pandini]''<br />
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=== ATLAS: The Next Generation ===<br />
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After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks is very new [1] and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays) and advanced analysis techiques (using deep learning methods).<br />
<br />
[https://atlas.cern/updates/briefing/charming-Higgs-decay][https://arxiv.org/abs/1802.04329 https://atlas.cern/updates/briefing/charming-Higgs-decay]<br />
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''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
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=== ATLAS: Searching for new particles in very energetic diboson production ===<br />
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The discovery of new phenomena in high-energy proton–proton collisions is one of the main goals of the Large Hadron Collider (LHC). New heavy particles decaying into a pair of vector bosons (WW, WZ, ZZ) are predicted in several extensions to the Standard Model (e.g. extended gauge-symmetry models, Grand Unified theories, theories with warped extra dimensions, etc). In this project we will investigate new ideas to look for these resonances in promising regions. We will focus on final states where both vector bosons decay into quarks, or where one decays into quarks and one into leptons. These have the potential to bring the highest sensitivity to the search for Beyond the Standard Model physics [1, 2]. We will try to reconstruct and exploit new ways to identify vector bosons (using machine learning methods) and then tackle the problem of estimating contributions from beyond the Standard Model processes in the tails of the mass distribution.<br />
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[1] https://arxiv.org/abs/1906.08589<br />
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[2] https://arxiv.org/abs/2004.14636<br />
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''Contact: [mailto:f.dias@nikhef.nl Flavia de Almeida Dias], [mailto:rhayes@nikhef.nl Robin Hayes], Elizaveta Cherepanova and Dylan van Arneman''<br />
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=== ATLAS: Top-quark and Higgs-boson analysis combination, and Effective Field Theory interpretation [not available in 2023] ===<br />
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We are looking for a master student with interest in theory and data-analysis in the search for physics beyond the Standard Model in the top-quark and Higgs-boson sectors.<br />
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Your master-project starts just at the right time for preparing the Run-3 analysis of the ATLAS experiment at the LHC. In Run-3 (2022-2026), three times more data becomes available, enabling analysis of rare processes with innovative software tools and techniques.<br />
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This project aims to explore the newest strategy to combine the top-quark and Higgs-boson measurements in the perspective of constraining the existence of new physics beyond the Standard Model (SM) of Particle Physics. We selected the pp->tZq and gg->HZ processes as promising candidates for a combination to constrain new physics in the context of Standard Model Effective Field Theory (SMEFT). SMEFT is the state-of-the-art framework for theoretical interpretation of LHC data. In particular, you will study the SMEFT OtZ and Ophit operators, which are not well constrained by current measurements.<br />
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Besides affinity with particle physics theory, the ideal candidate for this project has developed python/C++ skills and is eager to learn advanced techniques. You start with a simulation of the signal and background samples using existing software tools. Then, an event selection study is required using Machine Learning techniques. To evaluate the SMEFT effects, a fitting procedure based on the innovative Morphing technique is foreseen, for which the basic tools in the ROOT and RooFit framework are available. The work is carried out in the ATLAS group at Nikhef and may lead to an ATLAS note.<br />
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''Contact: [mailto:geoffrey.gilles@cern.ch Geoffrey Gilles] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:h73@nikhef.nl Marcel Vreeswijk]''<br />
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=== ATLAS: Machine learning to search for very rare Higgs decays ===<br />
<br />
Since the Higgs boson discovery in 2012 at the ATLAS experiment, the investigation of the properties of the Higgs boson has been a priority for research at the Large Hadron Collider (LHC). However, there are still a many open questions: Is the Higgs boson the only origin of Electroweak Symmetry Breaking? Is there a mechanism which can explain the observed mass pattern of SM particles? Many of these questions are linked to the Higgs boson coupling structure. <br />
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While the Higgs boson coupling to fermions of the third generation has been established experimentally, the investigation of the Higgs boson coupling to the light fermions of the second generation will be a major project for the upcoming data-taking period (2022-2025). The Higgs boson decay to muons is the most sensitive channel for probing this coupling. In this project, you will optimize the event selection for Higgs boson decays to muons in the Vector Boson Fusion (VBF) production channel with a focus on distinguishing signal events from background processes like Drell-Yan and electroweak Z boson production. For this purpose, you will develop, implement and validate advanced machine learning and deep learning algorithms. <br />
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''Contact: [mailto:oliver.rieger@nikhef.nl Oliver Rieger] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:s01@nikhef.nl Peter Kluit]''<br />
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=== ATLAS: Interpretation of experimental data using SMEFT ===<br />
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The Standard Model Effective Field Theory (SMEFT) provides a systematic approach to test the impact of new physics at the energy scale of the LHC through higher-dimensional operators. The interpretation of experimental data using SMEFT requires a particular interest in solving complex technical challenges, advanced statistical techniques, and a deep understanding of particle physics. We would be happy to discuss different project opportunities based on your interests with you.<br />
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''Contact: [mailto:oliver.rieger@nikhef.nl Oliver Rieger] and [mailto:verkerke@nikhef.nl Wouter Verkerke]''<br />
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=== ATLAS: Reconstructing tracks from particle physics detector hits with state-of-the-art machine learning techniques ===<br />
This project concerns the application of new machine learning techniques to tackle the problem of track reconstruction at the ATLAS detector in CERN. While algorithms to construct particle tracks from low-level detector information such as particle hits and timestamps have been around for decades, recent developments in the field of machine learning open up new opportunities to improve these algorithms significantly. Some recent developments that could help in this context include graph-based neural networks, which embed the input data in the format of a graph and as such have the capability to enhance underlying correlations within events. Transformer neural networks are a particular extension of graph-based neural networks proposed only in 2017 which could also provide helpful in this case. Another option would be to build upon some of the work done within the field of computer vision and see if image segmentation networks can help solve this problem. There are a range of available options and this project includes the freedom for the student to choose particular types of networks, but more explicit guidance could be provided in case it is desired.<br />
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In this project the student will develop and compare the performance of various machine learning models to initially reconstruct tracks from simplified test data. Upon successful completion of this, simulated data from the actual ATLAS detector can be analysed as well in the scope of this project. The student will need some familiarity with programming in python and an interest in machine learning, but a physics background is not required. In this project the student will be able to contribute to fundamental physics research and will familiarize themselves with state-of-the-art machine learning models.<br />
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Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
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=== ATLAS: New machine learning approaches to target Higgs interference signatures in LHC data ===<br />
In this project we aim to improve an ongoing analysis to determine the lifetime of the Higgs Boson through state-of-the-art machine learning techniques, in particular by addressing a ''novel solution to an as of yet unsolved fundamental problem in modeling quantum interference''. While the Higgs is an elusive particle that generally only appears in physics processes with small cross sections, its signature can be amplified in the Large Hadron Collider (LHC) through quantum interference with larger background (non-Higgs) processes. This is the effect that the Higgs’ lifetime analysis relies on to be able to measure the relevant Higgs signature. A fundamental physics modelling problem arises though in the simulation of individual events for this interference due to the fact that these events are in reality described by a superposition of underlying Higgs and non-Higgs processes.<br />
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Since machine learning models in particle physics are typically trained to characterise individual physics events, the fact that interference events cannot currently be generated is a significant problem when interference is the target. In the currently existing Higgs lifetime analysis, a machine learning model was trained which instead focuses only on the explicit Higgs-mediated processes as a proxy, which is suboptimal. The aim of this project is to improve upon this current machine learning strategy used in this analysis by implementing either of the inference-aware approaches suggested in [1] and [2]. The idea behind these inference-aware machine learning algorithms is that they do not optimise for a simplified goal such as the loss function which is common in traditional machine learning, but rather for the end-goal of the analysis. In this case, this would omit the need for interference event generation altogether and allow the machine learning models to be trained optimally regardless.<br />
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The first checkpoint of this project is to use either of the frameworks used in [1] and [2] (which are both publicly available) and run them with a simplified dataset from the aforementioned analysis. After this proof-of-principle is achieved, the next goal would be to actually implement the newly developed machine learning models in the full analysis and to determine the improvement upon the existing result. A successful completion of these tasks would not only benefit the Higgs lifetime analysis, but would be an important stepping stone to future developments to make machine learning approaches also aware of other hard to model effects such as systematic uncertainties. Finally, there are further options to improve this analysis such as the generation of actual interference training data, which could be attempted in case the primary project finishes earlier than expected.<br />
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[1] De Castro, P., & Dorigo, T. (2019). INFERNO: inference-aware neural optimisation. ''Computer Physics Communications'', ''244'', 170-179.<br />
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[2] Simpson, N., & Heinrich, L. (2023, February). neos: End-to-end-optimised summary statistics for high energy physics. In ''Journal of Physics: Conference Series'' (Vol. 2438, No. 1, p. 012105). IOP Publishing.<br />
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Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
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=== ATLAS: Development of state-of-the art modeling techniques to generate Higgs interference events ===<br />
In this project we aim to improve an ongoing analysis to determine the lifetime of the Higgs Boson through new event generation strategies, in particular by addressing a novel solution to an as of yet unsolved fundamental problem in modeling quantum interference. While the Higgs is an elusive particle that generally only appears in physics processes with small cross sections, its signature can be amplified in the Large Hadron Collider (LHC) through quantum interference with larger background (non-Higgs) processes. This is the effect that the Higgs’ lifetime analysis relies on to be able to measure the relevant Higgs signature. A fundamental physics modelling problem arises though in the simulation of individual events for this interference due to the fact that these events are in reality described by a superposition of underlying Higgs and non-Higgs processes.<br />
<br />
The current approach to deal with this problem is to ignore the interference in analysis optimization and instead optimize only for explicitly Higgs mediated processes, but this severely impacts analysis performance. In the context of Effective Field Theories (EFT) however, a similar problem arises and has been solved for simple (leading order) processes. In this project we plan to take the machinery developed for EFT and apply it to the Higgs lifetime analysis. Furthermore, with the recent development of a Next-to-Leading Order (NLO) Higgs event generation tool [1] a subsequent goal would be to use this to also generate interference at the NLO level. Successful completion of this project would lead to a much improved analysis result, significantly constraining the lifetime of the Higgs Boson. Besides, the techniques developed would almost certainly be used in future analyses on Large Hadron Collider (LHC) run 3 data.<br />
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[1] Alioli, S., Ravasio, S. F., Lindert, J. M., & Röntsch, R. (2021). Four-lepton production in gluon fusion at NLO matched to parton showers. ''The European Physical Journal C'', ''81''(8), 687.<br />
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Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák], [mailto:b.kortman@nikhef.nl Bryan Kortman] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
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=== ATLAS: Approaching the Higgs from a new direction: Constraining new physics with off shell Higgs data from the LHC ===<br />
The Heisenberg uncertainly principle allows for all elementary particles---including the Higgs Boson---to momentarily disobey the fundamental energy-momentum relation, allowing the particle in question to have a significantly larger mass than usual. A description of the Higgs Boson in this state (“off shell Higgs Boson”) can provide a portal to the discovery of potential new physics, albeit very difficult to do due to its infrequent appearance. The goal of this project is to constrain or hint at new physics by estimating parameters of a generalized model which allows for new physics, Effective Field Theory (EFT), using off shell Higgs data.<br />
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Most of the underlying analysis to measure the prevalence of off shell Higgs bosons has already been set up, so the goal of this project is to do the aforementioned EFT interpretation on top of this existing analysis. From a theoretical point of view much of the groundwork has also been done on simulated data which showed the potential for this EFT interpretation to constrain new physics [1]. Being on the interface between experimental and theoretical physics this project allows the student to gain a deeper understanding of both, furthermore its successful completion could be one of the first hints towards as of yet not understood physics.<br />
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[1] Azatov, A., de Blas, J., Falkowski, A., Gritsan, A. V., Grojean, C., Kang, L., ... & Vryonidou, E. (2022). Off-shell Higgs Interpretations Task Force: Models and Effective Field Theories Subgroup Report. arXiv preprint arXiv:2203.02418.<br />
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Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák], [mailto:b.kortman@nikhef.nl Bryan Kortman] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
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=== ATLAS: A new timing detector - the HGTD ===<br />
The ATLAS is going to get a new ability: a timing detector. This allows us to reconstruct tracks not only in the 3 dimensions of space but adds the ability of measuring very precisely also the time (at picosecond level) at which the particles pass the sensitive layers of the HGTD detector. This allows to construct the trajectories of the particles created at the LHC in 4 dimensions and ultimately will lead to a better reconstruction of physics at ATLAS. The new HGTD detector is still in construction and work needs to be done on different levels such as understanding the detector response (taking measurements in the lab and performing simulations) or developing algorithms to reconstruct the particle trajectories (programming and analysis work). With this work you will be part of the Atlas group and/or the Fast Timing detector group together with the R&D department at Nikhef. <br />
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'''In this project there are two possibilities:''' <br />
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One can choose to either focus on the impact on physics performance by studying how the timing measurements can be included in the reconstruction of tracks, and what effect this has on how much better we can understand the physical processes occurring in the particles produced in the LHC collisions. <br />
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The second possibility is to focus on the working of the fast-timing detectors themselves and participate in measurements in the lab and in test-beam campaigns at CERN. <br />
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If you are interested, contact me to discuss the possibilities. <br />
Contact: ''[mailto:hella.snoek@nikhef.nl Hella Snoek]''<br />
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=== ATLAS: The next full-silicon Inner Tracker: ITk ===<br />
[[File:ITk endcap structure.jpg|210x210px|thumb|alt=]]The inner detector of the present ATLAS experiment has been designed and developed to function in the environment of the present Large Hadron Collider (LHC). At the ATLAS Phase-II Upgrade, the particle densities and radiation levels will exceed current levels by a factor of ten. The instantaneous luminosity is expected to reach unprecedented values, resulting in up to 200 proton-proton interactions in a typical bunch crossing. The new detectors must be faster and they need to be more highly segmented. The sensors used also need to be far more resistant to radiation, and they require much greater power delivery to the front-end systems. At the same time, they cannot introduce excess material which could undermine tracking performance. For those reasons, the inner tracker of the ATLAS detector (ITk) was redesigned and will be rebuilt completely.<br />
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Nikhef is one of the sites in charge of building and integrating some big parts of ITk. One of the next steps consists of testing the sensors that we will install in the structures we have built (check one of the structures in the picture of our cleanroom). This project offers the possibility of working on a full hardware project, doing something completely new, by testing the sensors of a future component of the next ATLAS detector.<br />
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''Contact'': ''[mailto:aalonso@nikhef.nl Andrea García Alonso]''<br />
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=== Cosmic Rays/Neutrinos: Seasonal muon flux variations and the pion/kaon ratio ===<br />
The KM3NeT ARCA and ORCA detectors, located kilometers deep in the Mediterranean Sea, have neutrinos as primary probes. Muons from cosmic ray interactions reach the detectors in relatively large quantities too. These muons, exploiting the capabilities and location of the detectors allow the study of cosmic rays and their interactions. In this way, questions about their origin, type, propagation can be addressed. In particular these muons are tracers of hadronic interactions at energies inaccessible at particle accelerators.<br />
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The muons reaching the depths of the detectors result from decays of mesons, mostly pions and kaons, created in interactions of high-energy cosmic rays with atoms in the upper atmosphere. Seasonal changes of the temperature – and thus density - profile of the atmosphere modulate the balance between the probability for these mesons to decay (producing muons) or to re-interact. Pions and kaons are affected differently, allowing to extract their production ratio by determining how changes in muon rate depend on changes in the effective temperature – an integral over the atmospheric temperature profile weighted by a depth dependent meson production rate.<br />
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In this project, the aim is to measure the rate of muons in the detectors and to calculate the effective temperature above the KM3NeT detectors from atmospheric data, both as function of time. The relation between these two can be used to extract the pion to kaon ratio.<br />
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''Contact: [mailto:rbruijn@nikhef.nl Ronald Bruijn]''<br />
=== Dark Matter: Building better Dark Matter Detectors - the XAMS R&D Setup===<br />
The Amsterdam Dark Matter group operates an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 0.5kg of ultra-pure liquid xenon in the central volume. We use this detector for the development of new detection techniques - such as utilizing our newly installed silicon photomultipliers - and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENONnT experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory, or for future Dark Matter experiments like DARWIN. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data themselves You will "own" this experiment. <br />
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''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
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===Dark Matter: Searching for Dark Matter Particles - XENONnT Data Analysis ===<br />
The XENON collaboration has used the XENON1T detector to achieve the world’s most sensitive direct detection dark matter results and is currently operating the XENONnT successor experiment. The detectors operate at the Gran Sasso underground laboratory and consist of so-called dual-phase xenon time-projection chambers filled with ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the new data coming from the XENONnT detector. The work will consist of understanding the detector signals and applying a deep neural network to improve the (gas-) background discrimination in our Python-based analysis tool to improve the sensitivity for low-mass dark matter particles. The work will continue a study started by a recent graduate. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy.<br />
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''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
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=== Dark Matter: Signal reconstruction and correction in XENONnT ===<br />
XENONnT is a low background experiment operating at the INFN - Gran Sasso underground laboratory with the main goal of detecting Dark Matter interactions with xenon target nuclei. The detector, consisting of a dual-phase time projection chamber, is filled with ultra-pure xenon, which acts as a target and detection medium. Understanding the detector's response to various calibration sources is a mandatory step in exploiting the scientific data acquired. This MSc thesis aims to develop new methods to improve the reconstruction and correction of scintillation/ ionization signals from calibration data. The student will work with modern analysis techniques (python-based) and will collaborate with other analysts within the international XENON Collaboration.<br />
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''Contact: [mailto:mpierre@nikhef.nl Maxime Pierre], [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
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===Dark Matter: The Ultimate Dark Matter Experiment - DARWIN Sensitivity Studies===<br />
DARWIN is the “ultimate” direct detection dark matter experiment, with the goal to reach the so-called “neutrino floor”, when neutrinos become a hard-to-reduce background. The large and exquisitely clean xenon mass will allow DARWIN to also be sensitive to other physics signals such as solar neutrinos, double-beta decay from Xe-136, axions and axion-like particles etc. While the experiment will only start in 2027, we are in the midst of optimizing the experiment, which is driven by simulations. We have an opening for a student to work on the GEANT4 Monte Carlo simulations for DARWIN. We are also working on a “fast simulation” that could be included in this framework. It is your opportunity to steer the optimization of a large and unique experiment. This project requires good programming skills (Python and C++) and data analysis/physics interpretation skills.<br />
<br />
''Contact: [mailto:t.pollmann@nikhef.nl Tina Pollmann], [mailto:decowski@nikhef.nl Patrick Decowski] or [mailto:z37@nikhef.nl Auke Colijn]''<br />
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=== Dark Matter: Exploring new background sources for DARWIN ===<br />
Experiments based on the xenon dual-phase time projection chamber detection technology have already demonstrated their leading role in the search for Dark Matter. The unprecedented low level of background reached by the current generation, such as XENONnT, allows such experiments to be sensitive to new rare-events physics searches, broadening their physics program. The next generation of experiments is already under consideration with the DARWIN observatory, which aims to surpass its predecessors in terms of background level and mass of xenon target. With the increased sensitivity to new physics channels, such as the study of neutrino properties, new sources of backgrounds may arise. This MSc thesis aims to investigate potential new sources of background for DARWIN and is a good opportunity for the student to contribute to the design of the experiment. This project will rely on Monte Carlo simulation tools such as GEANT4 and FLUKA, and good programming skills (Python and C++) are advantageous.<br />
<br />
''Contact: [mailto:mpierre@nikhef.nl Maxime Pierre], [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
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===Dark Matter: Sensitive tests of wavelength-shifting properties of materials for dark matter detectors===<br />
Rare event search experiments that look for neutrino and dark matter interactions are performed with highly sensitive detector systems, often relying on scintillators, especially liquid noble gases, to detect particle interactions. Detectors consist of structural materials that are assumed to be optically passive, and light detection systems that use reflectors, light detectors, and sometimes, wavelength-shifting materials. MSc theses are available related to measuring the efficiency of light detection systems that might be used in future detectors. Furthermore, measurements to ensure that presumably passive materials do not fluoresce, at the low level relevant to the detectors, can be done. Part of the thesis work can include Monte Carlo simulations and data analysis for current and upcoming dark matter detectors, to study the effect of different levels of desired and nuisance wavelength shifting. In this project, students will acquire skills in photon detection, wavelength shifting technologies, vacuum systems, UV and extreme-UV optics, detector design, and optionally in Python and C++ programming, data analysis, and Monte Carlo techniques.<br />
<br />
''Contact: [mailto:Tina.Pollmann@tum.de Tina Pollmann]'' <br />
<br />
=== Detector R&D: Studies of wafer-scale sensors for ALICE detector upgrade and beyond ===<br />
One of the biggest milestones of the ALICE detector upgrade (foreseen in 2026) is the implementation of wafer-scale (~ 28 cm x 18 cm) monolithic silicon active pixel sensors in the tracking detector, with the goal of having truly cylindrical barrels around the beam pipe. To demonstrate such an unprecedented technology in high energy physics detectors, few chips will be soon available in Nikhef laboratories for testing and characterization purposes.<br />
The goal of the project is to contribute to the validation of the samples against the ALICE tracking detector requirements, with a focus on timing performance in view of other applications in future high energy physics experiments beyond ALICE.<br />
We are looking for a student with a focus on lab work and interested in high precision measurements with cutting-edge instrumentation. You will be part of the Nikhef Detector R&D group and you will have, at the same time, the chance to work in an international collaboration where you will report about the performance of these novel sensors. There may even be the opportunity to join beam tests at CERN or DESY facilities. Besides interest in hardware, some proficiency in computing is required (Python or C++/ROOT).<br />
<br />
''Contact: [mailto:(jory.sonneveld@nikhef.nl Jory Sonneveld ], [mailto:rrusso@nikhef.nl Roberto Russo]''<br />
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=== Detector R&D: Time resolution of monolithic silicon detectors ===<br />
Monolithic silicon detectors based on industrial Complementary Metal Oxide Semiconductor (CMOS) processes offer a promising approach for large scale detectors due to their ease of production and low material budget. Until recently, their low radiation tolerance has hindered their applicability in high energy particle physics experiments. However, new prototypes ~~such as the one in this project~~ have overcome these hurdles, making them feasible candidates for future experiments in high energy particle physics. Achieving the required radiation tolerance has brought the spatial and temporal resolution of these detectors to the forefront. In this project, you will investigate the temporal performance of a radiation hard monolithic detector prototype, using laser setups in the laboratory. You will also participate in meetings with the international collaboration working on this detector, where you will report on the prototype's performance. Depending on the progress of the work, there may be a chance to participate in test beams performed at the CERN accelerator complex and a first full three dimensional characterization of the prototypes performance using a state-of-the-art two-photon absorption laser setup at Nikhef. This project is looking for someone interested in working hands on with cutting edge detector and laser systems at the Nikhef laboratory. Python programming skills and linux experience are an advantage.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld], [mailto:uwe.kraemer@nikhef.nl Uwe Kraemer]''<br />
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=== Detector R&D: Improving a Laser Setup for Testing Fast Silicon Pixel Detectors ===<br />
For the upgrades of the innermost detectors of experiments at the Large Hadron Collider in Geneva, in particular to cope with the large number of collisions per second from 2027, the Detector R&D group at Nikhef tests new pixel detector prototypes with a variety of laser equipment with several wavelengths. The lasers can be focused down to a small spot to scan over the pixels on a pixel chip. Since the laser penetrates the silicon, the pixels will not be illuminated by just the focal spot, but by the entire three dimensional hourglass or double cone like light intensity distribution. So, how well defined is the volume in which charge is released? And can that be made much smaller than a pixel? And, if so, what would the optimum focus be? For this project the student will first estimate the intensity distribution inside a sensor that can be expected. This will correspond to the density of released charge within the silicon. To verify predictions, you will measure real pixel sensors for the LHC experiments.<br />
This project will involve a lot of 'hands on work' in the lab and involve programming and work on unix machines.<br />
<br />
''Contact: [mailto:martinfr@nikhef.nl Martin Fransen]''<br />
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=== Detector R&D: Time resolution of hybrid pixel detectors with the Timepix4 chip ===<br />
Precise time measurements with silicon pixel detectors are very important for experiments at the High-Luminosity LHC and the future circular collider. The spatial resolution of current silicon trackers will not be sufficient to distinguish the large number of collisions that will occur within individual bunch crossings. In a new method, typically referred to as 4D tracking, spatial measurements of pixel detectors will be combined with time measurements to better distinguish collision vertices that occur close together.<br />
New sensor technologies are being explored to reach the required time measurement resolution of tens of picoseconds, and the results are promising. However, the signals that these pixelated sensors produce have to be processed by front-end electronics, which hence also play a role in the total time resolution of the detector. An important contribution comes from the systematic differences between the front-end electronics of different pixels. Many of these systematic effects can be corrected by performing detailed calibrations of the readout electronics. To achieve the required time resolution at future experiments, it is vital that these effects are understood and corrected.<br />
In this project you will be working with the Timepix4 chip. This is a so-called application specific integrated circuit (ASIC) that is designed to read out pixelated sensors. This ASIC will be used extensively in detector R&D for the characterisation of new sensor technologies requiring precise timing (< 50 ps). In order to do so, it is necessary to first study the systematic differences between the pixels, which you will do using a laser setup in our lab. This will be combined with data analysis of proton beam measurements, or with measurements performed using the built-in test-pulse mechanism of the Timepix4 ASIC. Your work will enable further research performed with this ASIC, <br />
and serve as input to the design and operation of future ASICs for experiments at the High-Luminosity LHC.<br />
<br />
''Contact: [mailto:k.heijhoff@nikhef.nl Kevin Heijhoff] and [mailto:martinb@nikhef.nl Martin van Beuzekom]''<br />
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===Detector R&D: Performance studies of Trench Isolated Low Gain Avalanche Detectors (TI-LGAD) ===<br />
The future vertex detector of the LHCb Experiment needs to measure the spatial coordinates and time of the particles originating in the LHC proton-proton collisions with resolutions better than 10 um and 50 ps, respectively. Several technologies are being considered to achieve these resolutions. Among those is a novel sensor technology called Trench Isolated Low Gain Avalanche Detector. <br />
Prototype pixelated sensors have been manufactured recently and have to be characterised. Therefore these new sensors will be bump bonded to a Timepix4 ASIC which provides charge and time measurements in each of 230 thousand pixels. Characterisation will be done using a lab setup at Nikhef, and includes tests with a micro-focused laser beam, radioactive sources, and possibly with particle tracks obtained in a test-beam. This project involves data taking with these new devices and analysing the data to determine the performance parameters such as the spatial and temporal resolution. as function of temperature and other operational conditions. <br />
<br />
''Contacts: [mailto:kazu.akiba@nikhef.nl Kazu Akiba] and [mailto:martinb@nikhef.nl Martin van Beuzekom]''<br />
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===Detector R&D: A Telescope with Ultrathin Sensors for Beam Tests ===<br />
To measure the performance of new prototypes for upgrades of the LHC experiments and beyond, typically a telescope is used in a beam line of charged particles that can be used to compare the results in the prototype to particle tracks measured with this telescope. In this project, you will continue work on a very lightweight, compact telescope using ALICE PIxel DEtectors (ALPIDEs). This includes work on the mechanics, data acquisition software, and a moveable stage. You will foreseeably test this telescope in the Delft Proton Therapy Center. If time allows, you will add a timing plane and perform a measurement with one of our prototypes. Apart from travel to Delft, there is a possiblity to travel to other beam line facilities.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
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===Detector R&D: Other projects ===<br />
Are you looking for a slightly different project? Are the above projects already taken? Are you coming in at an unusual time of the year? Do not hesitate to contact us! We always have new projects coming up at different times in the year and we are open to your ideas.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
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===FCC: The Next Collider===<br />
<br />
After the LHC, the next planned large collider at CERN is the proposed 100 kilometer circular collider "FCC". In the first stage of the project, as a high-luminosity electron-positron collider, precision measurements of the Higgs boson are the main goal. One of the channels that will improve by orders of magnitude at this new accelerator is the decay of the Higgs boson to a pair of charm quarks. This project will estimate a projected sensitivity for the coupling of the Higgs boson to second generation quarks, and in particular target the improved reconstruction of the topology of long-lived mesons in the clean environment of a precision e+e- machine.<br />
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''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
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===Gravitational Waves: Computer modelling to design the laser interferometers for the Einstein telescope===<br />
<br />
A new field of instrument science led to the successful detection of gravitational waves by the LIGO detectors in 2015. We are now preparing the next generation of gravitational wave observatories, such as the Einstein Telescope, with the aim to increase the detector sensitivity by a factor of ten, which would allow, for example, to detect stellar-mass black holes from early in the universe when the first stars began to form. This ambitious goal requires us to find ways to significantly improve the best laser interferometers in the world.<br />
<br />
Gravitational wave detectors, such as LIGO and VIRGO, are complex Michelson-type interferometers enhanced with optical cavities. We develop and use numerical models to study these laser interferometers, to invent new optical techniques and to quantify their performance. For example, we synthesize virtual mirror surfaces to study the effects of higher-order optical modes in the interferometers, and we use opto-mechanical models to test schemes for suppressing quantum fluctuations of the light field. We can offer several projects based on numerical modelling of laser interferometers. All projects will be directly linked to the ongoing design of the Einstein Telescope.<br />
<br />
''Contact: [mailto:a.freise@nikhef.nl Andreas Freise]''<br />
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===LHCb: Search for light dark particles===<br />
The Standard Model of elementary particles does not contain a proper Dark Matter candidate. One of the most tantalizing theoretical developments is the so-called ''Hidden Valley models'': a mirror-like copy of the ''Standard Model'', with dark particles that communicate with standard ones via a very feeble interaction. These models predict the existence of ''dark hadrons'' – composite particles that are bound similarly to ordinary hadrons in the ''Standard Model''. Such ''dark hadrons'' can be abundantly produced in high-energy proton-proton collisions, making the LHC a unique place to search for them. Some ''dark hadrons'' are stable like a proton, which makes them excellent ''Dark Matter'' candidates, while others decay to ordinary particles after flying a certain distance in the collider experiment. The LHCb detector has a unique capability to identify such decays, particularly if the new particles have a mass below ten times the proton mass. <br />
<br />
This project assumes a unique search for light ''dark hadrons'' that covers a mass range not accessible to other experiments. It assumes an interesting program on data analysis (python-based) with non-trivial machine learning solutions and phenomenology research using fast simulation framework. Depending on the interest, there is quite a bit of flexibility in the precise focus of the project.<br />
<br />
''Contact: [mailto:andrii.usachov@nikhef.nl Andrii Usachov]''<br />
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===LHCb: Searching for dark matter in exotic six-quark particles===<br />
<br />
Three quarters of the mass in the Universe is of unknown type. Many hypotheses about this dark matter have been proposed, but none confirmed. Recently it has been proposed that it could be made of particles made of the six quarks uuddss, which would be a Standard-Model solution to the dark matter problem. This idea has recently gained credibility as many similar multi-quarks states are being discovered by the LHCb experiment. Such a particle could be produced in decays of heavy baryons, or directly in proton-proton collisions. The anti-particle, made of six antiquarks, could be seen when annihilating with detector material. It is also proposed to use Xi_b baryons produced at LHCb to search for such a state where the state would appear as missing 4-momentum in a kinematically constrained decay. The project consists in defining a selection and applying it to LHCb data. See [https://arxiv.org/abs/2007.10378 arXiv:2007.10378].<br />
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Contact: ''[mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
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===LHCb: Measuring lepton flavour universality with excited Ds states in semileptonic Bs decays===<br />
One of the most striking discrepancies between the Standard Model and measurements are the lepton flavour universality (LFU) measurements with tau decays. At the moment, we have observed an excess of 3-4 sigma in ''B → Dτν'' decays. This could point even to a new force of nature! To understand this discrepancy, we need to make further measurements. <br />
<br />
One very exciting (pun intended) projects to verify these discrepancies involves measuring the ''B<sub>s</sub> → D<sub>s2</sub><sup>*</sup>τν'' and/or ''B<sub>s</sub> → D<sub>s1</sub><sup>*</sup>τν'' decays. These decays with excited states of the ''D<sub>s</sub>'' meson have not been observed before in the tau decay mode, and have a unique way of coupling to potential new physics candidates that can only be measured in ''B<sub>s</sub>'' decays [1]. See slides for more detail: [[File:LHCbLFUwithExcitedDs.pdf|thumb]]<br />
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[1] https://arxiv.org/abs/1606.09300<br />
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''Contact: [mailto:suzannek@nikhef.nl Suzanne Klaver]''<br />
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===LHCb: New physics in the angular distributions of B decays to K*ee===<br />
<br />
Lepton flavour violation in B decays can be explained by a variety of non-standard model interactions. Angular distributions in decays of a B meson to a hadron and two leptons are an important source of information to understand which model is correct. Previous analyses at the LHCb experiment have considered final states with a pair of muons. Our LHCb group at Nikhef concentrates on a new measurement of angular distributions in decays with two electrons. The main challenge in this measurement is the calibration of the detection efficiency. In this project you will confront estimates of the detection efficiency derived from simulation with decay distributions in a well known B decay. Once the calibration is understood, the very first analysis of the angular distributions in the electron final state can be performed. <br />
<br />
Contact: [mailto:m.senghi.soares@nikhef.nl Mara Soares] and [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
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===LHCb: Discovering heavy neutrinos in B decays===<br />
<br />
Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, much heavier, neutral leptons. If the mass of these new neutrinos is below the b-quark mass, they can be observed in B hadron decays.<br />
<br />
In this project we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undiscovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The analysis will be performed within the LHCb group at Nikhef using LHCb run-2 data.<br />
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===LHCb: Scintillating Fibre tracker software===<br />
The installation of the scintillating-fibre tracker in LHCb’s underground cavern was recently completed. This detector uses 10000 km of fibres to track particle trajectories in the LHCb detector when the LHC starts up again later this year. The light emitted by the scintillating fibres when a particle interacts with them is measured using photon multiplier tubes. The studies proposed for this project will focus on software, and could include writing a framework to monitor the detector output, improving the detector simulation or working on the data processing.<br />
<br />
''Contact: [mailto:e.gabriel@nikhef.nl Emmy Gabriel]''<br />
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===LHCb: Vertex detector calibration===<br />
In summer 2022 LHCb has started data taking will an almost entirely new detector. At the point closest to the interaction point, the trajectories of charge particles are reconstructed with a so-called silicon pixel detector. The design hit resolution of this detector is about 15 micron. However, to actually reach this resolution a precise calibration of the spatial positions of the silicon sensors needs to be performed. In this project, you will use the first data of the new LHCb detector to perform this calibration and measure the detector performance.<br />
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''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen]''<br />
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===Neutrinos: Neutrino scattering: the ultimate resolution===<br />
<br />
Neutrino telescopes like IceCube and KM3NeT aim at detecting neutrinos from cosmic sources. The neutrinos are detected with the best resolution when charged current interactions with nucleons produce a muon, which can be detected with high accuracy (depending on the detector). A crucial ingredient in the ultimate achievable pointing accuracy of neutrino telescopes is the scattering angle between the neutrino and the muon. While published computations have investigated the cross-section of the process in great detail, this important scattering angle has not received much attention. The aim of the project is to compute and characterize the distribution of this angle, and that the ultimate resolution of a neutrino telescope. If successful, the results of this project can lead to publication of interest to the neutrino telescope community.<br />
<br />
Depending on your interests, the study could be based on a first-principles calculation (using the deep-inelastic scattering formalism), include state-of-the-art parton distribution functions, and/or exploit existing event-generation software for a more experimental approach. <br />
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''Contacts: [mailto:aart.heijboer@nikhef.nl Aart Heijboer]''<br />
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===Neutrinos: acoustic detection of ultra-high energy neutrinos===<br />
<br />
The study of the cosmic neutrinos of energies above 1017 eV, the so-called ultra-high energy neutrinos, provides a unique view on the universe and may provide insight in the origin of the most violent astrophysical sources, such as gamma ray bursts, supernovae or even dark matter. In addition, the observation of high energy neutrinos may provide a unique tool to study interactions at high energies. The energy deposition of these extreme neutrinos in water induce a thermo-acoustic signal, which can be detected using sensitive hydrophones. The expected neutrino flux is however extremely low and the signal that neutrinos induce is small. TNO is presently developing sensitive hydrophone technology based on fiber optics. Optical fibers form a natural way to create a distributed sensing system. Using this technology a large scale neutrino telescope can be built in the deep sea. TNO is aiming for a prototype hydrophone which will form the building block of a future telescope.<br />
<br />
The work will be executed at the Nikhef institute and/or the TNO laboratories in Delft. In this project master students have the opportunity to contribute in the following ways:<br />
<br />
'''Project 1:''' Hardware development on fiber optics hydrophones technology Goal: characterize existing prototype optical fibre hydrophones in an anechoic basin at TNO laboratory. Data collection, calibration, characterization, analysis of consequences for design future acoustic hydrophone neutrino telescopes;<br />
Keywords: Optical fiber technology, signal processing, electronics, lab.<br />
<br />
'''Project 2:''' Investigation of ultra-high energy neutrinos and their interactions with matter. Goal: Discriminate the neutrino signals from the background noises, in particular clicks from whales and dolphins in the deep sea. Study impact on physics reach for future acoustic hydrophone neutrino telescopes;<br />
Keywords: Monte Carlo simulations, particle physics, neutrino physics, data analysis algorithms.<br />
<br />
Further information: Info on ultra-high energy neutrinos can be found at: http://arxiv.org/abs/1102.3591; Info on acoustic detection of neutrinos can be found at: http://arxiv.org/abs/1311.7588<br />
<br />
''Contact: [mailto:ernst-jan.buis@tno.nl Ernst Jan Buis]'' or ''[mailto:ivo.van.vulpen@nikhef.nl Ivo van Vulpen]''<br />
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===Neutrinos: Oscillation analysis with the first data of KM3NeT===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first few strings with sensitive photodetectors have been deployed at both the Italian and the French detector sites. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In this project the available data will be used together with simulations to best reconstruct the event topologies and optimally identify and reconstruct the first neutrino interactions in the KM3NeT detector. The data will then be used to measure neutrino oscillation parameters, and prepare for a future neutrino mass ordering determination.<br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
''Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn] [mailto:h26@nikhef.nl Paul de Jong]''<br />
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===Neutrinos: the Deep Underground Neutrino Experiment (DUNE)===<br />
<br />
The Deep Underground Neutrino Experiment (DUNE) is under construction in the USA, and will consist of a powerful neutrino beam originating at Fermilab, a near detector at Fermilab, and a far detector in the SURF facility in Lead, South Dakota, 1300 km away. During travelling, neutrinos oscillate and a fraction of the neutrino beam changes flavour; DUNE will determine the neutrino oscillation parameters to unrivaled precision, and try and make a first detection of CP-violation in neutrinos. In this project, various elements of DUNE can be studied, including the neutrino oscillation fit, neutrino physics with the near detector, event reconstruction and classification (including machine learning), or elements of data selection and triggering.<br />
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''Contact: [mailto:h26@nikhef.nl Paul de Jong]''<br />
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===Neutrinos: Searching for Majorana Neutrinos with KamLAND-Zen===<br />
The KamLAND-Zen experiment, located in the Kamioka mine in Japan, is a large liquid scintillator experiment with 750kg of ultra-pure Xe-136 to search for neutrinoless double-beta decay (0n2b). The observation of the 0n2b process would be evidence for lepton number violation and the Majorana nature of neutrinos, i.e. that neutrinos are their own anti-particles. Current limits on this extraordinary rare hypothetical decay process are presented as a half-life, with a lower limit of 10^26 years. KamLAND-Zen, the world’s most sensitive 0n2b experiment, is currently taking data and there is an opportunity to work on the data analysis, analyzing data with the possibility of taking part in a ground-breaking discovery. The main focus will be on developing new techniques to filter the spallation backgrounds, i.e. the production of radioactive isotopes by passing muons. There will be close collaboration with groups in the US (MIT, Berkeley, UW) and Japan (Tohoku Univ). <br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
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===Neutrinos: relic neutrino detection with PTOLEMY ===<br />
PTOLEMY aims to make the first direct observation of the Big Bang relic neutrinos (the cosmic neutrino background, CνB) by resolving the β-decay endpoint of atomic tritium (neutrino capture target) to O(meV) precision. This remains an outstanding test of the Standard Model in an expanding universe. Not only does the CνB carry with it a signal from the hot dense universe only one second after the Big Bang but helps to constrain the balance of hot versus cold dark matter responsible for its evolution. In doing so, the PTOLEMY experiment would also measure the lowest neutrino mass, an as-of-yet unknown fundamental constant. The experiment is currently in the prototyping phase and the group at Nikhef is responsible for developing the radio-frequency (RF) system used for cyclotron radiation (CR) based trigger and tracking. This component will provide the trajectory of electrons entering the novel transverse drift filter, constraining the electrons' energy losses before they reach the cryogenic calorimeter which in turn records their final energy. The focus of this project will be modelling CR and its detection for the purposes of single electron spectroscopy and optimised trajectory reconstruction. There is also the opportunity to test hardware and readout electronics for the prototype RF-system. <br />
''Contact: [mailto:jmead@nikhef.nl James Vincent Mead]''<br />
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=== Theoretical Particle Physics: Effective Field Theories of Particle Physics from low- to high-energies===<br />
Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations” seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature. The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Standard Model Effective Field Theory (SMEFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes with minimal assumptions on the nature of an eventual UV-complete theory that replaces the Standard Model. Specifically, the goal is to connect measurements from ATLAS, CMS, and LHCb experiments at the CERN's LHC among them and to jointly interpret this information with that provided by other experiments including very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
<br />
This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories. Depending on the student profile, sub-projects with a strong computational and/or machine learning component are also possible, for instance to construct new operators with optimal sensitivity to New Physics effects as encoded by the SMEFT higher-dimensional operators. Topics that can be considered in this project include the interpretation of novel physical observables at the LHC and their integration into the global SMEFiT analysis, matching of EFTs to UV-complete theories and their phenomenological analyses, projections for the impact in the SMEFT parameter space of data for future colliders, the synergies between EFT studies and proton structure fits, and the matching to the Weak Effective Field Theory to include data on flavour observables such as B-meson decays.<br />
<br />
References: https://arxiv.org/abs/2105.00006 , https://arxiv.org/abs/2302.06660, https://arxiv.org/abs/2211.02058 , https://arxiv.org/abs/1901.05965 , https://arxiv.org/abs/1906.05296 , https://arxiv.org/abs/1908.05588, https://arxiv.org/abs/1905.05215. see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description].<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
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===Theoretical Particle Physics: High-energy neutrino-nucleon interactions at the Forward Physics Facility ===<br />
High-energy collisions at the High-Luminosity Large Hadron Collider (HL-LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing experiments. The proposed Forward Physics Facility (FPF) to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe Standard Model (SM) processes and search for physics beyond the Standard Model (BSM). High statistics neutrino detection will provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. The FPF has the promising potential to probe our understanding of the strong interactions as well as of proton and nuclear structure, providing access to both the very low-x and the very high-x regions of the colliding protons. The former regime is sensitive to novel QCD production mechanisms, such as BFKL effects and non-linear dynamics, as well as the gluon parton distribution function (PDF) down to x=1e-7, well beyond the coverage of other experiments and providing key inputs for astroparticle physics. In addition, the FPF acts as a neutrino-induced deep-inelastic scattering (DIS) experiment with TeV-scale neutrino beams. The resulting measurements of neutrino DIS structure functions represent a valuable handle on the partonic structure of nucleons and nuclei, particularly their quark flavour separation, that is fully complementary to the charged-lepton DIS measurements expected at the upcoming Electron-Ion Collider (EIC).<br />
<br />
In this project, the student will carry out updated predictions for the neutrino fluxes expected at the FPF, assess the precision with which neutrino cross-sections will be measured, and quantify their impact on proton and nuclear structure by means of machine learning tools within the NNPDF framework and state-of-the-art calculations in perturbative Quantum Chromodynamics. This project contributes to ongoing work within the FPF Initiative towards a Conceptual Design Report (CDR) to be presented within two years. Topics that can be considered as part of this project include the assessment of to which extent nuclear modifications of the free-proton PDFs can be constrained by FPF measurements, the determination of the small-x gluon PDF from suitably defined observables at the FPF and the implications for ultra-high-energy particle astrophysics, the study of the intrinsic charm content in the proton and its consequences for the FPF physics program, and the validation of models for neutrino-nucleon cross-sections in the region beyond the validity of perturbative QCD.<br />
<br />
References: https://arxiv.org/abs/2203.05090, https://arxiv.org/abs/2109.10905 ,https://arxiv.org/abs/2208.08372 , https://arxiv.org/abs/2201.12363 , https://arxiv.org/abs/2109.02653, https://github.com/NNPDF/ see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description]. <br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theoretical Particle Physics: Probing the origin of the proton spin with machine learning===<br />
At energy-frontier facilities such as the Large Hadron Collider (LHC), scientists study the laws of nature in their quest for novel phenomena both within and beyond the Standard Model of particle physics. An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions from the nature of the Higgs boson to the origin of cosmic neutrinos. The key to address some of these questions is by carrying out an universal analysis of nucleon structure from the simultaneous determination of the momentum and spin distributions of quarks and gluons and their fragmentation into hadrons. This effort requires combining an extensive experimental dataset and cutting-edge theory calculations within a machine learning framework where neural networks parametrise the underlying physical laws while minimising ad-hoc model assumptions. The upcoming Electron Ion Collider (EIC), to start taking data in 2029, will be the world's first ever polarised lepton-hadron collider and will offer a plethora of opportunities to address key open questions in our understanding of the strong nuclear force, such as the origin of the mass and the intrinsic angular momentum (spin) of hadrons and whether there exists a state of matter which is entirely dominated by gluons. To fully exploit this scientific potential, novel analysis methodologies need to be develop that make it possible to carry out large-scale, coherent interpretations of measurements from the EIC and other high-energy colliders.<br />
<br />
In this project, the student will carry out a new global analysis of the spin structure of the proton by means of the machine learning tools provided by the NNPDF open-source fitting framework and state-of-the-art calculations in perturbative Quantum Chromodynamics, and integrate it within the corresponding global NNPDF analyses of unpolarised proton and nuclear structure in the framework of a combined integrated global analysis of non-perturbative QCD. Specifically, the project aims to realise a NNLO global fit of polarised quark and gluon PDFs that combines all available data and state-of-the-art perturbative QCD calculations, and study the phenomenological implications for other experiments, including the EIC, for the spin content of the proton, for comparisons with lattice QCD calculations, and for nonpperturbative models of hadron structure.<br />
<br />
References: https://arxiv.org/abs/2201.12363, https://arxiv.org/abs/2109.02653 , https://arxiv.org/abs/2103.05419, https://arxiv.org/abs/1404.4293 , https://inspirehep.net/literature/1302398, https://github.com/NNPDF/ see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description].<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
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== Finished master projects ==<br />
<br />
See: <br />
* https://wiki.nikhef.nl/education/Master_Theses<br />
* https://www.nikhef.nl/master-theses-2021/<br />
* https://www.nikhef.nl/facts-figures-2020/master-theses-2020/<br />
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<br />
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----<br />
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<br />
<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=917Master Projects2023-03-29T06:54:09Z<p>Rojo@nikhef.nl: /* Theoretical Particle Physics: High-energy neutrino-nucleon interactions at the Forward Physics Facility */</p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
== Projects with a 2023 start ==<br />
<br />
=== ALICE: The next-generation multi-purpose detector at the LHC ===<br />
This main goal of this project is to focus on the next-generation multi-purpose detector planned to be built at the LHC. Its core will be a nearly massless barrel detector consisting of truly cylindrical layers based on curved wafer-scale ultra-thin silicon sensors with MAPS technology, featuring an unprecedented low material budget of 0.05% X0 per layer, with the innermost layers possibly positioned inside the beam pipe. The proposed detector is conceived for studies of pp, pA and AA collisions at luminosities a factor of 20 to 50 times higher than possible with the upgraded ALICE detector, enabling a rich physics program ranging from measurements with electromagnetic probes at ultra-low transverse momenta to precision physics in the charm and beauty sector. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli] and [mailto:marco.van.leeuwen@cern.ch Marco van Leeuwen]''<br />
<br />
=== ALICE: Searching for the strongest magnetic field in nature ===<br />
In a non-central collision between two Pb ions, with a large value of impact parameter, the charged nucleons that do not participate in the interaction (called spectators) create strong magnetic fields. A back of the envelope calculation using the Biot-Savart law brings the magnitude of this filed close to 10^19Gauss in agreement with state of the art theoretical calculation, making it the strongest magnetic field in nature. The presence of this field could have direct implications in the motion of final state particles. The magnetic field, however, decays rapidly. The decay rate depends on the electric conductivity of the medium which is experimentally poorly constrained. Overall, the presence of the magnetic field, the main goal of this project, is so far not confirmed experimentally.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Looking for parity violating effects in strong interactions ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions, in the presence of a deconfined state, gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, what is called the Chiral Magnetic Effect (CME).<br />
The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, however further studies are needed to constrain background effects. These highly anticipated results have the potential to reveal exiting, new physics.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Machine learning techniques as a tool to study the production of heavy flavour particles ===<br />
There was recently a shift in the field of heavy-ion physics triggered by experimental results obtained in collisions between small systems (e.g. protons on protons). These results resemble the ones obtained in collisions between heavy ions. This consequently raises the question of whether we create the smallest QGP droplet in collisions between small systems. The main objective of this project will be to study the production of charm particles such as D-mesons and Λc-baryons in pp collisions at the LHC. This will be done with the help of a new and innovative technique which is based on machine learning (ML). The student will also extend the studies to investigate how this production rate depends on the event activity e.g. on how many particles are created after every collision.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli]''<br />
<br />
=== ALICE: Search for new physics with 4D tracking at the most sensitive vertex detector at the LHC ===<br />
<br />
With the newly installed Inner Tracking System consisting fully of monolithic detectors, ALICE is very sensitive to particles with low transverse momenta, more so than ATLAS and CMS. This will be even more so for the ALICE upgrade detector in 2033. This detector could potentially be even more sensitive to longlived particles that leave peculiar tracks such as disappearing or kinked tracks in the tracker by using timing information along a track. In this project you will investigate how timing information in the different tracking layers can improve or even enable a search for new physics beyond the Standard Model in ALICE. If you show a possibility for major improvements, this can have real consequences for the choice of sensors for this ALICE inner tracker upgrade.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld] and [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ATLAS: The Higgs boson's self-coupling ===<br />
<br />
The coupling of the Higgs boson to itself is one of the main unobserved interactions of the Standard Model and its observation is crucial to understand the shape of the Higgs potential. Here we propose to study the 'ttHH' final state: two top quarks and two Higgs bosons produced in a single collision. This topology is yet unexplored at the ATLAS experiment and the project consists of setting up the new analysis (including multivariate analysis techniques to recognise the complicated final state), optimising the sensitivity and including the result in the full ATLAS study of the Higgs boson's coupling to itself. With the LHC data from the upcoming Run-3, we might be able to see its first glimpses! <br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree] and [mailto:cpandini@nikhef.nl Carlo Pandini]'' <br />
<br />
=== ATLAS: Triple-Higgs production as a probe of the Higgs potential ===<br />
So far, the investigation of Higgs self-couplings (the coupling of the Higgs boson to itself) at the LHC has focused on the measurement of the Higgs tri-linear coupling λ3 mainly through direct double-Higgs production searches. In this research project we propose the investigation of Higgs tri-linear and quartic coupling parameters λ3 and λ4, via a novel measurement of triple-Higgs production at the LHC (HHH) with the ATLAS experiment. While in the SM these parameters are expected to be identical, only a combined measurement can provide an answer regarding how the Higgs potential is realised in Nature. Processes in which three Higgs bosons are produced simultaneously are extremely rare, and very difficult to measure and disentangle from background. In this project we plan to investigate different decay channels (to bottom quarks and tau leptons), and to study advanced machine learning techniques to reconstruct such a complex hadronic final state. This kind of processes is still quite unexplored in ATLAS, and the goal of this project is to put the basis for the first measurement of HHH production at the LHC.<br />
<br />
Furthermore, we'd like to study the possible implication of a precise measurement of the self-coupling parameters from HHH production from a phenomenological point of view: what could be the impact of a deviation in the HHH measurements on the big open questions in physics (for instance, the mechanisms at the root of baryogenesis)?<br />
<br />
Contact: ''[mailto:tdupree@nikhef.nl Tristan du Pree] and [mailto:cpandini@nikhef.nl Carlo Pandini]''<br />
<br />
=== ATLAS: The Next Generation ===<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks is very new [1] and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays) and advanced analysis techiques (using deep learning methods).<br />
<br />
[https://atlas.cern/updates/briefing/charming-Higgs-decay][https://arxiv.org/abs/1802.04329 https://atlas.cern/updates/briefing/charming-Higgs-decay]<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
=== ATLAS: Searching for new particles in very energetic diboson production ===<br />
<br />
The discovery of new phenomena in high-energy proton–proton collisions is one of the main goals of the Large Hadron Collider (LHC). New heavy particles decaying into a pair of vector bosons (WW, WZ, ZZ) are predicted in several extensions to the Standard Model (e.g. extended gauge-symmetry models, Grand Unified theories, theories with warped extra dimensions, etc). In this project we will investigate new ideas to look for these resonances in promising regions. We will focus on final states where both vector bosons decay into quarks, or where one decays into quarks and one into leptons. These have the potential to bring the highest sensitivity to the search for Beyond the Standard Model physics [1, 2]. We will try to reconstruct and exploit new ways to identify vector bosons (using machine learning methods) and then tackle the problem of estimating contributions from beyond the Standard Model processes in the tails of the mass distribution.<br />
<br />
[1] https://arxiv.org/abs/1906.08589<br />
<br />
[2] https://arxiv.org/abs/2004.14636<br />
<br />
''Contact: [mailto:f.dias@nikhef.nl Flavia de Almeida Dias], [mailto:rhayes@nikhef.nl Robin Hayes], Elizaveta Cherepanova and Dylan van Arneman''<br />
<br />
=== ATLAS: Top-quark and Higgs-boson analysis combination, and Effective Field Theory interpretation [not available in 2023] ===<br />
<br />
We are looking for a master student with interest in theory and data-analysis in the search for physics beyond the Standard Model in the top-quark and Higgs-boson sectors.<br />
<br />
Your master-project starts just at the right time for preparing the Run-3 analysis of the ATLAS experiment at the LHC. In Run-3 (2022-2026), three times more data becomes available, enabling analysis of rare processes with innovative software tools and techniques.<br />
<br />
This project aims to explore the newest strategy to combine the top-quark and Higgs-boson measurements in the perspective of constraining the existence of new physics beyond the Standard Model (SM) of Particle Physics. We selected the pp->tZq and gg->HZ processes as promising candidates for a combination to constrain new physics in the context of Standard Model Effective Field Theory (SMEFT). SMEFT is the state-of-the-art framework for theoretical interpretation of LHC data. In particular, you will study the SMEFT OtZ and Ophit operators, which are not well constrained by current measurements.<br />
<br />
Besides affinity with particle physics theory, the ideal candidate for this project has developed python/C++ skills and is eager to learn advanced techniques. You start with a simulation of the signal and background samples using existing software tools. Then, an event selection study is required using Machine Learning techniques. To evaluate the SMEFT effects, a fitting procedure based on the innovative Morphing technique is foreseen, for which the basic tools in the ROOT and RooFit framework are available. The work is carried out in the ATLAS group at Nikhef and may lead to an ATLAS note.<br />
<br />
''Contact: [mailto:geoffrey.gilles@cern.ch Geoffrey Gilles] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:h73@nikhef.nl Marcel Vreeswijk]''<br />
<br />
=== ATLAS: Machine learning to search for very rare Higgs decays ===<br />
<br />
Since the Higgs boson discovery in 2012 at the ATLAS experiment, the investigation of the properties of the Higgs boson has been a priority for research at the Large Hadron Collider (LHC). However, there are still a many open questions: Is the Higgs boson the only origin of Electroweak Symmetry Breaking? Is there a mechanism which can explain the observed mass pattern of SM particles? Many of these questions are linked to the Higgs boson coupling structure. <br />
<br />
While the Higgs boson coupling to fermions of the third generation has been established experimentally, the investigation of the Higgs boson coupling to the light fermions of the second generation will be a major project for the upcoming data-taking period (2022-2025). The Higgs boson decay to muons is the most sensitive channel for probing this coupling. In this project, you will optimize the event selection for Higgs boson decays to muons in the Vector Boson Fusion (VBF) production channel with a focus on distinguishing signal events from background processes like Drell-Yan and electroweak Z boson production. For this purpose, you will develop, implement and validate advanced machine learning and deep learning algorithms. <br />
<br />
''Contact: [mailto:oliver.rieger@nikhef.nl Oliver Rieger] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:s01@nikhef.nl Peter Kluit]''<br />
<br />
=== ATLAS: Interpretation of experimental data using SMEFT ===<br />
<br />
The Standard Model Effective Field Theory (SMEFT) provides a systematic approach to test the impact of new physics at the energy scale of the LHC through higher-dimensional operators. The interpretation of experimental data using SMEFT requires a particular interest in solving complex technical challenges, advanced statistical techniques, and a deep understanding of particle physics. We would be happy to discuss different project opportunities based on your interests with you.<br />
<br />
''Contact: [mailto:oliver.rieger@nikhef.nl Oliver Rieger] and [mailto:verkerke@nikhef.nl Wouter Verkerke]''<br />
<br />
=== ATLAS: Reconstructing tracks from particle physics detector hits with state-of-the-art machine learning techniques ===<br />
This project concerns the application of new machine learning techniques to tackle the problem of track reconstruction at the ATLAS detector in CERN. While algorithms to construct particle tracks from low-level detector information such as particle hits and timestamps have been around for decades, recent developments in the field of machine learning open up new opportunities to improve these algorithms significantly. Some recent developments that could help in this context include graph-based neural networks, which embed the input data in the format of a graph and as such have the capability to enhance underlying correlations within events. Transformer neural networks are a particular extension of graph-based neural networks proposed only in 2017 which could also provide helpful in this case. Another option would be to build upon some of the work done within the field of computer vision and see if image segmentation networks can help solve this problem. There are a range of available options and this project includes the freedom for the student to choose particular types of networks, but more explicit guidance could be provided in case it is desired.<br />
<br />
In this project the student will develop and compare the performance of various machine learning models to initially reconstruct tracks from simplified test data. Upon successful completion of this, simulated data from the actual ATLAS detector can be analysed as well in the scope of this project. The student will need some familiarity with programming in python and an interest in machine learning, but a physics background is not required. In this project the student will be able to contribute to fundamental physics research and will familiarize themselves with state-of-the-art machine learning models.<br />
<br />
Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
=== ATLAS: New machine learning approaches to target Higgs interference signatures in LHC data ===<br />
In this project we aim to improve an ongoing analysis to determine the lifetime of the Higgs Boson through state-of-the-art machine learning techniques, in particular by addressing a ''novel solution to an as of yet unsolved fundamental problem in modeling quantum interference''. While the Higgs is an elusive particle that generally only appears in physics processes with small cross sections, its signature can be amplified in the Large Hadron Collider (LHC) through quantum interference with larger background (non-Higgs) processes. This is the effect that the Higgs’ lifetime analysis relies on to be able to measure the relevant Higgs signature. A fundamental physics modelling problem arises though in the simulation of individual events for this interference due to the fact that these events are in reality described by a superposition of underlying Higgs and non-Higgs processes.<br />
<br />
Since machine learning models in particle physics are typically trained to characterise individual physics events, the fact that interference events cannot currently be generated is a significant problem when interference is the target. In the currently existing Higgs lifetime analysis, a machine learning model was trained which instead focuses only on the explicit Higgs-mediated processes as a proxy, which is suboptimal. The aim of this project is to improve upon this current machine learning strategy used in this analysis by implementing either of the inference-aware approaches suggested in [1] and [2]. The idea behind these inference-aware machine learning algorithms is that they do not optimise for a simplified goal such as the loss function which is common in traditional machine learning, but rather for the end-goal of the analysis. In this case, this would omit the need for interference event generation altogether and allow the machine learning models to be trained optimally regardless.<br />
<br />
The first checkpoint of this project is to use either of the frameworks used in [1] and [2] (which are both publicly available) and run them with a simplified dataset from the aforementioned analysis. After this proof-of-principle is achieved, the next goal would be to actually implement the newly developed machine learning models in the full analysis and to determine the improvement upon the existing result. A successful completion of these tasks would not only benefit the Higgs lifetime analysis, but would be an important stepping stone to future developments to make machine learning approaches also aware of other hard to model effects such as systematic uncertainties. Finally, there are further options to improve this analysis such as the generation of actual interference training data, which could be attempted in case the primary project finishes earlier than expected.<br />
<br />
[1] De Castro, P., & Dorigo, T. (2019). INFERNO: inference-aware neural optimisation. ''Computer Physics Communications'', ''244'', 170-179.<br />
<br />
[2] Simpson, N., & Heinrich, L. (2023, February). neos: End-to-end-optimised summary statistics for high energy physics. In ''Journal of Physics: Conference Series'' (Vol. 2438, No. 1, p. 012105). IOP Publishing.<br />
<br />
Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
=== ATLAS: Development of state-of-the art modeling techniques to generate Higgs interference events ===<br />
In this project we aim to improve an ongoing analysis to determine the lifetime of the Higgs Boson through new event generation strategies, in particular by addressing a novel solution to an as of yet unsolved fundamental problem in modeling quantum interference. While the Higgs is an elusive particle that generally only appears in physics processes with small cross sections, its signature can be amplified in the Large Hadron Collider (LHC) through quantum interference with larger background (non-Higgs) processes. This is the effect that the Higgs’ lifetime analysis relies on to be able to measure the relevant Higgs signature. A fundamental physics modelling problem arises though in the simulation of individual events for this interference due to the fact that these events are in reality described by a superposition of underlying Higgs and non-Higgs processes.<br />
<br />
The current approach to deal with this problem is to ignore the interference in analysis optimization and instead optimize only for explicitly Higgs mediated processes, but this severely impacts analysis performance. In the context of Effective Field Theories (EFT) however, a similar problem arises and has been solved for simple (leading order) processes. In this project we plan to take the machinery developed for EFT and apply it to the Higgs lifetime analysis. Furthermore, with the recent development of a Next-to-Leading Order (NLO) Higgs event generation tool [1] a subsequent goal would be to use this to also generate interference at the NLO level. Successful completion of this project would lead to a much improved analysis result, significantly constraining the lifetime of the Higgs Boson. Besides, the techniques developed would almost certainly be used in future analyses on Large Hadron Collider (LHC) run 3 data.<br />
<br />
[1] Alioli, S., Ravasio, S. F., Lindert, J. M., & Röntsch, R. (2021). Four-lepton production in gluon fusion at NLO matched to parton showers. ''The European Physical Journal C'', ''81''(8), 687.<br />
<br />
Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák], [mailto:b.kortman@nikhef.nl Bryan Kortman] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
=== ATLAS: Approaching the Higgs from a new direction: Constraining new physics with off shell Higgs data from the LHC ===<br />
The Heisenberg uncertainly principle allows for all elementary particles---including the Higgs Boson---to momentarily disobey the fundamental energy-momentum relation, allowing the particle in question to have a significantly larger mass than usual. A description of the Higgs Boson in this state (“off shell Higgs Boson”) can provide a portal to the discovery of potential new physics, albeit very difficult to do due to its infrequent appearance. The goal of this project is to constrain or hint at new physics by estimating parameters of a generalized model which allows for new physics, Effective Field Theory (EFT), using off shell Higgs data.<br />
<br />
Most of the underlying analysis to measure the prevalence of off shell Higgs bosons has already been set up, so the goal of this project is to do the aforementioned EFT interpretation on top of this existing analysis. From a theoretical point of view much of the groundwork has also been done on simulated data which showed the potential for this EFT interpretation to constrain new physics [1]. Being on the interface between experimental and theoretical physics this project allows the student to gain a deeper understanding of both, furthermore its successful completion could be one of the first hints towards as of yet not understood physics.<br />
<br />
[1] Azatov, A., de Blas, J., Falkowski, A., Gritsan, A. V., Grojean, C., Kang, L., ... & Vryonidou, E. (2022). Off-shell Higgs Interpretations Task Force: Models and Effective Field Theories Subgroup Report. arXiv preprint arXiv:2203.02418.<br />
<br />
Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák], [mailto:b.kortman@nikhef.nl Bryan Kortman] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
=== ATLAS: A new timing detector - the HGTD ===<br />
The ATLAS is going to get a new ability: a timing detector. This allows us to reconstruct tracks not only in the 3 dimensions of space but adds the ability of measuring very precisely also the time (at picosecond level) at which the particles pass the sensitive layers of the HGTD detector. This allows to construct the trajectories of the particles created at the LHC in 4 dimensions and ultimately will lead to a better reconstruction of physics at ATLAS. The new HGTD detector is still in construction and work needs to be done on different levels such as understanding the detector response (taking measurements in the lab and performing simulations) or developing algorithms to reconstruct the particle trajectories (programming and analysis work). With this work you will be part of the Atlas group and/or the Fast Timing detector group together with the R&D department at Nikhef. <br />
<br />
'''In this project there are two possibilities:''' <br />
<br />
One can choose to either focus on the impact on physics performance by studying how the timing measurements can be included in the reconstruction of tracks, and what effect this has on how much better we can understand the physical processes occurring in the particles produced in the LHC collisions. <br />
<br />
The second possibility is to focus on the working of the fast-timing detectors themselves and participate in measurements in the lab and in test-beam campaigns at CERN. <br />
<br />
If you are interested, contact me to discuss the possibilities. <br />
Contact: ''[mailto:hella.snoek@nikhef.nl Hella Snoek]''<br />
<br />
<br />
=== ATLAS: The next full-silicon Inner Tracker: ITk ===<br />
[[File:ITk endcap structure.jpg|210x210px|thumb|alt=]]The inner detector of the present ATLAS experiment has been designed and developed to function in the environment of the present Large Hadron Collider (LHC). At the ATLAS Phase-II Upgrade, the particle densities and radiation levels will exceed current levels by a factor of ten. The instantaneous luminosity is expected to reach unprecedented values, resulting in up to 200 proton-proton interactions in a typical bunch crossing. The new detectors must be faster and they need to be more highly segmented. The sensors used also need to be far more resistant to radiation, and they require much greater power delivery to the front-end systems. At the same time, they cannot introduce excess material which could undermine tracking performance. For those reasons, the inner tracker of the ATLAS detector (ITk) was redesigned and will be rebuilt completely.<br />
<br />
Nikhef is one of the sites in charge of building and integrating some big parts of ITk. One of the next steps consists of testing the sensors that we will install in the structures we have built (check one of the structures in the picture of our cleanroom). This project offers the possibility of working on a full hardware project, doing something completely new, by testing the sensors of a future component of the next ATLAS detector.<br />
<br />
''Contact'': ''[mailto:aalonso@nikhef.nl Andrea García Alonso]''<br />
<br />
=== Cosmic Rays/Neutrinos: Seasonal muon flux variations and the pion/kaon ratio ===<br />
The KM3NeT ARCA and ORCA detectors, located kilometers deep in the Mediterranean Sea, have neutrinos as primary probes. Muons from cosmic ray interactions reach the detectors in relatively large quantities too. These muons, exploiting the capabilities and location of the detectors allow the study of cosmic rays and their interactions. In this way, questions about their origin, type, propagation can be addressed. In particular these muons are tracers of hadronic interactions at energies inaccessible at particle accelerators.<br />
<br />
The muons reaching the depths of the detectors result from decays of mesons, mostly pions and kaons, created in interactions of high-energy cosmic rays with atoms in the upper atmosphere. Seasonal changes of the temperature – and thus density - profile of the atmosphere modulate the balance between the probability for these mesons to decay (producing muons) or to re-interact. Pions and kaons are affected differently, allowing to extract their production ratio by determining how changes in muon rate depend on changes in the effective temperature – an integral over the atmospheric temperature profile weighted by a depth dependent meson production rate.<br />
<br />
In this project, the aim is to measure the rate of muons in the detectors and to calculate the effective temperature above the KM3NeT detectors from atmospheric data, both as function of time. The relation between these two can be used to extract the pion to kaon ratio.<br />
<br />
''Contact: [mailto:rbruijn@nikhef.nl Ronald Bruijn]''<br />
=== Dark Matter: Building better Dark Matter Detectors - the XAMS R&D Setup===<br />
The Amsterdam Dark Matter group operates an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 0.5kg of ultra-pure liquid xenon in the central volume. We use this detector for the development of new detection techniques - such as utilizing our newly installed silicon photomultipliers - and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENONnT experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory, or for future Dark Matter experiments like DARWIN. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data themselves You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
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===Dark Matter: Searching for Dark Matter Particles - XENONnT Data Analysis ===<br />
The XENON collaboration has used the XENON1T detector to achieve the world’s most sensitive direct detection dark matter results and is currently operating the XENONnT successor experiment. The detectors operate at the Gran Sasso underground laboratory and consist of so-called dual-phase xenon time-projection chambers filled with ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the new data coming from the XENONnT detector. The work will consist of understanding the detector signals and applying a deep neural network to improve the (gas-) background discrimination in our Python-based analysis tool to improve the sensitivity for low-mass dark matter particles. The work will continue a study started by a recent graduate. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy.<br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter: Signal reconstruction and correction in XENONnT ===<br />
XENONnT is a low background experiment operating at the INFN - Gran Sasso underground laboratory with the main goal of detecting Dark Matter interactions with xenon target nuclei. The detector, consisting of a dual-phase time projection chamber, is filled with ultra-pure xenon, which acts as a target and detection medium. Understanding the detector's response to various calibration sources is a mandatory step in exploiting the scientific data acquired. This MSc thesis aims to develop new methods to improve the reconstruction and correction of scintillation/ ionization signals from calibration data. The student will work with modern analysis techniques (python-based) and will collaborate with other analysts within the international XENON Collaboration.<br />
<br />
''Contact: [mailto:mpierre@nikhef.nl Maxime Pierre], [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
===Dark Matter: The Ultimate Dark Matter Experiment - DARWIN Sensitivity Studies===<br />
DARWIN is the “ultimate” direct detection dark matter experiment, with the goal to reach the so-called “neutrino floor”, when neutrinos become a hard-to-reduce background. The large and exquisitely clean xenon mass will allow DARWIN to also be sensitive to other physics signals such as solar neutrinos, double-beta decay from Xe-136, axions and axion-like particles etc. While the experiment will only start in 2027, we are in the midst of optimizing the experiment, which is driven by simulations. We have an opening for a student to work on the GEANT4 Monte Carlo simulations for DARWIN. We are also working on a “fast simulation” that could be included in this framework. It is your opportunity to steer the optimization of a large and unique experiment. This project requires good programming skills (Python and C++) and data analysis/physics interpretation skills.<br />
<br />
''Contact: [mailto:t.pollmann@nikhef.nl Tina Pollmann], [mailto:decowski@nikhef.nl Patrick Decowski] or [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter: Exploring new background sources for DARWIN ===<br />
Experiments based on the xenon dual-phase time projection chamber detection technology have already demonstrated their leading role in the search for Dark Matter. The unprecedented low level of background reached by the current generation, such as XENONnT, allows such experiments to be sensitive to new rare-events physics searches, broadening their physics program. The next generation of experiments is already under consideration with the DARWIN observatory, which aims to surpass its predecessors in terms of background level and mass of xenon target. With the increased sensitivity to new physics channels, such as the study of neutrino properties, new sources of backgrounds may arise. This MSc thesis aims to investigate potential new sources of background for DARWIN and is a good opportunity for the student to contribute to the design of the experiment. This project will rely on Monte Carlo simulation tools such as GEANT4 and FLUKA, and good programming skills (Python and C++) are advantageous.<br />
<br />
''Contact: [mailto:mpierre@nikhef.nl Maxime Pierre], [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
===Dark Matter: Sensitive tests of wavelength-shifting properties of materials for dark matter detectors===<br />
Rare event search experiments that look for neutrino and dark matter interactions are performed with highly sensitive detector systems, often relying on scintillators, especially liquid noble gases, to detect particle interactions. Detectors consist of structural materials that are assumed to be optically passive, and light detection systems that use reflectors, light detectors, and sometimes, wavelength-shifting materials. MSc theses are available related to measuring the efficiency of light detection systems that might be used in future detectors. Furthermore, measurements to ensure that presumably passive materials do not fluoresce, at the low level relevant to the detectors, can be done. Part of the thesis work can include Monte Carlo simulations and data analysis for current and upcoming dark matter detectors, to study the effect of different levels of desired and nuisance wavelength shifting. In this project, students will acquire skills in photon detection, wavelength shifting technologies, vacuum systems, UV and extreme-UV optics, detector design, and optionally in Python and C++ programming, data analysis, and Monte Carlo techniques.<br />
<br />
''Contact: [mailto:Tina.Pollmann@tum.de Tina Pollmann]'' <br />
<br />
=== Detector R&D: Studies of wafer-scale sensors for ALICE detector upgrade and beyond ===<br />
One of the biggest milestones of the ALICE detector upgrade (foreseen in 2026) is the implementation of wafer-scale (~ 28 cm x 18 cm) monolithic silicon active pixel sensors in the tracking detector, with the goal of having truly cylindrical barrels around the beam pipe. To demonstrate such an unprecedented technology in high energy physics detectors, few chips will be soon available in Nikhef laboratories for testing and characterization purposes.<br />
The goal of the project is to contribute to the validation of the samples against the ALICE tracking detector requirements, with a focus on timing performance in view of other applications in future high energy physics experiments beyond ALICE.<br />
We are looking for a student with a focus on lab work and interested in high precision measurements with cutting-edge instrumentation. You will be part of the Nikhef Detector R&D group and you will have, at the same time, the chance to work in an international collaboration where you will report about the performance of these novel sensors. There may even be the opportunity to join beam tests at CERN or DESY facilities. Besides interest in hardware, some proficiency in computing is required (Python or C++/ROOT).<br />
<br />
''Contact: [mailto:(jory.sonneveld@nikhef.nl Jory Sonneveld ], [mailto:rrusso@nikhef.nl Roberto Russo]''<br />
<br />
=== Detector R&D: Time resolution of monolithic silicon detectors ===<br />
Monolithic silicon detectors based on industrial Complementary Metal Oxide Semiconductor (CMOS) processes offer a promising approach for large scale detectors due to their ease of production and low material budget. Until recently, their low radiation tolerance has hindered their applicability in high energy particle physics experiments. However, new prototypes ~~such as the one in this project~~ have overcome these hurdles, making them feasible candidates for future experiments in high energy particle physics. Achieving the required radiation tolerance has brought the spatial and temporal resolution of these detectors to the forefront. In this project, you will investigate the temporal performance of a radiation hard monolithic detector prototype, using laser setups in the laboratory. You will also participate in meetings with the international collaboration working on this detector, where you will report on the prototype's performance. Depending on the progress of the work, there may be a chance to participate in test beams performed at the CERN accelerator complex and a first full three dimensional characterization of the prototypes performance using a state-of-the-art two-photon absorption laser setup at Nikhef. This project is looking for someone interested in working hands on with cutting edge detector and laser systems at the Nikhef laboratory. Python programming skills and linux experience are an advantage.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld], [mailto:uwe.kraemer@nikhef.nl Uwe Kraemer]''<br />
<br />
=== Detector R&D: Improving a Laser Setup for Testing Fast Silicon Pixel Detectors ===<br />
For the upgrades of the innermost detectors of experiments at the Large Hadron Collider in Geneva, in particular to cope with the large number of collisions per second from 2027, the Detector R&D group at Nikhef tests new pixel detector prototypes with a variety of laser equipment with several wavelengths. The lasers can be focused down to a small spot to scan over the pixels on a pixel chip. Since the laser penetrates the silicon, the pixels will not be illuminated by just the focal spot, but by the entire three dimensional hourglass or double cone like light intensity distribution. So, how well defined is the volume in which charge is released? And can that be made much smaller than a pixel? And, if so, what would the optimum focus be? For this project the student will first estimate the intensity distribution inside a sensor that can be expected. This will correspond to the density of released charge within the silicon. To verify predictions, you will measure real pixel sensors for the LHC experiments.<br />
This project will involve a lot of 'hands on work' in the lab and involve programming and work on unix machines.<br />
<br />
''Contact: [mailto:martinfr@nikhef.nl Martin Fransen]''<br />
<br />
=== Detector R&D: Time resolution of hybrid pixel detectors with the Timepix4 chip ===<br />
Precise time measurements with silicon pixel detectors are very important for experiments at the High-Luminosity LHC and the future circular collider. The spatial resolution of current silicon trackers will not be sufficient to distinguish the large number of collisions that will occur within individual bunch crossings. In a new method, typically referred to as 4D tracking, spatial measurements of pixel detectors will be combined with time measurements to better distinguish collision vertices that occur close together.<br />
New sensor technologies are being explored to reach the required time measurement resolution of tens of picoseconds, and the results are promising. However, the signals that these pixelated sensors produce have to be processed by front-end electronics, which hence also play a role in the total time resolution of the detector. An important contribution comes from the systematic differences between the front-end electronics of different pixels. Many of these systematic effects can be corrected by performing detailed calibrations of the readout electronics. To achieve the required time resolution at future experiments, it is vital that these effects are understood and corrected.<br />
In this project you will be working with the Timepix4 chip. This is a so-called application specific integrated circuit (ASIC) that is designed to read out pixelated sensors. This ASIC will be used extensively in detector R&D for the characterisation of new sensor technologies requiring precise timing (< 50 ps). In order to do so, it is necessary to first study the systematic differences between the pixels, which you will do using a laser setup in our lab. This will be combined with data analysis of proton beam measurements, or with measurements performed using the built-in test-pulse mechanism of the Timepix4 ASIC. Your work will enable further research performed with this ASIC, <br />
and serve as input to the design and operation of future ASICs for experiments at the High-Luminosity LHC.<br />
<br />
''Contact: [mailto:k.heijhoff@nikhef.nl Kevin Heijhoff] and [mailto:martinb@nikhef.nl Martin van Beuzekom]''<br />
<br />
===Detector R&D: Performance studies of Trench Isolated Low Gain Avalanche Detectors (TI-LGAD) ===<br />
The future vertex detector of the LHCb Experiment needs to measure the spatial coordinates and time of the particles originating in the LHC proton-proton collisions with resolutions better than 10 um and 50 ps, respectively. Several technologies are being considered to achieve these resolutions. Among those is a novel sensor technology called Trench Isolated Low Gain Avalanche Detector. <br />
Prototype pixelated sensors have been manufactured recently and have to be characterised. Therefore these new sensors will be bump bonded to a Timepix4 ASIC which provides charge and time measurements in each of 230 thousand pixels. Characterisation will be done using a lab setup at Nikhef, and includes tests with a micro-focused laser beam, radioactive sources, and possibly with particle tracks obtained in a test-beam. This project involves data taking with these new devices and analysing the data to determine the performance parameters such as the spatial and temporal resolution. as function of temperature and other operational conditions. <br />
<br />
''Contacts: [mailto:kazu.akiba@nikhef.nl Kazu Akiba] and [mailto:martinb@nikhef.nl Martin van Beuzekom]''<br />
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===Detector R&D: A Telescope with Ultrathin Sensors for Beam Tests ===<br />
To measure the performance of new prototypes for upgrades of the LHC experiments and beyond, typically a telescope is used in a beam line of charged particles that can be used to compare the results in the prototype to particle tracks measured with this telescope. In this project, you will continue work on a very lightweight, compact telescope using ALICE PIxel DEtectors (ALPIDEs). This includes work on the mechanics, data acquisition software, and a moveable stage. You will foreseeably test this telescope in the Delft Proton Therapy Center. If time allows, you will add a timing plane and perform a measurement with one of our prototypes. Apart from travel to Delft, there is a possiblity to travel to other beam line facilities.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
===Detector R&D: Other projects ===<br />
Are you looking for a slightly different project? Are the above projects already taken? Are you coming in at an unusual time of the year? Do not hesitate to contact us! We always have new projects coming up at different times in the year and we are open to your ideas.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
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===FCC: The Next Collider===<br />
<br />
After the LHC, the next planned large collider at CERN is the proposed 100 kilometer circular collider "FCC". In the first stage of the project, as a high-luminosity electron-positron collider, precision measurements of the Higgs boson are the main goal. One of the channels that will improve by orders of magnitude at this new accelerator is the decay of the Higgs boson to a pair of charm quarks. This project will estimate a projected sensitivity for the coupling of the Higgs boson to second generation quarks, and in particular target the improved reconstruction of the topology of long-lived mesons in the clean environment of a precision e+e- machine.<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
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===Gravitational Waves: Computer modelling to design the laser interferometers for the Einstein telescope===<br />
<br />
A new field of instrument science led to the successful detection of gravitational waves by the LIGO detectors in 2015. We are now preparing the next generation of gravitational wave observatories, such as the Einstein Telescope, with the aim to increase the detector sensitivity by a factor of ten, which would allow, for example, to detect stellar-mass black holes from early in the universe when the first stars began to form. This ambitious goal requires us to find ways to significantly improve the best laser interferometers in the world.<br />
<br />
Gravitational wave detectors, such as LIGO and VIRGO, are complex Michelson-type interferometers enhanced with optical cavities. We develop and use numerical models to study these laser interferometers, to invent new optical techniques and to quantify their performance. For example, we synthesize virtual mirror surfaces to study the effects of higher-order optical modes in the interferometers, and we use opto-mechanical models to test schemes for suppressing quantum fluctuations of the light field. We can offer several projects based on numerical modelling of laser interferometers. All projects will be directly linked to the ongoing design of the Einstein Telescope.<br />
<br />
''Contact: [mailto:a.freise@nikhef.nl Andreas Freise]''<br />
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===LHCb: Search for light dark particles===<br />
The Standard Model of elementary particles does not contain a proper Dark Matter candidate. One of the most tantalizing theoretical developments is the so-called ''Hidden Valley models'': a mirror-like copy of the ''Standard Model'', with dark particles that communicate with standard ones via a very feeble interaction. These models predict the existence of ''dark hadrons'' – composite particles that are bound similarly to ordinary hadrons in the ''Standard Model''. Such ''dark hadrons'' can be abundantly produced in high-energy proton-proton collisions, making the LHC a unique place to search for them. Some ''dark hadrons'' are stable like a proton, which makes them excellent ''Dark Matter'' candidates, while others decay to ordinary particles after flying a certain distance in the collider experiment. The LHCb detector has a unique capability to identify such decays, particularly if the new particles have a mass below ten times the proton mass. <br />
<br />
This project assumes a unique search for light ''dark hadrons'' that covers a mass range not accessible to other experiments. It assumes an interesting program on data analysis (python-based) with non-trivial machine learning solutions and phenomenology research using fast simulation framework. Depending on the interest, there is quite a bit of flexibility in the precise focus of the project.<br />
<br />
''Contact: [mailto:andrii.usachov@nikhef.nl Andrii Usachov]''<br />
<br />
===LHCb: Searching for dark matter in exotic six-quark particles===<br />
<br />
Three quarters of the mass in the Universe is of unknown type. Many hypotheses about this dark matter have been proposed, but none confirmed. Recently it has been proposed that it could be made of particles made of the six quarks uuddss, which would be a Standard-Model solution to the dark matter problem. This idea has recently gained credibility as many similar multi-quarks states are being discovered by the LHCb experiment. Such a particle could be produced in decays of heavy baryons, or directly in proton-proton collisions. The anti-particle, made of six antiquarks, could be seen when annihilating with detector material. It is also proposed to use Xi_b baryons produced at LHCb to search for such a state where the state would appear as missing 4-momentum in a kinematically constrained decay. The project consists in defining a selection and applying it to LHCb data. See [https://arxiv.org/abs/2007.10378 arXiv:2007.10378].<br />
<br />
Contact: ''[mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
<br />
===LHCb: Measuring lepton flavour universality with excited Ds states in semileptonic Bs decays===<br />
One of the most striking discrepancies between the Standard Model and measurements are the lepton flavour universality (LFU) measurements with tau decays. At the moment, we have observed an excess of 3-4 sigma in ''B → Dτν'' decays. This could point even to a new force of nature! To understand this discrepancy, we need to make further measurements. <br />
<br />
One very exciting (pun intended) projects to verify these discrepancies involves measuring the ''B<sub>s</sub> → D<sub>s2</sub><sup>*</sup>τν'' and/or ''B<sub>s</sub> → D<sub>s1</sub><sup>*</sup>τν'' decays. These decays with excited states of the ''D<sub>s</sub>'' meson have not been observed before in the tau decay mode, and have a unique way of coupling to potential new physics candidates that can only be measured in ''B<sub>s</sub>'' decays [1]. See slides for more detail: [[File:LHCbLFUwithExcitedDs.pdf|thumb]]<br />
<br />
[1] https://arxiv.org/abs/1606.09300<br />
<br />
''Contact: [mailto:suzannek@nikhef.nl Suzanne Klaver]''<br />
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===LHCb: New physics in the angular distributions of B decays to K*ee===<br />
<br />
Lepton flavour violation in B decays can be explained by a variety of non-standard model interactions. Angular distributions in decays of a B meson to a hadron and two leptons are an important source of information to understand which model is correct. Previous analyses at the LHCb experiment have considered final states with a pair of muons. Our LHCb group at Nikhef concentrates on a new measurement of angular distributions in decays with two electrons. The main challenge in this measurement is the calibration of the detection efficiency. In this project you will confront estimates of the detection efficiency derived from simulation with decay distributions in a well known B decay. Once the calibration is understood, the very first analysis of the angular distributions in the electron final state can be performed. <br />
<br />
Contact: [mailto:m.senghi.soares@nikhef.nl Mara Soares] and [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
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===LHCb: Discovering heavy neutrinos in B decays===<br />
<br />
Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, much heavier, neutral leptons. If the mass of these new neutrinos is below the b-quark mass, they can be observed in B hadron decays.<br />
<br />
In this project we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undiscovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The analysis will be performed within the LHCb group at Nikhef using LHCb run-2 data.<br />
<br />
===LHCb: Scintillating Fibre tracker software===<br />
The installation of the scintillating-fibre tracker in LHCb’s underground cavern was recently completed. This detector uses 10000 km of fibres to track particle trajectories in the LHCb detector when the LHC starts up again later this year. The light emitted by the scintillating fibres when a particle interacts with them is measured using photon multiplier tubes. The studies proposed for this project will focus on software, and could include writing a framework to monitor the detector output, improving the detector simulation or working on the data processing.<br />
<br />
''Contact: [mailto:e.gabriel@nikhef.nl Emmy Gabriel]''<br />
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===LHCb: Vertex detector calibration===<br />
In summer 2022 LHCb has started data taking will an almost entirely new detector. At the point closest to the interaction point, the trajectories of charge particles are reconstructed with a so-called silicon pixel detector. The design hit resolution of this detector is about 15 micron. However, to actually reach this resolution a precise calibration of the spatial positions of the silicon sensors needs to be performed. In this project, you will use the first data of the new LHCb detector to perform this calibration and measure the detector performance.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen]''<br />
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<br />
===Neutrinos: Neutrino scattering: the ultimate resolution===<br />
<br />
Neutrino telescopes like IceCube and KM3NeT aim at detecting neutrinos from cosmic sources. The neutrinos are detected with the best resolution when charged current interactions with nucleons produce a muon, which can be detected with high accuracy (depending on the detector). A crucial ingredient in the ultimate achievable pointing accuracy of neutrino telescopes is the scattering angle between the neutrino and the muon. While published computations have investigated the cross-section of the process in great detail, this important scattering angle has not received much attention. The aim of the project is to compute and characterize the distribution of this angle, and that the ultimate resolution of a neutrino telescope. If successful, the results of this project can lead to publication of interest to the neutrino telescope community.<br />
<br />
Depending on your interests, the study could be based on a first-principles calculation (using the deep-inelastic scattering formalism), include state-of-the-art parton distribution functions, and/or exploit existing event-generation software for a more experimental approach. <br />
<br />
''Contacts: [mailto:aart.heijboer@nikhef.nl Aart Heijboer]''<br />
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===Neutrinos: acoustic detection of ultra-high energy neutrinos===<br />
<br />
The study of the cosmic neutrinos of energies above 1017 eV, the so-called ultra-high energy neutrinos, provides a unique view on the universe and may provide insight in the origin of the most violent astrophysical sources, such as gamma ray bursts, supernovae or even dark matter. In addition, the observation of high energy neutrinos may provide a unique tool to study interactions at high energies. The energy deposition of these extreme neutrinos in water induce a thermo-acoustic signal, which can be detected using sensitive hydrophones. The expected neutrino flux is however extremely low and the signal that neutrinos induce is small. TNO is presently developing sensitive hydrophone technology based on fiber optics. Optical fibers form a natural way to create a distributed sensing system. Using this technology a large scale neutrino telescope can be built in the deep sea. TNO is aiming for a prototype hydrophone which will form the building block of a future telescope.<br />
<br />
The work will be executed at the Nikhef institute and/or the TNO laboratories in Delft. In this project master students have the opportunity to contribute in the following ways:<br />
<br />
'''Project 1:''' Hardware development on fiber optics hydrophones technology Goal: characterize existing prototype optical fibre hydrophones in an anechoic basin at TNO laboratory. Data collection, calibration, characterization, analysis of consequences for design future acoustic hydrophone neutrino telescopes;<br />
Keywords: Optical fiber technology, signal processing, electronics, lab.<br />
<br />
'''Project 2:''' Investigation of ultra-high energy neutrinos and their interactions with matter. Goal: Discriminate the neutrino signals from the background noises, in particular clicks from whales and dolphins in the deep sea. Study impact on physics reach for future acoustic hydrophone neutrino telescopes;<br />
Keywords: Monte Carlo simulations, particle physics, neutrino physics, data analysis algorithms.<br />
<br />
Further information: Info on ultra-high energy neutrinos can be found at: http://arxiv.org/abs/1102.3591; Info on acoustic detection of neutrinos can be found at: http://arxiv.org/abs/1311.7588<br />
<br />
''Contact: [mailto:ernst-jan.buis@tno.nl Ernst Jan Buis]'' or ''[mailto:ivo.van.vulpen@nikhef.nl Ivo van Vulpen]''<br />
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===Neutrinos: Oscillation analysis with the first data of KM3NeT===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first few strings with sensitive photodetectors have been deployed at both the Italian and the French detector sites. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In this project the available data will be used together with simulations to best reconstruct the event topologies and optimally identify and reconstruct the first neutrino interactions in the KM3NeT detector. The data will then be used to measure neutrino oscillation parameters, and prepare for a future neutrino mass ordering determination.<br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
''Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn] [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
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===Neutrinos: the Deep Underground Neutrino Experiment (DUNE)===<br />
<br />
The Deep Underground Neutrino Experiment (DUNE) is under construction in the USA, and will consist of a powerful neutrino beam originating at Fermilab, a near detector at Fermilab, and a far detector in the SURF facility in Lead, South Dakota, 1300 km away. During travelling, neutrinos oscillate and a fraction of the neutrino beam changes flavour; DUNE will determine the neutrino oscillation parameters to unrivaled precision, and try and make a first detection of CP-violation in neutrinos. In this project, various elements of DUNE can be studied, including the neutrino oscillation fit, neutrino physics with the near detector, event reconstruction and classification (including machine learning), or elements of data selection and triggering.<br />
<br />
''Contact: [mailto:h26@nikhef.nl Paul de Jong]''<br />
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===Neutrinos: Searching for Majorana Neutrinos with KamLAND-Zen===<br />
The KamLAND-Zen experiment, located in the Kamioka mine in Japan, is a large liquid scintillator experiment with 750kg of ultra-pure Xe-136 to search for neutrinoless double-beta decay (0n2b). The observation of the 0n2b process would be evidence for lepton number violation and the Majorana nature of neutrinos, i.e. that neutrinos are their own anti-particles. Current limits on this extraordinary rare hypothetical decay process are presented as a half-life, with a lower limit of 10^26 years. KamLAND-Zen, the world’s most sensitive 0n2b experiment, is currently taking data and there is an opportunity to work on the data analysis, analyzing data with the possibility of taking part in a ground-breaking discovery. The main focus will be on developing new techniques to filter the spallation backgrounds, i.e. the production of radioactive isotopes by passing muons. There will be close collaboration with groups in the US (MIT, Berkeley, UW) and Japan (Tohoku Univ). <br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
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===Neutrinos: relic neutrino detection with PTOLEMY ===<br />
PTOLEMY aims to make the first direct observation of the Big Bang relic neutrinos (the cosmic neutrino background, CνB) by resolving the β-decay endpoint of atomic tritium (neutrino capture target) to O(meV) precision. This remains an outstanding test of the Standard Model in an expanding universe. Not only does the CνB carry with it a signal from the hot dense universe only one second after the Big Bang but helps to constrain the balance of hot versus cold dark matter responsible for its evolution. In doing so, the PTOLEMY experiment would also measure the lowest neutrino mass, an as-of-yet unknown fundamental constant. The experiment is currently in the prototyping phase and the group at Nikhef is responsible for developing the radio-frequency (RF) system used for cyclotron radiation (CR) based trigger and tracking. This component will provide the trajectory of electrons entering the novel transverse drift filter, constraining the electrons' energy losses before they reach the cryogenic calorimeter which in turn records their final energy. The focus of this project will be modelling CR and its detection for the purposes of single electron spectroscopy and optimised trajectory reconstruction. There is also the opportunity to test hardware and readout electronics for the prototype RF-system. <br />
''Contact: [mailto:jmead@nikhef.nl James Vincent Mead]''<br />
<br />
=== Theoretical Particle Physics: Effective Field Theories of Particle Physics from low- to high-energies===<br />
Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations” seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature. The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Standard Model Effective Field Theory (SMEFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes with minimal assumptions on the nature of an eventual UV-complete theory that replaces the Standard Model. Specifically, the goal is to connect measurements from ATLAS, CMS, and LHCb experiments at the CERN's LHC among them and to jointly interpret this information with that provided by other experiments including very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
<br />
This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories. Depending on the student profile, sub-projects with a strong computational and/or machine learning component are also possible, for instance to construct new operators with optimal sensitivity to New Physics effects as encoded by the SMEFT higher-dimensional operators. Topics that can be considered in this project include the interpretation of novel physical observables at the LHC and their integration into the global SMEFiT analysis, matching of EFTs to UV-complete theories and their phenomenological analyses, projections for the impact in the SMEFT parameter space of data for future colliders, the synergies between EFT studies and proton structure fits, and the matching to the Weak Effective Field Theory to include data on flavour observables such as B-meson decays.<br />
<br />
References: https://arxiv.org/abs/2105.00006 , https://arxiv.org/abs/2302.06660, https://arxiv.org/abs/2211.02058 , https://arxiv.org/abs/1901.05965 , https://arxiv.org/abs/1906.05296 , https://arxiv.org/abs/1908.05588, https://arxiv.org/abs/1905.05215. see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description].<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theoretical Particle Physics: High-energy neutrino-nucleon interactions at the Forward Physics Facility ===<br />
High-energy collisions at the High-Luminosity Large Hadron Collider (HL-LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing experiments. The proposed Forward Physics Facility (FPF) to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe Standard Model (SM) processes and search for physics beyond the Standard Model (BSM). High statistics neutrino detection will provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. The FPF has the promising potential to probe our understanding of the strong interactions as well as of proton and nuclear structure, providing access to both the very low-x and the very high-x regions of the colliding protons. The former regime is sensitive to novel QCD production mechanisms, such as BFKL effects and non-linear dynamics, as well as the gluon parton distribution function (PDF) down to x=1e-7, well beyond the coverage of other experiments and providing key inputs for astroparticle physics. In addition, the FPF acts as a neutrino-induced deep-inelastic scattering (DIS) experiment with TeV-scale neutrino beams. The resulting measurements of neutrino DIS structure functions represent a valuable handle on the partonic structure of nucleons and nuclei, particularly their quark flavour separation, that is fully complementary to the charged-lepton DIS measurements expected at the upcoming Electron-Ion Collider (EIC).<br />
<br />
In this project, the student will carry out updated predictions for the neutrino fluxes expected at the FPF, assess the precision with which neutrino cross-sections will be measured, and quantify their impact on proton and nuclear structure by means of machine learning tools within the NNPDF framework and state-of-the-art calculations in perturbative Quantum Chromodynamics. This project contributes to ongoing work within the FPF Initiative towards a Conceptual Design Report (CDR) to be presented within two years. Topics that can be considered as part of this project include the assessment of to which extent nuclear modifications of the free-proton PDFs can be constrained by FPF measurements, the determination of the small-x gluon PDF from suitably defined observables at the FPF and the implications for ultra-high-energy particle astrophysics, the study of the intrinsic charm content in the proton and its consequences for the FPF physics program, and the validation of models for neutrino-nucleon cross-sections in the region beyond the validity of perturbative QCD.<br />
<br />
References: https://arxiv.org/abs/2203.05090, https://arxiv.org/abs/2109.10905 ,https://arxiv.org/abs/2208.08372 , https://arxiv.org/abs/2201.12363 , https://arxiv.org/abs/2109.02653, https://github.com/NNPDF/ see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description]. <br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theoretical Particle Physics: Probing the origin of the proton spin with machine learning===<br />
At energy-frontier facilities such as the Large Hadron Collider (LHC), scientists study the laws of nature in their quest for novel phenomena both within and beyond the Standard Model of particle physics. An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions from the nature of the Higgs boson to the origin of cosmic neutrinos. The key to address some of these questions is by carrying out an universal analysis of nucleon structure from the simultaneous determination of the momentum and spin distributions of quarks and gluons and their fragmentation into hadrons. This effort requires combining an extensive experimental dataset and cutting-edge theory calculations within a machine learning framework where neural networks parametrise the underlying physical laws while minimising ad-hoc model assumptions. The upcoming Electron Ion Collider (EIC), to start taking data in 2029, will be the world's first ever polarised lepton-hadron collider and will offer a plethora of opportunities to address key open questions in our understanding of the strong nuclear force, such as the origin of the mass and the intrinsic angular momentum (spin) of hadrons and whether there exists a state of matter which is entirely dominated by gluons. To fully exploit this scientific potential, novel analysis methodologies need to be develop that make it possible to carry out large-scale, coherent interpretations of measurements from the EIC and other high-energy colliders.<br />
<br />
In this project, the student will carry out a new global analysis of the spin structure of the proton by means of the machine learning tools provided by the NNPDF open-source fitting framework and state-of-the-art calculations in perturbative Quantum Chromodynamics, and integrate it within the corresponding global NNPDF analyses of unpolarised proton and nuclear structure in the framework of a combined integrated global analysis of non-perturbative QCD. Specifically, the project aims to realise a NNLO global fit of polarised quark and gluon PDFs that combines all available data and state-of-the-art perturbative QCD calculations, and study the phenomenological implications for other experiments, including the EIC, for the spin content of the proton, for comparisons with lattice QCD calculations, and for nonpperturbative models of hadron structure.<br />
<br />
References: https://arxiv.org/abs/2201.12363, https://arxiv.org/abs/2109.02653 , https://arxiv.org/abs/2103.05419, https://arxiv.org/abs/1404.4293 , https://inspirehep.net/literature/1302398, https://github.com/NNPDF/<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
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== Finished master projects ==<br />
<br />
See: <br />
* https://wiki.nikhef.nl/education/Master_Theses<br />
* https://www.nikhef.nl/master-theses-2021/<br />
* https://www.nikhef.nl/facts-figures-2020/master-theses-2020/<br />
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[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=916Master Projects2023-03-29T06:53:55Z<p>Rojo@nikhef.nl: /* Theoretical Particle Physics: Effective Field Theories of Particle Physics from low- to high-energies */</p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
== Projects with a 2023 start ==<br />
<br />
=== ALICE: The next-generation multi-purpose detector at the LHC ===<br />
This main goal of this project is to focus on the next-generation multi-purpose detector planned to be built at the LHC. Its core will be a nearly massless barrel detector consisting of truly cylindrical layers based on curved wafer-scale ultra-thin silicon sensors with MAPS technology, featuring an unprecedented low material budget of 0.05% X0 per layer, with the innermost layers possibly positioned inside the beam pipe. The proposed detector is conceived for studies of pp, pA and AA collisions at luminosities a factor of 20 to 50 times higher than possible with the upgraded ALICE detector, enabling a rich physics program ranging from measurements with electromagnetic probes at ultra-low transverse momenta to precision physics in the charm and beauty sector. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli] and [mailto:marco.van.leeuwen@cern.ch Marco van Leeuwen]''<br />
<br />
=== ALICE: Searching for the strongest magnetic field in nature ===<br />
In a non-central collision between two Pb ions, with a large value of impact parameter, the charged nucleons that do not participate in the interaction (called spectators) create strong magnetic fields. A back of the envelope calculation using the Biot-Savart law brings the magnitude of this filed close to 10^19Gauss in agreement with state of the art theoretical calculation, making it the strongest magnetic field in nature. The presence of this field could have direct implications in the motion of final state particles. The magnetic field, however, decays rapidly. The decay rate depends on the electric conductivity of the medium which is experimentally poorly constrained. Overall, the presence of the magnetic field, the main goal of this project, is so far not confirmed experimentally.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Looking for parity violating effects in strong interactions ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions, in the presence of a deconfined state, gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, what is called the Chiral Magnetic Effect (CME).<br />
The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, however further studies are needed to constrain background effects. These highly anticipated results have the potential to reveal exiting, new physics.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Machine learning techniques as a tool to study the production of heavy flavour particles ===<br />
There was recently a shift in the field of heavy-ion physics triggered by experimental results obtained in collisions between small systems (e.g. protons on protons). These results resemble the ones obtained in collisions between heavy ions. This consequently raises the question of whether we create the smallest QGP droplet in collisions between small systems. The main objective of this project will be to study the production of charm particles such as D-mesons and Λc-baryons in pp collisions at the LHC. This will be done with the help of a new and innovative technique which is based on machine learning (ML). The student will also extend the studies to investigate how this production rate depends on the event activity e.g. on how many particles are created after every collision.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli]''<br />
<br />
=== ALICE: Search for new physics with 4D tracking at the most sensitive vertex detector at the LHC ===<br />
<br />
With the newly installed Inner Tracking System consisting fully of monolithic detectors, ALICE is very sensitive to particles with low transverse momenta, more so than ATLAS and CMS. This will be even more so for the ALICE upgrade detector in 2033. This detector could potentially be even more sensitive to longlived particles that leave peculiar tracks such as disappearing or kinked tracks in the tracker by using timing information along a track. In this project you will investigate how timing information in the different tracking layers can improve or even enable a search for new physics beyond the Standard Model in ALICE. If you show a possibility for major improvements, this can have real consequences for the choice of sensors for this ALICE inner tracker upgrade.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld] and [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ATLAS: The Higgs boson's self-coupling ===<br />
<br />
The coupling of the Higgs boson to itself is one of the main unobserved interactions of the Standard Model and its observation is crucial to understand the shape of the Higgs potential. Here we propose to study the 'ttHH' final state: two top quarks and two Higgs bosons produced in a single collision. This topology is yet unexplored at the ATLAS experiment and the project consists of setting up the new analysis (including multivariate analysis techniques to recognise the complicated final state), optimising the sensitivity and including the result in the full ATLAS study of the Higgs boson's coupling to itself. With the LHC data from the upcoming Run-3, we might be able to see its first glimpses! <br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree] and [mailto:cpandini@nikhef.nl Carlo Pandini]'' <br />
<br />
=== ATLAS: Triple-Higgs production as a probe of the Higgs potential ===<br />
So far, the investigation of Higgs self-couplings (the coupling of the Higgs boson to itself) at the LHC has focused on the measurement of the Higgs tri-linear coupling λ3 mainly through direct double-Higgs production searches. In this research project we propose the investigation of Higgs tri-linear and quartic coupling parameters λ3 and λ4, via a novel measurement of triple-Higgs production at the LHC (HHH) with the ATLAS experiment. While in the SM these parameters are expected to be identical, only a combined measurement can provide an answer regarding how the Higgs potential is realised in Nature. Processes in which three Higgs bosons are produced simultaneously are extremely rare, and very difficult to measure and disentangle from background. In this project we plan to investigate different decay channels (to bottom quarks and tau leptons), and to study advanced machine learning techniques to reconstruct such a complex hadronic final state. This kind of processes is still quite unexplored in ATLAS, and the goal of this project is to put the basis for the first measurement of HHH production at the LHC.<br />
<br />
Furthermore, we'd like to study the possible implication of a precise measurement of the self-coupling parameters from HHH production from a phenomenological point of view: what could be the impact of a deviation in the HHH measurements on the big open questions in physics (for instance, the mechanisms at the root of baryogenesis)?<br />
<br />
Contact: ''[mailto:tdupree@nikhef.nl Tristan du Pree] and [mailto:cpandini@nikhef.nl Carlo Pandini]''<br />
<br />
=== ATLAS: The Next Generation ===<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks is very new [1] and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays) and advanced analysis techiques (using deep learning methods).<br />
<br />
[https://atlas.cern/updates/briefing/charming-Higgs-decay][https://arxiv.org/abs/1802.04329 https://atlas.cern/updates/briefing/charming-Higgs-decay]<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
=== ATLAS: Searching for new particles in very energetic diboson production ===<br />
<br />
The discovery of new phenomena in high-energy proton–proton collisions is one of the main goals of the Large Hadron Collider (LHC). New heavy particles decaying into a pair of vector bosons (WW, WZ, ZZ) are predicted in several extensions to the Standard Model (e.g. extended gauge-symmetry models, Grand Unified theories, theories with warped extra dimensions, etc). In this project we will investigate new ideas to look for these resonances in promising regions. We will focus on final states where both vector bosons decay into quarks, or where one decays into quarks and one into leptons. These have the potential to bring the highest sensitivity to the search for Beyond the Standard Model physics [1, 2]. We will try to reconstruct and exploit new ways to identify vector bosons (using machine learning methods) and then tackle the problem of estimating contributions from beyond the Standard Model processes in the tails of the mass distribution.<br />
<br />
[1] https://arxiv.org/abs/1906.08589<br />
<br />
[2] https://arxiv.org/abs/2004.14636<br />
<br />
''Contact: [mailto:f.dias@nikhef.nl Flavia de Almeida Dias], [mailto:rhayes@nikhef.nl Robin Hayes], Elizaveta Cherepanova and Dylan van Arneman''<br />
<br />
=== ATLAS: Top-quark and Higgs-boson analysis combination, and Effective Field Theory interpretation [not available in 2023] ===<br />
<br />
We are looking for a master student with interest in theory and data-analysis in the search for physics beyond the Standard Model in the top-quark and Higgs-boson sectors.<br />
<br />
Your master-project starts just at the right time for preparing the Run-3 analysis of the ATLAS experiment at the LHC. In Run-3 (2022-2026), three times more data becomes available, enabling analysis of rare processes with innovative software tools and techniques.<br />
<br />
This project aims to explore the newest strategy to combine the top-quark and Higgs-boson measurements in the perspective of constraining the existence of new physics beyond the Standard Model (SM) of Particle Physics. We selected the pp->tZq and gg->HZ processes as promising candidates for a combination to constrain new physics in the context of Standard Model Effective Field Theory (SMEFT). SMEFT is the state-of-the-art framework for theoretical interpretation of LHC data. In particular, you will study the SMEFT OtZ and Ophit operators, which are not well constrained by current measurements.<br />
<br />
Besides affinity with particle physics theory, the ideal candidate for this project has developed python/C++ skills and is eager to learn advanced techniques. You start with a simulation of the signal and background samples using existing software tools. Then, an event selection study is required using Machine Learning techniques. To evaluate the SMEFT effects, a fitting procedure based on the innovative Morphing technique is foreseen, for which the basic tools in the ROOT and RooFit framework are available. The work is carried out in the ATLAS group at Nikhef and may lead to an ATLAS note.<br />
<br />
''Contact: [mailto:geoffrey.gilles@cern.ch Geoffrey Gilles] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:h73@nikhef.nl Marcel Vreeswijk]''<br />
<br />
=== ATLAS: Machine learning to search for very rare Higgs decays ===<br />
<br />
Since the Higgs boson discovery in 2012 at the ATLAS experiment, the investigation of the properties of the Higgs boson has been a priority for research at the Large Hadron Collider (LHC). However, there are still a many open questions: Is the Higgs boson the only origin of Electroweak Symmetry Breaking? Is there a mechanism which can explain the observed mass pattern of SM particles? Many of these questions are linked to the Higgs boson coupling structure. <br />
<br />
While the Higgs boson coupling to fermions of the third generation has been established experimentally, the investigation of the Higgs boson coupling to the light fermions of the second generation will be a major project for the upcoming data-taking period (2022-2025). The Higgs boson decay to muons is the most sensitive channel for probing this coupling. In this project, you will optimize the event selection for Higgs boson decays to muons in the Vector Boson Fusion (VBF) production channel with a focus on distinguishing signal events from background processes like Drell-Yan and electroweak Z boson production. For this purpose, you will develop, implement and validate advanced machine learning and deep learning algorithms. <br />
<br />
''Contact: [mailto:oliver.rieger@nikhef.nl Oliver Rieger] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:s01@nikhef.nl Peter Kluit]''<br />
<br />
=== ATLAS: Interpretation of experimental data using SMEFT ===<br />
<br />
The Standard Model Effective Field Theory (SMEFT) provides a systematic approach to test the impact of new physics at the energy scale of the LHC through higher-dimensional operators. The interpretation of experimental data using SMEFT requires a particular interest in solving complex technical challenges, advanced statistical techniques, and a deep understanding of particle physics. We would be happy to discuss different project opportunities based on your interests with you.<br />
<br />
''Contact: [mailto:oliver.rieger@nikhef.nl Oliver Rieger] and [mailto:verkerke@nikhef.nl Wouter Verkerke]''<br />
<br />
=== ATLAS: Reconstructing tracks from particle physics detector hits with state-of-the-art machine learning techniques ===<br />
This project concerns the application of new machine learning techniques to tackle the problem of track reconstruction at the ATLAS detector in CERN. While algorithms to construct particle tracks from low-level detector information such as particle hits and timestamps have been around for decades, recent developments in the field of machine learning open up new opportunities to improve these algorithms significantly. Some recent developments that could help in this context include graph-based neural networks, which embed the input data in the format of a graph and as such have the capability to enhance underlying correlations within events. Transformer neural networks are a particular extension of graph-based neural networks proposed only in 2017 which could also provide helpful in this case. Another option would be to build upon some of the work done within the field of computer vision and see if image segmentation networks can help solve this problem. There are a range of available options and this project includes the freedom for the student to choose particular types of networks, but more explicit guidance could be provided in case it is desired.<br />
<br />
In this project the student will develop and compare the performance of various machine learning models to initially reconstruct tracks from simplified test data. Upon successful completion of this, simulated data from the actual ATLAS detector can be analysed as well in the scope of this project. The student will need some familiarity with programming in python and an interest in machine learning, but a physics background is not required. In this project the student will be able to contribute to fundamental physics research and will familiarize themselves with state-of-the-art machine learning models.<br />
<br />
Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
=== ATLAS: New machine learning approaches to target Higgs interference signatures in LHC data ===<br />
In this project we aim to improve an ongoing analysis to determine the lifetime of the Higgs Boson through state-of-the-art machine learning techniques, in particular by addressing a ''novel solution to an as of yet unsolved fundamental problem in modeling quantum interference''. While the Higgs is an elusive particle that generally only appears in physics processes with small cross sections, its signature can be amplified in the Large Hadron Collider (LHC) through quantum interference with larger background (non-Higgs) processes. This is the effect that the Higgs’ lifetime analysis relies on to be able to measure the relevant Higgs signature. A fundamental physics modelling problem arises though in the simulation of individual events for this interference due to the fact that these events are in reality described by a superposition of underlying Higgs and non-Higgs processes.<br />
<br />
Since machine learning models in particle physics are typically trained to characterise individual physics events, the fact that interference events cannot currently be generated is a significant problem when interference is the target. In the currently existing Higgs lifetime analysis, a machine learning model was trained which instead focuses only on the explicit Higgs-mediated processes as a proxy, which is suboptimal. The aim of this project is to improve upon this current machine learning strategy used in this analysis by implementing either of the inference-aware approaches suggested in [1] and [2]. The idea behind these inference-aware machine learning algorithms is that they do not optimise for a simplified goal such as the loss function which is common in traditional machine learning, but rather for the end-goal of the analysis. In this case, this would omit the need for interference event generation altogether and allow the machine learning models to be trained optimally regardless.<br />
<br />
The first checkpoint of this project is to use either of the frameworks used in [1] and [2] (which are both publicly available) and run them with a simplified dataset from the aforementioned analysis. After this proof-of-principle is achieved, the next goal would be to actually implement the newly developed machine learning models in the full analysis and to determine the improvement upon the existing result. A successful completion of these tasks would not only benefit the Higgs lifetime analysis, but would be an important stepping stone to future developments to make machine learning approaches also aware of other hard to model effects such as systematic uncertainties. Finally, there are further options to improve this analysis such as the generation of actual interference training data, which could be attempted in case the primary project finishes earlier than expected.<br />
<br />
[1] De Castro, P., & Dorigo, T. (2019). INFERNO: inference-aware neural optimisation. ''Computer Physics Communications'', ''244'', 170-179.<br />
<br />
[2] Simpson, N., & Heinrich, L. (2023, February). neos: End-to-end-optimised summary statistics for high energy physics. In ''Journal of Physics: Conference Series'' (Vol. 2438, No. 1, p. 012105). IOP Publishing.<br />
<br />
Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
=== ATLAS: Development of state-of-the art modeling techniques to generate Higgs interference events ===<br />
In this project we aim to improve an ongoing analysis to determine the lifetime of the Higgs Boson through new event generation strategies, in particular by addressing a novel solution to an as of yet unsolved fundamental problem in modeling quantum interference. While the Higgs is an elusive particle that generally only appears in physics processes with small cross sections, its signature can be amplified in the Large Hadron Collider (LHC) through quantum interference with larger background (non-Higgs) processes. This is the effect that the Higgs’ lifetime analysis relies on to be able to measure the relevant Higgs signature. A fundamental physics modelling problem arises though in the simulation of individual events for this interference due to the fact that these events are in reality described by a superposition of underlying Higgs and non-Higgs processes.<br />
<br />
The current approach to deal with this problem is to ignore the interference in analysis optimization and instead optimize only for explicitly Higgs mediated processes, but this severely impacts analysis performance. In the context of Effective Field Theories (EFT) however, a similar problem arises and has been solved for simple (leading order) processes. In this project we plan to take the machinery developed for EFT and apply it to the Higgs lifetime analysis. Furthermore, with the recent development of a Next-to-Leading Order (NLO) Higgs event generation tool [1] a subsequent goal would be to use this to also generate interference at the NLO level. Successful completion of this project would lead to a much improved analysis result, significantly constraining the lifetime of the Higgs Boson. Besides, the techniques developed would almost certainly be used in future analyses on Large Hadron Collider (LHC) run 3 data.<br />
<br />
[1] Alioli, S., Ravasio, S. F., Lindert, J. M., & Röntsch, R. (2021). Four-lepton production in gluon fusion at NLO matched to parton showers. ''The European Physical Journal C'', ''81''(8), 687.<br />
<br />
Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák], [mailto:b.kortman@nikhef.nl Bryan Kortman] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
=== ATLAS: Approaching the Higgs from a new direction: Constraining new physics with off shell Higgs data from the LHC ===<br />
The Heisenberg uncertainly principle allows for all elementary particles---including the Higgs Boson---to momentarily disobey the fundamental energy-momentum relation, allowing the particle in question to have a significantly larger mass than usual. A description of the Higgs Boson in this state (“off shell Higgs Boson”) can provide a portal to the discovery of potential new physics, albeit very difficult to do due to its infrequent appearance. The goal of this project is to constrain or hint at new physics by estimating parameters of a generalized model which allows for new physics, Effective Field Theory (EFT), using off shell Higgs data.<br />
<br />
Most of the underlying analysis to measure the prevalence of off shell Higgs bosons has already been set up, so the goal of this project is to do the aforementioned EFT interpretation on top of this existing analysis. From a theoretical point of view much of the groundwork has also been done on simulated data which showed the potential for this EFT interpretation to constrain new physics [1]. Being on the interface between experimental and theoretical physics this project allows the student to gain a deeper understanding of both, furthermore its successful completion could be one of the first hints towards as of yet not understood physics.<br />
<br />
[1] Azatov, A., de Blas, J., Falkowski, A., Gritsan, A. V., Grojean, C., Kang, L., ... & Vryonidou, E. (2022). Off-shell Higgs Interpretations Task Force: Models and Effective Field Theories Subgroup Report. arXiv preprint arXiv:2203.02418.<br />
<br />
Contact: ''[mailto:zwolffs@nikhef.nl Zef Wolffs], [mailto:mvozak@cern.ch Matouš Vozák], [mailto:b.kortman@nikhef.nl Bryan Kortman] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
=== ATLAS: A new timing detector - the HGTD ===<br />
The ATLAS is going to get a new ability: a timing detector. This allows us to reconstruct tracks not only in the 3 dimensions of space but adds the ability of measuring very precisely also the time (at picosecond level) at which the particles pass the sensitive layers of the HGTD detector. This allows to construct the trajectories of the particles created at the LHC in 4 dimensions and ultimately will lead to a better reconstruction of physics at ATLAS. The new HGTD detector is still in construction and work needs to be done on different levels such as understanding the detector response (taking measurements in the lab and performing simulations) or developing algorithms to reconstruct the particle trajectories (programming and analysis work). With this work you will be part of the Atlas group and/or the Fast Timing detector group together with the R&D department at Nikhef. <br />
<br />
'''In this project there are two possibilities:''' <br />
<br />
One can choose to either focus on the impact on physics performance by studying how the timing measurements can be included in the reconstruction of tracks, and what effect this has on how much better we can understand the physical processes occurring in the particles produced in the LHC collisions. <br />
<br />
The second possibility is to focus on the working of the fast-timing detectors themselves and participate in measurements in the lab and in test-beam campaigns at CERN. <br />
<br />
If you are interested, contact me to discuss the possibilities. <br />
Contact: ''[mailto:hella.snoek@nikhef.nl Hella Snoek]''<br />
<br />
<br />
=== ATLAS: The next full-silicon Inner Tracker: ITk ===<br />
[[File:ITk endcap structure.jpg|210x210px|thumb|alt=]]The inner detector of the present ATLAS experiment has been designed and developed to function in the environment of the present Large Hadron Collider (LHC). At the ATLAS Phase-II Upgrade, the particle densities and radiation levels will exceed current levels by a factor of ten. The instantaneous luminosity is expected to reach unprecedented values, resulting in up to 200 proton-proton interactions in a typical bunch crossing. The new detectors must be faster and they need to be more highly segmented. The sensors used also need to be far more resistant to radiation, and they require much greater power delivery to the front-end systems. At the same time, they cannot introduce excess material which could undermine tracking performance. For those reasons, the inner tracker of the ATLAS detector (ITk) was redesigned and will be rebuilt completely.<br />
<br />
Nikhef is one of the sites in charge of building and integrating some big parts of ITk. One of the next steps consists of testing the sensors that we will install in the structures we have built (check one of the structures in the picture of our cleanroom). This project offers the possibility of working on a full hardware project, doing something completely new, by testing the sensors of a future component of the next ATLAS detector.<br />
<br />
''Contact'': ''[mailto:aalonso@nikhef.nl Andrea García Alonso]''<br />
<br />
=== Cosmic Rays/Neutrinos: Seasonal muon flux variations and the pion/kaon ratio ===<br />
The KM3NeT ARCA and ORCA detectors, located kilometers deep in the Mediterranean Sea, have neutrinos as primary probes. Muons from cosmic ray interactions reach the detectors in relatively large quantities too. These muons, exploiting the capabilities and location of the detectors allow the study of cosmic rays and their interactions. In this way, questions about their origin, type, propagation can be addressed. In particular these muons are tracers of hadronic interactions at energies inaccessible at particle accelerators.<br />
<br />
The muons reaching the depths of the detectors result from decays of mesons, mostly pions and kaons, created in interactions of high-energy cosmic rays with atoms in the upper atmosphere. Seasonal changes of the temperature – and thus density - profile of the atmosphere modulate the balance between the probability for these mesons to decay (producing muons) or to re-interact. Pions and kaons are affected differently, allowing to extract their production ratio by determining how changes in muon rate depend on changes in the effective temperature – an integral over the atmospheric temperature profile weighted by a depth dependent meson production rate.<br />
<br />
In this project, the aim is to measure the rate of muons in the detectors and to calculate the effective temperature above the KM3NeT detectors from atmospheric data, both as function of time. The relation between these two can be used to extract the pion to kaon ratio.<br />
<br />
''Contact: [mailto:rbruijn@nikhef.nl Ronald Bruijn]''<br />
=== Dark Matter: Building better Dark Matter Detectors - the XAMS R&D Setup===<br />
The Amsterdam Dark Matter group operates an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 0.5kg of ultra-pure liquid xenon in the central volume. We use this detector for the development of new detection techniques - such as utilizing our newly installed silicon photomultipliers - and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENONnT experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory, or for future Dark Matter experiments like DARWIN. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data themselves You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
===Dark Matter: Searching for Dark Matter Particles - XENONnT Data Analysis ===<br />
The XENON collaboration has used the XENON1T detector to achieve the world’s most sensitive direct detection dark matter results and is currently operating the XENONnT successor experiment. The detectors operate at the Gran Sasso underground laboratory and consist of so-called dual-phase xenon time-projection chambers filled with ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the new data coming from the XENONnT detector. The work will consist of understanding the detector signals and applying a deep neural network to improve the (gas-) background discrimination in our Python-based analysis tool to improve the sensitivity for low-mass dark matter particles. The work will continue a study started by a recent graduate. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy.<br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter: Signal reconstruction and correction in XENONnT ===<br />
XENONnT is a low background experiment operating at the INFN - Gran Sasso underground laboratory with the main goal of detecting Dark Matter interactions with xenon target nuclei. The detector, consisting of a dual-phase time projection chamber, is filled with ultra-pure xenon, which acts as a target and detection medium. Understanding the detector's response to various calibration sources is a mandatory step in exploiting the scientific data acquired. This MSc thesis aims to develop new methods to improve the reconstruction and correction of scintillation/ ionization signals from calibration data. The student will work with modern analysis techniques (python-based) and will collaborate with other analysts within the international XENON Collaboration.<br />
<br />
''Contact: [mailto:mpierre@nikhef.nl Maxime Pierre], [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
===Dark Matter: The Ultimate Dark Matter Experiment - DARWIN Sensitivity Studies===<br />
DARWIN is the “ultimate” direct detection dark matter experiment, with the goal to reach the so-called “neutrino floor”, when neutrinos become a hard-to-reduce background. The large and exquisitely clean xenon mass will allow DARWIN to also be sensitive to other physics signals such as solar neutrinos, double-beta decay from Xe-136, axions and axion-like particles etc. While the experiment will only start in 2027, we are in the midst of optimizing the experiment, which is driven by simulations. We have an opening for a student to work on the GEANT4 Monte Carlo simulations for DARWIN. We are also working on a “fast simulation” that could be included in this framework. It is your opportunity to steer the optimization of a large and unique experiment. This project requires good programming skills (Python and C++) and data analysis/physics interpretation skills.<br />
<br />
''Contact: [mailto:t.pollmann@nikhef.nl Tina Pollmann], [mailto:decowski@nikhef.nl Patrick Decowski] or [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter: Exploring new background sources for DARWIN ===<br />
Experiments based on the xenon dual-phase time projection chamber detection technology have already demonstrated their leading role in the search for Dark Matter. The unprecedented low level of background reached by the current generation, such as XENONnT, allows such experiments to be sensitive to new rare-events physics searches, broadening their physics program. The next generation of experiments is already under consideration with the DARWIN observatory, which aims to surpass its predecessors in terms of background level and mass of xenon target. With the increased sensitivity to new physics channels, such as the study of neutrino properties, new sources of backgrounds may arise. This MSc thesis aims to investigate potential new sources of background for DARWIN and is a good opportunity for the student to contribute to the design of the experiment. This project will rely on Monte Carlo simulation tools such as GEANT4 and FLUKA, and good programming skills (Python and C++) are advantageous.<br />
<br />
''Contact: [mailto:mpierre@nikhef.nl Maxime Pierre], [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
===Dark Matter: Sensitive tests of wavelength-shifting properties of materials for dark matter detectors===<br />
Rare event search experiments that look for neutrino and dark matter interactions are performed with highly sensitive detector systems, often relying on scintillators, especially liquid noble gases, to detect particle interactions. Detectors consist of structural materials that are assumed to be optically passive, and light detection systems that use reflectors, light detectors, and sometimes, wavelength-shifting materials. MSc theses are available related to measuring the efficiency of light detection systems that might be used in future detectors. Furthermore, measurements to ensure that presumably passive materials do not fluoresce, at the low level relevant to the detectors, can be done. Part of the thesis work can include Monte Carlo simulations and data analysis for current and upcoming dark matter detectors, to study the effect of different levels of desired and nuisance wavelength shifting. In this project, students will acquire skills in photon detection, wavelength shifting technologies, vacuum systems, UV and extreme-UV optics, detector design, and optionally in Python and C++ programming, data analysis, and Monte Carlo techniques.<br />
<br />
''Contact: [mailto:Tina.Pollmann@tum.de Tina Pollmann]'' <br />
<br />
=== Detector R&D: Studies of wafer-scale sensors for ALICE detector upgrade and beyond ===<br />
One of the biggest milestones of the ALICE detector upgrade (foreseen in 2026) is the implementation of wafer-scale (~ 28 cm x 18 cm) monolithic silicon active pixel sensors in the tracking detector, with the goal of having truly cylindrical barrels around the beam pipe. To demonstrate such an unprecedented technology in high energy physics detectors, few chips will be soon available in Nikhef laboratories for testing and characterization purposes.<br />
The goal of the project is to contribute to the validation of the samples against the ALICE tracking detector requirements, with a focus on timing performance in view of other applications in future high energy physics experiments beyond ALICE.<br />
We are looking for a student with a focus on lab work and interested in high precision measurements with cutting-edge instrumentation. You will be part of the Nikhef Detector R&D group and you will have, at the same time, the chance to work in an international collaboration where you will report about the performance of these novel sensors. There may even be the opportunity to join beam tests at CERN or DESY facilities. Besides interest in hardware, some proficiency in computing is required (Python or C++/ROOT).<br />
<br />
''Contact: [mailto:(jory.sonneveld@nikhef.nl Jory Sonneveld ], [mailto:rrusso@nikhef.nl Roberto Russo]''<br />
<br />
=== Detector R&D: Time resolution of monolithic silicon detectors ===<br />
Monolithic silicon detectors based on industrial Complementary Metal Oxide Semiconductor (CMOS) processes offer a promising approach for large scale detectors due to their ease of production and low material budget. Until recently, their low radiation tolerance has hindered their applicability in high energy particle physics experiments. However, new prototypes ~~such as the one in this project~~ have overcome these hurdles, making them feasible candidates for future experiments in high energy particle physics. Achieving the required radiation tolerance has brought the spatial and temporal resolution of these detectors to the forefront. In this project, you will investigate the temporal performance of a radiation hard monolithic detector prototype, using laser setups in the laboratory. You will also participate in meetings with the international collaboration working on this detector, where you will report on the prototype's performance. Depending on the progress of the work, there may be a chance to participate in test beams performed at the CERN accelerator complex and a first full three dimensional characterization of the prototypes performance using a state-of-the-art two-photon absorption laser setup at Nikhef. This project is looking for someone interested in working hands on with cutting edge detector and laser systems at the Nikhef laboratory. Python programming skills and linux experience are an advantage.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld], [mailto:uwe.kraemer@nikhef.nl Uwe Kraemer]''<br />
<br />
=== Detector R&D: Improving a Laser Setup for Testing Fast Silicon Pixel Detectors ===<br />
For the upgrades of the innermost detectors of experiments at the Large Hadron Collider in Geneva, in particular to cope with the large number of collisions per second from 2027, the Detector R&D group at Nikhef tests new pixel detector prototypes with a variety of laser equipment with several wavelengths. The lasers can be focused down to a small spot to scan over the pixels on a pixel chip. Since the laser penetrates the silicon, the pixels will not be illuminated by just the focal spot, but by the entire three dimensional hourglass or double cone like light intensity distribution. So, how well defined is the volume in which charge is released? And can that be made much smaller than a pixel? And, if so, what would the optimum focus be? For this project the student will first estimate the intensity distribution inside a sensor that can be expected. This will correspond to the density of released charge within the silicon. To verify predictions, you will measure real pixel sensors for the LHC experiments.<br />
This project will involve a lot of 'hands on work' in the lab and involve programming and work on unix machines.<br />
<br />
''Contact: [mailto:martinfr@nikhef.nl Martin Fransen]''<br />
<br />
=== Detector R&D: Time resolution of hybrid pixel detectors with the Timepix4 chip ===<br />
Precise time measurements with silicon pixel detectors are very important for experiments at the High-Luminosity LHC and the future circular collider. The spatial resolution of current silicon trackers will not be sufficient to distinguish the large number of collisions that will occur within individual bunch crossings. In a new method, typically referred to as 4D tracking, spatial measurements of pixel detectors will be combined with time measurements to better distinguish collision vertices that occur close together.<br />
New sensor technologies are being explored to reach the required time measurement resolution of tens of picoseconds, and the results are promising. However, the signals that these pixelated sensors produce have to be processed by front-end electronics, which hence also play a role in the total time resolution of the detector. An important contribution comes from the systematic differences between the front-end electronics of different pixels. Many of these systematic effects can be corrected by performing detailed calibrations of the readout electronics. To achieve the required time resolution at future experiments, it is vital that these effects are understood and corrected.<br />
In this project you will be working with the Timepix4 chip. This is a so-called application specific integrated circuit (ASIC) that is designed to read out pixelated sensors. This ASIC will be used extensively in detector R&D for the characterisation of new sensor technologies requiring precise timing (< 50 ps). In order to do so, it is necessary to first study the systematic differences between the pixels, which you will do using a laser setup in our lab. This will be combined with data analysis of proton beam measurements, or with measurements performed using the built-in test-pulse mechanism of the Timepix4 ASIC. Your work will enable further research performed with this ASIC, <br />
and serve as input to the design and operation of future ASICs for experiments at the High-Luminosity LHC.<br />
<br />
''Contact: [mailto:k.heijhoff@nikhef.nl Kevin Heijhoff] and [mailto:martinb@nikhef.nl Martin van Beuzekom]''<br />
<br />
===Detector R&D: Performance studies of Trench Isolated Low Gain Avalanche Detectors (TI-LGAD) ===<br />
The future vertex detector of the LHCb Experiment needs to measure the spatial coordinates and time of the particles originating in the LHC proton-proton collisions with resolutions better than 10 um and 50 ps, respectively. Several technologies are being considered to achieve these resolutions. Among those is a novel sensor technology called Trench Isolated Low Gain Avalanche Detector. <br />
Prototype pixelated sensors have been manufactured recently and have to be characterised. Therefore these new sensors will be bump bonded to a Timepix4 ASIC which provides charge and time measurements in each of 230 thousand pixels. Characterisation will be done using a lab setup at Nikhef, and includes tests with a micro-focused laser beam, radioactive sources, and possibly with particle tracks obtained in a test-beam. This project involves data taking with these new devices and analysing the data to determine the performance parameters such as the spatial and temporal resolution. as function of temperature and other operational conditions. <br />
<br />
''Contacts: [mailto:kazu.akiba@nikhef.nl Kazu Akiba] and [mailto:martinb@nikhef.nl Martin van Beuzekom]''<br />
<br />
===Detector R&D: A Telescope with Ultrathin Sensors for Beam Tests ===<br />
To measure the performance of new prototypes for upgrades of the LHC experiments and beyond, typically a telescope is used in a beam line of charged particles that can be used to compare the results in the prototype to particle tracks measured with this telescope. In this project, you will continue work on a very lightweight, compact telescope using ALICE PIxel DEtectors (ALPIDEs). This includes work on the mechanics, data acquisition software, and a moveable stage. You will foreseeably test this telescope in the Delft Proton Therapy Center. If time allows, you will add a timing plane and perform a measurement with one of our prototypes. Apart from travel to Delft, there is a possiblity to travel to other beam line facilities.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
===Detector R&D: Other projects ===<br />
Are you looking for a slightly different project? Are the above projects already taken? Are you coming in at an unusual time of the year? Do not hesitate to contact us! We always have new projects coming up at different times in the year and we are open to your ideas.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
===FCC: The Next Collider===<br />
<br />
After the LHC, the next planned large collider at CERN is the proposed 100 kilometer circular collider "FCC". In the first stage of the project, as a high-luminosity electron-positron collider, precision measurements of the Higgs boson are the main goal. One of the channels that will improve by orders of magnitude at this new accelerator is the decay of the Higgs boson to a pair of charm quarks. This project will estimate a projected sensitivity for the coupling of the Higgs boson to second generation quarks, and in particular target the improved reconstruction of the topology of long-lived mesons in the clean environment of a precision e+e- machine.<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
===Gravitational Waves: Computer modelling to design the laser interferometers for the Einstein telescope===<br />
<br />
A new field of instrument science led to the successful detection of gravitational waves by the LIGO detectors in 2015. We are now preparing the next generation of gravitational wave observatories, such as the Einstein Telescope, with the aim to increase the detector sensitivity by a factor of ten, which would allow, for example, to detect stellar-mass black holes from early in the universe when the first stars began to form. This ambitious goal requires us to find ways to significantly improve the best laser interferometers in the world.<br />
<br />
Gravitational wave detectors, such as LIGO and VIRGO, are complex Michelson-type interferometers enhanced with optical cavities. We develop and use numerical models to study these laser interferometers, to invent new optical techniques and to quantify their performance. For example, we synthesize virtual mirror surfaces to study the effects of higher-order optical modes in the interferometers, and we use opto-mechanical models to test schemes for suppressing quantum fluctuations of the light field. We can offer several projects based on numerical modelling of laser interferometers. All projects will be directly linked to the ongoing design of the Einstein Telescope.<br />
<br />
''Contact: [mailto:a.freise@nikhef.nl Andreas Freise]''<br />
<br />
===LHCb: Search for light dark particles===<br />
The Standard Model of elementary particles does not contain a proper Dark Matter candidate. One of the most tantalizing theoretical developments is the so-called ''Hidden Valley models'': a mirror-like copy of the ''Standard Model'', with dark particles that communicate with standard ones via a very feeble interaction. These models predict the existence of ''dark hadrons'' – composite particles that are bound similarly to ordinary hadrons in the ''Standard Model''. Such ''dark hadrons'' can be abundantly produced in high-energy proton-proton collisions, making the LHC a unique place to search for them. Some ''dark hadrons'' are stable like a proton, which makes them excellent ''Dark Matter'' candidates, while others decay to ordinary particles after flying a certain distance in the collider experiment. The LHCb detector has a unique capability to identify such decays, particularly if the new particles have a mass below ten times the proton mass. <br />
<br />
This project assumes a unique search for light ''dark hadrons'' that covers a mass range not accessible to other experiments. It assumes an interesting program on data analysis (python-based) with non-trivial machine learning solutions and phenomenology research using fast simulation framework. Depending on the interest, there is quite a bit of flexibility in the precise focus of the project.<br />
<br />
''Contact: [mailto:andrii.usachov@nikhef.nl Andrii Usachov]''<br />
<br />
===LHCb: Searching for dark matter in exotic six-quark particles===<br />
<br />
Three quarters of the mass in the Universe is of unknown type. Many hypotheses about this dark matter have been proposed, but none confirmed. Recently it has been proposed that it could be made of particles made of the six quarks uuddss, which would be a Standard-Model solution to the dark matter problem. This idea has recently gained credibility as many similar multi-quarks states are being discovered by the LHCb experiment. Such a particle could be produced in decays of heavy baryons, or directly in proton-proton collisions. The anti-particle, made of six antiquarks, could be seen when annihilating with detector material. It is also proposed to use Xi_b baryons produced at LHCb to search for such a state where the state would appear as missing 4-momentum in a kinematically constrained decay. The project consists in defining a selection and applying it to LHCb data. See [https://arxiv.org/abs/2007.10378 arXiv:2007.10378].<br />
<br />
Contact: ''[mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
<br />
===LHCb: Measuring lepton flavour universality with excited Ds states in semileptonic Bs decays===<br />
One of the most striking discrepancies between the Standard Model and measurements are the lepton flavour universality (LFU) measurements with tau decays. At the moment, we have observed an excess of 3-4 sigma in ''B → Dτν'' decays. This could point even to a new force of nature! To understand this discrepancy, we need to make further measurements. <br />
<br />
One very exciting (pun intended) projects to verify these discrepancies involves measuring the ''B<sub>s</sub> → D<sub>s2</sub><sup>*</sup>τν'' and/or ''B<sub>s</sub> → D<sub>s1</sub><sup>*</sup>τν'' decays. These decays with excited states of the ''D<sub>s</sub>'' meson have not been observed before in the tau decay mode, and have a unique way of coupling to potential new physics candidates that can only be measured in ''B<sub>s</sub>'' decays [1]. See slides for more detail: [[File:LHCbLFUwithExcitedDs.pdf|thumb]]<br />
<br />
[1] https://arxiv.org/abs/1606.09300<br />
<br />
''Contact: [mailto:suzannek@nikhef.nl Suzanne Klaver]''<br />
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===LHCb: New physics in the angular distributions of B decays to K*ee===<br />
<br />
Lepton flavour violation in B decays can be explained by a variety of non-standard model interactions. Angular distributions in decays of a B meson to a hadron and two leptons are an important source of information to understand which model is correct. Previous analyses at the LHCb experiment have considered final states with a pair of muons. Our LHCb group at Nikhef concentrates on a new measurement of angular distributions in decays with two electrons. The main challenge in this measurement is the calibration of the detection efficiency. In this project you will confront estimates of the detection efficiency derived from simulation with decay distributions in a well known B decay. Once the calibration is understood, the very first analysis of the angular distributions in the electron final state can be performed. <br />
<br />
Contact: [mailto:m.senghi.soares@nikhef.nl Mara Soares] and [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
<br />
===LHCb: Discovering heavy neutrinos in B decays===<br />
<br />
Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, much heavier, neutral leptons. If the mass of these new neutrinos is below the b-quark mass, they can be observed in B hadron decays.<br />
<br />
In this project we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undiscovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The analysis will be performed within the LHCb group at Nikhef using LHCb run-2 data.<br />
<br />
===LHCb: Scintillating Fibre tracker software===<br />
The installation of the scintillating-fibre tracker in LHCb’s underground cavern was recently completed. This detector uses 10000 km of fibres to track particle trajectories in the LHCb detector when the LHC starts up again later this year. The light emitted by the scintillating fibres when a particle interacts with them is measured using photon multiplier tubes. The studies proposed for this project will focus on software, and could include writing a framework to monitor the detector output, improving the detector simulation or working on the data processing.<br />
<br />
''Contact: [mailto:e.gabriel@nikhef.nl Emmy Gabriel]''<br />
<br />
===LHCb: Vertex detector calibration===<br />
In summer 2022 LHCb has started data taking will an almost entirely new detector. At the point closest to the interaction point, the trajectories of charge particles are reconstructed with a so-called silicon pixel detector. The design hit resolution of this detector is about 15 micron. However, to actually reach this resolution a precise calibration of the spatial positions of the silicon sensors needs to be performed. In this project, you will use the first data of the new LHCb detector to perform this calibration and measure the detector performance.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen]''<br />
<br />
<br />
===Neutrinos: Neutrino scattering: the ultimate resolution===<br />
<br />
Neutrino telescopes like IceCube and KM3NeT aim at detecting neutrinos from cosmic sources. The neutrinos are detected with the best resolution when charged current interactions with nucleons produce a muon, which can be detected with high accuracy (depending on the detector). A crucial ingredient in the ultimate achievable pointing accuracy of neutrino telescopes is the scattering angle between the neutrino and the muon. While published computations have investigated the cross-section of the process in great detail, this important scattering angle has not received much attention. The aim of the project is to compute and characterize the distribution of this angle, and that the ultimate resolution of a neutrino telescope. If successful, the results of this project can lead to publication of interest to the neutrino telescope community.<br />
<br />
Depending on your interests, the study could be based on a first-principles calculation (using the deep-inelastic scattering formalism), include state-of-the-art parton distribution functions, and/or exploit existing event-generation software for a more experimental approach. <br />
<br />
''Contacts: [mailto:aart.heijboer@nikhef.nl Aart Heijboer]''<br />
<br />
===Neutrinos: acoustic detection of ultra-high energy neutrinos===<br />
<br />
The study of the cosmic neutrinos of energies above 1017 eV, the so-called ultra-high energy neutrinos, provides a unique view on the universe and may provide insight in the origin of the most violent astrophysical sources, such as gamma ray bursts, supernovae or even dark matter. In addition, the observation of high energy neutrinos may provide a unique tool to study interactions at high energies. The energy deposition of these extreme neutrinos in water induce a thermo-acoustic signal, which can be detected using sensitive hydrophones. The expected neutrino flux is however extremely low and the signal that neutrinos induce is small. TNO is presently developing sensitive hydrophone technology based on fiber optics. Optical fibers form a natural way to create a distributed sensing system. Using this technology a large scale neutrino telescope can be built in the deep sea. TNO is aiming for a prototype hydrophone which will form the building block of a future telescope.<br />
<br />
The work will be executed at the Nikhef institute and/or the TNO laboratories in Delft. In this project master students have the opportunity to contribute in the following ways:<br />
<br />
'''Project 1:''' Hardware development on fiber optics hydrophones technology Goal: characterize existing prototype optical fibre hydrophones in an anechoic basin at TNO laboratory. Data collection, calibration, characterization, analysis of consequences for design future acoustic hydrophone neutrino telescopes;<br />
Keywords: Optical fiber technology, signal processing, electronics, lab.<br />
<br />
'''Project 2:''' Investigation of ultra-high energy neutrinos and their interactions with matter. Goal: Discriminate the neutrino signals from the background noises, in particular clicks from whales and dolphins in the deep sea. Study impact on physics reach for future acoustic hydrophone neutrino telescopes;<br />
Keywords: Monte Carlo simulations, particle physics, neutrino physics, data analysis algorithms.<br />
<br />
Further information: Info on ultra-high energy neutrinos can be found at: http://arxiv.org/abs/1102.3591; Info on acoustic detection of neutrinos can be found at: http://arxiv.org/abs/1311.7588<br />
<br />
''Contact: [mailto:ernst-jan.buis@tno.nl Ernst Jan Buis]'' or ''[mailto:ivo.van.vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
===Neutrinos: Oscillation analysis with the first data of KM3NeT===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first few strings with sensitive photodetectors have been deployed at both the Italian and the French detector sites. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In this project the available data will be used together with simulations to best reconstruct the event topologies and optimally identify and reconstruct the first neutrino interactions in the KM3NeT detector. The data will then be used to measure neutrino oscillation parameters, and prepare for a future neutrino mass ordering determination.<br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
''Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn] [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
<br />
===Neutrinos: the Deep Underground Neutrino Experiment (DUNE)===<br />
<br />
The Deep Underground Neutrino Experiment (DUNE) is under construction in the USA, and will consist of a powerful neutrino beam originating at Fermilab, a near detector at Fermilab, and a far detector in the SURF facility in Lead, South Dakota, 1300 km away. During travelling, neutrinos oscillate and a fraction of the neutrino beam changes flavour; DUNE will determine the neutrino oscillation parameters to unrivaled precision, and try and make a first detection of CP-violation in neutrinos. In this project, various elements of DUNE can be studied, including the neutrino oscillation fit, neutrino physics with the near detector, event reconstruction and classification (including machine learning), or elements of data selection and triggering.<br />
<br />
''Contact: [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
===Neutrinos: Searching for Majorana Neutrinos with KamLAND-Zen===<br />
The KamLAND-Zen experiment, located in the Kamioka mine in Japan, is a large liquid scintillator experiment with 750kg of ultra-pure Xe-136 to search for neutrinoless double-beta decay (0n2b). The observation of the 0n2b process would be evidence for lepton number violation and the Majorana nature of neutrinos, i.e. that neutrinos are their own anti-particles. Current limits on this extraordinary rare hypothetical decay process are presented as a half-life, with a lower limit of 10^26 years. KamLAND-Zen, the world’s most sensitive 0n2b experiment, is currently taking data and there is an opportunity to work on the data analysis, analyzing data with the possibility of taking part in a ground-breaking discovery. The main focus will be on developing new techniques to filter the spallation backgrounds, i.e. the production of radioactive isotopes by passing muons. There will be close collaboration with groups in the US (MIT, Berkeley, UW) and Japan (Tohoku Univ). <br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
===Neutrinos: relic neutrino detection with PTOLEMY ===<br />
PTOLEMY aims to make the first direct observation of the Big Bang relic neutrinos (the cosmic neutrino background, CνB) by resolving the β-decay endpoint of atomic tritium (neutrino capture target) to O(meV) precision. This remains an outstanding test of the Standard Model in an expanding universe. Not only does the CνB carry with it a signal from the hot dense universe only one second after the Big Bang but helps to constrain the balance of hot versus cold dark matter responsible for its evolution. In doing so, the PTOLEMY experiment would also measure the lowest neutrino mass, an as-of-yet unknown fundamental constant. The experiment is currently in the prototyping phase and the group at Nikhef is responsible for developing the radio-frequency (RF) system used for cyclotron radiation (CR) based trigger and tracking. This component will provide the trajectory of electrons entering the novel transverse drift filter, constraining the electrons' energy losses before they reach the cryogenic calorimeter which in turn records their final energy. The focus of this project will be modelling CR and its detection for the purposes of single electron spectroscopy and optimised trajectory reconstruction. There is also the opportunity to test hardware and readout electronics for the prototype RF-system. <br />
''Contact: [mailto:jmead@nikhef.nl James Vincent Mead]''<br />
<br />
=== Theoretical Particle Physics: Effective Field Theories of Particle Physics from low- to high-energies===<br />
Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations” seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature. The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Standard Model Effective Field Theory (SMEFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes with minimal assumptions on the nature of an eventual UV-complete theory that replaces the Standard Model. Specifically, the goal is to connect measurements from ATLAS, CMS, and LHCb experiments at the CERN's LHC among them and to jointly interpret this information with that provided by other experiments including very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
<br />
This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories. Depending on the student profile, sub-projects with a strong computational and/or machine learning component are also possible, for instance to construct new operators with optimal sensitivity to New Physics effects as encoded by the SMEFT higher-dimensional operators. Topics that can be considered in this project include the interpretation of novel physical observables at the LHC and their integration into the global SMEFiT analysis, matching of EFTs to UV-complete theories and their phenomenological analyses, projections for the impact in the SMEFT parameter space of data for future colliders, the synergies between EFT studies and proton structure fits, and the matching to the Weak Effective Field Theory to include data on flavour observables such as B-meson decays.<br />
<br />
References: https://arxiv.org/abs/2105.00006 , https://arxiv.org/abs/2302.06660, https://arxiv.org/abs/2211.02058 , https://arxiv.org/abs/1901.05965 , https://arxiv.org/abs/1906.05296 , https://arxiv.org/abs/1908.05588, https://arxiv.org/abs/1905.05215. see also this [https://www.dropbox.com/s/30co188f1almzq2/rojo-GRAPPA-MSc-2023.pdf?dl=0 project description].<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theoretical Particle Physics: High-energy neutrino-nucleon interactions at the Forward Physics Facility ===<br />
High-energy collisions at the High-Luminosity Large Hadron Collider (HL-LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing experiments. The proposed Forward Physics Facility (FPF) to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe Standard Model (SM) processes and search for physics beyond the Standard Model (BSM). High statistics neutrino detection will provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. The FPF has the promising potential to probe our understanding of the strong interactions as well as of proton and nuclear structure, providing access to both the very low-x and the very high-x regions of the colliding protons. The former regime is sensitive to novel QCD production mechanisms, such as BFKL effects and non-linear dynamics, as well as the gluon parton distribution function (PDF) down to x=1e-7, well beyond the coverage of other experiments and providing key inputs for astroparticle physics. In addition, the FPF acts as a neutrino-induced deep-inelastic scattering (DIS) experiment with TeV-scale neutrino beams. The resulting measurements of neutrino DIS structure functions represent a valuable handle on the partonic structure of nucleons and nuclei, particularly their quark flavour separation, that is fully complementary to the charged-lepton DIS measurements expected at the upcoming Electron-Ion Collider (EIC).<br />
<br />
In this project, the student will carry out updated predictions for the neutrino fluxes expected at the FPF, assess the precision with which neutrino cross-sections will be measured, and quantify their impact on proton and nuclear structure by means of machine learning tools within the NNPDF framework and state-of-the-art calculations in perturbative Quantum Chromodynamics. This project contributes to ongoing work within the FPF Initiative towards a Conceptual Design Report (CDR) to be presented within two years. Topics that can be considered as part of this project include the assessment of to which extent nuclear modifications of the free-proton PDFs can be constrained by FPF measurements, the determination of the small-x gluon PDF from suitably defined observables at the FPF and the implications for ultra-high-energy particle astrophysics, the study of the intrinsic charm content in the proton and its consequences for the FPF physics program, and the validation of models for neutrino-nucleon cross-sections in the region beyond the validity of perturbative QCD.<br />
<br />
References: https://arxiv.org/abs/2203.05090, https://arxiv.org/abs/2109.10905 ,https://arxiv.org/abs/2208.08372 , https://arxiv.org/abs/2201.12363 , https://arxiv.org/abs/2109.02653, https://github.com/NNPDF/ <br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theoretical Particle Physics: Probing the origin of the proton spin with machine learning===<br />
At energy-frontier facilities such as the Large Hadron Collider (LHC), scientists study the laws of nature in their quest for novel phenomena both within and beyond the Standard Model of particle physics. An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions from the nature of the Higgs boson to the origin of cosmic neutrinos. The key to address some of these questions is by carrying out an universal analysis of nucleon structure from the simultaneous determination of the momentum and spin distributions of quarks and gluons and their fragmentation into hadrons. This effort requires combining an extensive experimental dataset and cutting-edge theory calculations within a machine learning framework where neural networks parametrise the underlying physical laws while minimising ad-hoc model assumptions. The upcoming Electron Ion Collider (EIC), to start taking data in 2029, will be the world's first ever polarised lepton-hadron collider and will offer a plethora of opportunities to address key open questions in our understanding of the strong nuclear force, such as the origin of the mass and the intrinsic angular momentum (spin) of hadrons and whether there exists a state of matter which is entirely dominated by gluons. To fully exploit this scientific potential, novel analysis methodologies need to be develop that make it possible to carry out large-scale, coherent interpretations of measurements from the EIC and other high-energy colliders.<br />
<br />
In this project, the student will carry out a new global analysis of the spin structure of the proton by means of the machine learning tools provided by the NNPDF open-source fitting framework and state-of-the-art calculations in perturbative Quantum Chromodynamics, and integrate it within the corresponding global NNPDF analyses of unpolarised proton and nuclear structure in the framework of a combined integrated global analysis of non-perturbative QCD. Specifically, the project aims to realise a NNLO global fit of polarised quark and gluon PDFs that combines all available data and state-of-the-art perturbative QCD calculations, and study the phenomenological implications for other experiments, including the EIC, for the spin content of the proton, for comparisons with lattice QCD calculations, and for nonpperturbative models of hadron structure.<br />
<br />
References: https://arxiv.org/abs/2201.12363, https://arxiv.org/abs/2109.02653 , https://arxiv.org/abs/2103.05419, https://arxiv.org/abs/1404.4293 , https://inspirehep.net/literature/1302398, https://github.com/NNPDF/<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
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== Finished master projects ==<br />
<br />
See: <br />
* https://wiki.nikhef.nl/education/Master_Theses<br />
* https://www.nikhef.nl/master-theses-2021/<br />
* https://www.nikhef.nl/facts-figures-2020/master-theses-2020/<br />
<br />
<br />
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<br />
[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=871Master Projects2023-02-19T09:35:34Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
== Projects with a 2023 start ==<br />
<br />
=== ALICE: The next-generation multi-purpose detector at the LHC ===<br />
This main goal of this project is to focus on the next-generation multi-purpose detector planned to be built at the LHC. Its core will be a nearly massless barrel detector consisting of truly cylindrical layers based on curved wafer-scale ultra-thin silicon sensors with MAPS technology, featuring an unprecedented low material budget of 0.05% X0 per layer, with the innermost layers possibly positioned inside the beam pipe. The proposed detector is conceived for studies of pp, pA and AA collisions at luminosities a factor of 20 to 50 times higher than possible with the upgraded ALICE detector, enabling a rich physics program ranging from measurements with electromagnetic probes at ultra-low transverse momenta to precision physics in the charm and beauty sector. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli] and [mailto:marco.van.leeuwen@cern.ch Marco van Leeuwen]''<br />
<br />
=== ALICE: Searching for the strongest magnetic field in nature ===<br />
In a non-central collision between two Pb ions, with a large value of impact parameter, the charged nucleons that do not participate in the interaction (called spectators) create strong magnetic fields. A back of the envelope calculation using the Biot-Savart law brings the magnitude of this filed close to 10^19Gauss in agreement with state of the art theoretical calculation, making it the strongest magnetic field in nature. The presence of this field could have direct implications in the motion of final state particles. The magnetic field, however, decays rapidly. The decay rate depends on the electric conductivity of the medium which is experimentally poorly constrained. Overall, the presence of the magnetic field, the main goal of this project, is so far not confirmed experimentally.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Looking for parity violating effects in strong interactions ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions, in the presence of a deconfined state, gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, what is called the Chiral Magnetic Effect (CME).<br />
The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, however further studies are needed to constrain background effects. These highly anticipated results have the potential to reveal exiting, new physics.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Machine learning techniques as a tool to study the production of heavy flavour particles ===<br />
There was recently a shift in the field of heavy-ion physics triggered by experimental results obtained in collisions between small systems (e.g. protons on protons). These results resemble the ones obtained in collisions between heavy ions. This consequently raises the question of whether we create the smallest QGP droplet in collisions between small systems. The main objective of this project will be to study the production of charm particles such as D-mesons and Λc-baryons in pp collisions at the LHC. This will be done with the help of a new and innovative technique which is based on machine learning (ML). The student will also extend the studies to investigate how this production rate depends on the event activity e.g. on how many particles are created after every collision.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli]''<br />
<br />
===ATLAS: The Higgs boson's self-coupling===<br />
<br />
The coupling of the Higgs boson to itself is one of the main unobserved interactions of the Standard Model and its observation is crucial to understand the shape of the Higgs potential. Here we propose to study the 'ttHH' final state: two top quarks and two Higgs bosons produced in a single collision. This topology is yet unexplored at the ATLAS experiment and the project consists of setting up the new analysis (including multivariate analysis techniques to recognise the complicated final state), optimising the sensitivity and including the result in the full ATLAS study of the Higgs boson's coupling to itself. With the LHC data from the upcoming Run-3, we might be able to see its first glimpses! <br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
===ATLAS: The Next Generation===<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks is very new [1] and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays) and advanced analysis techiques (using deep learning methods).<br />
<br />
[https://atlas.cern/updates/briefing/charming-Higgs-decay][https://arxiv.org/abs/1802.04329 https://atlas.cern/updates/briefing/charming-Higgs-decay]<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
===ATLAS: Searching for new particles in very energetic diboson production===<br />
<br />
The discovery of new phenomena in high-energy proton–proton collisions is one of the main goals of the Large Hadron Collider (LHC). New heavy particles decaying into a pair of vector bosons (WW, WZ, ZZ) are predicted in several extensions to the Standard Model (e.g. extended gauge-symmetry models, Grand Unified theories, theories with warped extra dimensions, etc). In this project we will investigate new ideas to look for these resonances in a region that is yet unexplored in the data. We will focus on the final states where both vector bosons decay into quarks as they are expected to bring the highest sensitivity [1]. We will try to reconstruct and exploit new ways to identify vector bosons (using machine learning methods) and then tackle the problem of estimating contributions from beyond the Standard Model processes in the tails of the mass distribution.<br />
<br />
[1] https://arxiv.org/abs/1906.08589<br />
<br />
''Contact: [mailto:f.dias@nikhef.nl Flavia de Almeida Dias]''<br />
<br />
===ATLAS top-quark and Higgs-boson analysis combination, and Effective Field Theory interpretation===<br />
<br />
We are looking for a master student with interest in theory and data-analysis in the search for physics beyond the Standard Model in the top-quark and Higgs-boson sectors.<br />
<br />
Your master-project starts just at the right time for preparing the Run-3 analysis of the ATLAS experiment at the LHC. In Run-3 (2022-2026), three times more data becomes available, enabling analysis of rare processes with innovative software tools and techniques.<br />
<br />
This project aims to explore the newest strategy to combine the top-quark and Higgs-boson measurements in the perspective of constraining the existence of new physics beyond the Standard Model (SM) of Particle Physics. We selected the pp->tZq and gg->HZ processes as promising candidates for a combination to constrain new physics in the context of Standard Model Effective Field Theory (SMEFT). SMEFT is the state-of-the-art framework for theoretical interpretation of LHC data. In particular, you will study the SMEFT OtZ and Ophit operators, which are not well constrained by current measurements.<br />
<br />
Besides affinity with particle physics theory, the ideal candidate for this project has developed python/C++ skills and is eager to learn advanced techniques. You start with a simulation of the signal and background samples using existing software tools. Then, an event selection study is required using Machine Learning techniques. To evaluate the SMEFT effects, a fitting procedure based on the innovative Morphing technique is foreseen, for which the basic tools in the ROOT and RooFit framework are available. The work is carried out in the ATLAS group at Nikhef and may lead to an ATLAS note.<br />
<br />
''Contact: [mailto:geoffrey.gilles@cern.ch> Geoffrey Gilles] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:h73@nikhef.nl Marcel Vreeswijk]''<br />
<br />
=== ATLAS Machine learning to enhance reconstruction of very rare Higgs decays ===<br />
Since the Higgs boson discovery in 2012 at the ATLAS experiment, the investigation of the properties of the Higgs boson has been a priority for research at the Large Hadron Collider (LHC). However, there are still a many open questions: Is the Higgs boson the only origin of Electroweak Symmetry Breaking? Is there a mechanism which can explain the observed mass pattern of SM particles? Many of these questions are linked to the Higgs boson coupling structure. <br />
<br />
While the Higgs boson coupling to fermions of the third generation has been clearly, the investigation of the Higgs boson coupling to the light fermions of the second generation will be a major project for the upcoming data-taking period starting this year. The Higgs boson decay to muons is most sensitive channel to establish a coupling of the Higgs boson to second generation fermions. In this project you will work on an improvement of the H-->mumu search: In about 5% of the events, a photon is radiated off the outgoing muons. By recognizing these photons and taking their effect into account we can improve the reconstruct these events better. For this project we will use machine learning to best identify these special events and to take their energy contribution into account to improve the overall sensitivity. <br />
<br />
''Contact: [mailto:oliver.rieger@nikhef.nl Oliver Rieger] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:s01@nikhef.nl Peter Kluit]''<br />
<br />
=== ATLAS: Scrutinising Higgs decaying into W bosons ===<br />
Observation of the Higgs boson happened 10 years ago and since then scientists’ interest has shifted towards measuring precisely its properties. An example is a coupling strength telling us how does the Higgs boson interact with different particles such as W bosons. Measuring H→ WW →lnu lnu process allows us to not only probe the Standard Model (SM), by measuring the coupling strength or indirectly probe Higgs boson width, but also test against the theories beyond (for instance in the context of the effective field theory framework).<br />
<br />
The student will take active part in the ATLAS HWW group. There are multiple possible areas of contribution within the group depending on the interest of the student. For instance, utilising machine learning techniques to optimise for the selection of HWW signal process, determining the fake background processes, interpreting the results through the beyond SM theories and others.<br />
Contact: ''[mailto:mvozak@cern.ch Matouš Vozák] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
=== ATLAS: HGTD detector ===<br />
The ATLAS is going to get a new ability: a Timing Layer. This allows us to reconstruct tracks not only in the 3 dimensions of space but adds the ability of measuring very precisely also the time (at picosecond level) at which the particles pass the sensitive layers of the HGTD detector. This allow to construct the trajectories of the particles created at the LHC in 4 dimensions and ultimately will lead to a better reconstruction of physics at ATLAS. The new HGTD detector is still in construction and work needs to be done on different levels such as understanding the detector response (taking measurements in the lab and performing simulations) or developing algorithms to reconstruct the particle trajectories (programming and analysis work). With this work you will be part of the Atlas group and/or the Fast Timing detector group together with the R&D department at Nikhef. <br />
<br />
Contact me to discuss the possibilities. <br />
Contact: ''[mailto:hella.snoek@nikhef.nl Hella Snoek]''<br />
<br />
=== Cosmic Rays/Neutrinos: Seasonal muon flux variations and the pion/kaon ratio ===<br />
The KM3NeT ARCA and ORCA detectors, located kilometers deep in the Mediterranean Sea, have neutrinos as primary probes. Muons from cosmic ray interactions reach the detectors in relatively large quantities too. These muons, exploiting the capabilities and location of the detectors allow the study of cosmic rays and their interactions. In this way, questions about their origin, type, propagation can be addressed. In particular these muons are tracers of hadronic interactions at energies inaccessible at particle accelerators.<br />
<br />
The muons reaching the depths of the detectors result from decays of mesons, mostly pions and kaons, created in interactions of high-energy cosmic rays with atoms in the upper atmosphere. Seasonal changes of the temperature – and thus density - profile of the atmosphere modulate the balance between the probability for these mesons to decay (producing muons) or to re-interact. Pions and kaons are affected differently, allowing to extract their production ratio by determining how changes in muon rate depend on changes in the effective temperature – an integral over the atmospheric temperature profile weighted by a depth dependent meson production rate.<br />
<br />
In this project, the aim is to measure the rate of muons in the detectors and to calculate the effective temperature above the KM3NeT detectors from atmospheric data, both as function of time. The relation between these two can be used to extract the pion to kaon ratio.<br />
<br />
''Contact: [mailto:rbruijn@nikhef.nl Ronald Bruijn]''<br />
=== Dark Matter: Building better Dark Matter Detectors - the XAMS R&D Setup===<br />
The Amsterdam Dark Matter group operates an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 0.5kg of ultra-pure liquid xenon in the central volume. We use this detector for the development of new detection techniques - such as utilizing our newly installed silicon photomultipliers - and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENONnT experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory, or for future Dark Matter experiments like DARWIN. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data themselves You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
===Dark Matter: Searching for Dark Matter Particles - XENONnT Data Analysis ===<br />
The XENON collaboration has used the XENON1T detector to achieve the world’s most sensitive direct detection dark matter results and is currently operating the XENONnT successor experiment. The detectors operate at the Gran Sasso underground laboratory and consist of so-called dual-phase xenon time-projection chambers filled with ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the new data coming from the XENONnT detector. The work will consist of understanding the detector signals and applying a deep neural network to improve the (gas-) background discrimination in our Python-based analysis tool to improve the sensitivity for low-mass dark matter particles. The work will continue a study started by a recent graduate. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy.<br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
===Dark Matter: The Ultimate Dark Matter Experiment - DARWIN Sensitivity Studies===<br />
DARWIN is the “ultimate” direct detection dark matter experiment, with the goal to reach the so-called “neutrino floor”, when neutrinos become a hard-to-reduce background. The large and exquisitely clean xenon mass will allow DARWIN to also be sensitive to other physics signals such as solar neutrinos, double-beta decay from Xe-136, axions and axion-like particles etc. While the experiment will only start in 2027, we are in the midst of optimizing the experiment, which is driven by simulations. We have an opening for a student to work on the GEANT4 Monte Carlo simulations for DARWIN. We are also working on a “fast simulation” that could be included in this framework. It is your opportunity to steer the optimization of a large and unique experiment. This project requires good programming skills (Python and C++) and data analysis/physics interpretation skills.<br />
<br />
''Contact: [mailto:t.pollmann@nikhef.nl Tina Pollmann], [mailto:decowski@nikhef.nl Patrick Decowski] or [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
===Dark Matter: Sensitive tests of wavelength-shifting properties of materials for dark matter detectors===<br />
Rare event search experiments that look for neutrino and dark matter interactions are performed with highly sensitive detector systems, often relying on scintillators, especially liquid noble gases, to detect particle interactions. Detectors consist of structural materials that are assumed to be optically passive, and light detection systems that use reflectors, light detectors, and sometimes, wavelength-shifting materials. MSc theses are available related to measuring the efficiency of light detection systems that might be used in future detectors. Furthermore, measurements to ensure that presumably passive materials do not fluoresce, at the low level relevant to the detectors, can be done. Part of the thesis work can include Monte Carlo simulations and data analysis for current and upcoming dark matter detectors, to study the effect of different levels of desired and nuisance wavelength shifting. In this project, students will acquire skills in photon detection, wavelength shifting technologies, vacuum systems, UV and extreme-UV optics, detector design, and optionally in Python and C++ programming, data analysis, and Monte Carlo techniques.<br />
<br />
''Contact: [mailto:Tina.Pollmann@tum.de Tina Pollmann] and [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
=== Detector R&D: Time resolution of ultrathin monolithic timing detectors ===<br />
For the upgrade of ALICE and LHCb vertex detectors, new silicon pixel detectors are being developed now that can register the passing particles with a time precision of tens of picoseconds. ALICE is the first experiment at the LHC to have installed monolithic sensors where electronics is integrated into the sensor. New prototypes of their sensors have arrived at Nikhef. New prototypes of other sensors able to withstand very high radiation fluences of the LHC are arriving soon. In this project, you will tackle the challenge to accurately measure the time resolution of one of these sensors with our laser setups in the laboratory. You will have the chance to work in an international collaboration where you will report about the performance of these novel sensors. There may even be an opportunity to join beam tests at CERN. For this project, we are looking for someone who is interested to work with high-tech sensors and equipment in our Nikhef laboratory and with python programming skills.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
=== Detector R&D: Performance of monolithic sensors for the ALICE upgrade from test beam data ===<br />
For the upgrade of the ALICE detector, ultrathin picosecond timing integrated sensors are being developed now, of which the first prototypes are now at Nikhef and are being studied in test beams at CERN and DESY in Hamburg. Sensors are studied with the ALPIDE (ALICE PIxel DEtector) telescope that uses the same sensors that have recently installed in the heart of the ALICE experiment at CERN. In this project, you will analyze data from beam tests to measure the efficiency and time resolution of the new prototypes for the ALICE upgrade with the latest data from test beams at CERN. If the travel situation allows, you will have the opportunity to join the ALICE test beam group at CERN or in Hamburg at DESY to take part in the exciting experience of taking real data. We are looking for someone with good programming and data analysis skills.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
=== Detector R&D: Modeling radiation damage in silicon sensors ===<br />
In the coming years, the ATLAS experiment at the LHC works on upgrades to prepare for the high-luminosity LHC, where many more collisions will take place than today. Both analysis of data and decisions made in preparation of these detectors and on data taking heavily rely on simulations, especially those that model the damage done to sensors after many collisions. It may sound counterintuitive, but particle detectors do not actually like particles: after many collisions at the LHC, a silicon pixel detector has seen so many particles that its bulk gathers defects. Charge generated by traversing particles can get trapped in defects resulting in less charge induced in the readout electrodes, reducing detector performance in resolution and efficiency. In this project, you will be a member of the international ATLAS collaboration where you will compare different models of radiation damage with measured data. You will learn technology computer aided design (TCAD), widely used in industry, and contribute to the open source program Allpix Squared that is widely used for simulations in many areas of particle physics. Here we are looking for someone with good programming and data analysis skills who would like to contribute to upgrades of collider experiments.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
=== Detector R&D: Fast trigger ===<br />
Muons in cosmic rays are for free! In this project we are not looking for where cosmic rays come from or what physics can be studied with them. Instead, we are using them to test some of our particle detectors. Muons are short lived particles that carry the same charge as electrons, have a high penetrating power and can be detected relatively easy. In practice a test set-up consists of a ‘trigger’ and a device under test. The ‘trigger’ is a detector that gives a signal when a muon passes by, which is a signal to check the result in the device under test. Did the device under test respond to the muon in the expected way? <br />
<br />
For the planned upgrades of particle detectors at CERN, for LHC experiments (LHCb, ATLAS, ALICE, CMS), new particle detectors are under development. Some of these new detectors must be able to measure within tens of ps (10e-12 s) precise when a particle was detected.<br />
<br />
To facilitate testing these new detectors by using muons we need a trigger set up with a matching precision in timing (order tens of ps). We want to investigate several potentially interesting technologies to develop such a fast trigger. In one scenario the trigger could be based on the use of Cherenkov light. Cherenkov light is generated when a charged particle traverses a medium faster than the speed of light in that medium. This light can be generated in for example plexiglass, which in turn can be mounted on top of a light sensor. In our case the light sensor could be a so called silicon photo multiplier, which is capable of detecting only a few photons and gives a signal within a few hundred ps. Another possible scenario would be to use a so called LGAD (Low Gain Avalanche Diode) to measure the signal that a muon generates as it traverses the sensor.<br />
<br />
The Question(s): Which technology should we use for a fast trigger and what is the best timing precision that we can achieve? <br />
<br />
This project will involve a lot of 'hands on work' in the lab. <br />
<br />
''Contact: [mailto:martinfr@nikhef.nl Martin Fransen] and [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
=== Detector R&D: Characterisation of Trench Isolated Low Gain Avalanche Detectors (TI-LGAD) ===<br />
The future vertex detector of the LHCb Experiment needs to measure the spatial coordinates and time of the particles originating in the LHC proton-proton collisions with resolutions better than 10 um and 50 ps, respectively. Several technologies are being considered to achieve these resolutions. Among those is a novel sensor technology called Trench Isolated Low Gain Avalanche Detector. Prototype pixelated sensors have been manufactured recently and have to be characterised. Therefore these new sensors will be bump bonded to a Timepix4 ASIC which provides charge and time measurements in each of 230 thousand pixels. Characterisation will be done using a lab setup at Nikhef, and includes tests with a micro-focused laser beam, radioactive sources, and possibly with particle tracks obtained in a test-beam. This project involves data taking with these new devices and analysing the data to determine the performance parameters such as the spatial and temporal resolution. as function of temperature and other operational conditions.<br />
<br />
''Contacts: [mailto:kazu.akiba@nikhef.nl Kazu Akiba] and [mailto:martinb@nikhef.nl Martin van Beuzekom]''<br />
<br />
=== Detector R&D: Simulation of 3D silicon sensors ===<br />
For the upgrade of the vertex detector of the LHCb experiment novel silicon pixel detectors have to be developed that can register the passing particles with a time precision of tens of picoseconds. Given the harsh radiation environment very close to the LHCb interaction point only a limited number of technologies can be applied. One of the most promising technologies are the so-called 3D sensors whose readout electrodes are pillars that are placed into the sensor perpendicular to the surface; this in contrast to ’standard’ planar silicon sensors where the pixel electrodes are at the surface, similar to the camera in your smartphone. To understand the time response of these 3D sensors, simulations with TCAD software have to be performed and the results will be compared to measured data. These simulations involve the creation/adaptation of the 3D structures of the model, optimising the simulation speed, and analysing the signals as function voltage, track impact point and deposited charge. Hands-on experience with such 3D sensors in the R&D labs at Nikhef is planned within the scope of this project.<br />
<br />
''Contacts: [mailto:martinb@nikhef.nl Martin van Beuzekom] and [mailto:kazu.akiba@nikhef.nl Kazu Akiba]''<br />
<br />
===Detector R&D: Laser Interferometer Space Antenna (LISA) - Wavefront sensors for gravitational wave detection ===<br />
<br />
The space-based gravitational wave antenna LISA is one of the most challenging space missions ever proposed. ESA plans to launch around 2034 three spacecraft separated by a few million kilometres. This constellation measures tiny variations in the distances between test-masses located in each satellite to detect gravitational waves from sources such as supermassive black holes. LISA is based on laser interferometry, and the three satellites form a giant Michelson interferometer. LISA measures a relative phase shift between one local laser and one distant laser by light interference. The phase shift measurement requires sensitive wavefront sensors. The Nikhef DR&D group fabricated prototype sensors in 2020 together with the Photonics industry and the Dutch institute for space research SRON. Nikhef & SRON are responsible for the Quadrant PhotoReceiver (QPR) system: the sensors, the housing including a complex mount to align the sensors with 10's of nanometer accuracy, various environmental tests at the European Space Research and Technology Centre (ESTEC), and the overall performance of the QPR in the LISA instrument. Currently we are discussing possible sensor improvements for a second fabrication run in 2022, optimizing the mechanics and preparing environmental tests. As a MSc student, you will work on various aspects of the wavefront sensor development: study the performance of the epitaxial stacks of Indium-Gallium-Arsenide, setting up test benches to characterize the sensors and QPR system, performing the actual tests and data analysis, in combination with performance studies and simulations of the LISA instrument.<br />
<br />
''Contact: [mailto:nielsvb@nikhef.nl Niels van Bakel]''<br />
<br />
===FCC: The Next Collider===<br />
<br />
After the LHC, the next planned large collider at CERN is the proposed 100 kilometer circular collider "FCC". In the first stage of the project, as a high-luminosity electron-positron collider, precision measurements of the Higgs boson are the main goal. One of the channels that will improve by orders of magnitude at this new accelerator is the decay of the Higgs boson to a pair of charm quarks. This project will estimate a projected sensitivity for the coupling of the Higgs boson to second generation quarks, and in particular target the improved reconstruction of the topology of long-lived mesons in the clean environment of a precision e+e- machine.<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
===Gravitational Waves: Computer modelling to design the laser interferometers for the Einstein telescope===<br />
<br />
A new field of instrument science led to the successful detection of gravitational waves by the LIGO detectors in 2015. We are now preparing the next generation of gravitational wave observatories, such as the Einstein Telescope, with the aim to increase the detector sensitivity by a factor of ten, which would allow, for example, to detect stellar-mass black holes from early in the universe when the first stars began to form. This ambitious goal requires us to find ways to significantly improve the best laser interferometers in the world.<br />
<br />
Gravitational wave detectors, such as LIGO and VIRGO, are complex Michelson-type interferometers enhanced with optical cavities. We develop and use numerical models to study these laser interferometers, to invent new optical techniques and to quantify their performance. For example, we synthesize virtual mirror surfaces to study the effects of higher-order optical modes in the interferometers, and we use opto-mechanical models to test schemes for suppressing quantum fluctuations of the light field. We can offer several projects based on numerical modelling of laser interferometers. All projects will be directly linked to the ongoing design of the Einstein Telescope.<br />
<br />
''Contact: [mailto:a.freise@nikhef.nl Andreas Freise]''<br />
<br />
===LHCb: Search for light dark particles===<br />
The Standard Model of elementary particles does not contain a proper Dark Matter candidate. One of the most tantalizing theoretical developments is the so-called ''Hidden Valley models'': a mirror-like copy of the ''Standard Model'', with dark particles that communicate with standard ones via a very feeble interaction. These models predict the existence of ''dark hadrons'' – composite particles that are bound similarly to ordinary hadrons in the ''Standard Model''. Such ''dark hadrons'' can be abundantly produced in high-energy proton-proton collisions, making the LHC a unique place to search for them. Some ''dark hadrons'' are stable like a proton, which makes them excellent ''Dark Matter'' candidates, while others decay to ordinary particles after flying a certain distance in the collider experiment. The LHCb detector has a unique capability to identify such decays, particularly if the new particles have a mass below ten times the proton mass. <br />
<br />
This project assumes a unique search for light ''dark hadrons'' that covers a mass range not accessible to other experiments. It assumes an interesting program on data analysis (python-based) with non-trivial machine learning solutions and phenomenology research using fast simulation framework. Depending on the interest, there is quite a bit of flexibility in the precise focus of the project.<br />
<br />
''Contact: [mailto:andrii.usachov@nikhef.nl Andrii Usachov]''<br />
<br />
===LHCb: Measuring lepton flavour universality with excited Ds states in semileptonic Bs decays===<br />
One of the most striking discrepancies between the Standard Model and measurements are the lepton flavour universality (LFU) measurements with tau decays. At the moment, we have observed an excess of 3-4 sigma in ''B → Dτν'' decays. This could point even to a new force of nature! To understand this discrepancy, we need to make further measurements. <br />
<br />
One very exciting (pun intended) projects to verify these discrepancies involves measuring the ''B<sub>s</sub> → D<sub>s2</sub><sup>*</sup>τν'' and/or ''B<sub>s</sub> → D<sub>s1</sub><sup>*</sup>τν'' decays. These decays with excited states of the ''D<sub>s</sub>'' meson have not been observed before in the tau decay mode, and have a unique way of coupling to potential new physics candidates that can only be measured in ''B<sub>s</sub>'' decays [1]. See slides for more detail: [[File:LHCbLFUwithExcitedDs.pdf|thumb]]<br />
<br />
[1] https://arxiv.org/abs/1606.09300<br />
<br />
''Contact: [mailto:suzannek@nikhef.nl Suzanne Klaver]''<br />
<br />
===LHCb: New physics in the angular distributions of B decays to K*ee===<br />
<br />
Lepton flavour violation in B decays can be explained by a variety of non-standard model interactions. Angular distributions in decays of a B meson to a hadron and two leptons are an important source of information to understand which model is correct. Previous analyses at the LHCb experiment have considered final states with a pair of muons. Our LHCb group at Nikhef concentrates on a new measurement of angular distributions in decays with two electrons. The main challenge in this measurement is the calibration of the detection efficiency. In this project you will confront estimates of the detection efficiency derived from simulation with decay distributions in a well known B decay. Once the calibration is understood, the very first analysis of the angular distributions in the electron final state can be performed. <br />
<br />
Contact: [mailto:m.senghi.soares@nikhef.nl Mara Soares] and [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
<br />
===LHCb: Discovering heavy neutrinos in B decays===<br />
<br />
Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, much heavier, neutral leptons. If the mass of these new neutrinos is below the b-quark mass, they can be observed in B hadron decays.<br />
<br />
In this project we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undiscovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The analysis will be performed within the LHCb group at Nikhef using LHCb run-2 data.<br />
<br />
''Contact: [mailto:v.lukashenko@nikhef.nl Lera Lukashenko] and'' [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
===LHCb: The exotic 4-quark state X(3872) in exclusive production===<br />
The nature of the X(3872) is still unknown. Is it a regular charmonium with an unexpected mass, a compact 4-quark state, or a DD molecule? Or a quantum superposition of all that? Either way, finding out will tell us something about how quark organise in hadrons and colour confinement. The project is to measure a very peculiar production mode: pp->Xpp. Only the X is seen in the detector and nothing else. Data from LHCb run 2 will be used and the analysis will build on previous work. <br />
<br />
''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
<br />
===LHCb: Scintillating Fibre tracker software===<br />
The installation of the scintillating-fibre tracker in LHCb’s underground cavern was recently completed. This detector uses 10000 km of fibres to track particle trajectories in the LHCb detector when the LHC starts up again later this year. The light emitted by the scintillating fibres when a particle interacts with them is measured using photon multiplier tubes. The studies proposed for this project will focus on software, and could include writing a framework to monitor the detector output, improving the detector simulation or working on the data processing.<br />
<br />
''Contact: [mailto:e.gabriel@nikhef.nl Emmy Gabriel]''<br />
<br />
===LHCb: Vertex detector calibration===<br />
In summer 2022 LHCb has started data taking will an almost entirely new detector. At the point closest to the interaction point, the trajectories of charge particles are reconstructed with a so-called silicon pixel detector. The design hit resolution of this detector is about 15 micron. However, to actually reach this resolution a precise calibration of the spatial positions of the silicon sensors needs to be performed. In this project, you will use the first data of the new LHCb detector to perform this calibration and measure the detector performance.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen]''<br />
<br />
<br />
===Neutrinos: Neutrino scattering: the ultimate resolution===<br />
<br />
Neutrino telescopes like IceCube and KM3NeT aim at detecting neutrinos from cosmic sources. The neutrinos are detected with the best resolution when charged current interactions with nucleons produce a muon, which can be detected with high accuracy (depending on the detector). A crucial ingredient in the ultimate achievable pointing accuracy of neutrino telescopes is the scattering angle between the neutrino and the muon. While published computations have investigated the cross-section of the process in great detail, this important scattering angle has not received much attention. The aim of the project is to compute and characterize the distribution of this angle, and that the ultimate resolution of a neutrino telescope. If successful, the results of this project can lead to publication of interest to the neutrino telescope community.<br />
<br />
Depending on your interests, the study could be based on a first-principles calculation (using the deep-inelastic scattering formalism), include state-of-the-art parton distribution functions, and/or exploit existing event-generation software for a more experimental approach. <br />
<br />
''Contacts: [mailto:aart.heijboer@nikhef.nl Aart Heijboer]''<br />
<br />
===Neutrinos: acoustic detection of ultra-high energy neutrinos===<br />
<br />
The study of the cosmic neutrinos of energies above 1017 eV, the so-called ultra-high energy neutrinos, provides a unique view on the universe and may provide insight in the origin of the most violent astrophysical sources, such as gamma ray bursts, supernovae or even dark matter. In addition, the observation of high energy neutrinos may provide a unique tool to study interactions at high energies. The energy deposition of these extreme neutrinos in water induce a thermo-acoustic signal, which can be detected using sensitive hydrophones. The expected neutrino flux is however extremely low and the signal that neutrinos induce is small. TNO is presently developing sensitive hydrophone technology based on fiber optics. Optical fibers form a natural way to create a distributed sensing system. Using this technology a large scale neutrino telescope can be built in the deep sea. TNO is aiming for a prototype hydrophone which will form the building block of a future telescope.<br />
<br />
The work will be executed at the Nikhef institute and/or the TNO laboratories in Delft. In this project master students have the opportunity to contribute in the following ways:<br />
<br />
'''Project 1:''' Hardware development on fiber optics hydrophones technology Goal: characterize existing prototype optical fibre hydrophones in an anechoic basin at TNO laboratory. Data collection, calibration, characterization, analysis of consequences for design future acoustic hydrophone neutrino telescopes;<br />
Keywords: Optical fiber technology, signal processing, electronics, lab.<br />
<br />
'''Project 2:''' Investigation of ultra-high energy neutrinos and their interactions with matter. Goal: Discriminate the neutrino signals from the background noises, in particular clicks from whales and dolphins in the deep sea. Study impact on physics reach for future acoustic hydrophone neutrino telescopes;<br />
Keywords: Monte Carlo simulations, particle physics, neutrino physics, data analysis algorithms.<br />
<br />
Further information: Info on ultra-high energy neutrinos can be found at: http://arxiv.org/abs/1102.3591; Info on acoustic detection of neutrinos can be found at: http://arxiv.org/abs/1311.7588<br />
<br />
''Contact: [mailto:ernst-jan.buis@tno.nl Ernst Jan Buis]'' or ''[mailto:ivo.van.vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
===Neutrinos: Oscillation analysis with the first data of KM3NeT===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first few strings with sensitive photodetectors have been deployed at both the Italian and the French detector sites. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In this project the available data will be used together with simulations to best reconstruct the event topologies and optimally identify and reconstruct the first neutrino interactions in the KM3NeT detector. The data will then be used to measure neutrino oscillation parameters, and prepare for a future neutrino mass ordering determination.<br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
''Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn] [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
<br />
===Neutrinos: the Deep Underground Neutrino Experiment (DUNE)===<br />
<br />
The Deep Underground Neutrino Experiment (DUNE) is under construction in the USA, and will consist of a powerful neutrino beam originating at Fermilab, a near detector at Fermilab, and a far detector in the SURF facility in Lead, South Dakota, 1300 km away. During travelling, neutrinos oscillate and a fraction of the neutrino beam changes flavour; DUNE will determine the neutrino oscillation parameters to unrivaled precision, and try and make a first detection of CP-violation in neutrinos. In this project, various elements of DUNE can be studied, including the neutrino oscillation fit, neutrino physics with the near detector, event reconstruction and classification (including machine learning), or elements of data selection and triggering.<br />
<br />
''Contact: [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
===Neutrinos: Searching for Majorana Neutrinos with KamLAND-Zen===<br />
The KamLAND-Zen experiment, located in the Kamioka mine in Japan, is a large liquid scintillator experiment with 750kg of ultra-pure Xe-136 to search for neutrinoless double-beta decay (0n2b). The observation of the 0n2b process would be evidence for lepton number violation and the Majorana nature of neutrinos, i.e. that neutrinos are their own anti-particles. Current limits on this extraordinary rare hypothetical decay process are presented as a half-life, with a lower limit of 10^26 years. KamLAND-Zen, the world’s most sensitive 0n2b experiment, is currently taking data and there is an opportunity to work on the data analysis, analyzing data with the possibility of taking part in a ground-breaking discovery. The main focus will be on developing new techniques to filter the spallation backgrounds, i.e. the production of radioactive isotopes by passing muons. There will be close collaboration with groups in the US (MIT, Berkeley, UW) and Japan (Tohoku Univ). <br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== Theoretical Particle Physics: Effective Field Theories of Particle Physics from low- to high-energies===<br />
Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations” seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature. The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Standard Model Effective Field Theory (SMEFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes with minimal assumptions on the nature of an eventual UV-complete theory that replaces the Standard Model. Specifically, the goal is to connect measurements from ATLAS, CMS, and LHCb experiments at the CERN's LHC among them and to jointly interpret this information with that provided by other experiments including very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
<br />
This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories. Depending on the student profile, sub-projects with a strong computational and/or machine learning component are also possible, for instance to construct new operators with optimal sensitivity to New Physics effects as encoded by the SMEFT higher-dimensional operators. Topics that can be considered in this project include the interpretation of novel physical observables at the LHC and their integration into the global SMEFiT analysis, matching of EFTs to UV-complete theories and their phenomenological analyses, projections for the impact in the SMEFT parameter space of data for future colliders, the synergies between EFT studies and proton structure fits, and the matching to the Weak Effective Field Theory to include data on flavour observables such as B-meson decays.<br />
<br />
References: https://arxiv.org/abs/2105.00006 , https://arxiv.org/abs/2302.06660, https://arxiv.org/abs/2211.02058 , https://arxiv.org/abs/1901.05965 , https://arxiv.org/abs/1906.05296 , https://arxiv.org/abs/1908.05588, https://arxiv.org/abs/1905.05215<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theoretical Particle Physics: High-energy neutrino-nucleon interactions at the Forward Physics Facility ===<br />
High-energy collisions at the High-Luminosity Large Hadron Collider (HL-LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing experiments. The proposed Forward Physics Facility (FPF) to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe Standard Model (SM) processes and search for physics beyond the Standard Model (BSM). High statistics neutrino detection will provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. The FPF has the promising potential to probe our understanding of the strong interactions as well as of proton and nuclear structure, providing access to both the very low-x and the very high-x regions of the colliding protons. The former regime is sensitive to novel QCD production mechanisms, such as BFKL effects and non-linear dynamics, as well as the gluon parton distribution function (PDF) down to x=1e-7, well beyond the coverage of other experiments and providing key inputs for astroparticle physics. In addition, the FPF acts as a neutrino-induced deep-inelastic scattering (DIS) experiment with TeV-scale neutrino beams. The resulting measurements of neutrino DIS structure functions represent a valuable handle on the partonic structure of nucleons and nuclei, particularly their quark flavour separation, that is fully complementary to the charged-lepton DIS measurements expected at the upcoming Electron-Ion Collider (EIC).<br />
<br />
In this project, the student will carry out updated predictions for the neutrino fluxes expected at the FPF, assess the precision with which neutrino cross-sections will be measured, and quantify their impact on proton and nuclear structure by means of machine learning tools within the NNPDF framework and state-of-the-art calculations in perturbative Quantum Chromodynamics. This project contributes to ongoing work within the FPF Initiative towards a Conceptual Design Report (CDR) to be presented within two years. Topics that can be considered as part of this project include the assessment of to which extent nuclear modifications of the free-proton PDFs can be constrained by FPF measurements, the determination of the small-x gluon PDF from suitably defined observables at the FPF and the implications for ultra-high-energy particle astrophysics, the study of the intrinsic charm content in the proton and its consequences for the FPF physics program, and the validation of models for neutrino-nucleon cross-sections in the region beyond the validity of perturbative QCD.<br />
<br />
References: https://arxiv.org/abs/2203.05090, https://arxiv.org/abs/2109.10905 ,https://arxiv.org/abs/2208.08372 , https://arxiv.org/abs/2201.12363 , https://arxiv.org/abs/2109.02653, https://github.com/NNPDF/ <br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theoretical Particle Physics: Probing the origin of the proton spin with machine learning===<br />
At energy-frontier facilities such as the Large Hadron Collider (LHC), scientists study the laws of nature in their quest for novel phenomena both within and beyond the Standard Model of particle physics. An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions from the nature of the Higgs boson to the origin of cosmic neutrinos. The key to address some of these questions is by carrying out an universal analysis of nucleon structure from the simultaneous determination of the momentum and spin distributions of quarks and gluons and their fragmentation into hadrons. This effort requires combining an extensive experimental dataset and cutting-edge theory calculations within a machine learning framework where neural networks parametrise the underlying physical laws while minimising ad-hoc model assumptions. The upcoming Electron Ion Collider (EIC), to start taking data in 2029, will be the world's first ever polarised lepton-hadron collider and will offer a plethora of opportunities to address key open questions in our understanding of the strong nuclear force, such as the origin of the mass and the intrinsic angular momentum (spin) of hadrons and whether there exists a state of matter which is entirely dominated by gluons. To fully exploit this scientific potential, novel analysis methodologies need to be develop that make it possible to carry out large-scale, coherent interpretations of measurements from the EIC and other high-energy colliders.<br />
<br />
In this project, the student will carry out a new global analysis of the spin structure of the proton by means of the machine learning tools provided by the NNPDF open-source fitting framework and state-of-the-art calculations in perturbative Quantum Chromodynamics, and integrate it within the corresponding global NNPDF analyses of unpolarised proton and nuclear structure in the framework of a combined integrated global analysis of non-perturbative QCD. Specifically, the project aims to realise a NNLO global fit of polarised quark and gluon PDFs that combines all available data and state-of-the-art perturbative QCD calculations, and study the phenomenological implications for other experiments, including the EIC, for the spin content of the proton, for comparisons with lattice QCD calculations, and for nonpperturbative models of hadron structure.<br />
<br />
References: https://arxiv.org/abs/2201.12363, https://arxiv.org/abs/2109.02653 , https://arxiv.org/abs/2103.05419, https://arxiv.org/abs/1404.4293 , https://inspirehep.net/literature/1302398, https://github.com/NNPDF/<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
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<br />
== Finished master projects ==<br />
<br />
See: <br />
* https://wiki.nikhef.nl/education/Master_Theses<br />
* https://www.nikhef.nl/master-theses-2021/<br />
* https://www.nikhef.nl/facts-figures-2020/master-theses-2020/<br />
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[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=870Master Projects2023-02-19T09:33:28Z<p>Rojo@nikhef.nl: /* Theory: Probing the origin of the proton spin with machine learning */</p>
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<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
== Projects with a 2023 start ==<br />
<br />
=== ALICE: The next-generation multi-purpose detector at the LHC ===<br />
This main goal of this project is to focus on the next-generation multi-purpose detector planned to be built at the LHC. Its core will be a nearly massless barrel detector consisting of truly cylindrical layers based on curved wafer-scale ultra-thin silicon sensors with MAPS technology, featuring an unprecedented low material budget of 0.05% X0 per layer, with the innermost layers possibly positioned inside the beam pipe. The proposed detector is conceived for studies of pp, pA and AA collisions at luminosities a factor of 20 to 50 times higher than possible with the upgraded ALICE detector, enabling a rich physics program ranging from measurements with electromagnetic probes at ultra-low transverse momenta to precision physics in the charm and beauty sector. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli] and [mailto:marco.van.leeuwen@cern.ch Marco van Leeuwen]''<br />
<br />
=== ALICE: Searching for the strongest magnetic field in nature ===<br />
In a non-central collision between two Pb ions, with a large value of impact parameter, the charged nucleons that do not participate in the interaction (called spectators) create strong magnetic fields. A back of the envelope calculation using the Biot-Savart law brings the magnitude of this filed close to 10^19Gauss in agreement with state of the art theoretical calculation, making it the strongest magnetic field in nature. The presence of this field could have direct implications in the motion of final state particles. The magnetic field, however, decays rapidly. The decay rate depends on the electric conductivity of the medium which is experimentally poorly constrained. Overall, the presence of the magnetic field, the main goal of this project, is so far not confirmed experimentally.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
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=== ALICE: Looking for parity violating effects in strong interactions ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions, in the presence of a deconfined state, gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, what is called the Chiral Magnetic Effect (CME).<br />
The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, however further studies are needed to constrain background effects. These highly anticipated results have the potential to reveal exiting, new physics.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Machine learning techniques as a tool to study the production of heavy flavour particles ===<br />
There was recently a shift in the field of heavy-ion physics triggered by experimental results obtained in collisions between small systems (e.g. protons on protons). These results resemble the ones obtained in collisions between heavy ions. This consequently raises the question of whether we create the smallest QGP droplet in collisions between small systems. The main objective of this project will be to study the production of charm particles such as D-mesons and Λc-baryons in pp collisions at the LHC. This will be done with the help of a new and innovative technique which is based on machine learning (ML). The student will also extend the studies to investigate how this production rate depends on the event activity e.g. on how many particles are created after every collision.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli]''<br />
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===ATLAS: The Higgs boson's self-coupling===<br />
<br />
The coupling of the Higgs boson to itself is one of the main unobserved interactions of the Standard Model and its observation is crucial to understand the shape of the Higgs potential. Here we propose to study the 'ttHH' final state: two top quarks and two Higgs bosons produced in a single collision. This topology is yet unexplored at the ATLAS experiment and the project consists of setting up the new analysis (including multivariate analysis techniques to recognise the complicated final state), optimising the sensitivity and including the result in the full ATLAS study of the Higgs boson's coupling to itself. With the LHC data from the upcoming Run-3, we might be able to see its first glimpses! <br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
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===ATLAS: The Next Generation===<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks is very new [1] and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays) and advanced analysis techiques (using deep learning methods).<br />
<br />
[https://atlas.cern/updates/briefing/charming-Higgs-decay][https://arxiv.org/abs/1802.04329 https://atlas.cern/updates/briefing/charming-Higgs-decay]<br />
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''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
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===ATLAS: Searching for new particles in very energetic diboson production===<br />
<br />
The discovery of new phenomena in high-energy proton–proton collisions is one of the main goals of the Large Hadron Collider (LHC). New heavy particles decaying into a pair of vector bosons (WW, WZ, ZZ) are predicted in several extensions to the Standard Model (e.g. extended gauge-symmetry models, Grand Unified theories, theories with warped extra dimensions, etc). In this project we will investigate new ideas to look for these resonances in a region that is yet unexplored in the data. We will focus on the final states where both vector bosons decay into quarks as they are expected to bring the highest sensitivity [1]. We will try to reconstruct and exploit new ways to identify vector bosons (using machine learning methods) and then tackle the problem of estimating contributions from beyond the Standard Model processes in the tails of the mass distribution.<br />
<br />
[1] https://arxiv.org/abs/1906.08589<br />
<br />
''Contact: [mailto:f.dias@nikhef.nl Flavia de Almeida Dias]''<br />
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===ATLAS top-quark and Higgs-boson analysis combination, and Effective Field Theory interpretation===<br />
<br />
We are looking for a master student with interest in theory and data-analysis in the search for physics beyond the Standard Model in the top-quark and Higgs-boson sectors.<br />
<br />
Your master-project starts just at the right time for preparing the Run-3 analysis of the ATLAS experiment at the LHC. In Run-3 (2022-2026), three times more data becomes available, enabling analysis of rare processes with innovative software tools and techniques.<br />
<br />
This project aims to explore the newest strategy to combine the top-quark and Higgs-boson measurements in the perspective of constraining the existence of new physics beyond the Standard Model (SM) of Particle Physics. We selected the pp->tZq and gg->HZ processes as promising candidates for a combination to constrain new physics in the context of Standard Model Effective Field Theory (SMEFT). SMEFT is the state-of-the-art framework for theoretical interpretation of LHC data. In particular, you will study the SMEFT OtZ and Ophit operators, which are not well constrained by current measurements.<br />
<br />
Besides affinity with particle physics theory, the ideal candidate for this project has developed python/C++ skills and is eager to learn advanced techniques. You start with a simulation of the signal and background samples using existing software tools. Then, an event selection study is required using Machine Learning techniques. To evaluate the SMEFT effects, a fitting procedure based on the innovative Morphing technique is foreseen, for which the basic tools in the ROOT and RooFit framework are available. The work is carried out in the ATLAS group at Nikhef and may lead to an ATLAS note.<br />
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''Contact: [mailto:geoffrey.gilles@cern.ch> Geoffrey Gilles] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:h73@nikhef.nl Marcel Vreeswijk]''<br />
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=== ATLAS Machine learning to enhance reconstruction of very rare Higgs decays ===<br />
Since the Higgs boson discovery in 2012 at the ATLAS experiment, the investigation of the properties of the Higgs boson has been a priority for research at the Large Hadron Collider (LHC). However, there are still a many open questions: Is the Higgs boson the only origin of Electroweak Symmetry Breaking? Is there a mechanism which can explain the observed mass pattern of SM particles? Many of these questions are linked to the Higgs boson coupling structure. <br />
<br />
While the Higgs boson coupling to fermions of the third generation has been clearly, the investigation of the Higgs boson coupling to the light fermions of the second generation will be a major project for the upcoming data-taking period starting this year. The Higgs boson decay to muons is most sensitive channel to establish a coupling of the Higgs boson to second generation fermions. In this project you will work on an improvement of the H-->mumu search: In about 5% of the events, a photon is radiated off the outgoing muons. By recognizing these photons and taking their effect into account we can improve the reconstruct these events better. For this project we will use machine learning to best identify these special events and to take their energy contribution into account to improve the overall sensitivity. <br />
<br />
''Contact: [mailto:oliver.rieger@nikhef.nl Oliver Rieger] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:s01@nikhef.nl Peter Kluit]''<br />
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=== ATLAS: Scrutinising Higgs decaying into W bosons ===<br />
Observation of the Higgs boson happened 10 years ago and since then scientists’ interest has shifted towards measuring precisely its properties. An example is a coupling strength telling us how does the Higgs boson interact with different particles such as W bosons. Measuring H→ WW →lnu lnu process allows us to not only probe the Standard Model (SM), by measuring the coupling strength or indirectly probe Higgs boson width, but also test against the theories beyond (for instance in the context of the effective field theory framework).<br />
<br />
The student will take active part in the ATLAS HWW group. There are multiple possible areas of contribution within the group depending on the interest of the student. For instance, utilising machine learning techniques to optimise for the selection of HWW signal process, determining the fake background processes, interpreting the results through the beyond SM theories and others.<br />
Contact: ''[mailto:mvozak@cern.ch Matouš Vozák] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
=== ATLAS: HGTD detector ===<br />
The ATLAS is going to get a new ability: a Timing Layer. This allows us to reconstruct tracks not only in the 3 dimensions of space but adds the ability of measuring very precisely also the time (at picosecond level) at which the particles pass the sensitive layers of the HGTD detector. This allow to construct the trajectories of the particles created at the LHC in 4 dimensions and ultimately will lead to a better reconstruction of physics at ATLAS. The new HGTD detector is still in construction and work needs to be done on different levels such as understanding the detector response (taking measurements in the lab and performing simulations) or developing algorithms to reconstruct the particle trajectories (programming and analysis work). With this work you will be part of the Atlas group and/or the Fast Timing detector group together with the R&D department at Nikhef. <br />
<br />
Contact me to discuss the possibilities. <br />
Contact: ''[mailto:hella.snoek@nikhef.nl Hella Snoek]''<br />
=== Dark Matter: Building better Dark Matter Detectors - the XAMS R&D Setup===<br />
The Amsterdam Dark Matter group operates an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 0.5kg of ultra-pure liquid xenon in the central volume. We use this detector for the development of new detection techniques - such as utilizing our newly installed silicon photomultipliers - and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENONnT experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory, or for future Dark Matter experiments like DARWIN. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data themselves You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
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===Dark Matter: Searching for Dark Matter Particles - XENONnT Data Analysis ===<br />
The XENON collaboration has used the XENON1T detector to achieve the world’s most sensitive direct detection dark matter results and is currently operating the XENONnT successor experiment. The detectors operate at the Gran Sasso underground laboratory and consist of so-called dual-phase xenon time-projection chambers filled with ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the new data coming from the XENONnT detector. The work will consist of understanding the detector signals and applying a deep neural network to improve the (gas-) background discrimination in our Python-based analysis tool to improve the sensitivity for low-mass dark matter particles. The work will continue a study started by a recent graduate. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy.<br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
===Dark Matter: The Ultimate Dark Matter Experiment - DARWIN Sensitivity Studies===<br />
DARWIN is the “ultimate” direct detection dark matter experiment, with the goal to reach the so-called “neutrino floor”, when neutrinos become a hard-to-reduce background. The large and exquisitely clean xenon mass will allow DARWIN to also be sensitive to other physics signals such as solar neutrinos, double-beta decay from Xe-136, axions and axion-like particles etc. While the experiment will only start in 2027, we are in the midst of optimizing the experiment, which is driven by simulations. We have an opening for a student to work on the GEANT4 Monte Carlo simulations for DARWIN. We are also working on a “fast simulation” that could be included in this framework. It is your opportunity to steer the optimization of a large and unique experiment. This project requires good programming skills (Python and C++) and data analysis/physics interpretation skills.<br />
<br />
''Contact: [mailto:t.pollmann@nikhef.nl Tina Pollmann], [mailto:decowski@nikhef.nl Patrick Decowski] or [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
===Dark Matter: Sensitive tests of wavelength-shifting properties of materials for dark matter detectors===<br />
Rare event search experiments that look for neutrino and dark matter interactions are performed with highly sensitive detector systems, often relying on scintillators, especially liquid noble gases, to detect particle interactions. Detectors consist of structural materials that are assumed to be optically passive, and light detection systems that use reflectors, light detectors, and sometimes, wavelength-shifting materials. MSc theses are available related to measuring the efficiency of light detection systems that might be used in future detectors. Furthermore, measurements to ensure that presumably passive materials do not fluoresce, at the low level relevant to the detectors, can be done. Part of the thesis work can include Monte Carlo simulations and data analysis for current and upcoming dark matter detectors, to study the effect of different levels of desired and nuisance wavelength shifting. In this project, students will acquire skills in photon detection, wavelength shifting technologies, vacuum systems, UV and extreme-UV optics, detector design, and optionally in Python and C++ programming, data analysis, and Monte Carlo techniques.<br />
<br />
''Contact: [mailto:Tina.Pollmann@tum.de Tina Pollmann] and [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
=== Detector R&D: Time resolution of ultrathin monolithic timing detectors ===<br />
For the upgrade of ALICE and LHCb vertex detectors, new silicon pixel detectors are being developed now that can register the passing particles with a time precision of tens of picoseconds. ALICE is the first experiment at the LHC to have installed monolithic sensors where electronics is integrated into the sensor. New prototypes of their sensors have arrived at Nikhef. New prototypes of other sensors able to withstand very high radiation fluences of the LHC are arriving soon. In this project, you will tackle the challenge to accurately measure the time resolution of one of these sensors with our laser setups in the laboratory. You will have the chance to work in an international collaboration where you will report about the performance of these novel sensors. There may even be an opportunity to join beam tests at CERN. For this project, we are looking for someone who is interested to work with high-tech sensors and equipment in our Nikhef laboratory and with python programming skills.<br />
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''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
=== Detector R&D: Performance of monolithic sensors for the ALICE upgrade from test beam data ===<br />
For the upgrade of the ALICE detector, ultrathin picosecond timing integrated sensors are being developed now, of which the first prototypes are now at Nikhef and are being studied in test beams at CERN and DESY in Hamburg. Sensors are studied with the ALPIDE (ALICE PIxel DEtector) telescope that uses the same sensors that have recently installed in the heart of the ALICE experiment at CERN. In this project, you will analyze data from beam tests to measure the efficiency and time resolution of the new prototypes for the ALICE upgrade with the latest data from test beams at CERN. If the travel situation allows, you will have the opportunity to join the ALICE test beam group at CERN or in Hamburg at DESY to take part in the exciting experience of taking real data. We are looking for someone with good programming and data analysis skills.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
=== Detector R&D: Modeling radiation damage in silicon sensors ===<br />
In the coming years, the ATLAS experiment at the LHC works on upgrades to prepare for the high-luminosity LHC, where many more collisions will take place than today. Both analysis of data and decisions made in preparation of these detectors and on data taking heavily rely on simulations, especially those that model the damage done to sensors after many collisions. It may sound counterintuitive, but particle detectors do not actually like particles: after many collisions at the LHC, a silicon pixel detector has seen so many particles that its bulk gathers defects. Charge generated by traversing particles can get trapped in defects resulting in less charge induced in the readout electrodes, reducing detector performance in resolution and efficiency. In this project, you will be a member of the international ATLAS collaboration where you will compare different models of radiation damage with measured data. You will learn technology computer aided design (TCAD), widely used in industry, and contribute to the open source program Allpix Squared that is widely used for simulations in many areas of particle physics. Here we are looking for someone with good programming and data analysis skills who would like to contribute to upgrades of collider experiments.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
=== Detector R&D: Fast trigger ===<br />
Muons in cosmic rays are for free! In this project we are not looking for where cosmic rays come from or what physics can be studied with them. Instead, we are using them to test some of our particle detectors. Muons are short lived particles that carry the same charge as electrons, have a high penetrating power and can be detected relatively easy. In practice a test set-up consists of a ‘trigger’ and a device under test. The ‘trigger’ is a detector that gives a signal when a muon passes by, which is a signal to check the result in the device under test. Did the device under test respond to the muon in the expected way? <br />
<br />
For the planned upgrades of particle detectors at CERN, for LHC experiments (LHCb, ATLAS, ALICE, CMS), new particle detectors are under development. Some of these new detectors must be able to measure within tens of ps (10e-12 s) precise when a particle was detected.<br />
<br />
To facilitate testing these new detectors by using muons we need a trigger set up with a matching precision in timing (order tens of ps). We want to investigate several potentially interesting technologies to develop such a fast trigger. In one scenario the trigger could be based on the use of Cherenkov light. Cherenkov light is generated when a charged particle traverses a medium faster than the speed of light in that medium. This light can be generated in for example plexiglass, which in turn can be mounted on top of a light sensor. In our case the light sensor could be a so called silicon photo multiplier, which is capable of detecting only a few photons and gives a signal within a few hundred ps. Another possible scenario would be to use a so called LGAD (Low Gain Avalanche Diode) to measure the signal that a muon generates as it traverses the sensor.<br />
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The Question(s): Which technology should we use for a fast trigger and what is the best timing precision that we can achieve? <br />
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This project will involve a lot of 'hands on work' in the lab. <br />
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''Contact: [mailto:martinfr@nikhef.nl Martin Fransen] and [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
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=== Detector R&D: Characterisation of Trench Isolated Low Gain Avalanche Detectors (TI-LGAD) ===<br />
The future vertex detector of the LHCb Experiment needs to measure the spatial coordinates and time of the particles originating in the LHC proton-proton collisions with resolutions better than 10 um and 50 ps, respectively. Several technologies are being considered to achieve these resolutions. Among those is a novel sensor technology called Trench Isolated Low Gain Avalanche Detector. Prototype pixelated sensors have been manufactured recently and have to be characterised. Therefore these new sensors will be bump bonded to a Timepix4 ASIC which provides charge and time measurements in each of 230 thousand pixels. Characterisation will be done using a lab setup at Nikhef, and includes tests with a micro-focused laser beam, radioactive sources, and possibly with particle tracks obtained in a test-beam. This project involves data taking with these new devices and analysing the data to determine the performance parameters such as the spatial and temporal resolution. as function of temperature and other operational conditions.<br />
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''Contacts: [mailto:kazu.akiba@nikhef.nl Kazu Akiba] and [mailto:martinb@nikhef.nl Martin van Beuzekom]''<br />
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=== Detector R&D: Simulation of 3D silicon sensors ===<br />
For the upgrade of the vertex detector of the LHCb experiment novel silicon pixel detectors have to be developed that can register the passing particles with a time precision of tens of picoseconds. Given the harsh radiation environment very close to the LHCb interaction point only a limited number of technologies can be applied. One of the most promising technologies are the so-called 3D sensors whose readout electrodes are pillars that are placed into the sensor perpendicular to the surface; this in contrast to ’standard’ planar silicon sensors where the pixel electrodes are at the surface, similar to the camera in your smartphone. To understand the time response of these 3D sensors, simulations with TCAD software have to be performed and the results will be compared to measured data. These simulations involve the creation/adaptation of the 3D structures of the model, optimising the simulation speed, and analysing the signals as function voltage, track impact point and deposited charge. Hands-on experience with such 3D sensors in the R&D labs at Nikhef is planned within the scope of this project.<br />
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''Contacts: [mailto:martinb@nikhef.nl Martin van Beuzekom] and [mailto:kazu.akiba@nikhef.nl Kazu Akiba]''<br />
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===Detector R&D: Laser Interferometer Space Antenna (LISA) - Wavefront sensors for gravitational wave detection ===<br />
<br />
The space-based gravitational wave antenna LISA is one of the most challenging space missions ever proposed. ESA plans to launch around 2034 three spacecraft separated by a few million kilometres. This constellation measures tiny variations in the distances between test-masses located in each satellite to detect gravitational waves from sources such as supermassive black holes. LISA is based on laser interferometry, and the three satellites form a giant Michelson interferometer. LISA measures a relative phase shift between one local laser and one distant laser by light interference. The phase shift measurement requires sensitive wavefront sensors. The Nikhef DR&D group fabricated prototype sensors in 2020 together with the Photonics industry and the Dutch institute for space research SRON. Nikhef & SRON are responsible for the Quadrant PhotoReceiver (QPR) system: the sensors, the housing including a complex mount to align the sensors with 10's of nanometer accuracy, various environmental tests at the European Space Research and Technology Centre (ESTEC), and the overall performance of the QPR in the LISA instrument. Currently we are discussing possible sensor improvements for a second fabrication run in 2022, optimizing the mechanics and preparing environmental tests. As a MSc student, you will work on various aspects of the wavefront sensor development: study the performance of the epitaxial stacks of Indium-Gallium-Arsenide, setting up test benches to characterize the sensors and QPR system, performing the actual tests and data analysis, in combination with performance studies and simulations of the LISA instrument.<br />
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''Contact: [mailto:nielsvb@nikhef.nl Niels van Bakel]''<br />
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===FCC: The Next Collider===<br />
<br />
After the LHC, the next planned large collider at CERN is the proposed 100 kilometer circular collider "FCC". In the first stage of the project, as a high-luminosity electron-positron collider, precision measurements of the Higgs boson are the main goal. One of the channels that will improve by orders of magnitude at this new accelerator is the decay of the Higgs boson to a pair of charm quarks. This project will estimate a projected sensitivity for the coupling of the Higgs boson to second generation quarks, and in particular target the improved reconstruction of the topology of long-lived mesons in the clean environment of a precision e+e- machine.<br />
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''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
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===LHCb: Search for light dark particles===<br />
The Standard Model of elementary particles does not contain a proper Dark Matter candidate. One of the most tantalizing theoretical developments is the so-called ''Hidden Valley models'': a mirror-like copy of the ''Standard Model'', with dark particles that communicate with standard ones via a very feeble interaction. These models predict the existence of ''dark hadrons'' – composite particles that are bound similarly to ordinary hadrons in the ''Standard Model''. Such ''dark hadrons'' can be abundantly produced in high-energy proton-proton collisions, making the LHC a unique place to search for them. Some ''dark hadrons'' are stable like a proton, which makes them excellent ''Dark Matter'' candidates, while others decay to ordinary particles after flying a certain distance in the collider experiment. The LHCb detector has a unique capability to identify such decays, particularly if the new particles have a mass below ten times the proton mass. <br />
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This project assumes a unique search for light ''dark hadrons'' that covers a mass range not accessible to other experiments. It assumes an interesting program on data analysis (python-based) with non-trivial machine learning solutions and phenomenology research using fast simulation framework. Depending on the interest, there is quite a bit of flexibility in the precise focus of the project.<br />
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''Contact: [mailto:andrii.usachov@nikhef.nl Andrii Usachov]''<br />
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===LHCb: Measuring lepton flavour universality with excited Ds states in semileptonic Bs decays===<br />
One of the most striking discrepancies between the Standard Model and measurements are the lepton flavour universality (LFU) measurements with tau decays. At the moment, we have observed an excess of 3-4 sigma in ''B → Dτν'' decays. This could point even to a new force of nature! To understand this discrepancy, we need to make further measurements. <br />
<br />
One very exciting (pun intended) projects to verify these discrepancies involves measuring the ''B<sub>s</sub> → D<sub>s2</sub><sup>*</sup>τν'' and/or ''B<sub>s</sub> → D<sub>s1</sub><sup>*</sup>τν'' decays. These decays with excited states of the ''D<sub>s</sub>'' meson have not been observed before in the tau decay mode, and have a unique way of coupling to potential new physics candidates that can only be measured in ''B<sub>s</sub>'' decays [1]. See slides for more detail: [[File:LHCbLFUwithExcitedDs.pdf|thumb]]<br />
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[1] https://arxiv.org/abs/1606.09300<br />
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''Contact: [mailto:suzannek@nikhef.nl Suzanne Klaver]''<br />
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===LHCb: New physics in the angular distributions of B decays to K*ee===<br />
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Lepton flavour violation in B decays can be explained by a variety of non-standard model interactions. Angular distributions in decays of a B meson to a hadron and two leptons are an important source of information to understand which model is correct. Previous analyses at the LHCb experiment have considered final states with a pair of muons. Our LHCb group at Nikhef concentrates on a new measurement of angular distributions in decays with two electrons. The main challenge in this measurement is the calibration of the detection efficiency. In this project you will confront estimates of the detection efficiency derived from simulation with decay distributions in a well known B decay. Once the calibration is understood, the very first analysis of the angular distributions in the electron final state can be performed. <br />
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Contact: [mailto:m.senghi.soares@nikhef.nl Mara Soares] and [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
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===LHCb: Discovering heavy neutrinos in B decays===<br />
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Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, much heavier, neutral leptons. If the mass of these new neutrinos is below the b-quark mass, they can be observed in B hadron decays.<br />
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In this project we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undiscovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The analysis will be performed within the LHCb group at Nikhef using LHCb run-2 data.<br />
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''Contact: [mailto:v.lukashenko@nikhef.nl Lera Lukashenko] and'' [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
===LHCb: The exotic 4-quark state X(3872) in exclusive production===<br />
The nature of the X(3872) is still unknown. Is it a regular charmonium with an unexpected mass, a compact 4-quark state, or a DD molecule? Or a quantum superposition of all that? Either way, finding out will tell us something about how quark organise in hadrons and colour confinement. The project is to measure a very peculiar production mode: pp->Xpp. Only the X is seen in the detector and nothing else. Data from LHCb run 2 will be used and the analysis will build on previous work. <br />
<br />
''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
<br />
===LHCb: Scintillating Fibre tracker software===<br />
The installation of the scintillating-fibre tracker in LHCb’s underground cavern was recently completed. This detector uses 10000 km of fibres to track particle trajectories in the LHCb detector when the LHC starts up again later this year. The light emitted by the scintillating fibres when a particle interacts with them is measured using photon multiplier tubes. The studies proposed for this project will focus on software, and could include writing a framework to monitor the detector output, improving the detector simulation or working on the data processing.<br />
<br />
''Contact: [mailto:e.gabriel@nikhef.nl Emmy Gabriel]''<br />
<br />
===LHCb: Vertex detector calibration===<br />
In summer 2022 LHCb has started data taking will an almost entirely new detector. At the point closest to the interaction point, the trajectories of charge particles are reconstructed with a so-called silicon pixel detector. The design hit resolution of this detector is about 15 micron. However, to actually reach this resolution a precise calibration of the spatial positions of the silicon sensors needs to be performed. In this project, you will use the first data of the new LHCb detector to perform this calibration and measure the detector performance.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen]''<br />
<br />
<br />
===Neutrinos: Neutrino scattering: the ultimate resolution===<br />
<br />
Neutrino telescopes like IceCube and KM3NeT aim at detecting neutrinos from cosmic sources. The neutrinos are detected with the best resolution when charged current interactions with nucleons produce a muon, which can be detected with high accuracy (depending on the detector). A crucial ingredient in the ultimate achievable pointing accuracy of neutrino telescopes is the scattering angle between the neutrino and the muon. While published computations have investigated the cross-section of the process in great detail, this important scattering angle has not received much attention. The aim of the project is to compute and characterize the distribution of this angle, and that the ultimate resolution of a neutrino telescope. If successful, the results of this project can lead to publication of interest to the neutrino telescope community.<br />
<br />
Depending on your interests, the study could be based on a first-principles calculation (using the deep-inelastic scattering formalism), include state-of-the-art parton distribution functions, and/or exploit existing event-generation software for a more experimental approach. <br />
<br />
''Contacts: [mailto:aart.heijboer@nikhef.nl Aart Heijboer]''<br />
<br />
===Neutrinos: acoustic detection of ultra-high energy neutrinos===<br />
<br />
The study of the cosmic neutrinos of energies above 1017 eV, the so-called ultra-high energy neutrinos, provides a unique view on the universe and may provide insight in the origin of the most violent astrophysical sources, such as gamma ray bursts, supernovae or even dark matter. In addition, the observation of high energy neutrinos may provide a unique tool to study interactions at high energies. The energy deposition of these extreme neutrinos in water induce a thermo-acoustic signal, which can be detected using sensitive hydrophones. The expected neutrino flux is however extremely low and the signal that neutrinos induce is small. TNO is presently developing sensitive hydrophone technology based on fiber optics. Optical fibers form a natural way to create a distributed sensing system. Using this technology a large scale neutrino telescope can be built in the deep sea. TNO is aiming for a prototype hydrophone which will form the building block of a future telescope.<br />
<br />
The work will be executed at the Nikhef institute and/or the TNO laboratories in Delft. In this project master students have the opportunity to contribute in the following ways:<br />
<br />
'''Project 1:''' Hardware development on fiber optics hydrophones technology Goal: characterize existing prototype optical fibre hydrophones in an anechoic basin at TNO laboratory. Data collection, calibration, characterization, analysis of consequences for design future acoustic hydrophone neutrino telescopes;<br />
Keywords: Optical fiber technology, signal processing, electronics, lab.<br />
<br />
'''Project 2:''' Investigation of ultra-high energy neutrinos and their interactions with matter. Goal: Discriminate the neutrino signals from the background noises, in particular clicks from whales and dolphins in the deep sea. Study impact on physics reach for future acoustic hydrophone neutrino telescopes;<br />
Keywords: Monte Carlo simulations, particle physics, neutrino physics, data analysis algorithms.<br />
<br />
Further information: Info on ultra-high energy neutrinos can be found at: http://arxiv.org/abs/1102.3591; Info on acoustic detection of neutrinos can be found at: http://arxiv.org/abs/1311.7588<br />
<br />
''Contact: [mailto:ernst-jan.buis@tno.nl Ernst Jan Buis]'' or ''[mailto:ivo.van.vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
===Neutrinos: Oscillation analysis with the first data of KM3NeT===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first few strings with sensitive photodetectors have been deployed at both the Italian and the French detector sites. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In this project the available data will be used together with simulations to best reconstruct the event topologies and optimally identify and reconstruct the first neutrino interactions in the KM3NeT detector. The data will then be used to measure neutrino oscillation parameters, and prepare for a future neutrino mass ordering determination.<br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
''Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn] [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
<br />
===Neutrinos: the Deep Underground Neutrino Experiment (DUNE)===<br />
<br />
The Deep Underground Neutrino Experiment (DUNE) is under construction in the USA, and will consist of a powerful neutrino beam originating at Fermilab, a near detector at Fermilab, and a far detector in the SURF facility in Lead, South Dakota, 1300 km away. During travelling, neutrinos oscillate and a fraction of the neutrino beam changes flavour; DUNE will determine the neutrino oscillation parameters to unrivaled precision, and try and make a first detection of CP-violation in neutrinos. In this project, various elements of DUNE can be studied, including the neutrino oscillation fit, neutrino physics with the near detector, event reconstruction and classification (including machine learning), or elements of data selection and triggering.<br />
<br />
''Contact: [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
===Neutrinos: Searching for Majorana Neutrinos with KamLAND-Zen===<br />
The KamLAND-Zen experiment, located in the Kamioka mine in Japan, is a large liquid scintillator experiment with 750kg of ultra-pure Xe-136 to search for neutrinoless double-beta decay (0n2b). The observation of the 0n2b process would be evidence for lepton number violation and the Majorana nature of neutrinos, i.e. that neutrinos are their own anti-particles. Current limits on this extraordinary rare hypothetical decay process are presented as a half-life, with a lower limit of 10^26 years. KamLAND-Zen, the world’s most sensitive 0n2b experiment, is currently taking data and there is an opportunity to work on the data analysis, analyzing data with the possibility of taking part in a ground-breaking discovery. The main focus will be on developing new techniques to filter the spallation backgrounds, i.e. the production of radioactive isotopes by passing muons. There will be close collaboration with groups in the US (MIT, Berkeley, UW) and Japan (Tohoku Univ). <br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== Cosmic Rays/Neutrinos: Seasonal muon flux variations and the pion/kaon ratio ===<br />
The KM3NeT ARCA and ORCA detectors, located kilometers deep in the Mediterranean Sea, have neutrinos as primary probes. Muons from cosmic ray interactions reach the detectors in relatively large quantities too. These muons, exploiting the capabilities and location of the detectors allow the study of cosmic rays and their interactions. In this way, questions about their origin, type, propagation can be addressed. In particular these muons are tracers of hadronic interactions at energies inaccessible at particle accelerators.<br />
<br />
The muons reaching the depths of the detectors result from decays of mesons, mostly pions and kaons, created in interactions of high-energy cosmic rays with atoms in the upper atmosphere. Seasonal changes of the temperature – and thus density - profile of the atmosphere modulate the balance between the probability for these mesons to decay (producing muons) or to re-interact. Pions and kaons are affected differently, allowing to extract their production ratio by determining how changes in muon rate depend on changes in the effective temperature – an integral over the atmospheric temperature profile weighted by a depth dependent meson production rate.<br />
<br />
In this project, the aim is to measure the rate of muons in the detectors and to calculate the effective temperature above the KM3NeT detectors from atmospheric data, both as function of time. The relation between these two can be used to extract the pion to kaon ratio.<br />
<br />
''Contact: [mailto:rbruijn@nikhef.nl Ronald Bruijn]''<br />
<br />
===Gravitational Waves: Computer modelling to design the laser interferometers for the Einstein telescope===<br />
<br />
A new field of instrument science led to the successful detection of gravitational waves by the LIGO detectors in 2015. We are now preparing the next generation of gravitational wave observatories, such as the Einstein Telescope, with the aim to increase the detector sensitivity by a factor of ten, which would allow, for example, to detect stellar-mass black holes from early in the universe when the first stars began to form. This ambitious goal requires us to find ways to significantly improve the best laser interferometers in the world.<br />
<br />
Gravitational wave detectors, such as LIGO and VIRGO, are complex Michelson-type interferometers enhanced with optical cavities. We develop and use numerical models to study these laser interferometers, to invent new optical techniques and to quantify their performance. For example, we synthesize virtual mirror surfaces to study the effects of higher-order optical modes in the interferometers, and we use opto-mechanical models to test schemes for suppressing quantum fluctuations of the light field. We can offer several projects based on numerical modelling of laser interferometers. All projects will be directly linked to the ongoing design of the Einstein Telescope.<br />
<br />
''Contact: [mailto:a.freise@nikhef.nl Andreas Freise]''<br />
<br />
=== Theory: Effective Field Theories of Particle Physics from low- to high-energies===<br />
Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations” seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature. The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Standard Model Effective Field Theory (SMEFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes with minimal assumptions on the nature of an eventual UV-complete theory that replaces the Standard Model. Specifically, the goal is to connect measurements from ATLAS, CMS, and LHCb experiments at the CERN's LHC among them and to jointly interpret this information with that provided by other experiments including very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
<br />
This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories. Depending on the student profile, sub-projects with a strong computational and/or machine learning component are also possible, for instance to construct new operators with optimal sensitivity to New Physics effects as encoded by the SMEFT higher-dimensional operators. Topics that can be considered in this project include the interpretation of novel physical observables at the LHC and their integration into the global SMEFiT analysis, matching of EFTs to UV-complete theories and their phenomenological analyses, projections for the impact in the SMEFT parameter space of data for future colliders, the synergies between EFT studies and proton structure fits, and the matching to the Weak Effective Field Theory to include data on flavour observables such as B-meson decays.<br />
<br />
References: https://arxiv.org/abs/2105.00006 , https://arxiv.org/abs/2302.06660, https://arxiv.org/abs/2211.02058 , https://arxiv.org/abs/1901.05965 , https://arxiv.org/abs/1906.05296 , https://arxiv.org/abs/1908.05588, https://arxiv.org/abs/1905.05215<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theory: High-energy neutrino-nucleon interactions at the Forward Physics Facility ===<br />
High-energy collisions at the High-Luminosity Large Hadron Collider (HL-LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing experiments. The proposed Forward Physics Facility (FPF) to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe Standard Model (SM) processes and search for physics beyond the Standard Model (BSM). High statistics neutrino detection will provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. The FPF has the promising potential to probe our understanding of the strong interactions as well as of proton and nuclear structure, providing access to both the very low-x and the very high-x regions of the colliding protons. The former regime is sensitive to novel QCD production mechanisms, such as BFKL effects and non-linear dynamics, as well as the gluon parton distribution function (PDF) down to x=1e-7, well beyond the coverage of other experiments and providing key inputs for astroparticle physics. In addition, the FPF acts as a neutrino-induced deep-inelastic scattering (DIS) experiment with TeV-scale neutrino beams. The resulting measurements of neutrino DIS structure functions represent a valuable handle on the partonic structure of nucleons and nuclei, particularly their quark flavour separation, that is fully complementary to the charged-lepton DIS measurements expected at the upcoming Electron-Ion Collider (EIC).<br />
<br />
In this project, the student will carry out updated predictions for the neutrino fluxes expected at the FPF, assess the precision with which neutrino cross-sections will be measured, and quantify their impact on proton and nuclear structure by means of machine learning tools within the NNPDF framework and state-of-the-art calculations in perturbative Quantum Chromodynamics. This project contributes to ongoing work within the FPF Initiative towards a Conceptual Design Report (CDR) to be presented within two years. Topics that can be considered as part of this project include the assessment of to which extent nuclear modifications of the free-proton PDFs can be constrained by FPF measurements, the determination of the small-x gluon PDF from suitably defined observables at the FPF and the implications for ultra-high-energy particle astrophysics, the study of the intrinsic charm content in the proton and its consequences for the FPF physics program, and the validation of models for neutrino-nucleon cross-sections in the region beyond the validity of perturbative QCD.<br />
<br />
References: https://arxiv.org/abs/2203.05090, https://arxiv.org/abs/2109.10905 ,https://arxiv.org/abs/2208.08372 , https://arxiv.org/abs/2201.12363 , https://arxiv.org/abs/2109.02653, https://github.com/NNPDF/ <br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theory: Probing the origin of the proton spin with machine learning===<br />
At energy-frontier facilities such as the Large Hadron Collider (LHC), scientists study the laws of nature in their quest for novel phenomena both within and beyond the Standard Model of particle physics. An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions from the nature of the Higgs boson to the origin of cosmic neutrinos. The key to address some of these questions is by carrying out an universal analysis of nucleon structure from the simultaneous determination of the momentum and spin distributions of quarks and gluons and their fragmentation into hadrons. This effort requires combining an extensive experimental dataset and cutting-edge theory calculations within a machine learning framework where neural networks parametrise the underlying physical laws while minimising ad-hoc model assumptions. The upcoming Electron Ion Collider (EIC), to start taking data in 2029, will be the world's first ever polarised lepton-hadron collider and will offer a plethora of opportunities to address key open questions in our understanding of the strong nuclear force, such as the origin of the mass and the intrinsic angular momentum (spin) of hadrons and whether there exists a state of matter which is entirely dominated by gluons. To fully exploit this scientific potential, novel analysis methodologies need to be develop that make it possible to carry out large-scale, coherent interpretations of measurements from the EIC and other high-energy colliders.<br />
<br />
In this project, the student will carry out a new global analysis of the spin structure of the proton by means of the machine learning tools provided by the NNPDF open-source fitting framework and state-of-the-art calculations in perturbative Quantum Chromodynamics, and integrate it within the corresponding global NNPDF analyses of unpolarised proton and nuclear structure in the framework of a combined integrated global analysis of non-perturbative QCD. Specifically, the project aims to realise a NNLO global fit of polarised quark and gluon PDFs that combines all available data and state-of-the-art perturbative QCD calculations, and study the phenomenological implications for other experiments, including the EIC, for the spin content of the proton, for comparisons with lattice QCD calculations, and for nonpperturbative models of hadron structure.<br />
<br />
References: https://arxiv.org/abs/2201.12363, https://arxiv.org/abs/2109.02653 , https://arxiv.org/abs/2103.05419, https://arxiv.org/abs/1404.4293 , https://inspirehep.net/literature/1302398, https://github.com/NNPDF/<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
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== Finished master projects ==<br />
<br />
See: <br />
* https://wiki.nikhef.nl/education/Master_Theses<br />
* https://www.nikhef.nl/master-theses-2021/<br />
* https://www.nikhef.nl/facts-figures-2020/master-theses-2020/<br />
<br />
<br />
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----<br />
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<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=869Master Projects2023-02-19T09:22:53Z<p>Rojo@nikhef.nl: /* Theory: High-energy neutrino-nucleon interactions at the Forward Physics Facility */</p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
== Projects with a 2023 start ==<br />
<br />
=== ALICE: The next-generation multi-purpose detector at the LHC ===<br />
This main goal of this project is to focus on the next-generation multi-purpose detector planned to be built at the LHC. Its core will be a nearly massless barrel detector consisting of truly cylindrical layers based on curved wafer-scale ultra-thin silicon sensors with MAPS technology, featuring an unprecedented low material budget of 0.05% X0 per layer, with the innermost layers possibly positioned inside the beam pipe. The proposed detector is conceived for studies of pp, pA and AA collisions at luminosities a factor of 20 to 50 times higher than possible with the upgraded ALICE detector, enabling a rich physics program ranging from measurements with electromagnetic probes at ultra-low transverse momenta to precision physics in the charm and beauty sector. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli] and [mailto:marco.van.leeuwen@cern.ch Marco van Leeuwen]''<br />
<br />
=== ALICE: Searching for the strongest magnetic field in nature ===<br />
In a non-central collision between two Pb ions, with a large value of impact parameter, the charged nucleons that do not participate in the interaction (called spectators) create strong magnetic fields. A back of the envelope calculation using the Biot-Savart law brings the magnitude of this filed close to 10^19Gauss in agreement with state of the art theoretical calculation, making it the strongest magnetic field in nature. The presence of this field could have direct implications in the motion of final state particles. The magnetic field, however, decays rapidly. The decay rate depends on the electric conductivity of the medium which is experimentally poorly constrained. Overall, the presence of the magnetic field, the main goal of this project, is so far not confirmed experimentally.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Looking for parity violating effects in strong interactions ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions, in the presence of a deconfined state, gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, what is called the Chiral Magnetic Effect (CME).<br />
The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, however further studies are needed to constrain background effects. These highly anticipated results have the potential to reveal exiting, new physics.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Machine learning techniques as a tool to study the production of heavy flavour particles ===<br />
There was recently a shift in the field of heavy-ion physics triggered by experimental results obtained in collisions between small systems (e.g. protons on protons). These results resemble the ones obtained in collisions between heavy ions. This consequently raises the question of whether we create the smallest QGP droplet in collisions between small systems. The main objective of this project will be to study the production of charm particles such as D-mesons and Λc-baryons in pp collisions at the LHC. This will be done with the help of a new and innovative technique which is based on machine learning (ML). The student will also extend the studies to investigate how this production rate depends on the event activity e.g. on how many particles are created after every collision.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli]''<br />
<br />
===ATLAS: The Higgs boson's self-coupling===<br />
<br />
The coupling of the Higgs boson to itself is one of the main unobserved interactions of the Standard Model and its observation is crucial to understand the shape of the Higgs potential. Here we propose to study the 'ttHH' final state: two top quarks and two Higgs bosons produced in a single collision. This topology is yet unexplored at the ATLAS experiment and the project consists of setting up the new analysis (including multivariate analysis techniques to recognise the complicated final state), optimising the sensitivity and including the result in the full ATLAS study of the Higgs boson's coupling to itself. With the LHC data from the upcoming Run-3, we might be able to see its first glimpses! <br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
===ATLAS: The Next Generation===<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks is very new [1] and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays) and advanced analysis techiques (using deep learning methods).<br />
<br />
[https://atlas.cern/updates/briefing/charming-Higgs-decay][https://arxiv.org/abs/1802.04329 https://atlas.cern/updates/briefing/charming-Higgs-decay]<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
===ATLAS: Searching for new particles in very energetic diboson production===<br />
<br />
The discovery of new phenomena in high-energy proton–proton collisions is one of the main goals of the Large Hadron Collider (LHC). New heavy particles decaying into a pair of vector bosons (WW, WZ, ZZ) are predicted in several extensions to the Standard Model (e.g. extended gauge-symmetry models, Grand Unified theories, theories with warped extra dimensions, etc). In this project we will investigate new ideas to look for these resonances in a region that is yet unexplored in the data. We will focus on the final states where both vector bosons decay into quarks as they are expected to bring the highest sensitivity [1]. We will try to reconstruct and exploit new ways to identify vector bosons (using machine learning methods) and then tackle the problem of estimating contributions from beyond the Standard Model processes in the tails of the mass distribution.<br />
<br />
[1] https://arxiv.org/abs/1906.08589<br />
<br />
''Contact: [mailto:f.dias@nikhef.nl Flavia de Almeida Dias]''<br />
<br />
===ATLAS top-quark and Higgs-boson analysis combination, and Effective Field Theory interpretation===<br />
<br />
We are looking for a master student with interest in theory and data-analysis in the search for physics beyond the Standard Model in the top-quark and Higgs-boson sectors.<br />
<br />
Your master-project starts just at the right time for preparing the Run-3 analysis of the ATLAS experiment at the LHC. In Run-3 (2022-2026), three times more data becomes available, enabling analysis of rare processes with innovative software tools and techniques.<br />
<br />
This project aims to explore the newest strategy to combine the top-quark and Higgs-boson measurements in the perspective of constraining the existence of new physics beyond the Standard Model (SM) of Particle Physics. We selected the pp->tZq and gg->HZ processes as promising candidates for a combination to constrain new physics in the context of Standard Model Effective Field Theory (SMEFT). SMEFT is the state-of-the-art framework for theoretical interpretation of LHC data. In particular, you will study the SMEFT OtZ and Ophit operators, which are not well constrained by current measurements.<br />
<br />
Besides affinity with particle physics theory, the ideal candidate for this project has developed python/C++ skills and is eager to learn advanced techniques. You start with a simulation of the signal and background samples using existing software tools. Then, an event selection study is required using Machine Learning techniques. To evaluate the SMEFT effects, a fitting procedure based on the innovative Morphing technique is foreseen, for which the basic tools in the ROOT and RooFit framework are available. The work is carried out in the ATLAS group at Nikhef and may lead to an ATLAS note.<br />
<br />
''Contact: [mailto:geoffrey.gilles@cern.ch> Geoffrey Gilles] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:h73@nikhef.nl Marcel Vreeswijk]''<br />
<br />
=== ATLAS Machine learning to enhance reconstruction of very rare Higgs decays ===<br />
Since the Higgs boson discovery in 2012 at the ATLAS experiment, the investigation of the properties of the Higgs boson has been a priority for research at the Large Hadron Collider (LHC). However, there are still a many open questions: Is the Higgs boson the only origin of Electroweak Symmetry Breaking? Is there a mechanism which can explain the observed mass pattern of SM particles? Many of these questions are linked to the Higgs boson coupling structure. <br />
<br />
While the Higgs boson coupling to fermions of the third generation has been clearly, the investigation of the Higgs boson coupling to the light fermions of the second generation will be a major project for the upcoming data-taking period starting this year. The Higgs boson decay to muons is most sensitive channel to establish a coupling of the Higgs boson to second generation fermions. In this project you will work on an improvement of the H-->mumu search: In about 5% of the events, a photon is radiated off the outgoing muons. By recognizing these photons and taking their effect into account we can improve the reconstruct these events better. For this project we will use machine learning to best identify these special events and to take their energy contribution into account to improve the overall sensitivity. <br />
<br />
''Contact: [mailto:oliver.rieger@nikhef.nl Oliver Rieger] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:s01@nikhef.nl Peter Kluit]''<br />
<br />
=== ATLAS: Scrutinising Higgs decaying into W bosons ===<br />
Observation of the Higgs boson happened 10 years ago and since then scientists’ interest has shifted towards measuring precisely its properties. An example is a coupling strength telling us how does the Higgs boson interact with different particles such as W bosons. Measuring H→ WW →lnu lnu process allows us to not only probe the Standard Model (SM), by measuring the coupling strength or indirectly probe Higgs boson width, but also test against the theories beyond (for instance in the context of the effective field theory framework).<br />
<br />
The student will take active part in the ATLAS HWW group. There are multiple possible areas of contribution within the group depending on the interest of the student. For instance, utilising machine learning techniques to optimise for the selection of HWW signal process, determining the fake background processes, interpreting the results through the beyond SM theories and others.<br />
Contact: ''[mailto:mvozak@cern.ch Matouš Vozák] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
=== ATLAS: HGTD detector ===<br />
The ATLAS is going to get a new ability: a Timing Layer. This allows us to reconstruct tracks not only in the 3 dimensions of space but adds the ability of measuring very precisely also the time (at picosecond level) at which the particles pass the sensitive layers of the HGTD detector. This allow to construct the trajectories of the particles created at the LHC in 4 dimensions and ultimately will lead to a better reconstruction of physics at ATLAS. The new HGTD detector is still in construction and work needs to be done on different levels such as understanding the detector response (taking measurements in the lab and performing simulations) or developing algorithms to reconstruct the particle trajectories (programming and analysis work). With this work you will be part of the Atlas group and/or the Fast Timing detector group together with the R&D department at Nikhef. <br />
<br />
Contact me to discuss the possibilities. <br />
Contact: ''[mailto:hella.snoek@nikhef.nl Hella Snoek]''<br />
=== Dark Matter: Building better Dark Matter Detectors - the XAMS R&D Setup===<br />
The Amsterdam Dark Matter group operates an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 0.5kg of ultra-pure liquid xenon in the central volume. We use this detector for the development of new detection techniques - such as utilizing our newly installed silicon photomultipliers - and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENONnT experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory, or for future Dark Matter experiments like DARWIN. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data themselves You will "own" this experiment. <br />
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''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
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===Dark Matter: Searching for Dark Matter Particles - XENONnT Data Analysis ===<br />
The XENON collaboration has used the XENON1T detector to achieve the world’s most sensitive direct detection dark matter results and is currently operating the XENONnT successor experiment. The detectors operate at the Gran Sasso underground laboratory and consist of so-called dual-phase xenon time-projection chambers filled with ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the new data coming from the XENONnT detector. The work will consist of understanding the detector signals and applying a deep neural network to improve the (gas-) background discrimination in our Python-based analysis tool to improve the sensitivity for low-mass dark matter particles. The work will continue a study started by a recent graduate. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy.<br />
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''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
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===Dark Matter: The Ultimate Dark Matter Experiment - DARWIN Sensitivity Studies===<br />
DARWIN is the “ultimate” direct detection dark matter experiment, with the goal to reach the so-called “neutrino floor”, when neutrinos become a hard-to-reduce background. The large and exquisitely clean xenon mass will allow DARWIN to also be sensitive to other physics signals such as solar neutrinos, double-beta decay from Xe-136, axions and axion-like particles etc. While the experiment will only start in 2027, we are in the midst of optimizing the experiment, which is driven by simulations. We have an opening for a student to work on the GEANT4 Monte Carlo simulations for DARWIN. We are also working on a “fast simulation” that could be included in this framework. It is your opportunity to steer the optimization of a large and unique experiment. This project requires good programming skills (Python and C++) and data analysis/physics interpretation skills.<br />
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''Contact: [mailto:t.pollmann@nikhef.nl Tina Pollmann], [mailto:decowski@nikhef.nl Patrick Decowski] or [mailto:z37@nikhef.nl Auke Colijn]''<br />
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===Dark Matter: Sensitive tests of wavelength-shifting properties of materials for dark matter detectors===<br />
Rare event search experiments that look for neutrino and dark matter interactions are performed with highly sensitive detector systems, often relying on scintillators, especially liquid noble gases, to detect particle interactions. Detectors consist of structural materials that are assumed to be optically passive, and light detection systems that use reflectors, light detectors, and sometimes, wavelength-shifting materials. MSc theses are available related to measuring the efficiency of light detection systems that might be used in future detectors. Furthermore, measurements to ensure that presumably passive materials do not fluoresce, at the low level relevant to the detectors, can be done. Part of the thesis work can include Monte Carlo simulations and data analysis for current and upcoming dark matter detectors, to study the effect of different levels of desired and nuisance wavelength shifting. In this project, students will acquire skills in photon detection, wavelength shifting technologies, vacuum systems, UV and extreme-UV optics, detector design, and optionally in Python and C++ programming, data analysis, and Monte Carlo techniques.<br />
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''Contact: [mailto:Tina.Pollmann@tum.de Tina Pollmann] and [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
=== Detector R&D: Time resolution of ultrathin monolithic timing detectors ===<br />
For the upgrade of ALICE and LHCb vertex detectors, new silicon pixel detectors are being developed now that can register the passing particles with a time precision of tens of picoseconds. ALICE is the first experiment at the LHC to have installed monolithic sensors where electronics is integrated into the sensor. New prototypes of their sensors have arrived at Nikhef. New prototypes of other sensors able to withstand very high radiation fluences of the LHC are arriving soon. In this project, you will tackle the challenge to accurately measure the time resolution of one of these sensors with our laser setups in the laboratory. You will have the chance to work in an international collaboration where you will report about the performance of these novel sensors. There may even be an opportunity to join beam tests at CERN. For this project, we are looking for someone who is interested to work with high-tech sensors and equipment in our Nikhef laboratory and with python programming skills.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
=== Detector R&D: Performance of monolithic sensors for the ALICE upgrade from test beam data ===<br />
For the upgrade of the ALICE detector, ultrathin picosecond timing integrated sensors are being developed now, of which the first prototypes are now at Nikhef and are being studied in test beams at CERN and DESY in Hamburg. Sensors are studied with the ALPIDE (ALICE PIxel DEtector) telescope that uses the same sensors that have recently installed in the heart of the ALICE experiment at CERN. In this project, you will analyze data from beam tests to measure the efficiency and time resolution of the new prototypes for the ALICE upgrade with the latest data from test beams at CERN. If the travel situation allows, you will have the opportunity to join the ALICE test beam group at CERN or in Hamburg at DESY to take part in the exciting experience of taking real data. We are looking for someone with good programming and data analysis skills.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
=== Detector R&D: Modeling radiation damage in silicon sensors ===<br />
In the coming years, the ATLAS experiment at the LHC works on upgrades to prepare for the high-luminosity LHC, where many more collisions will take place than today. Both analysis of data and decisions made in preparation of these detectors and on data taking heavily rely on simulations, especially those that model the damage done to sensors after many collisions. It may sound counterintuitive, but particle detectors do not actually like particles: after many collisions at the LHC, a silicon pixel detector has seen so many particles that its bulk gathers defects. Charge generated by traversing particles can get trapped in defects resulting in less charge induced in the readout electrodes, reducing detector performance in resolution and efficiency. In this project, you will be a member of the international ATLAS collaboration where you will compare different models of radiation damage with measured data. You will learn technology computer aided design (TCAD), widely used in industry, and contribute to the open source program Allpix Squared that is widely used for simulations in many areas of particle physics. Here we are looking for someone with good programming and data analysis skills who would like to contribute to upgrades of collider experiments.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
=== Detector R&D: Fast trigger ===<br />
Muons in cosmic rays are for free! In this project we are not looking for where cosmic rays come from or what physics can be studied with them. Instead, we are using them to test some of our particle detectors. Muons are short lived particles that carry the same charge as electrons, have a high penetrating power and can be detected relatively easy. In practice a test set-up consists of a ‘trigger’ and a device under test. The ‘trigger’ is a detector that gives a signal when a muon passes by, which is a signal to check the result in the device under test. Did the device under test respond to the muon in the expected way? <br />
<br />
For the planned upgrades of particle detectors at CERN, for LHC experiments (LHCb, ATLAS, ALICE, CMS), new particle detectors are under development. Some of these new detectors must be able to measure within tens of ps (10e-12 s) precise when a particle was detected.<br />
<br />
To facilitate testing these new detectors by using muons we need a trigger set up with a matching precision in timing (order tens of ps). We want to investigate several potentially interesting technologies to develop such a fast trigger. In one scenario the trigger could be based on the use of Cherenkov light. Cherenkov light is generated when a charged particle traverses a medium faster than the speed of light in that medium. This light can be generated in for example plexiglass, which in turn can be mounted on top of a light sensor. In our case the light sensor could be a so called silicon photo multiplier, which is capable of detecting only a few photons and gives a signal within a few hundred ps. Another possible scenario would be to use a so called LGAD (Low Gain Avalanche Diode) to measure the signal that a muon generates as it traverses the sensor.<br />
<br />
The Question(s): Which technology should we use for a fast trigger and what is the best timing precision that we can achieve? <br />
<br />
This project will involve a lot of 'hands on work' in the lab. <br />
<br />
''Contact: [mailto:martinfr@nikhef.nl Martin Fransen] and [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
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=== Detector R&D: Characterisation of Trench Isolated Low Gain Avalanche Detectors (TI-LGAD) ===<br />
The future vertex detector of the LHCb Experiment needs to measure the spatial coordinates and time of the particles originating in the LHC proton-proton collisions with resolutions better than 10 um and 50 ps, respectively. Several technologies are being considered to achieve these resolutions. Among those is a novel sensor technology called Trench Isolated Low Gain Avalanche Detector. Prototype pixelated sensors have been manufactured recently and have to be characterised. Therefore these new sensors will be bump bonded to a Timepix4 ASIC which provides charge and time measurements in each of 230 thousand pixels. Characterisation will be done using a lab setup at Nikhef, and includes tests with a micro-focused laser beam, radioactive sources, and possibly with particle tracks obtained in a test-beam. This project involves data taking with these new devices and analysing the data to determine the performance parameters such as the spatial and temporal resolution. as function of temperature and other operational conditions.<br />
<br />
''Contacts: [mailto:kazu.akiba@nikhef.nl Kazu Akiba] and [mailto:martinb@nikhef.nl Martin van Beuzekom]''<br />
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=== Detector R&D: Simulation of 3D silicon sensors ===<br />
For the upgrade of the vertex detector of the LHCb experiment novel silicon pixel detectors have to be developed that can register the passing particles with a time precision of tens of picoseconds. Given the harsh radiation environment very close to the LHCb interaction point only a limited number of technologies can be applied. One of the most promising technologies are the so-called 3D sensors whose readout electrodes are pillars that are placed into the sensor perpendicular to the surface; this in contrast to ’standard’ planar silicon sensors where the pixel electrodes are at the surface, similar to the camera in your smartphone. To understand the time response of these 3D sensors, simulations with TCAD software have to be performed and the results will be compared to measured data. These simulations involve the creation/adaptation of the 3D structures of the model, optimising the simulation speed, and analysing the signals as function voltage, track impact point and deposited charge. Hands-on experience with such 3D sensors in the R&D labs at Nikhef is planned within the scope of this project.<br />
<br />
''Contacts: [mailto:martinb@nikhef.nl Martin van Beuzekom] and [mailto:kazu.akiba@nikhef.nl Kazu Akiba]''<br />
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===Detector R&D: Laser Interferometer Space Antenna (LISA) - Wavefront sensors for gravitational wave detection ===<br />
<br />
The space-based gravitational wave antenna LISA is one of the most challenging space missions ever proposed. ESA plans to launch around 2034 three spacecraft separated by a few million kilometres. This constellation measures tiny variations in the distances between test-masses located in each satellite to detect gravitational waves from sources such as supermassive black holes. LISA is based on laser interferometry, and the three satellites form a giant Michelson interferometer. LISA measures a relative phase shift between one local laser and one distant laser by light interference. The phase shift measurement requires sensitive wavefront sensors. The Nikhef DR&D group fabricated prototype sensors in 2020 together with the Photonics industry and the Dutch institute for space research SRON. Nikhef & SRON are responsible for the Quadrant PhotoReceiver (QPR) system: the sensors, the housing including a complex mount to align the sensors with 10's of nanometer accuracy, various environmental tests at the European Space Research and Technology Centre (ESTEC), and the overall performance of the QPR in the LISA instrument. Currently we are discussing possible sensor improvements for a second fabrication run in 2022, optimizing the mechanics and preparing environmental tests. As a MSc student, you will work on various aspects of the wavefront sensor development: study the performance of the epitaxial stacks of Indium-Gallium-Arsenide, setting up test benches to characterize the sensors and QPR system, performing the actual tests and data analysis, in combination with performance studies and simulations of the LISA instrument.<br />
<br />
''Contact: [mailto:nielsvb@nikhef.nl Niels van Bakel]''<br />
<br />
===FCC: The Next Collider===<br />
<br />
After the LHC, the next planned large collider at CERN is the proposed 100 kilometer circular collider "FCC". In the first stage of the project, as a high-luminosity electron-positron collider, precision measurements of the Higgs boson are the main goal. One of the channels that will improve by orders of magnitude at this new accelerator is the decay of the Higgs boson to a pair of charm quarks. This project will estimate a projected sensitivity for the coupling of the Higgs boson to second generation quarks, and in particular target the improved reconstruction of the topology of long-lived mesons in the clean environment of a precision e+e- machine.<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
<br />
===LHCb: Search for light dark particles===<br />
The Standard Model of elementary particles does not contain a proper Dark Matter candidate. One of the most tantalizing theoretical developments is the so-called ''Hidden Valley models'': a mirror-like copy of the ''Standard Model'', with dark particles that communicate with standard ones via a very feeble interaction. These models predict the existence of ''dark hadrons'' – composite particles that are bound similarly to ordinary hadrons in the ''Standard Model''. Such ''dark hadrons'' can be abundantly produced in high-energy proton-proton collisions, making the LHC a unique place to search for them. Some ''dark hadrons'' are stable like a proton, which makes them excellent ''Dark Matter'' candidates, while others decay to ordinary particles after flying a certain distance in the collider experiment. The LHCb detector has a unique capability to identify such decays, particularly if the new particles have a mass below ten times the proton mass. <br />
<br />
This project assumes a unique search for light ''dark hadrons'' that covers a mass range not accessible to other experiments. It assumes an interesting program on data analysis (python-based) with non-trivial machine learning solutions and phenomenology research using fast simulation framework. Depending on the interest, there is quite a bit of flexibility in the precise focus of the project.<br />
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''Contact: [mailto:andrii.usachov@nikhef.nl Andrii Usachov]''<br />
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===LHCb: Measuring lepton flavour universality with excited Ds states in semileptonic Bs decays===<br />
One of the most striking discrepancies between the Standard Model and measurements are the lepton flavour universality (LFU) measurements with tau decays. At the moment, we have observed an excess of 3-4 sigma in ''B → Dτν'' decays. This could point even to a new force of nature! To understand this discrepancy, we need to make further measurements. <br />
<br />
One very exciting (pun intended) projects to verify these discrepancies involves measuring the ''B<sub>s</sub> → D<sub>s2</sub><sup>*</sup>τν'' and/or ''B<sub>s</sub> → D<sub>s1</sub><sup>*</sup>τν'' decays. These decays with excited states of the ''D<sub>s</sub>'' meson have not been observed before in the tau decay mode, and have a unique way of coupling to potential new physics candidates that can only be measured in ''B<sub>s</sub>'' decays [1]. See slides for more detail: [[File:LHCbLFUwithExcitedDs.pdf|thumb]]<br />
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[1] https://arxiv.org/abs/1606.09300<br />
<br />
''Contact: [mailto:suzannek@nikhef.nl Suzanne Klaver]''<br />
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===LHCb: New physics in the angular distributions of B decays to K*ee===<br />
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Lepton flavour violation in B decays can be explained by a variety of non-standard model interactions. Angular distributions in decays of a B meson to a hadron and two leptons are an important source of information to understand which model is correct. Previous analyses at the LHCb experiment have considered final states with a pair of muons. Our LHCb group at Nikhef concentrates on a new measurement of angular distributions in decays with two electrons. The main challenge in this measurement is the calibration of the detection efficiency. In this project you will confront estimates of the detection efficiency derived from simulation with decay distributions in a well known B decay. Once the calibration is understood, the very first analysis of the angular distributions in the electron final state can be performed. <br />
<br />
Contact: [mailto:m.senghi.soares@nikhef.nl Mara Soares] and [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
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===LHCb: Discovering heavy neutrinos in B decays===<br />
<br />
Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, much heavier, neutral leptons. If the mass of these new neutrinos is below the b-quark mass, they can be observed in B hadron decays.<br />
<br />
In this project we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undiscovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The analysis will be performed within the LHCb group at Nikhef using LHCb run-2 data.<br />
<br />
''Contact: [mailto:v.lukashenko@nikhef.nl Lera Lukashenko] and'' [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
===LHCb: The exotic 4-quark state X(3872) in exclusive production===<br />
The nature of the X(3872) is still unknown. Is it a regular charmonium with an unexpected mass, a compact 4-quark state, or a DD molecule? Or a quantum superposition of all that? Either way, finding out will tell us something about how quark organise in hadrons and colour confinement. The project is to measure a very peculiar production mode: pp->Xpp. Only the X is seen in the detector and nothing else. Data from LHCb run 2 will be used and the analysis will build on previous work. <br />
<br />
''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
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===LHCb: Scintillating Fibre tracker software===<br />
The installation of the scintillating-fibre tracker in LHCb’s underground cavern was recently completed. This detector uses 10000 km of fibres to track particle trajectories in the LHCb detector when the LHC starts up again later this year. The light emitted by the scintillating fibres when a particle interacts with them is measured using photon multiplier tubes. The studies proposed for this project will focus on software, and could include writing a framework to monitor the detector output, improving the detector simulation or working on the data processing.<br />
<br />
''Contact: [mailto:e.gabriel@nikhef.nl Emmy Gabriel]''<br />
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===LHCb: Vertex detector calibration===<br />
In summer 2022 LHCb has started data taking will an almost entirely new detector. At the point closest to the interaction point, the trajectories of charge particles are reconstructed with a so-called silicon pixel detector. The design hit resolution of this detector is about 15 micron. However, to actually reach this resolution a precise calibration of the spatial positions of the silicon sensors needs to be performed. In this project, you will use the first data of the new LHCb detector to perform this calibration and measure the detector performance.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen]''<br />
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<br />
===Neutrinos: Neutrino scattering: the ultimate resolution===<br />
<br />
Neutrino telescopes like IceCube and KM3NeT aim at detecting neutrinos from cosmic sources. The neutrinos are detected with the best resolution when charged current interactions with nucleons produce a muon, which can be detected with high accuracy (depending on the detector). A crucial ingredient in the ultimate achievable pointing accuracy of neutrino telescopes is the scattering angle between the neutrino and the muon. While published computations have investigated the cross-section of the process in great detail, this important scattering angle has not received much attention. The aim of the project is to compute and characterize the distribution of this angle, and that the ultimate resolution of a neutrino telescope. If successful, the results of this project can lead to publication of interest to the neutrino telescope community.<br />
<br />
Depending on your interests, the study could be based on a first-principles calculation (using the deep-inelastic scattering formalism), include state-of-the-art parton distribution functions, and/or exploit existing event-generation software for a more experimental approach. <br />
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''Contacts: [mailto:aart.heijboer@nikhef.nl Aart Heijboer]''<br />
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===Neutrinos: acoustic detection of ultra-high energy neutrinos===<br />
<br />
The study of the cosmic neutrinos of energies above 1017 eV, the so-called ultra-high energy neutrinos, provides a unique view on the universe and may provide insight in the origin of the most violent astrophysical sources, such as gamma ray bursts, supernovae or even dark matter. In addition, the observation of high energy neutrinos may provide a unique tool to study interactions at high energies. The energy deposition of these extreme neutrinos in water induce a thermo-acoustic signal, which can be detected using sensitive hydrophones. The expected neutrino flux is however extremely low and the signal that neutrinos induce is small. TNO is presently developing sensitive hydrophone technology based on fiber optics. Optical fibers form a natural way to create a distributed sensing system. Using this technology a large scale neutrino telescope can be built in the deep sea. TNO is aiming for a prototype hydrophone which will form the building block of a future telescope.<br />
<br />
The work will be executed at the Nikhef institute and/or the TNO laboratories in Delft. In this project master students have the opportunity to contribute in the following ways:<br />
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'''Project 1:''' Hardware development on fiber optics hydrophones technology Goal: characterize existing prototype optical fibre hydrophones in an anechoic basin at TNO laboratory. Data collection, calibration, characterization, analysis of consequences for design future acoustic hydrophone neutrino telescopes;<br />
Keywords: Optical fiber technology, signal processing, electronics, lab.<br />
<br />
'''Project 2:''' Investigation of ultra-high energy neutrinos and their interactions with matter. Goal: Discriminate the neutrino signals from the background noises, in particular clicks from whales and dolphins in the deep sea. Study impact on physics reach for future acoustic hydrophone neutrino telescopes;<br />
Keywords: Monte Carlo simulations, particle physics, neutrino physics, data analysis algorithms.<br />
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Further information: Info on ultra-high energy neutrinos can be found at: http://arxiv.org/abs/1102.3591; Info on acoustic detection of neutrinos can be found at: http://arxiv.org/abs/1311.7588<br />
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''Contact: [mailto:ernst-jan.buis@tno.nl Ernst Jan Buis]'' or ''[mailto:ivo.van.vulpen@nikhef.nl Ivo van Vulpen]''<br />
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===Neutrinos: Oscillation analysis with the first data of KM3NeT===<br />
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The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first few strings with sensitive photodetectors have been deployed at both the Italian and the French detector sites. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In this project the available data will be used together with simulations to best reconstruct the event topologies and optimally identify and reconstruct the first neutrino interactions in the KM3NeT detector. The data will then be used to measure neutrino oscillation parameters, and prepare for a future neutrino mass ordering determination.<br />
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Programming skills are essential, mostly root and C++ will be used.<br />
''Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn] [mailto:h26@nikhef.nl Paul de Jong]''<br />
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===Neutrinos: the Deep Underground Neutrino Experiment (DUNE)===<br />
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The Deep Underground Neutrino Experiment (DUNE) is under construction in the USA, and will consist of a powerful neutrino beam originating at Fermilab, a near detector at Fermilab, and a far detector in the SURF facility in Lead, South Dakota, 1300 km away. During travelling, neutrinos oscillate and a fraction of the neutrino beam changes flavour; DUNE will determine the neutrino oscillation parameters to unrivaled precision, and try and make a first detection of CP-violation in neutrinos. In this project, various elements of DUNE can be studied, including the neutrino oscillation fit, neutrino physics with the near detector, event reconstruction and classification (including machine learning), or elements of data selection and triggering.<br />
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''Contact: [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
===Neutrinos: Searching for Majorana Neutrinos with KamLAND-Zen===<br />
The KamLAND-Zen experiment, located in the Kamioka mine in Japan, is a large liquid scintillator experiment with 750kg of ultra-pure Xe-136 to search for neutrinoless double-beta decay (0n2b). The observation of the 0n2b process would be evidence for lepton number violation and the Majorana nature of neutrinos, i.e. that neutrinos are their own anti-particles. Current limits on this extraordinary rare hypothetical decay process are presented as a half-life, with a lower limit of 10^26 years. KamLAND-Zen, the world’s most sensitive 0n2b experiment, is currently taking data and there is an opportunity to work on the data analysis, analyzing data with the possibility of taking part in a ground-breaking discovery. The main focus will be on developing new techniques to filter the spallation backgrounds, i.e. the production of radioactive isotopes by passing muons. There will be close collaboration with groups in the US (MIT, Berkeley, UW) and Japan (Tohoku Univ). <br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
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=== Cosmic Rays/Neutrinos: Seasonal muon flux variations and the pion/kaon ratio ===<br />
The KM3NeT ARCA and ORCA detectors, located kilometers deep in the Mediterranean Sea, have neutrinos as primary probes. Muons from cosmic ray interactions reach the detectors in relatively large quantities too. These muons, exploiting the capabilities and location of the detectors allow the study of cosmic rays and their interactions. In this way, questions about their origin, type, propagation can be addressed. In particular these muons are tracers of hadronic interactions at energies inaccessible at particle accelerators.<br />
<br />
The muons reaching the depths of the detectors result from decays of mesons, mostly pions and kaons, created in interactions of high-energy cosmic rays with atoms in the upper atmosphere. Seasonal changes of the temperature – and thus density - profile of the atmosphere modulate the balance between the probability for these mesons to decay (producing muons) or to re-interact. Pions and kaons are affected differently, allowing to extract their production ratio by determining how changes in muon rate depend on changes in the effective temperature – an integral over the atmospheric temperature profile weighted by a depth dependent meson production rate.<br />
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In this project, the aim is to measure the rate of muons in the detectors and to calculate the effective temperature above the KM3NeT detectors from atmospheric data, both as function of time. The relation between these two can be used to extract the pion to kaon ratio.<br />
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''Contact: [mailto:rbruijn@nikhef.nl Ronald Bruijn]''<br />
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===Gravitational Waves: Computer modelling to design the laser interferometers for the Einstein telescope===<br />
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A new field of instrument science led to the successful detection of gravitational waves by the LIGO detectors in 2015. We are now preparing the next generation of gravitational wave observatories, such as the Einstein Telescope, with the aim to increase the detector sensitivity by a factor of ten, which would allow, for example, to detect stellar-mass black holes from early in the universe when the first stars began to form. This ambitious goal requires us to find ways to significantly improve the best laser interferometers in the world.<br />
<br />
Gravitational wave detectors, such as LIGO and VIRGO, are complex Michelson-type interferometers enhanced with optical cavities. We develop and use numerical models to study these laser interferometers, to invent new optical techniques and to quantify their performance. For example, we synthesize virtual mirror surfaces to study the effects of higher-order optical modes in the interferometers, and we use opto-mechanical models to test schemes for suppressing quantum fluctuations of the light field. We can offer several projects based on numerical modelling of laser interferometers. All projects will be directly linked to the ongoing design of the Einstein Telescope.<br />
<br />
''Contact: [mailto:a.freise@nikhef.nl Andreas Freise]''<br />
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=== Theory: Effective Field Theories of Particle Physics from low- to high-energies===<br />
Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations” seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature. The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Standard Model Effective Field Theory (SMEFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes with minimal assumptions on the nature of an eventual UV-complete theory that replaces the Standard Model. Specifically, the goal is to connect measurements from ATLAS, CMS, and LHCb experiments at the CERN's LHC among them and to jointly interpret this information with that provided by other experiments including very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
<br />
This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories. Depending on the student profile, sub-projects with a strong computational and/or machine learning component are also possible, for instance to construct new operators with optimal sensitivity to New Physics effects as encoded by the SMEFT higher-dimensional operators. Topics that can be considered in this project include the interpretation of novel physical observables at the LHC and their integration into the global SMEFiT analysis, matching of EFTs to UV-complete theories and their phenomenological analyses, projections for the impact in the SMEFT parameter space of data for future colliders, the synergies between EFT studies and proton structure fits, and the matching to the Weak Effective Field Theory to include data on flavour observables such as B-meson decays.<br />
<br />
References: https://arxiv.org/abs/2105.00006 , https://arxiv.org/abs/2302.06660, https://arxiv.org/abs/2211.02058 , https://arxiv.org/abs/1901.05965 , https://arxiv.org/abs/1906.05296 , https://arxiv.org/abs/1908.05588, https://arxiv.org/abs/1905.05215<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theory: High-energy neutrino-nucleon interactions at the Forward Physics Facility ===<br />
High-energy collisions at the High-Luminosity Large Hadron Collider (HL-LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing experiments. The proposed Forward Physics Facility (FPF) to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe Standard Model (SM) processes and search for physics beyond the Standard Model (BSM). High statistics neutrino detection will provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. The FPF has the promising potential to probe our understanding of the strong interactions as well as of proton and nuclear structure, providing access to both the very low-x and the very high-x regions of the colliding protons. The former regime is sensitive to novel QCD production mechanisms, such as BFKL effects and non-linear dynamics, as well as the gluon parton distribution function (PDF) down to x=1e-7, well beyond the coverage of other experiments and providing key inputs for astroparticle physics. In addition, the FPF acts as a neutrino-induced deep-inelastic scattering (DIS) experiment with TeV-scale neutrino beams. The resulting measurements of neutrino DIS structure functions represent a valuable handle on the partonic structure of nucleons and nuclei, particularly their quark flavour separation, that is fully complementary to the charged-lepton DIS measurements expected at the upcoming Electron-Ion Collider (EIC).<br />
<br />
In this project, the student will carry out updated predictions for the neutrino fluxes expected at the FPF, assess the precision with which neutrino cross-sections will be measured, and quantify their impact on proton and nuclear structure by means of machine learning tools within the NNPDF framework and state-of-the-art calculations in perturbative Quantum Chromodynamics. This project contributes to ongoing work within the FPF Initiative towards a Conceptual Design Report (CDR) to be presented within two years. Topics that can be considered as part of this project include the assessment of to which extent nuclear modifications of the free-proton PDFs can be constrained by FPF measurements, the determination of the small-x gluon PDF from suitably defined observables at the FPF and the implications for ultra-high-energy particle astrophysics, the study of the intrinsic charm content in the proton and its consequences for the FPF physics program, and the validation of models for neutrino-nucleon cross-sections in the region beyond the validity of perturbative QCD.<br />
<br />
References: https://arxiv.org/abs/2203.05090, https://arxiv.org/abs/2109.10905 ,https://arxiv.org/abs/2208.08372 , https://arxiv.org/abs/2201.12363 , https://arxiv.org/abs/2109.02653 <br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theory: Probing the origin of the proton spin with machine learning===<br />
At energy-frontier facilities such as the Large Hadron Collider (LHC), scientists study the laws of Nature in their quest for novel phenomena both within and beyond the Standard Model of particle physics. An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions from the nature of the Higgs boson to the origin of cosmic neutrinos. The key to address some of these questions is by carrying out an universal analysis of nucleon structure from the simultaneous determination of the momentum and spin distributions of quarks and gluons and their fragmentation into hadrons. This effort requires combining an extensive experimental dataset and cutting-edge theory calculations within a machine learning framework where neural networks parametrise the underlying physical laws while minimizing ad-hoc model assumptions.<br />
<br />
In this project, the student(s) will carry out a new global analysis of the spin structure of the proton by means of machine learning tools and state-of-the-art calculations in perturbative Quantum Chromodynamics, and integrate it within the corresponding global NNPDF analyses of unpolarised proton and nuclear structure in the framework of a combined integrated global analysis of non-perturbative QCD.<br />
<br />
References: arXiv:2201.12363 , arXiv:2109.02653<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
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== Finished master projects ==<br />
<br />
See: <br />
* https://wiki.nikhef.nl/education/Master_Theses<br />
* https://www.nikhef.nl/master-theses-2021/<br />
* https://www.nikhef.nl/facts-figures-2020/master-theses-2020/<br />
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<br />
[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=868Master Projects2023-02-19T09:20:48Z<p>Rojo@nikhef.nl: /* Theory: High-energy neutrino-nucleon interactions at the Forward Physics Facility */</p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
== Projects with a 2023 start ==<br />
<br />
=== ALICE: The next-generation multi-purpose detector at the LHC ===<br />
This main goal of this project is to focus on the next-generation multi-purpose detector planned to be built at the LHC. Its core will be a nearly massless barrel detector consisting of truly cylindrical layers based on curved wafer-scale ultra-thin silicon sensors with MAPS technology, featuring an unprecedented low material budget of 0.05% X0 per layer, with the innermost layers possibly positioned inside the beam pipe. The proposed detector is conceived for studies of pp, pA and AA collisions at luminosities a factor of 20 to 50 times higher than possible with the upgraded ALICE detector, enabling a rich physics program ranging from measurements with electromagnetic probes at ultra-low transverse momenta to precision physics in the charm and beauty sector. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli] and [mailto:marco.van.leeuwen@cern.ch Marco van Leeuwen]''<br />
<br />
=== ALICE: Searching for the strongest magnetic field in nature ===<br />
In a non-central collision between two Pb ions, with a large value of impact parameter, the charged nucleons that do not participate in the interaction (called spectators) create strong magnetic fields. A back of the envelope calculation using the Biot-Savart law brings the magnitude of this filed close to 10^19Gauss in agreement with state of the art theoretical calculation, making it the strongest magnetic field in nature. The presence of this field could have direct implications in the motion of final state particles. The magnetic field, however, decays rapidly. The decay rate depends on the electric conductivity of the medium which is experimentally poorly constrained. Overall, the presence of the magnetic field, the main goal of this project, is so far not confirmed experimentally.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Looking for parity violating effects in strong interactions ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions, in the presence of a deconfined state, gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, what is called the Chiral Magnetic Effect (CME).<br />
The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, however further studies are needed to constrain background effects. These highly anticipated results have the potential to reveal exiting, new physics.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Machine learning techniques as a tool to study the production of heavy flavour particles ===<br />
There was recently a shift in the field of heavy-ion physics triggered by experimental results obtained in collisions between small systems (e.g. protons on protons). These results resemble the ones obtained in collisions between heavy ions. This consequently raises the question of whether we create the smallest QGP droplet in collisions between small systems. The main objective of this project will be to study the production of charm particles such as D-mesons and Λc-baryons in pp collisions at the LHC. This will be done with the help of a new and innovative technique which is based on machine learning (ML). The student will also extend the studies to investigate how this production rate depends on the event activity e.g. on how many particles are created after every collision.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli]''<br />
<br />
===ATLAS: The Higgs boson's self-coupling===<br />
<br />
The coupling of the Higgs boson to itself is one of the main unobserved interactions of the Standard Model and its observation is crucial to understand the shape of the Higgs potential. Here we propose to study the 'ttHH' final state: two top quarks and two Higgs bosons produced in a single collision. This topology is yet unexplored at the ATLAS experiment and the project consists of setting up the new analysis (including multivariate analysis techniques to recognise the complicated final state), optimising the sensitivity and including the result in the full ATLAS study of the Higgs boson's coupling to itself. With the LHC data from the upcoming Run-3, we might be able to see its first glimpses! <br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
===ATLAS: The Next Generation===<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks is very new [1] and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays) and advanced analysis techiques (using deep learning methods).<br />
<br />
[https://atlas.cern/updates/briefing/charming-Higgs-decay][https://arxiv.org/abs/1802.04329 https://atlas.cern/updates/briefing/charming-Higgs-decay]<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
===ATLAS: Searching for new particles in very energetic diboson production===<br />
<br />
The discovery of new phenomena in high-energy proton–proton collisions is one of the main goals of the Large Hadron Collider (LHC). New heavy particles decaying into a pair of vector bosons (WW, WZ, ZZ) are predicted in several extensions to the Standard Model (e.g. extended gauge-symmetry models, Grand Unified theories, theories with warped extra dimensions, etc). In this project we will investigate new ideas to look for these resonances in a region that is yet unexplored in the data. We will focus on the final states where both vector bosons decay into quarks as they are expected to bring the highest sensitivity [1]. We will try to reconstruct and exploit new ways to identify vector bosons (using machine learning methods) and then tackle the problem of estimating contributions from beyond the Standard Model processes in the tails of the mass distribution.<br />
<br />
[1] https://arxiv.org/abs/1906.08589<br />
<br />
''Contact: [mailto:f.dias@nikhef.nl Flavia de Almeida Dias]''<br />
<br />
===ATLAS top-quark and Higgs-boson analysis combination, and Effective Field Theory interpretation===<br />
<br />
We are looking for a master student with interest in theory and data-analysis in the search for physics beyond the Standard Model in the top-quark and Higgs-boson sectors.<br />
<br />
Your master-project starts just at the right time for preparing the Run-3 analysis of the ATLAS experiment at the LHC. In Run-3 (2022-2026), three times more data becomes available, enabling analysis of rare processes with innovative software tools and techniques.<br />
<br />
This project aims to explore the newest strategy to combine the top-quark and Higgs-boson measurements in the perspective of constraining the existence of new physics beyond the Standard Model (SM) of Particle Physics. We selected the pp->tZq and gg->HZ processes as promising candidates for a combination to constrain new physics in the context of Standard Model Effective Field Theory (SMEFT). SMEFT is the state-of-the-art framework for theoretical interpretation of LHC data. In particular, you will study the SMEFT OtZ and Ophit operators, which are not well constrained by current measurements.<br />
<br />
Besides affinity with particle physics theory, the ideal candidate for this project has developed python/C++ skills and is eager to learn advanced techniques. You start with a simulation of the signal and background samples using existing software tools. Then, an event selection study is required using Machine Learning techniques. To evaluate the SMEFT effects, a fitting procedure based on the innovative Morphing technique is foreseen, for which the basic tools in the ROOT and RooFit framework are available. The work is carried out in the ATLAS group at Nikhef and may lead to an ATLAS note.<br />
<br />
''Contact: [mailto:geoffrey.gilles@cern.ch> Geoffrey Gilles] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:h73@nikhef.nl Marcel Vreeswijk]''<br />
<br />
=== ATLAS Machine learning to enhance reconstruction of very rare Higgs decays ===<br />
Since the Higgs boson discovery in 2012 at the ATLAS experiment, the investigation of the properties of the Higgs boson has been a priority for research at the Large Hadron Collider (LHC). However, there are still a many open questions: Is the Higgs boson the only origin of Electroweak Symmetry Breaking? Is there a mechanism which can explain the observed mass pattern of SM particles? Many of these questions are linked to the Higgs boson coupling structure. <br />
<br />
While the Higgs boson coupling to fermions of the third generation has been clearly, the investigation of the Higgs boson coupling to the light fermions of the second generation will be a major project for the upcoming data-taking period starting this year. The Higgs boson decay to muons is most sensitive channel to establish a coupling of the Higgs boson to second generation fermions. In this project you will work on an improvement of the H-->mumu search: In about 5% of the events, a photon is radiated off the outgoing muons. By recognizing these photons and taking their effect into account we can improve the reconstruct these events better. For this project we will use machine learning to best identify these special events and to take their energy contribution into account to improve the overall sensitivity. <br />
<br />
''Contact: [mailto:oliver.rieger@nikhef.nl Oliver Rieger] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:s01@nikhef.nl Peter Kluit]''<br />
<br />
=== ATLAS: Scrutinising Higgs decaying into W bosons ===<br />
Observation of the Higgs boson happened 10 years ago and since then scientists’ interest has shifted towards measuring precisely its properties. An example is a coupling strength telling us how does the Higgs boson interact with different particles such as W bosons. Measuring H→ WW →lnu lnu process allows us to not only probe the Standard Model (SM), by measuring the coupling strength or indirectly probe Higgs boson width, but also test against the theories beyond (for instance in the context of the effective field theory framework).<br />
<br />
The student will take active part in the ATLAS HWW group. There are multiple possible areas of contribution within the group depending on the interest of the student. For instance, utilising machine learning techniques to optimise for the selection of HWW signal process, determining the fake background processes, interpreting the results through the beyond SM theories and others.<br />
Contact: ''[mailto:mvozak@cern.ch Matouš Vozák] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
=== ATLAS: HGTD detector ===<br />
The ATLAS is going to get a new ability: a Timing Layer. This allows us to reconstruct tracks not only in the 3 dimensions of space but adds the ability of measuring very precisely also the time (at picosecond level) at which the particles pass the sensitive layers of the HGTD detector. This allow to construct the trajectories of the particles created at the LHC in 4 dimensions and ultimately will lead to a better reconstruction of physics at ATLAS. The new HGTD detector is still in construction and work needs to be done on different levels such as understanding the detector response (taking measurements in the lab and performing simulations) or developing algorithms to reconstruct the particle trajectories (programming and analysis work). With this work you will be part of the Atlas group and/or the Fast Timing detector group together with the R&D department at Nikhef. <br />
<br />
Contact me to discuss the possibilities. <br />
Contact: ''[mailto:hella.snoek@nikhef.nl Hella Snoek]''<br />
=== Dark Matter: Building better Dark Matter Detectors - the XAMS R&D Setup===<br />
The Amsterdam Dark Matter group operates an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 0.5kg of ultra-pure liquid xenon in the central volume. We use this detector for the development of new detection techniques - such as utilizing our newly installed silicon photomultipliers - and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENONnT experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory, or for future Dark Matter experiments like DARWIN. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data themselves You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
===Dark Matter: Searching for Dark Matter Particles - XENONnT Data Analysis ===<br />
The XENON collaboration has used the XENON1T detector to achieve the world’s most sensitive direct detection dark matter results and is currently operating the XENONnT successor experiment. The detectors operate at the Gran Sasso underground laboratory and consist of so-called dual-phase xenon time-projection chambers filled with ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the new data coming from the XENONnT detector. The work will consist of understanding the detector signals and applying a deep neural network to improve the (gas-) background discrimination in our Python-based analysis tool to improve the sensitivity for low-mass dark matter particles. The work will continue a study started by a recent graduate. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy.<br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
===Dark Matter: The Ultimate Dark Matter Experiment - DARWIN Sensitivity Studies===<br />
DARWIN is the “ultimate” direct detection dark matter experiment, with the goal to reach the so-called “neutrino floor”, when neutrinos become a hard-to-reduce background. The large and exquisitely clean xenon mass will allow DARWIN to also be sensitive to other physics signals such as solar neutrinos, double-beta decay from Xe-136, axions and axion-like particles etc. While the experiment will only start in 2027, we are in the midst of optimizing the experiment, which is driven by simulations. We have an opening for a student to work on the GEANT4 Monte Carlo simulations for DARWIN. We are also working on a “fast simulation” that could be included in this framework. It is your opportunity to steer the optimization of a large and unique experiment. This project requires good programming skills (Python and C++) and data analysis/physics interpretation skills.<br />
<br />
''Contact: [mailto:t.pollmann@nikhef.nl Tina Pollmann], [mailto:decowski@nikhef.nl Patrick Decowski] or [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
===Dark Matter: Sensitive tests of wavelength-shifting properties of materials for dark matter detectors===<br />
Rare event search experiments that look for neutrino and dark matter interactions are performed with highly sensitive detector systems, often relying on scintillators, especially liquid noble gases, to detect particle interactions. Detectors consist of structural materials that are assumed to be optically passive, and light detection systems that use reflectors, light detectors, and sometimes, wavelength-shifting materials. MSc theses are available related to measuring the efficiency of light detection systems that might be used in future detectors. Furthermore, measurements to ensure that presumably passive materials do not fluoresce, at the low level relevant to the detectors, can be done. Part of the thesis work can include Monte Carlo simulations and data analysis for current and upcoming dark matter detectors, to study the effect of different levels of desired and nuisance wavelength shifting. In this project, students will acquire skills in photon detection, wavelength shifting technologies, vacuum systems, UV and extreme-UV optics, detector design, and optionally in Python and C++ programming, data analysis, and Monte Carlo techniques.<br />
<br />
''Contact: [mailto:Tina.Pollmann@tum.de Tina Pollmann] and [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
=== Detector R&D: Time resolution of ultrathin monolithic timing detectors ===<br />
For the upgrade of ALICE and LHCb vertex detectors, new silicon pixel detectors are being developed now that can register the passing particles with a time precision of tens of picoseconds. ALICE is the first experiment at the LHC to have installed monolithic sensors where electronics is integrated into the sensor. New prototypes of their sensors have arrived at Nikhef. New prototypes of other sensors able to withstand very high radiation fluences of the LHC are arriving soon. In this project, you will tackle the challenge to accurately measure the time resolution of one of these sensors with our laser setups in the laboratory. You will have the chance to work in an international collaboration where you will report about the performance of these novel sensors. There may even be an opportunity to join beam tests at CERN. For this project, we are looking for someone who is interested to work with high-tech sensors and equipment in our Nikhef laboratory and with python programming skills.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
=== Detector R&D: Performance of monolithic sensors for the ALICE upgrade from test beam data ===<br />
For the upgrade of the ALICE detector, ultrathin picosecond timing integrated sensors are being developed now, of which the first prototypes are now at Nikhef and are being studied in test beams at CERN and DESY in Hamburg. Sensors are studied with the ALPIDE (ALICE PIxel DEtector) telescope that uses the same sensors that have recently installed in the heart of the ALICE experiment at CERN. In this project, you will analyze data from beam tests to measure the efficiency and time resolution of the new prototypes for the ALICE upgrade with the latest data from test beams at CERN. If the travel situation allows, you will have the opportunity to join the ALICE test beam group at CERN or in Hamburg at DESY to take part in the exciting experience of taking real data. We are looking for someone with good programming and data analysis skills.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
=== Detector R&D: Modeling radiation damage in silicon sensors ===<br />
In the coming years, the ATLAS experiment at the LHC works on upgrades to prepare for the high-luminosity LHC, where many more collisions will take place than today. Both analysis of data and decisions made in preparation of these detectors and on data taking heavily rely on simulations, especially those that model the damage done to sensors after many collisions. It may sound counterintuitive, but particle detectors do not actually like particles: after many collisions at the LHC, a silicon pixel detector has seen so many particles that its bulk gathers defects. Charge generated by traversing particles can get trapped in defects resulting in less charge induced in the readout electrodes, reducing detector performance in resolution and efficiency. In this project, you will be a member of the international ATLAS collaboration where you will compare different models of radiation damage with measured data. You will learn technology computer aided design (TCAD), widely used in industry, and contribute to the open source program Allpix Squared that is widely used for simulations in many areas of particle physics. Here we are looking for someone with good programming and data analysis skills who would like to contribute to upgrades of collider experiments.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
=== Detector R&D: Fast trigger ===<br />
Muons in cosmic rays are for free! In this project we are not looking for where cosmic rays come from or what physics can be studied with them. Instead, we are using them to test some of our particle detectors. Muons are short lived particles that carry the same charge as electrons, have a high penetrating power and can be detected relatively easy. In practice a test set-up consists of a ‘trigger’ and a device under test. The ‘trigger’ is a detector that gives a signal when a muon passes by, which is a signal to check the result in the device under test. Did the device under test respond to the muon in the expected way? <br />
<br />
For the planned upgrades of particle detectors at CERN, for LHC experiments (LHCb, ATLAS, ALICE, CMS), new particle detectors are under development. Some of these new detectors must be able to measure within tens of ps (10e-12 s) precise when a particle was detected.<br />
<br />
To facilitate testing these new detectors by using muons we need a trigger set up with a matching precision in timing (order tens of ps). We want to investigate several potentially interesting technologies to develop such a fast trigger. In one scenario the trigger could be based on the use of Cherenkov light. Cherenkov light is generated when a charged particle traverses a medium faster than the speed of light in that medium. This light can be generated in for example plexiglass, which in turn can be mounted on top of a light sensor. In our case the light sensor could be a so called silicon photo multiplier, which is capable of detecting only a few photons and gives a signal within a few hundred ps. Another possible scenario would be to use a so called LGAD (Low Gain Avalanche Diode) to measure the signal that a muon generates as it traverses the sensor.<br />
<br />
The Question(s): Which technology should we use for a fast trigger and what is the best timing precision that we can achieve? <br />
<br />
This project will involve a lot of 'hands on work' in the lab. <br />
<br />
''Contact: [mailto:martinfr@nikhef.nl Martin Fransen] and [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
=== Detector R&D: Characterisation of Trench Isolated Low Gain Avalanche Detectors (TI-LGAD) ===<br />
The future vertex detector of the LHCb Experiment needs to measure the spatial coordinates and time of the particles originating in the LHC proton-proton collisions with resolutions better than 10 um and 50 ps, respectively. Several technologies are being considered to achieve these resolutions. Among those is a novel sensor technology called Trench Isolated Low Gain Avalanche Detector. Prototype pixelated sensors have been manufactured recently and have to be characterised. Therefore these new sensors will be bump bonded to a Timepix4 ASIC which provides charge and time measurements in each of 230 thousand pixels. Characterisation will be done using a lab setup at Nikhef, and includes tests with a micro-focused laser beam, radioactive sources, and possibly with particle tracks obtained in a test-beam. This project involves data taking with these new devices and analysing the data to determine the performance parameters such as the spatial and temporal resolution. as function of temperature and other operational conditions.<br />
<br />
''Contacts: [mailto:kazu.akiba@nikhef.nl Kazu Akiba] and [mailto:martinb@nikhef.nl Martin van Beuzekom]''<br />
<br />
=== Detector R&D: Simulation of 3D silicon sensors ===<br />
For the upgrade of the vertex detector of the LHCb experiment novel silicon pixel detectors have to be developed that can register the passing particles with a time precision of tens of picoseconds. Given the harsh radiation environment very close to the LHCb interaction point only a limited number of technologies can be applied. One of the most promising technologies are the so-called 3D sensors whose readout electrodes are pillars that are placed into the sensor perpendicular to the surface; this in contrast to ’standard’ planar silicon sensors where the pixel electrodes are at the surface, similar to the camera in your smartphone. To understand the time response of these 3D sensors, simulations with TCAD software have to be performed and the results will be compared to measured data. These simulations involve the creation/adaptation of the 3D structures of the model, optimising the simulation speed, and analysing the signals as function voltage, track impact point and deposited charge. Hands-on experience with such 3D sensors in the R&D labs at Nikhef is planned within the scope of this project.<br />
<br />
''Contacts: [mailto:martinb@nikhef.nl Martin van Beuzekom] and [mailto:kazu.akiba@nikhef.nl Kazu Akiba]''<br />
<br />
===Detector R&D: Laser Interferometer Space Antenna (LISA) - Wavefront sensors for gravitational wave detection ===<br />
<br />
The space-based gravitational wave antenna LISA is one of the most challenging space missions ever proposed. ESA plans to launch around 2034 three spacecraft separated by a few million kilometres. This constellation measures tiny variations in the distances between test-masses located in each satellite to detect gravitational waves from sources such as supermassive black holes. LISA is based on laser interferometry, and the three satellites form a giant Michelson interferometer. LISA measures a relative phase shift between one local laser and one distant laser by light interference. The phase shift measurement requires sensitive wavefront sensors. The Nikhef DR&D group fabricated prototype sensors in 2020 together with the Photonics industry and the Dutch institute for space research SRON. Nikhef & SRON are responsible for the Quadrant PhotoReceiver (QPR) system: the sensors, the housing including a complex mount to align the sensors with 10's of nanometer accuracy, various environmental tests at the European Space Research and Technology Centre (ESTEC), and the overall performance of the QPR in the LISA instrument. Currently we are discussing possible sensor improvements for a second fabrication run in 2022, optimizing the mechanics and preparing environmental tests. As a MSc student, you will work on various aspects of the wavefront sensor development: study the performance of the epitaxial stacks of Indium-Gallium-Arsenide, setting up test benches to characterize the sensors and QPR system, performing the actual tests and data analysis, in combination with performance studies and simulations of the LISA instrument.<br />
<br />
''Contact: [mailto:nielsvb@nikhef.nl Niels van Bakel]''<br />
<br />
===FCC: The Next Collider===<br />
<br />
After the LHC, the next planned large collider at CERN is the proposed 100 kilometer circular collider "FCC". In the first stage of the project, as a high-luminosity electron-positron collider, precision measurements of the Higgs boson are the main goal. One of the channels that will improve by orders of magnitude at this new accelerator is the decay of the Higgs boson to a pair of charm quarks. This project will estimate a projected sensitivity for the coupling of the Higgs boson to second generation quarks, and in particular target the improved reconstruction of the topology of long-lived mesons in the clean environment of a precision e+e- machine.<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
<br />
===LHCb: Search for light dark particles===<br />
The Standard Model of elementary particles does not contain a proper Dark Matter candidate. One of the most tantalizing theoretical developments is the so-called ''Hidden Valley models'': a mirror-like copy of the ''Standard Model'', with dark particles that communicate with standard ones via a very feeble interaction. These models predict the existence of ''dark hadrons'' – composite particles that are bound similarly to ordinary hadrons in the ''Standard Model''. Such ''dark hadrons'' can be abundantly produced in high-energy proton-proton collisions, making the LHC a unique place to search for them. Some ''dark hadrons'' are stable like a proton, which makes them excellent ''Dark Matter'' candidates, while others decay to ordinary particles after flying a certain distance in the collider experiment. The LHCb detector has a unique capability to identify such decays, particularly if the new particles have a mass below ten times the proton mass. <br />
<br />
This project assumes a unique search for light ''dark hadrons'' that covers a mass range not accessible to other experiments. It assumes an interesting program on data analysis (python-based) with non-trivial machine learning solutions and phenomenology research using fast simulation framework. Depending on the interest, there is quite a bit of flexibility in the precise focus of the project.<br />
<br />
''Contact: [mailto:andrii.usachov@nikhef.nl Andrii Usachov]''<br />
<br />
===LHCb: Measuring lepton flavour universality with excited Ds states in semileptonic Bs decays===<br />
One of the most striking discrepancies between the Standard Model and measurements are the lepton flavour universality (LFU) measurements with tau decays. At the moment, we have observed an excess of 3-4 sigma in ''B → Dτν'' decays. This could point even to a new force of nature! To understand this discrepancy, we need to make further measurements. <br />
<br />
One very exciting (pun intended) projects to verify these discrepancies involves measuring the ''B<sub>s</sub> → D<sub>s2</sub><sup>*</sup>τν'' and/or ''B<sub>s</sub> → D<sub>s1</sub><sup>*</sup>τν'' decays. These decays with excited states of the ''D<sub>s</sub>'' meson have not been observed before in the tau decay mode, and have a unique way of coupling to potential new physics candidates that can only be measured in ''B<sub>s</sub>'' decays [1]. See slides for more detail: [[File:LHCbLFUwithExcitedDs.pdf|thumb]]<br />
<br />
[1] https://arxiv.org/abs/1606.09300<br />
<br />
''Contact: [mailto:suzannek@nikhef.nl Suzanne Klaver]''<br />
<br />
===LHCb: New physics in the angular distributions of B decays to K*ee===<br />
<br />
Lepton flavour violation in B decays can be explained by a variety of non-standard model interactions. Angular distributions in decays of a B meson to a hadron and two leptons are an important source of information to understand which model is correct. Previous analyses at the LHCb experiment have considered final states with a pair of muons. Our LHCb group at Nikhef concentrates on a new measurement of angular distributions in decays with two electrons. The main challenge in this measurement is the calibration of the detection efficiency. In this project you will confront estimates of the detection efficiency derived from simulation with decay distributions in a well known B decay. Once the calibration is understood, the very first analysis of the angular distributions in the electron final state can be performed. <br />
<br />
Contact: [mailto:m.senghi.soares@nikhef.nl Mara Soares] and [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
<br />
===LHCb: Discovering heavy neutrinos in B decays===<br />
<br />
Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, much heavier, neutral leptons. If the mass of these new neutrinos is below the b-quark mass, they can be observed in B hadron decays.<br />
<br />
In this project we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undiscovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The analysis will be performed within the LHCb group at Nikhef using LHCb run-2 data.<br />
<br />
''Contact: [mailto:v.lukashenko@nikhef.nl Lera Lukashenko] and'' [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
===LHCb: The exotic 4-quark state X(3872) in exclusive production===<br />
The nature of the X(3872) is still unknown. Is it a regular charmonium with an unexpected mass, a compact 4-quark state, or a DD molecule? Or a quantum superposition of all that? Either way, finding out will tell us something about how quark organise in hadrons and colour confinement. The project is to measure a very peculiar production mode: pp->Xpp. Only the X is seen in the detector and nothing else. Data from LHCb run 2 will be used and the analysis will build on previous work. <br />
<br />
''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
<br />
===LHCb: Scintillating Fibre tracker software===<br />
The installation of the scintillating-fibre tracker in LHCb’s underground cavern was recently completed. This detector uses 10000 km of fibres to track particle trajectories in the LHCb detector when the LHC starts up again later this year. The light emitted by the scintillating fibres when a particle interacts with them is measured using photon multiplier tubes. The studies proposed for this project will focus on software, and could include writing a framework to monitor the detector output, improving the detector simulation or working on the data processing.<br />
<br />
''Contact: [mailto:e.gabriel@nikhef.nl Emmy Gabriel]''<br />
<br />
===LHCb: Vertex detector calibration===<br />
In summer 2022 LHCb has started data taking will an almost entirely new detector. At the point closest to the interaction point, the trajectories of charge particles are reconstructed with a so-called silicon pixel detector. The design hit resolution of this detector is about 15 micron. However, to actually reach this resolution a precise calibration of the spatial positions of the silicon sensors needs to be performed. In this project, you will use the first data of the new LHCb detector to perform this calibration and measure the detector performance.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen]''<br />
<br />
<br />
===Neutrinos: Neutrino scattering: the ultimate resolution===<br />
<br />
Neutrino telescopes like IceCube and KM3NeT aim at detecting neutrinos from cosmic sources. The neutrinos are detected with the best resolution when charged current interactions with nucleons produce a muon, which can be detected with high accuracy (depending on the detector). A crucial ingredient in the ultimate achievable pointing accuracy of neutrino telescopes is the scattering angle between the neutrino and the muon. While published computations have investigated the cross-section of the process in great detail, this important scattering angle has not received much attention. The aim of the project is to compute and characterize the distribution of this angle, and that the ultimate resolution of a neutrino telescope. If successful, the results of this project can lead to publication of interest to the neutrino telescope community.<br />
<br />
Depending on your interests, the study could be based on a first-principles calculation (using the deep-inelastic scattering formalism), include state-of-the-art parton distribution functions, and/or exploit existing event-generation software for a more experimental approach. <br />
<br />
''Contacts: [mailto:aart.heijboer@nikhef.nl Aart Heijboer]''<br />
<br />
===Neutrinos: acoustic detection of ultra-high energy neutrinos===<br />
<br />
The study of the cosmic neutrinos of energies above 1017 eV, the so-called ultra-high energy neutrinos, provides a unique view on the universe and may provide insight in the origin of the most violent astrophysical sources, such as gamma ray bursts, supernovae or even dark matter. In addition, the observation of high energy neutrinos may provide a unique tool to study interactions at high energies. The energy deposition of these extreme neutrinos in water induce a thermo-acoustic signal, which can be detected using sensitive hydrophones. The expected neutrino flux is however extremely low and the signal that neutrinos induce is small. TNO is presently developing sensitive hydrophone technology based on fiber optics. Optical fibers form a natural way to create a distributed sensing system. Using this technology a large scale neutrino telescope can be built in the deep sea. TNO is aiming for a prototype hydrophone which will form the building block of a future telescope.<br />
<br />
The work will be executed at the Nikhef institute and/or the TNO laboratories in Delft. In this project master students have the opportunity to contribute in the following ways:<br />
<br />
'''Project 1:''' Hardware development on fiber optics hydrophones technology Goal: characterize existing prototype optical fibre hydrophones in an anechoic basin at TNO laboratory. Data collection, calibration, characterization, analysis of consequences for design future acoustic hydrophone neutrino telescopes;<br />
Keywords: Optical fiber technology, signal processing, electronics, lab.<br />
<br />
'''Project 2:''' Investigation of ultra-high energy neutrinos and their interactions with matter. Goal: Discriminate the neutrino signals from the background noises, in particular clicks from whales and dolphins in the deep sea. Study impact on physics reach for future acoustic hydrophone neutrino telescopes;<br />
Keywords: Monte Carlo simulations, particle physics, neutrino physics, data analysis algorithms.<br />
<br />
Further information: Info on ultra-high energy neutrinos can be found at: http://arxiv.org/abs/1102.3591; Info on acoustic detection of neutrinos can be found at: http://arxiv.org/abs/1311.7588<br />
<br />
''Contact: [mailto:ernst-jan.buis@tno.nl Ernst Jan Buis]'' or ''[mailto:ivo.van.vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
===Neutrinos: Oscillation analysis with the first data of KM3NeT===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first few strings with sensitive photodetectors have been deployed at both the Italian and the French detector sites. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In this project the available data will be used together with simulations to best reconstruct the event topologies and optimally identify and reconstruct the first neutrino interactions in the KM3NeT detector. The data will then be used to measure neutrino oscillation parameters, and prepare for a future neutrino mass ordering determination.<br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
''Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn] [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
<br />
===Neutrinos: the Deep Underground Neutrino Experiment (DUNE)===<br />
<br />
The Deep Underground Neutrino Experiment (DUNE) is under construction in the USA, and will consist of a powerful neutrino beam originating at Fermilab, a near detector at Fermilab, and a far detector in the SURF facility in Lead, South Dakota, 1300 km away. During travelling, neutrinos oscillate and a fraction of the neutrino beam changes flavour; DUNE will determine the neutrino oscillation parameters to unrivaled precision, and try and make a first detection of CP-violation in neutrinos. In this project, various elements of DUNE can be studied, including the neutrino oscillation fit, neutrino physics with the near detector, event reconstruction and classification (including machine learning), or elements of data selection and triggering.<br />
<br />
''Contact: [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
===Neutrinos: Searching for Majorana Neutrinos with KamLAND-Zen===<br />
The KamLAND-Zen experiment, located in the Kamioka mine in Japan, is a large liquid scintillator experiment with 750kg of ultra-pure Xe-136 to search for neutrinoless double-beta decay (0n2b). The observation of the 0n2b process would be evidence for lepton number violation and the Majorana nature of neutrinos, i.e. that neutrinos are their own anti-particles. Current limits on this extraordinary rare hypothetical decay process are presented as a half-life, with a lower limit of 10^26 years. KamLAND-Zen, the world’s most sensitive 0n2b experiment, is currently taking data and there is an opportunity to work on the data analysis, analyzing data with the possibility of taking part in a ground-breaking discovery. The main focus will be on developing new techniques to filter the spallation backgrounds, i.e. the production of radioactive isotopes by passing muons. There will be close collaboration with groups in the US (MIT, Berkeley, UW) and Japan (Tohoku Univ). <br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== Cosmic Rays/Neutrinos: Seasonal muon flux variations and the pion/kaon ratio ===<br />
The KM3NeT ARCA and ORCA detectors, located kilometers deep in the Mediterranean Sea, have neutrinos as primary probes. Muons from cosmic ray interactions reach the detectors in relatively large quantities too. These muons, exploiting the capabilities and location of the detectors allow the study of cosmic rays and their interactions. In this way, questions about their origin, type, propagation can be addressed. In particular these muons are tracers of hadronic interactions at energies inaccessible at particle accelerators.<br />
<br />
The muons reaching the depths of the detectors result from decays of mesons, mostly pions and kaons, created in interactions of high-energy cosmic rays with atoms in the upper atmosphere. Seasonal changes of the temperature – and thus density - profile of the atmosphere modulate the balance between the probability for these mesons to decay (producing muons) or to re-interact. Pions and kaons are affected differently, allowing to extract their production ratio by determining how changes in muon rate depend on changes in the effective temperature – an integral over the atmospheric temperature profile weighted by a depth dependent meson production rate.<br />
<br />
In this project, the aim is to measure the rate of muons in the detectors and to calculate the effective temperature above the KM3NeT detectors from atmospheric data, both as function of time. The relation between these two can be used to extract the pion to kaon ratio.<br />
<br />
''Contact: [mailto:rbruijn@nikhef.nl Ronald Bruijn]''<br />
<br />
===Gravitational Waves: Computer modelling to design the laser interferometers for the Einstein telescope===<br />
<br />
A new field of instrument science led to the successful detection of gravitational waves by the LIGO detectors in 2015. We are now preparing the next generation of gravitational wave observatories, such as the Einstein Telescope, with the aim to increase the detector sensitivity by a factor of ten, which would allow, for example, to detect stellar-mass black holes from early in the universe when the first stars began to form. This ambitious goal requires us to find ways to significantly improve the best laser interferometers in the world.<br />
<br />
Gravitational wave detectors, such as LIGO and VIRGO, are complex Michelson-type interferometers enhanced with optical cavities. We develop and use numerical models to study these laser interferometers, to invent new optical techniques and to quantify their performance. For example, we synthesize virtual mirror surfaces to study the effects of higher-order optical modes in the interferometers, and we use opto-mechanical models to test schemes for suppressing quantum fluctuations of the light field. We can offer several projects based on numerical modelling of laser interferometers. All projects will be directly linked to the ongoing design of the Einstein Telescope.<br />
<br />
''Contact: [mailto:a.freise@nikhef.nl Andreas Freise]''<br />
<br />
=== Theory: Effective Field Theories of Particle Physics from low- to high-energies===<br />
Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations” seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature. The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Standard Model Effective Field Theory (SMEFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes with minimal assumptions on the nature of an eventual UV-complete theory that replaces the Standard Model. Specifically, the goal is to connect measurements from ATLAS, CMS, and LHCb experiments at the CERN's LHC among them and to jointly interpret this information with that provided by other experiments including very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
<br />
This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories. Depending on the student profile, sub-projects with a strong computational and/or machine learning component are also possible, for instance to construct new operators with optimal sensitivity to New Physics effects as encoded by the SMEFT higher-dimensional operators. Topics that can be considered in this project include the interpretation of novel physical observables at the LHC and their integration into the global SMEFiT analysis, matching of EFTs to UV-complete theories and their phenomenological analyses, projections for the impact in the SMEFT parameter space of data for future colliders, the synergies between EFT studies and proton structure fits, and the matching to the Weak Effective Field Theory to include data on flavour observables such as B-meson decays.<br />
<br />
References: https://arxiv.org/abs/2105.00006 , https://arxiv.org/abs/2302.06660, https://arxiv.org/abs/2211.02058 , https://arxiv.org/abs/1901.05965 , https://arxiv.org/abs/1906.05296 , https://arxiv.org/abs/1908.05588, https://arxiv.org/abs/1905.05215<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theory: High-energy neutrino-nucleon interactions at the Forward Physics Facility ===<br />
High-energy collisions at the High-Luminosity Large Hadron Collider (HL-LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing experiments. The proposed Forward Physics Facility (FPF) to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe Standard Model (SM) processes and search for physics beyond the Standard Model (BSM). High statistics neutrino detection will provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. The FPF has the promising potential to probe our understanding of the strong interactions as well as of proton and nuclear structure, providing access to both the very low-x and the very high-x regions of the colliding protons. The former regime is sensitive to novel QCD production mechanisms, such as BFKL effects and non-linear dynamics, as well as the gluon parton distribution function (PDF) down to x=1e-7, well beyond the coverage of other experiments and providing key inputs for astroparticle physics. In addition, the FPF acts as a neutrino-induced deep-inelastic scattering (DIS) experiment with TeV-scale neutrino beams. The resulting measurements of neutrino DIS structure functions represent a valuable handle on the partonic structure of nucleons and nuclei, particularly their quark flavour separation, that is fully complementary to the charged-lepton DIS measurements expected at the upcoming Electron-Ion Collider (EIC).<br />
<br />
In this project, the student will carry out updated predictions for the neutrino fluxes expected at the FPF, assess the precision with which neutrino cross-sections will be measured, and quantify their impact on proton and nuclear structure by means of machine learning tools within the NNPDF framework and state-of-the-art calculations in perturbative Quantum Chromodynamics. This project contributes to ongoing work within the FPF Initiative towards a Conceptual Design Report (CDR) to be presented within two years. Topics that can be considered as part of this project include the assessment of to which extent nuclear modifications of the free-proton PDFs can be constrained by FPF measurements, the determination of the small-x gluon PDF from suitably defined observables at the FPF and the implications for ultra-high-energy particle astrophysics, the study of the intrinsic charm content in the proton and its consequences for the FPF physics program, and the validation of models for neutrino-nucleon cross-sections in the region beyond the validity of perturbative QCD.<br />
<br />
References: https://arxiv.org/abs/2203.05090, https://arxiv.org/abs/2109.10905 , https://arxiv.org/abs/2201.12363 , https://arxiv.org/abs/2109.02653 <br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theory: Probing the origin of the proton spin with machine learning===<br />
At energy-frontier facilities such as the Large Hadron Collider (LHC), scientists study the laws of Nature in their quest for novel phenomena both within and beyond the Standard Model of particle physics. An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions from the nature of the Higgs boson to the origin of cosmic neutrinos. The key to address some of these questions is by carrying out an universal analysis of nucleon structure from the simultaneous determination of the momentum and spin distributions of quarks and gluons and their fragmentation into hadrons. This effort requires combining an extensive experimental dataset and cutting-edge theory calculations within a machine learning framework where neural networks parametrise the underlying physical laws while minimizing ad-hoc model assumptions.<br />
<br />
In this project, the student(s) will carry out a new global analysis of the spin structure of the proton by means of machine learning tools and state-of-the-art calculations in perturbative Quantum Chromodynamics, and integrate it within the corresponding global NNPDF analyses of unpolarised proton and nuclear structure in the framework of a combined integrated global analysis of non-perturbative QCD.<br />
<br />
References: arXiv:2201.12363 , arXiv:2109.02653<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
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== Finished master projects ==<br />
<br />
See: <br />
* https://wiki.nikhef.nl/education/Master_Theses<br />
* https://www.nikhef.nl/master-theses-2021/<br />
* https://www.nikhef.nl/facts-figures-2020/master-theses-2020/<br />
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[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=867Master Projects2023-02-19T09:14:18Z<p>Rojo@nikhef.nl: /* Theory: Effective Field Theories of Particle Physics from low- to high-energies */</p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
== Projects with a 2023 start ==<br />
<br />
=== ALICE: The next-generation multi-purpose detector at the LHC ===<br />
This main goal of this project is to focus on the next-generation multi-purpose detector planned to be built at the LHC. Its core will be a nearly massless barrel detector consisting of truly cylindrical layers based on curved wafer-scale ultra-thin silicon sensors with MAPS technology, featuring an unprecedented low material budget of 0.05% X0 per layer, with the innermost layers possibly positioned inside the beam pipe. The proposed detector is conceived for studies of pp, pA and AA collisions at luminosities a factor of 20 to 50 times higher than possible with the upgraded ALICE detector, enabling a rich physics program ranging from measurements with electromagnetic probes at ultra-low transverse momenta to precision physics in the charm and beauty sector. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli] and [mailto:marco.van.leeuwen@cern.ch Marco van Leeuwen]''<br />
<br />
=== ALICE: Searching for the strongest magnetic field in nature ===<br />
In a non-central collision between two Pb ions, with a large value of impact parameter, the charged nucleons that do not participate in the interaction (called spectators) create strong magnetic fields. A back of the envelope calculation using the Biot-Savart law brings the magnitude of this filed close to 10^19Gauss in agreement with state of the art theoretical calculation, making it the strongest magnetic field in nature. The presence of this field could have direct implications in the motion of final state particles. The magnetic field, however, decays rapidly. The decay rate depends on the electric conductivity of the medium which is experimentally poorly constrained. Overall, the presence of the magnetic field, the main goal of this project, is so far not confirmed experimentally.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Looking for parity violating effects in strong interactions ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions, in the presence of a deconfined state, gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, what is called the Chiral Magnetic Effect (CME).<br />
The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, however further studies are needed to constrain background effects. These highly anticipated results have the potential to reveal exiting, new physics.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Machine learning techniques as a tool to study the production of heavy flavour particles ===<br />
There was recently a shift in the field of heavy-ion physics triggered by experimental results obtained in collisions between small systems (e.g. protons on protons). These results resemble the ones obtained in collisions between heavy ions. This consequently raises the question of whether we create the smallest QGP droplet in collisions between small systems. The main objective of this project will be to study the production of charm particles such as D-mesons and Λc-baryons in pp collisions at the LHC. This will be done with the help of a new and innovative technique which is based on machine learning (ML). The student will also extend the studies to investigate how this production rate depends on the event activity e.g. on how many particles are created after every collision.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli]''<br />
<br />
===ATLAS: The Higgs boson's self-coupling===<br />
<br />
The coupling of the Higgs boson to itself is one of the main unobserved interactions of the Standard Model and its observation is crucial to understand the shape of the Higgs potential. Here we propose to study the 'ttHH' final state: two top quarks and two Higgs bosons produced in a single collision. This topology is yet unexplored at the ATLAS experiment and the project consists of setting up the new analysis (including multivariate analysis techniques to recognise the complicated final state), optimising the sensitivity and including the result in the full ATLAS study of the Higgs boson's coupling to itself. With the LHC data from the upcoming Run-3, we might be able to see its first glimpses! <br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
===ATLAS: The Next Generation===<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks is very new [1] and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays) and advanced analysis techiques (using deep learning methods).<br />
<br />
[https://atlas.cern/updates/briefing/charming-Higgs-decay][https://arxiv.org/abs/1802.04329 https://atlas.cern/updates/briefing/charming-Higgs-decay]<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
===ATLAS: Searching for new particles in very energetic diboson production===<br />
<br />
The discovery of new phenomena in high-energy proton–proton collisions is one of the main goals of the Large Hadron Collider (LHC). New heavy particles decaying into a pair of vector bosons (WW, WZ, ZZ) are predicted in several extensions to the Standard Model (e.g. extended gauge-symmetry models, Grand Unified theories, theories with warped extra dimensions, etc). In this project we will investigate new ideas to look for these resonances in a region that is yet unexplored in the data. We will focus on the final states where both vector bosons decay into quarks as they are expected to bring the highest sensitivity [1]. We will try to reconstruct and exploit new ways to identify vector bosons (using machine learning methods) and then tackle the problem of estimating contributions from beyond the Standard Model processes in the tails of the mass distribution.<br />
<br />
[1] https://arxiv.org/abs/1906.08589<br />
<br />
''Contact: [mailto:f.dias@nikhef.nl Flavia de Almeida Dias]''<br />
<br />
===ATLAS top-quark and Higgs-boson analysis combination, and Effective Field Theory interpretation===<br />
<br />
We are looking for a master student with interest in theory and data-analysis in the search for physics beyond the Standard Model in the top-quark and Higgs-boson sectors.<br />
<br />
Your master-project starts just at the right time for preparing the Run-3 analysis of the ATLAS experiment at the LHC. In Run-3 (2022-2026), three times more data becomes available, enabling analysis of rare processes with innovative software tools and techniques.<br />
<br />
This project aims to explore the newest strategy to combine the top-quark and Higgs-boson measurements in the perspective of constraining the existence of new physics beyond the Standard Model (SM) of Particle Physics. We selected the pp->tZq and gg->HZ processes as promising candidates for a combination to constrain new physics in the context of Standard Model Effective Field Theory (SMEFT). SMEFT is the state-of-the-art framework for theoretical interpretation of LHC data. In particular, you will study the SMEFT OtZ and Ophit operators, which are not well constrained by current measurements.<br />
<br />
Besides affinity with particle physics theory, the ideal candidate for this project has developed python/C++ skills and is eager to learn advanced techniques. You start with a simulation of the signal and background samples using existing software tools. Then, an event selection study is required using Machine Learning techniques. To evaluate the SMEFT effects, a fitting procedure based on the innovative Morphing technique is foreseen, for which the basic tools in the ROOT and RooFit framework are available. The work is carried out in the ATLAS group at Nikhef and may lead to an ATLAS note.<br />
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''Contact: [mailto:geoffrey.gilles@cern.ch> Geoffrey Gilles] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:h73@nikhef.nl Marcel Vreeswijk]''<br />
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=== ATLAS Machine learning to enhance reconstruction of very rare Higgs decays ===<br />
Since the Higgs boson discovery in 2012 at the ATLAS experiment, the investigation of the properties of the Higgs boson has been a priority for research at the Large Hadron Collider (LHC). However, there are still a many open questions: Is the Higgs boson the only origin of Electroweak Symmetry Breaking? Is there a mechanism which can explain the observed mass pattern of SM particles? Many of these questions are linked to the Higgs boson coupling structure. <br />
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While the Higgs boson coupling to fermions of the third generation has been clearly, the investigation of the Higgs boson coupling to the light fermions of the second generation will be a major project for the upcoming data-taking period starting this year. The Higgs boson decay to muons is most sensitive channel to establish a coupling of the Higgs boson to second generation fermions. In this project you will work on an improvement of the H-->mumu search: In about 5% of the events, a photon is radiated off the outgoing muons. By recognizing these photons and taking their effect into account we can improve the reconstruct these events better. For this project we will use machine learning to best identify these special events and to take their energy contribution into account to improve the overall sensitivity. <br />
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''Contact: [mailto:oliver.rieger@nikhef.nl Oliver Rieger] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:s01@nikhef.nl Peter Kluit]''<br />
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=== ATLAS: Scrutinising Higgs decaying into W bosons ===<br />
Observation of the Higgs boson happened 10 years ago and since then scientists’ interest has shifted towards measuring precisely its properties. An example is a coupling strength telling us how does the Higgs boson interact with different particles such as W bosons. Measuring H→ WW →lnu lnu process allows us to not only probe the Standard Model (SM), by measuring the coupling strength or indirectly probe Higgs boson width, but also test against the theories beyond (for instance in the context of the effective field theory framework).<br />
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The student will take active part in the ATLAS HWW group. There are multiple possible areas of contribution within the group depending on the interest of the student. For instance, utilising machine learning techniques to optimise for the selection of HWW signal process, determining the fake background processes, interpreting the results through the beyond SM theories and others.<br />
Contact: ''[mailto:mvozak@cern.ch Matouš Vozák] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
=== ATLAS: HGTD detector ===<br />
The ATLAS is going to get a new ability: a Timing Layer. This allows us to reconstruct tracks not only in the 3 dimensions of space but adds the ability of measuring very precisely also the time (at picosecond level) at which the particles pass the sensitive layers of the HGTD detector. This allow to construct the trajectories of the particles created at the LHC in 4 dimensions and ultimately will lead to a better reconstruction of physics at ATLAS. The new HGTD detector is still in construction and work needs to be done on different levels such as understanding the detector response (taking measurements in the lab and performing simulations) or developing algorithms to reconstruct the particle trajectories (programming and analysis work). With this work you will be part of the Atlas group and/or the Fast Timing detector group together with the R&D department at Nikhef. <br />
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Contact me to discuss the possibilities. <br />
Contact: ''[mailto:hella.snoek@nikhef.nl Hella Snoek]''<br />
=== Dark Matter: Building better Dark Matter Detectors - the XAMS R&D Setup===<br />
The Amsterdam Dark Matter group operates an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 0.5kg of ultra-pure liquid xenon in the central volume. We use this detector for the development of new detection techniques - such as utilizing our newly installed silicon photomultipliers - and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENONnT experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory, or for future Dark Matter experiments like DARWIN. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data themselves You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
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===Dark Matter: Searching for Dark Matter Particles - XENONnT Data Analysis ===<br />
The XENON collaboration has used the XENON1T detector to achieve the world’s most sensitive direct detection dark matter results and is currently operating the XENONnT successor experiment. The detectors operate at the Gran Sasso underground laboratory and consist of so-called dual-phase xenon time-projection chambers filled with ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the new data coming from the XENONnT detector. The work will consist of understanding the detector signals and applying a deep neural network to improve the (gas-) background discrimination in our Python-based analysis tool to improve the sensitivity for low-mass dark matter particles. The work will continue a study started by a recent graduate. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy.<br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
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===Dark Matter: The Ultimate Dark Matter Experiment - DARWIN Sensitivity Studies===<br />
DARWIN is the “ultimate” direct detection dark matter experiment, with the goal to reach the so-called “neutrino floor”, when neutrinos become a hard-to-reduce background. The large and exquisitely clean xenon mass will allow DARWIN to also be sensitive to other physics signals such as solar neutrinos, double-beta decay from Xe-136, axions and axion-like particles etc. While the experiment will only start in 2027, we are in the midst of optimizing the experiment, which is driven by simulations. We have an opening for a student to work on the GEANT4 Monte Carlo simulations for DARWIN. We are also working on a “fast simulation” that could be included in this framework. It is your opportunity to steer the optimization of a large and unique experiment. This project requires good programming skills (Python and C++) and data analysis/physics interpretation skills.<br />
<br />
''Contact: [mailto:t.pollmann@nikhef.nl Tina Pollmann], [mailto:decowski@nikhef.nl Patrick Decowski] or [mailto:z37@nikhef.nl Auke Colijn]''<br />
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===Dark Matter: Sensitive tests of wavelength-shifting properties of materials for dark matter detectors===<br />
Rare event search experiments that look for neutrino and dark matter interactions are performed with highly sensitive detector systems, often relying on scintillators, especially liquid noble gases, to detect particle interactions. Detectors consist of structural materials that are assumed to be optically passive, and light detection systems that use reflectors, light detectors, and sometimes, wavelength-shifting materials. MSc theses are available related to measuring the efficiency of light detection systems that might be used in future detectors. Furthermore, measurements to ensure that presumably passive materials do not fluoresce, at the low level relevant to the detectors, can be done. Part of the thesis work can include Monte Carlo simulations and data analysis for current and upcoming dark matter detectors, to study the effect of different levels of desired and nuisance wavelength shifting. In this project, students will acquire skills in photon detection, wavelength shifting technologies, vacuum systems, UV and extreme-UV optics, detector design, and optionally in Python and C++ programming, data analysis, and Monte Carlo techniques.<br />
<br />
''Contact: [mailto:Tina.Pollmann@tum.de Tina Pollmann] and [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
=== Detector R&D: Time resolution of ultrathin monolithic timing detectors ===<br />
For the upgrade of ALICE and LHCb vertex detectors, new silicon pixel detectors are being developed now that can register the passing particles with a time precision of tens of picoseconds. ALICE is the first experiment at the LHC to have installed monolithic sensors where electronics is integrated into the sensor. New prototypes of their sensors have arrived at Nikhef. New prototypes of other sensors able to withstand very high radiation fluences of the LHC are arriving soon. In this project, you will tackle the challenge to accurately measure the time resolution of one of these sensors with our laser setups in the laboratory. You will have the chance to work in an international collaboration where you will report about the performance of these novel sensors. There may even be an opportunity to join beam tests at CERN. For this project, we are looking for someone who is interested to work with high-tech sensors and equipment in our Nikhef laboratory and with python programming skills.<br />
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''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
=== Detector R&D: Performance of monolithic sensors for the ALICE upgrade from test beam data ===<br />
For the upgrade of the ALICE detector, ultrathin picosecond timing integrated sensors are being developed now, of which the first prototypes are now at Nikhef and are being studied in test beams at CERN and DESY in Hamburg. Sensors are studied with the ALPIDE (ALICE PIxel DEtector) telescope that uses the same sensors that have recently installed in the heart of the ALICE experiment at CERN. In this project, you will analyze data from beam tests to measure the efficiency and time resolution of the new prototypes for the ALICE upgrade with the latest data from test beams at CERN. If the travel situation allows, you will have the opportunity to join the ALICE test beam group at CERN or in Hamburg at DESY to take part in the exciting experience of taking real data. We are looking for someone with good programming and data analysis skills.<br />
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''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
=== Detector R&D: Modeling radiation damage in silicon sensors ===<br />
In the coming years, the ATLAS experiment at the LHC works on upgrades to prepare for the high-luminosity LHC, where many more collisions will take place than today. Both analysis of data and decisions made in preparation of these detectors and on data taking heavily rely on simulations, especially those that model the damage done to sensors after many collisions. It may sound counterintuitive, but particle detectors do not actually like particles: after many collisions at the LHC, a silicon pixel detector has seen so many particles that its bulk gathers defects. Charge generated by traversing particles can get trapped in defects resulting in less charge induced in the readout electrodes, reducing detector performance in resolution and efficiency. In this project, you will be a member of the international ATLAS collaboration where you will compare different models of radiation damage with measured data. You will learn technology computer aided design (TCAD), widely used in industry, and contribute to the open source program Allpix Squared that is widely used for simulations in many areas of particle physics. Here we are looking for someone with good programming and data analysis skills who would like to contribute to upgrades of collider experiments.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
=== Detector R&D: Fast trigger ===<br />
Muons in cosmic rays are for free! In this project we are not looking for where cosmic rays come from or what physics can be studied with them. Instead, we are using them to test some of our particle detectors. Muons are short lived particles that carry the same charge as electrons, have a high penetrating power and can be detected relatively easy. In practice a test set-up consists of a ‘trigger’ and a device under test. The ‘trigger’ is a detector that gives a signal when a muon passes by, which is a signal to check the result in the device under test. Did the device under test respond to the muon in the expected way? <br />
<br />
For the planned upgrades of particle detectors at CERN, for LHC experiments (LHCb, ATLAS, ALICE, CMS), new particle detectors are under development. Some of these new detectors must be able to measure within tens of ps (10e-12 s) precise when a particle was detected.<br />
<br />
To facilitate testing these new detectors by using muons we need a trigger set up with a matching precision in timing (order tens of ps). We want to investigate several potentially interesting technologies to develop such a fast trigger. In one scenario the trigger could be based on the use of Cherenkov light. Cherenkov light is generated when a charged particle traverses a medium faster than the speed of light in that medium. This light can be generated in for example plexiglass, which in turn can be mounted on top of a light sensor. In our case the light sensor could be a so called silicon photo multiplier, which is capable of detecting only a few photons and gives a signal within a few hundred ps. Another possible scenario would be to use a so called LGAD (Low Gain Avalanche Diode) to measure the signal that a muon generates as it traverses the sensor.<br />
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The Question(s): Which technology should we use for a fast trigger and what is the best timing precision that we can achieve? <br />
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This project will involve a lot of 'hands on work' in the lab. <br />
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''Contact: [mailto:martinfr@nikhef.nl Martin Fransen] and [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
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=== Detector R&D: Characterisation of Trench Isolated Low Gain Avalanche Detectors (TI-LGAD) ===<br />
The future vertex detector of the LHCb Experiment needs to measure the spatial coordinates and time of the particles originating in the LHC proton-proton collisions with resolutions better than 10 um and 50 ps, respectively. Several technologies are being considered to achieve these resolutions. Among those is a novel sensor technology called Trench Isolated Low Gain Avalanche Detector. Prototype pixelated sensors have been manufactured recently and have to be characterised. Therefore these new sensors will be bump bonded to a Timepix4 ASIC which provides charge and time measurements in each of 230 thousand pixels. Characterisation will be done using a lab setup at Nikhef, and includes tests with a micro-focused laser beam, radioactive sources, and possibly with particle tracks obtained in a test-beam. This project involves data taking with these new devices and analysing the data to determine the performance parameters such as the spatial and temporal resolution. as function of temperature and other operational conditions.<br />
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''Contacts: [mailto:kazu.akiba@nikhef.nl Kazu Akiba] and [mailto:martinb@nikhef.nl Martin van Beuzekom]''<br />
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=== Detector R&D: Simulation of 3D silicon sensors ===<br />
For the upgrade of the vertex detector of the LHCb experiment novel silicon pixel detectors have to be developed that can register the passing particles with a time precision of tens of picoseconds. Given the harsh radiation environment very close to the LHCb interaction point only a limited number of technologies can be applied. One of the most promising technologies are the so-called 3D sensors whose readout electrodes are pillars that are placed into the sensor perpendicular to the surface; this in contrast to ’standard’ planar silicon sensors where the pixel electrodes are at the surface, similar to the camera in your smartphone. To understand the time response of these 3D sensors, simulations with TCAD software have to be performed and the results will be compared to measured data. These simulations involve the creation/adaptation of the 3D structures of the model, optimising the simulation speed, and analysing the signals as function voltage, track impact point and deposited charge. Hands-on experience with such 3D sensors in the R&D labs at Nikhef is planned within the scope of this project.<br />
<br />
''Contacts: [mailto:martinb@nikhef.nl Martin van Beuzekom] and [mailto:kazu.akiba@nikhef.nl Kazu Akiba]''<br />
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===Detector R&D: Laser Interferometer Space Antenna (LISA) - Wavefront sensors for gravitational wave detection ===<br />
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The space-based gravitational wave antenna LISA is one of the most challenging space missions ever proposed. ESA plans to launch around 2034 three spacecraft separated by a few million kilometres. This constellation measures tiny variations in the distances between test-masses located in each satellite to detect gravitational waves from sources such as supermassive black holes. LISA is based on laser interferometry, and the three satellites form a giant Michelson interferometer. LISA measures a relative phase shift between one local laser and one distant laser by light interference. The phase shift measurement requires sensitive wavefront sensors. The Nikhef DR&D group fabricated prototype sensors in 2020 together with the Photonics industry and the Dutch institute for space research SRON. Nikhef & SRON are responsible for the Quadrant PhotoReceiver (QPR) system: the sensors, the housing including a complex mount to align the sensors with 10's of nanometer accuracy, various environmental tests at the European Space Research and Technology Centre (ESTEC), and the overall performance of the QPR in the LISA instrument. Currently we are discussing possible sensor improvements for a second fabrication run in 2022, optimizing the mechanics and preparing environmental tests. As a MSc student, you will work on various aspects of the wavefront sensor development: study the performance of the epitaxial stacks of Indium-Gallium-Arsenide, setting up test benches to characterize the sensors and QPR system, performing the actual tests and data analysis, in combination with performance studies and simulations of the LISA instrument.<br />
<br />
''Contact: [mailto:nielsvb@nikhef.nl Niels van Bakel]''<br />
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===FCC: The Next Collider===<br />
<br />
After the LHC, the next planned large collider at CERN is the proposed 100 kilometer circular collider "FCC". In the first stage of the project, as a high-luminosity electron-positron collider, precision measurements of the Higgs boson are the main goal. One of the channels that will improve by orders of magnitude at this new accelerator is the decay of the Higgs boson to a pair of charm quarks. This project will estimate a projected sensitivity for the coupling of the Higgs boson to second generation quarks, and in particular target the improved reconstruction of the topology of long-lived mesons in the clean environment of a precision e+e- machine.<br />
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''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
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<br />
===LHCb: Search for light dark particles===<br />
The Standard Model of elementary particles does not contain a proper Dark Matter candidate. One of the most tantalizing theoretical developments is the so-called ''Hidden Valley models'': a mirror-like copy of the ''Standard Model'', with dark particles that communicate with standard ones via a very feeble interaction. These models predict the existence of ''dark hadrons'' – composite particles that are bound similarly to ordinary hadrons in the ''Standard Model''. Such ''dark hadrons'' can be abundantly produced in high-energy proton-proton collisions, making the LHC a unique place to search for them. Some ''dark hadrons'' are stable like a proton, which makes them excellent ''Dark Matter'' candidates, while others decay to ordinary particles after flying a certain distance in the collider experiment. The LHCb detector has a unique capability to identify such decays, particularly if the new particles have a mass below ten times the proton mass. <br />
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This project assumes a unique search for light ''dark hadrons'' that covers a mass range not accessible to other experiments. It assumes an interesting program on data analysis (python-based) with non-trivial machine learning solutions and phenomenology research using fast simulation framework. Depending on the interest, there is quite a bit of flexibility in the precise focus of the project.<br />
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''Contact: [mailto:andrii.usachov@nikhef.nl Andrii Usachov]''<br />
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===LHCb: Measuring lepton flavour universality with excited Ds states in semileptonic Bs decays===<br />
One of the most striking discrepancies between the Standard Model and measurements are the lepton flavour universality (LFU) measurements with tau decays. At the moment, we have observed an excess of 3-4 sigma in ''B → Dτν'' decays. This could point even to a new force of nature! To understand this discrepancy, we need to make further measurements. <br />
<br />
One very exciting (pun intended) projects to verify these discrepancies involves measuring the ''B<sub>s</sub> → D<sub>s2</sub><sup>*</sup>τν'' and/or ''B<sub>s</sub> → D<sub>s1</sub><sup>*</sup>τν'' decays. These decays with excited states of the ''D<sub>s</sub>'' meson have not been observed before in the tau decay mode, and have a unique way of coupling to potential new physics candidates that can only be measured in ''B<sub>s</sub>'' decays [1]. See slides for more detail: [[File:LHCbLFUwithExcitedDs.pdf|thumb]]<br />
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[1] https://arxiv.org/abs/1606.09300<br />
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''Contact: [mailto:suzannek@nikhef.nl Suzanne Klaver]''<br />
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===LHCb: New physics in the angular distributions of B decays to K*ee===<br />
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Lepton flavour violation in B decays can be explained by a variety of non-standard model interactions. Angular distributions in decays of a B meson to a hadron and two leptons are an important source of information to understand which model is correct. Previous analyses at the LHCb experiment have considered final states with a pair of muons. Our LHCb group at Nikhef concentrates on a new measurement of angular distributions in decays with two electrons. The main challenge in this measurement is the calibration of the detection efficiency. In this project you will confront estimates of the detection efficiency derived from simulation with decay distributions in a well known B decay. Once the calibration is understood, the very first analysis of the angular distributions in the electron final state can be performed. <br />
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Contact: [mailto:m.senghi.soares@nikhef.nl Mara Soares] and [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
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===LHCb: Discovering heavy neutrinos in B decays===<br />
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Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, much heavier, neutral leptons. If the mass of these new neutrinos is below the b-quark mass, they can be observed in B hadron decays.<br />
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In this project we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undiscovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The analysis will be performed within the LHCb group at Nikhef using LHCb run-2 data.<br />
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''Contact: [mailto:v.lukashenko@nikhef.nl Lera Lukashenko] and'' [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
===LHCb: The exotic 4-quark state X(3872) in exclusive production===<br />
The nature of the X(3872) is still unknown. Is it a regular charmonium with an unexpected mass, a compact 4-quark state, or a DD molecule? Or a quantum superposition of all that? Either way, finding out will tell us something about how quark organise in hadrons and colour confinement. The project is to measure a very peculiar production mode: pp->Xpp. Only the X is seen in the detector and nothing else. Data from LHCb run 2 will be used and the analysis will build on previous work. <br />
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''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
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===LHCb: Scintillating Fibre tracker software===<br />
The installation of the scintillating-fibre tracker in LHCb’s underground cavern was recently completed. This detector uses 10000 km of fibres to track particle trajectories in the LHCb detector when the LHC starts up again later this year. The light emitted by the scintillating fibres when a particle interacts with them is measured using photon multiplier tubes. The studies proposed for this project will focus on software, and could include writing a framework to monitor the detector output, improving the detector simulation or working on the data processing.<br />
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''Contact: [mailto:e.gabriel@nikhef.nl Emmy Gabriel]''<br />
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===LHCb: Vertex detector calibration===<br />
In summer 2022 LHCb has started data taking will an almost entirely new detector. At the point closest to the interaction point, the trajectories of charge particles are reconstructed with a so-called silicon pixel detector. The design hit resolution of this detector is about 15 micron. However, to actually reach this resolution a precise calibration of the spatial positions of the silicon sensors needs to be performed. In this project, you will use the first data of the new LHCb detector to perform this calibration and measure the detector performance.<br />
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''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen]''<br />
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<br />
===Neutrinos: Neutrino scattering: the ultimate resolution===<br />
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Neutrino telescopes like IceCube and KM3NeT aim at detecting neutrinos from cosmic sources. The neutrinos are detected with the best resolution when charged current interactions with nucleons produce a muon, which can be detected with high accuracy (depending on the detector). A crucial ingredient in the ultimate achievable pointing accuracy of neutrino telescopes is the scattering angle between the neutrino and the muon. While published computations have investigated the cross-section of the process in great detail, this important scattering angle has not received much attention. The aim of the project is to compute and characterize the distribution of this angle, and that the ultimate resolution of a neutrino telescope. If successful, the results of this project can lead to publication of interest to the neutrino telescope community.<br />
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Depending on your interests, the study could be based on a first-principles calculation (using the deep-inelastic scattering formalism), include state-of-the-art parton distribution functions, and/or exploit existing event-generation software for a more experimental approach. <br />
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''Contacts: [mailto:aart.heijboer@nikhef.nl Aart Heijboer]''<br />
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===Neutrinos: acoustic detection of ultra-high energy neutrinos===<br />
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The study of the cosmic neutrinos of energies above 1017 eV, the so-called ultra-high energy neutrinos, provides a unique view on the universe and may provide insight in the origin of the most violent astrophysical sources, such as gamma ray bursts, supernovae or even dark matter. In addition, the observation of high energy neutrinos may provide a unique tool to study interactions at high energies. The energy deposition of these extreme neutrinos in water induce a thermo-acoustic signal, which can be detected using sensitive hydrophones. The expected neutrino flux is however extremely low and the signal that neutrinos induce is small. TNO is presently developing sensitive hydrophone technology based on fiber optics. Optical fibers form a natural way to create a distributed sensing system. Using this technology a large scale neutrino telescope can be built in the deep sea. TNO is aiming for a prototype hydrophone which will form the building block of a future telescope.<br />
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The work will be executed at the Nikhef institute and/or the TNO laboratories in Delft. In this project master students have the opportunity to contribute in the following ways:<br />
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'''Project 1:''' Hardware development on fiber optics hydrophones technology Goal: characterize existing prototype optical fibre hydrophones in an anechoic basin at TNO laboratory. Data collection, calibration, characterization, analysis of consequences for design future acoustic hydrophone neutrino telescopes;<br />
Keywords: Optical fiber technology, signal processing, electronics, lab.<br />
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'''Project 2:''' Investigation of ultra-high energy neutrinos and their interactions with matter. Goal: Discriminate the neutrino signals from the background noises, in particular clicks from whales and dolphins in the deep sea. Study impact on physics reach for future acoustic hydrophone neutrino telescopes;<br />
Keywords: Monte Carlo simulations, particle physics, neutrino physics, data analysis algorithms.<br />
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Further information: Info on ultra-high energy neutrinos can be found at: http://arxiv.org/abs/1102.3591; Info on acoustic detection of neutrinos can be found at: http://arxiv.org/abs/1311.7588<br />
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''Contact: [mailto:ernst-jan.buis@tno.nl Ernst Jan Buis]'' or ''[mailto:ivo.van.vulpen@nikhef.nl Ivo van Vulpen]''<br />
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===Neutrinos: Oscillation analysis with the first data of KM3NeT===<br />
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The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first few strings with sensitive photodetectors have been deployed at both the Italian and the French detector sites. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In this project the available data will be used together with simulations to best reconstruct the event topologies and optimally identify and reconstruct the first neutrino interactions in the KM3NeT detector. The data will then be used to measure neutrino oscillation parameters, and prepare for a future neutrino mass ordering determination.<br />
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Programming skills are essential, mostly root and C++ will be used.<br />
''Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn] [mailto:h26@nikhef.nl Paul de Jong]''<br />
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<br />
===Neutrinos: the Deep Underground Neutrino Experiment (DUNE)===<br />
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The Deep Underground Neutrino Experiment (DUNE) is under construction in the USA, and will consist of a powerful neutrino beam originating at Fermilab, a near detector at Fermilab, and a far detector in the SURF facility in Lead, South Dakota, 1300 km away. During travelling, neutrinos oscillate and a fraction of the neutrino beam changes flavour; DUNE will determine the neutrino oscillation parameters to unrivaled precision, and try and make a first detection of CP-violation in neutrinos. In this project, various elements of DUNE can be studied, including the neutrino oscillation fit, neutrino physics with the near detector, event reconstruction and classification (including machine learning), or elements of data selection and triggering.<br />
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''Contact: [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
===Neutrinos: Searching for Majorana Neutrinos with KamLAND-Zen===<br />
The KamLAND-Zen experiment, located in the Kamioka mine in Japan, is a large liquid scintillator experiment with 750kg of ultra-pure Xe-136 to search for neutrinoless double-beta decay (0n2b). The observation of the 0n2b process would be evidence for lepton number violation and the Majorana nature of neutrinos, i.e. that neutrinos are their own anti-particles. Current limits on this extraordinary rare hypothetical decay process are presented as a half-life, with a lower limit of 10^26 years. KamLAND-Zen, the world’s most sensitive 0n2b experiment, is currently taking data and there is an opportunity to work on the data analysis, analyzing data with the possibility of taking part in a ground-breaking discovery. The main focus will be on developing new techniques to filter the spallation backgrounds, i.e. the production of radioactive isotopes by passing muons. There will be close collaboration with groups in the US (MIT, Berkeley, UW) and Japan (Tohoku Univ). <br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== Cosmic Rays/Neutrinos: Seasonal muon flux variations and the pion/kaon ratio ===<br />
The KM3NeT ARCA and ORCA detectors, located kilometers deep in the Mediterranean Sea, have neutrinos as primary probes. Muons from cosmic ray interactions reach the detectors in relatively large quantities too. These muons, exploiting the capabilities and location of the detectors allow the study of cosmic rays and their interactions. In this way, questions about their origin, type, propagation can be addressed. In particular these muons are tracers of hadronic interactions at energies inaccessible at particle accelerators.<br />
<br />
The muons reaching the depths of the detectors result from decays of mesons, mostly pions and kaons, created in interactions of high-energy cosmic rays with atoms in the upper atmosphere. Seasonal changes of the temperature – and thus density - profile of the atmosphere modulate the balance between the probability for these mesons to decay (producing muons) or to re-interact. Pions and kaons are affected differently, allowing to extract their production ratio by determining how changes in muon rate depend on changes in the effective temperature – an integral over the atmospheric temperature profile weighted by a depth dependent meson production rate.<br />
<br />
In this project, the aim is to measure the rate of muons in the detectors and to calculate the effective temperature above the KM3NeT detectors from atmospheric data, both as function of time. The relation between these two can be used to extract the pion to kaon ratio.<br />
<br />
''Contact: [mailto:rbruijn@nikhef.nl Ronald Bruijn]''<br />
<br />
===Gravitational Waves: Computer modelling to design the laser interferometers for the Einstein telescope===<br />
<br />
A new field of instrument science led to the successful detection of gravitational waves by the LIGO detectors in 2015. We are now preparing the next generation of gravitational wave observatories, such as the Einstein Telescope, with the aim to increase the detector sensitivity by a factor of ten, which would allow, for example, to detect stellar-mass black holes from early in the universe when the first stars began to form. This ambitious goal requires us to find ways to significantly improve the best laser interferometers in the world.<br />
<br />
Gravitational wave detectors, such as LIGO and VIRGO, are complex Michelson-type interferometers enhanced with optical cavities. We develop and use numerical models to study these laser interferometers, to invent new optical techniques and to quantify their performance. For example, we synthesize virtual mirror surfaces to study the effects of higher-order optical modes in the interferometers, and we use opto-mechanical models to test schemes for suppressing quantum fluctuations of the light field. We can offer several projects based on numerical modelling of laser interferometers. All projects will be directly linked to the ongoing design of the Einstein Telescope.<br />
<br />
''Contact: [mailto:a.freise@nikhef.nl Andreas Freise]''<br />
<br />
=== Theory: Effective Field Theories of Particle Physics from low- to high-energies===<br />
Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations” seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature. The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Standard Model Effective Field Theory (SMEFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes with minimal assumptions on the nature of an eventual UV-complete theory that replaces the Standard Model. Specifically, the goal is to connect measurements from ATLAS, CMS, and LHCb experiments at the CERN's LHC among them and to jointly interpret this information with that provided by other experiments including very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
<br />
This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories. Depending on the student profile, sub-projects with a strong computational and/or machine learning component are also possible, for instance to construct new operators with optimal sensitivity to New Physics effects as encoded by the SMEFT higher-dimensional operators. Topics that can be considered in this project include the interpretation of novel physical observables at the LHC and their integration into the global SMEFiT analysis, matching of EFTs to UV-complete theories and their phenomenological analyses, projections for the impact in the SMEFT parameter space of data for future colliders, the synergies between EFT studies and proton structure fits, and the matching to the Weak Effective Field Theory to include data on flavour observables such as B-meson decays.<br />
<br />
References: https://arxiv.org/abs/2105.00006 , https://arxiv.org/abs/2302.06660, https://arxiv.org/abs/2211.02058 , https://arxiv.org/abs/1901.05965 , https://arxiv.org/abs/1906.05296 , https://arxiv.org/abs/1908.05588, https://arxiv.org/abs/1905.05215<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theory: High-energy neutrino-nucleon interactions at the Forward Physics Facility ===<br />
High-energy collisions at the High-Luminosity Large Hadron Collider (HL-LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing experiments. The proposed Forward Physics Facility (FPF) to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe Standard Model (SM) processes and search for physics beyond the Standard Model (BSM). High statistics neutrino detection will provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. The FPF has the promising potential to probe our understanding of the strong interactions as well as of proton and nuclear structure, providing access to both the very low-x and the very high-x regions of the colliding protons. The former regime is sensitive to novel QCD production mechanisms, such as BFKL effects and non-linear dynamics, as well as the gluon parton distribution function (PDF) down to x=1e-7, well beyond the coverage of other experiments and providing key inputs for astroparticle physics. In addition, the FPF acts as a neutrino-induced deep-inelastic scattering (DIS) experiment with TeV-scale neutrino beams. The resulting measurements of neutrino DIS structure functions represent a valuable handle on the partonic structure of nucleons and nuclei, particularly their quark flavour separation, that is fully complementary to the charged-lepton DIS measurements expected at the upcoming Electron-Ion Collider (EIC).<br />
<br />
In this project, the student(s) will carry out updated predictions for the neutrino fluxes expected at the FPF, assess the precision with which neutrino cross-sections will be measured, and quantify their impact on proton and nuclear structure by means of machine learning tools and state-of-the-art calculations in perturbative Quantum Chromodynamics.<br />
<br />
References: arXiv:2109.10905, arXiv:2201.12363 , arXiv:2109.02653<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theory: Probing the origin of the proton spin with machine learning===<br />
At energy-frontier facilities such as the Large Hadron Collider (LHC), scientists study the laws of Nature in their quest for novel phenomena both within and beyond the Standard Model of particle physics. An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions from the nature of the Higgs boson to the origin of cosmic neutrinos. The key to address some of these questions is by carrying out an universal analysis of nucleon structure from the simultaneous determination of the momentum and spin distributions of quarks and gluons and their fragmentation into hadrons. This effort requires combining an extensive experimental dataset and cutting-edge theory calculations within a machine learning framework where neural networks parametrise the underlying physical laws while minimizing ad-hoc model assumptions.<br />
<br />
In this project, the student(s) will carry out a new global analysis of the spin structure of the proton by means of machine learning tools and state-of-the-art calculations in perturbative Quantum Chromodynamics, and integrate it within the corresponding global NNPDF analyses of unpolarised proton and nuclear structure in the framework of a combined integrated global analysis of non-perturbative QCD.<br />
<br />
References: arXiv:2201.12363 , arXiv:2109.02653<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
------------------------------------------------------------------<br />
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== Finished master projects ==<br />
<br />
See: <br />
* https://wiki.nikhef.nl/education/Master_Theses<br />
* https://www.nikhef.nl/master-theses-2021/<br />
* https://www.nikhef.nl/facts-figures-2020/master-theses-2020/<br />
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<br />
[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=866Master Projects2023-02-19T09:13:31Z<p>Rojo@nikhef.nl: /* Theory: Effective Field Theories of Particle Physics from low- to high-energies */</p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
== Projects with a 2023 start ==<br />
<br />
=== ALICE: The next-generation multi-purpose detector at the LHC ===<br />
This main goal of this project is to focus on the next-generation multi-purpose detector planned to be built at the LHC. Its core will be a nearly massless barrel detector consisting of truly cylindrical layers based on curved wafer-scale ultra-thin silicon sensors with MAPS technology, featuring an unprecedented low material budget of 0.05% X0 per layer, with the innermost layers possibly positioned inside the beam pipe. The proposed detector is conceived for studies of pp, pA and AA collisions at luminosities a factor of 20 to 50 times higher than possible with the upgraded ALICE detector, enabling a rich physics program ranging from measurements with electromagnetic probes at ultra-low transverse momenta to precision physics in the charm and beauty sector. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli] and [mailto:marco.van.leeuwen@cern.ch Marco van Leeuwen]''<br />
<br />
=== ALICE: Searching for the strongest magnetic field in nature ===<br />
In a non-central collision between two Pb ions, with a large value of impact parameter, the charged nucleons that do not participate in the interaction (called spectators) create strong magnetic fields. A back of the envelope calculation using the Biot-Savart law brings the magnitude of this filed close to 10^19Gauss in agreement with state of the art theoretical calculation, making it the strongest magnetic field in nature. The presence of this field could have direct implications in the motion of final state particles. The magnetic field, however, decays rapidly. The decay rate depends on the electric conductivity of the medium which is experimentally poorly constrained. Overall, the presence of the magnetic field, the main goal of this project, is so far not confirmed experimentally.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Looking for parity violating effects in strong interactions ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions, in the presence of a deconfined state, gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, what is called the Chiral Magnetic Effect (CME).<br />
The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, however further studies are needed to constrain background effects. These highly anticipated results have the potential to reveal exiting, new physics.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Machine learning techniques as a tool to study the production of heavy flavour particles ===<br />
There was recently a shift in the field of heavy-ion physics triggered by experimental results obtained in collisions between small systems (e.g. protons on protons). These results resemble the ones obtained in collisions between heavy ions. This consequently raises the question of whether we create the smallest QGP droplet in collisions between small systems. The main objective of this project will be to study the production of charm particles such as D-mesons and Λc-baryons in pp collisions at the LHC. This will be done with the help of a new and innovative technique which is based on machine learning (ML). The student will also extend the studies to investigate how this production rate depends on the event activity e.g. on how many particles are created after every collision.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli]''<br />
<br />
===ATLAS: The Higgs boson's self-coupling===<br />
<br />
The coupling of the Higgs boson to itself is one of the main unobserved interactions of the Standard Model and its observation is crucial to understand the shape of the Higgs potential. Here we propose to study the 'ttHH' final state: two top quarks and two Higgs bosons produced in a single collision. This topology is yet unexplored at the ATLAS experiment and the project consists of setting up the new analysis (including multivariate analysis techniques to recognise the complicated final state), optimising the sensitivity and including the result in the full ATLAS study of the Higgs boson's coupling to itself. With the LHC data from the upcoming Run-3, we might be able to see its first glimpses! <br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
===ATLAS: The Next Generation===<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks is very new [1] and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays) and advanced analysis techiques (using deep learning methods).<br />
<br />
[https://atlas.cern/updates/briefing/charming-Higgs-decay][https://arxiv.org/abs/1802.04329 https://atlas.cern/updates/briefing/charming-Higgs-decay]<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
===ATLAS: Searching for new particles in very energetic diboson production===<br />
<br />
The discovery of new phenomena in high-energy proton–proton collisions is one of the main goals of the Large Hadron Collider (LHC). New heavy particles decaying into a pair of vector bosons (WW, WZ, ZZ) are predicted in several extensions to the Standard Model (e.g. extended gauge-symmetry models, Grand Unified theories, theories with warped extra dimensions, etc). In this project we will investigate new ideas to look for these resonances in a region that is yet unexplored in the data. We will focus on the final states where both vector bosons decay into quarks as they are expected to bring the highest sensitivity [1]. We will try to reconstruct and exploit new ways to identify vector bosons (using machine learning methods) and then tackle the problem of estimating contributions from beyond the Standard Model processes in the tails of the mass distribution.<br />
<br />
[1] https://arxiv.org/abs/1906.08589<br />
<br />
''Contact: [mailto:f.dias@nikhef.nl Flavia de Almeida Dias]''<br />
<br />
===ATLAS top-quark and Higgs-boson analysis combination, and Effective Field Theory interpretation===<br />
<br />
We are looking for a master student with interest in theory and data-analysis in the search for physics beyond the Standard Model in the top-quark and Higgs-boson sectors.<br />
<br />
Your master-project starts just at the right time for preparing the Run-3 analysis of the ATLAS experiment at the LHC. In Run-3 (2022-2026), three times more data becomes available, enabling analysis of rare processes with innovative software tools and techniques.<br />
<br />
This project aims to explore the newest strategy to combine the top-quark and Higgs-boson measurements in the perspective of constraining the existence of new physics beyond the Standard Model (SM) of Particle Physics. We selected the pp->tZq and gg->HZ processes as promising candidates for a combination to constrain new physics in the context of Standard Model Effective Field Theory (SMEFT). SMEFT is the state-of-the-art framework for theoretical interpretation of LHC data. In particular, you will study the SMEFT OtZ and Ophit operators, which are not well constrained by current measurements.<br />
<br />
Besides affinity with particle physics theory, the ideal candidate for this project has developed python/C++ skills and is eager to learn advanced techniques. You start with a simulation of the signal and background samples using existing software tools. Then, an event selection study is required using Machine Learning techniques. To evaluate the SMEFT effects, a fitting procedure based on the innovative Morphing technique is foreseen, for which the basic tools in the ROOT and RooFit framework are available. The work is carried out in the ATLAS group at Nikhef and may lead to an ATLAS note.<br />
<br />
''Contact: [mailto:geoffrey.gilles@cern.ch> Geoffrey Gilles] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:h73@nikhef.nl Marcel Vreeswijk]''<br />
<br />
=== ATLAS Machine learning to enhance reconstruction of very rare Higgs decays ===<br />
Since the Higgs boson discovery in 2012 at the ATLAS experiment, the investigation of the properties of the Higgs boson has been a priority for research at the Large Hadron Collider (LHC). However, there are still a many open questions: Is the Higgs boson the only origin of Electroweak Symmetry Breaking? Is there a mechanism which can explain the observed mass pattern of SM particles? Many of these questions are linked to the Higgs boson coupling structure. <br />
<br />
While the Higgs boson coupling to fermions of the third generation has been clearly, the investigation of the Higgs boson coupling to the light fermions of the second generation will be a major project for the upcoming data-taking period starting this year. The Higgs boson decay to muons is most sensitive channel to establish a coupling of the Higgs boson to second generation fermions. In this project you will work on an improvement of the H-->mumu search: In about 5% of the events, a photon is radiated off the outgoing muons. By recognizing these photons and taking their effect into account we can improve the reconstruct these events better. For this project we will use machine learning to best identify these special events and to take their energy contribution into account to improve the overall sensitivity. <br />
<br />
''Contact: [mailto:oliver.rieger@nikhef.nl Oliver Rieger] and [mailto:verkerke@nikhef.nl Wouter Verkerke] and [mailto:s01@nikhef.nl Peter Kluit]''<br />
<br />
=== ATLAS: Scrutinising Higgs decaying into W bosons ===<br />
Observation of the Higgs boson happened 10 years ago and since then scientists’ interest has shifted towards measuring precisely its properties. An example is a coupling strength telling us how does the Higgs boson interact with different particles such as W bosons. Measuring H→ WW →lnu lnu process allows us to not only probe the Standard Model (SM), by measuring the coupling strength or indirectly probe Higgs boson width, but also test against the theories beyond (for instance in the context of the effective field theory framework).<br />
<br />
The student will take active part in the ATLAS HWW group. There are multiple possible areas of contribution within the group depending on the interest of the student. For instance, utilising machine learning techniques to optimise for the selection of HWW signal process, determining the fake background processes, interpreting the results through the beyond SM theories and others.<br />
Contact: ''[mailto:mvozak@cern.ch Matouš Vozák] and [mailto:Ivo.van.Vulpen@nikhef.nl Ivo van Vulpen]''<br />
=== ATLAS: HGTD detector ===<br />
The ATLAS is going to get a new ability: a Timing Layer. This allows us to reconstruct tracks not only in the 3 dimensions of space but adds the ability of measuring very precisely also the time (at picosecond level) at which the particles pass the sensitive layers of the HGTD detector. This allow to construct the trajectories of the particles created at the LHC in 4 dimensions and ultimately will lead to a better reconstruction of physics at ATLAS. The new HGTD detector is still in construction and work needs to be done on different levels such as understanding the detector response (taking measurements in the lab and performing simulations) or developing algorithms to reconstruct the particle trajectories (programming and analysis work). With this work you will be part of the Atlas group and/or the Fast Timing detector group together with the R&D department at Nikhef. <br />
<br />
Contact me to discuss the possibilities. <br />
Contact: ''[mailto:hella.snoek@nikhef.nl Hella Snoek]''<br />
=== Dark Matter: Building better Dark Matter Detectors - the XAMS R&D Setup===<br />
The Amsterdam Dark Matter group operates an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 0.5kg of ultra-pure liquid xenon in the central volume. We use this detector for the development of new detection techniques - such as utilizing our newly installed silicon photomultipliers - and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENONnT experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory, or for future Dark Matter experiments like DARWIN. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data themselves You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
===Dark Matter: Searching for Dark Matter Particles - XENONnT Data Analysis ===<br />
The XENON collaboration has used the XENON1T detector to achieve the world’s most sensitive direct detection dark matter results and is currently operating the XENONnT successor experiment. The detectors operate at the Gran Sasso underground laboratory and consist of so-called dual-phase xenon time-projection chambers filled with ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the new data coming from the XENONnT detector. The work will consist of understanding the detector signals and applying a deep neural network to improve the (gas-) background discrimination in our Python-based analysis tool to improve the sensitivity for low-mass dark matter particles. The work will continue a study started by a recent graduate. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy.<br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
===Dark Matter: The Ultimate Dark Matter Experiment - DARWIN Sensitivity Studies===<br />
DARWIN is the “ultimate” direct detection dark matter experiment, with the goal to reach the so-called “neutrino floor”, when neutrinos become a hard-to-reduce background. The large and exquisitely clean xenon mass will allow DARWIN to also be sensitive to other physics signals such as solar neutrinos, double-beta decay from Xe-136, axions and axion-like particles etc. While the experiment will only start in 2027, we are in the midst of optimizing the experiment, which is driven by simulations. We have an opening for a student to work on the GEANT4 Monte Carlo simulations for DARWIN. We are also working on a “fast simulation” that could be included in this framework. It is your opportunity to steer the optimization of a large and unique experiment. This project requires good programming skills (Python and C++) and data analysis/physics interpretation skills.<br />
<br />
''Contact: [mailto:t.pollmann@nikhef.nl Tina Pollmann], [mailto:decowski@nikhef.nl Patrick Decowski] or [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
===Dark Matter: Sensitive tests of wavelength-shifting properties of materials for dark matter detectors===<br />
Rare event search experiments that look for neutrino and dark matter interactions are performed with highly sensitive detector systems, often relying on scintillators, especially liquid noble gases, to detect particle interactions. Detectors consist of structural materials that are assumed to be optically passive, and light detection systems that use reflectors, light detectors, and sometimes, wavelength-shifting materials. MSc theses are available related to measuring the efficiency of light detection systems that might be used in future detectors. Furthermore, measurements to ensure that presumably passive materials do not fluoresce, at the low level relevant to the detectors, can be done. Part of the thesis work can include Monte Carlo simulations and data analysis for current and upcoming dark matter detectors, to study the effect of different levels of desired and nuisance wavelength shifting. In this project, students will acquire skills in photon detection, wavelength shifting technologies, vacuum systems, UV and extreme-UV optics, detector design, and optionally in Python and C++ programming, data analysis, and Monte Carlo techniques.<br />
<br />
''Contact: [mailto:Tina.Pollmann@tum.de Tina Pollmann] and [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
=== Detector R&D: Time resolution of ultrathin monolithic timing detectors ===<br />
For the upgrade of ALICE and LHCb vertex detectors, new silicon pixel detectors are being developed now that can register the passing particles with a time precision of tens of picoseconds. ALICE is the first experiment at the LHC to have installed monolithic sensors where electronics is integrated into the sensor. New prototypes of their sensors have arrived at Nikhef. New prototypes of other sensors able to withstand very high radiation fluences of the LHC are arriving soon. In this project, you will tackle the challenge to accurately measure the time resolution of one of these sensors with our laser setups in the laboratory. You will have the chance to work in an international collaboration where you will report about the performance of these novel sensors. There may even be an opportunity to join beam tests at CERN. For this project, we are looking for someone who is interested to work with high-tech sensors and equipment in our Nikhef laboratory and with python programming skills.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
=== Detector R&D: Performance of monolithic sensors for the ALICE upgrade from test beam data ===<br />
For the upgrade of the ALICE detector, ultrathin picosecond timing integrated sensors are being developed now, of which the first prototypes are now at Nikhef and are being studied in test beams at CERN and DESY in Hamburg. Sensors are studied with the ALPIDE (ALICE PIxel DEtector) telescope that uses the same sensors that have recently installed in the heart of the ALICE experiment at CERN. In this project, you will analyze data from beam tests to measure the efficiency and time resolution of the new prototypes for the ALICE upgrade with the latest data from test beams at CERN. If the travel situation allows, you will have the opportunity to join the ALICE test beam group at CERN or in Hamburg at DESY to take part in the exciting experience of taking real data. We are looking for someone with good programming and data analysis skills.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
=== Detector R&D: Modeling radiation damage in silicon sensors ===<br />
In the coming years, the ATLAS experiment at the LHC works on upgrades to prepare for the high-luminosity LHC, where many more collisions will take place than today. Both analysis of data and decisions made in preparation of these detectors and on data taking heavily rely on simulations, especially those that model the damage done to sensors after many collisions. It may sound counterintuitive, but particle detectors do not actually like particles: after many collisions at the LHC, a silicon pixel detector has seen so many particles that its bulk gathers defects. Charge generated by traversing particles can get trapped in defects resulting in less charge induced in the readout electrodes, reducing detector performance in resolution and efficiency. In this project, you will be a member of the international ATLAS collaboration where you will compare different models of radiation damage with measured data. You will learn technology computer aided design (TCAD), widely used in industry, and contribute to the open source program Allpix Squared that is widely used for simulations in many areas of particle physics. Here we are looking for someone with good programming and data analysis skills who would like to contribute to upgrades of collider experiments.<br />
<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
=== Detector R&D: Fast trigger ===<br />
Muons in cosmic rays are for free! In this project we are not looking for where cosmic rays come from or what physics can be studied with them. Instead, we are using them to test some of our particle detectors. Muons are short lived particles that carry the same charge as electrons, have a high penetrating power and can be detected relatively easy. In practice a test set-up consists of a ‘trigger’ and a device under test. The ‘trigger’ is a detector that gives a signal when a muon passes by, which is a signal to check the result in the device under test. Did the device under test respond to the muon in the expected way? <br />
<br />
For the planned upgrades of particle detectors at CERN, for LHC experiments (LHCb, ATLAS, ALICE, CMS), new particle detectors are under development. Some of these new detectors must be able to measure within tens of ps (10e-12 s) precise when a particle was detected.<br />
<br />
To facilitate testing these new detectors by using muons we need a trigger set up with a matching precision in timing (order tens of ps). We want to investigate several potentially interesting technologies to develop such a fast trigger. In one scenario the trigger could be based on the use of Cherenkov light. Cherenkov light is generated when a charged particle traverses a medium faster than the speed of light in that medium. This light can be generated in for example plexiglass, which in turn can be mounted on top of a light sensor. In our case the light sensor could be a so called silicon photo multiplier, which is capable of detecting only a few photons and gives a signal within a few hundred ps. Another possible scenario would be to use a so called LGAD (Low Gain Avalanche Diode) to measure the signal that a muon generates as it traverses the sensor.<br />
<br />
The Question(s): Which technology should we use for a fast trigger and what is the best timing precision that we can achieve? <br />
<br />
This project will involve a lot of 'hands on work' in the lab. <br />
<br />
''Contact: [mailto:martinfr@nikhef.nl Martin Fransen] and [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
=== Detector R&D: Characterisation of Trench Isolated Low Gain Avalanche Detectors (TI-LGAD) ===<br />
The future vertex detector of the LHCb Experiment needs to measure the spatial coordinates and time of the particles originating in the LHC proton-proton collisions with resolutions better than 10 um and 50 ps, respectively. Several technologies are being considered to achieve these resolutions. Among those is a novel sensor technology called Trench Isolated Low Gain Avalanche Detector. Prototype pixelated sensors have been manufactured recently and have to be characterised. Therefore these new sensors will be bump bonded to a Timepix4 ASIC which provides charge and time measurements in each of 230 thousand pixels. Characterisation will be done using a lab setup at Nikhef, and includes tests with a micro-focused laser beam, radioactive sources, and possibly with particle tracks obtained in a test-beam. This project involves data taking with these new devices and analysing the data to determine the performance parameters such as the spatial and temporal resolution. as function of temperature and other operational conditions.<br />
<br />
''Contacts: [mailto:kazu.akiba@nikhef.nl Kazu Akiba] and [mailto:martinb@nikhef.nl Martin van Beuzekom]''<br />
<br />
=== Detector R&D: Simulation of 3D silicon sensors ===<br />
For the upgrade of the vertex detector of the LHCb experiment novel silicon pixel detectors have to be developed that can register the passing particles with a time precision of tens of picoseconds. Given the harsh radiation environment very close to the LHCb interaction point only a limited number of technologies can be applied. One of the most promising technologies are the so-called 3D sensors whose readout electrodes are pillars that are placed into the sensor perpendicular to the surface; this in contrast to ’standard’ planar silicon sensors where the pixel electrodes are at the surface, similar to the camera in your smartphone. To understand the time response of these 3D sensors, simulations with TCAD software have to be performed and the results will be compared to measured data. These simulations involve the creation/adaptation of the 3D structures of the model, optimising the simulation speed, and analysing the signals as function voltage, track impact point and deposited charge. Hands-on experience with such 3D sensors in the R&D labs at Nikhef is planned within the scope of this project.<br />
<br />
''Contacts: [mailto:martinb@nikhef.nl Martin van Beuzekom] and [mailto:kazu.akiba@nikhef.nl Kazu Akiba]''<br />
<br />
===Detector R&D: Laser Interferometer Space Antenna (LISA) - Wavefront sensors for gravitational wave detection ===<br />
<br />
The space-based gravitational wave antenna LISA is one of the most challenging space missions ever proposed. ESA plans to launch around 2034 three spacecraft separated by a few million kilometres. This constellation measures tiny variations in the distances between test-masses located in each satellite to detect gravitational waves from sources such as supermassive black holes. LISA is based on laser interferometry, and the three satellites form a giant Michelson interferometer. LISA measures a relative phase shift between one local laser and one distant laser by light interference. The phase shift measurement requires sensitive wavefront sensors. The Nikhef DR&D group fabricated prototype sensors in 2020 together with the Photonics industry and the Dutch institute for space research SRON. Nikhef & SRON are responsible for the Quadrant PhotoReceiver (QPR) system: the sensors, the housing including a complex mount to align the sensors with 10's of nanometer accuracy, various environmental tests at the European Space Research and Technology Centre (ESTEC), and the overall performance of the QPR in the LISA instrument. Currently we are discussing possible sensor improvements for a second fabrication run in 2022, optimizing the mechanics and preparing environmental tests. As a MSc student, you will work on various aspects of the wavefront sensor development: study the performance of the epitaxial stacks of Indium-Gallium-Arsenide, setting up test benches to characterize the sensors and QPR system, performing the actual tests and data analysis, in combination with performance studies and simulations of the LISA instrument.<br />
<br />
''Contact: [mailto:nielsvb@nikhef.nl Niels van Bakel]''<br />
<br />
===FCC: The Next Collider===<br />
<br />
After the LHC, the next planned large collider at CERN is the proposed 100 kilometer circular collider "FCC". In the first stage of the project, as a high-luminosity electron-positron collider, precision measurements of the Higgs boson are the main goal. One of the channels that will improve by orders of magnitude at this new accelerator is the decay of the Higgs boson to a pair of charm quarks. This project will estimate a projected sensitivity for the coupling of the Higgs boson to second generation quarks, and in particular target the improved reconstruction of the topology of long-lived mesons in the clean environment of a precision e+e- machine.<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
<br />
===LHCb: Search for light dark particles===<br />
The Standard Model of elementary particles does not contain a proper Dark Matter candidate. One of the most tantalizing theoretical developments is the so-called ''Hidden Valley models'': a mirror-like copy of the ''Standard Model'', with dark particles that communicate with standard ones via a very feeble interaction. These models predict the existence of ''dark hadrons'' – composite particles that are bound similarly to ordinary hadrons in the ''Standard Model''. Such ''dark hadrons'' can be abundantly produced in high-energy proton-proton collisions, making the LHC a unique place to search for them. Some ''dark hadrons'' are stable like a proton, which makes them excellent ''Dark Matter'' candidates, while others decay to ordinary particles after flying a certain distance in the collider experiment. The LHCb detector has a unique capability to identify such decays, particularly if the new particles have a mass below ten times the proton mass. <br />
<br />
This project assumes a unique search for light ''dark hadrons'' that covers a mass range not accessible to other experiments. It assumes an interesting program on data analysis (python-based) with non-trivial machine learning solutions and phenomenology research using fast simulation framework. Depending on the interest, there is quite a bit of flexibility in the precise focus of the project.<br />
<br />
''Contact: [mailto:andrii.usachov@nikhef.nl Andrii Usachov]''<br />
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===LHCb: Measuring lepton flavour universality with excited Ds states in semileptonic Bs decays===<br />
One of the most striking discrepancies between the Standard Model and measurements are the lepton flavour universality (LFU) measurements with tau decays. At the moment, we have observed an excess of 3-4 sigma in ''B → Dτν'' decays. This could point even to a new force of nature! To understand this discrepancy, we need to make further measurements. <br />
<br />
One very exciting (pun intended) projects to verify these discrepancies involves measuring the ''B<sub>s</sub> → D<sub>s2</sub><sup>*</sup>τν'' and/or ''B<sub>s</sub> → D<sub>s1</sub><sup>*</sup>τν'' decays. These decays with excited states of the ''D<sub>s</sub>'' meson have not been observed before in the tau decay mode, and have a unique way of coupling to potential new physics candidates that can only be measured in ''B<sub>s</sub>'' decays [1]. See slides for more detail: [[File:LHCbLFUwithExcitedDs.pdf|thumb]]<br />
<br />
[1] https://arxiv.org/abs/1606.09300<br />
<br />
''Contact: [mailto:suzannek@nikhef.nl Suzanne Klaver]''<br />
<br />
===LHCb: New physics in the angular distributions of B decays to K*ee===<br />
<br />
Lepton flavour violation in B decays can be explained by a variety of non-standard model interactions. Angular distributions in decays of a B meson to a hadron and two leptons are an important source of information to understand which model is correct. Previous analyses at the LHCb experiment have considered final states with a pair of muons. Our LHCb group at Nikhef concentrates on a new measurement of angular distributions in decays with two electrons. The main challenge in this measurement is the calibration of the detection efficiency. In this project you will confront estimates of the detection efficiency derived from simulation with decay distributions in a well known B decay. Once the calibration is understood, the very first analysis of the angular distributions in the electron final state can be performed. <br />
<br />
Contact: [mailto:m.senghi.soares@nikhef.nl Mara Soares] and [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
<br />
===LHCb: Discovering heavy neutrinos in B decays===<br />
<br />
Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, much heavier, neutral leptons. If the mass of these new neutrinos is below the b-quark mass, they can be observed in B hadron decays.<br />
<br />
In this project we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undiscovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The analysis will be performed within the LHCb group at Nikhef using LHCb run-2 data.<br />
<br />
''Contact: [mailto:v.lukashenko@nikhef.nl Lera Lukashenko] and'' [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
===LHCb: The exotic 4-quark state X(3872) in exclusive production===<br />
The nature of the X(3872) is still unknown. Is it a regular charmonium with an unexpected mass, a compact 4-quark state, or a DD molecule? Or a quantum superposition of all that? Either way, finding out will tell us something about how quark organise in hadrons and colour confinement. The project is to measure a very peculiar production mode: pp->Xpp. Only the X is seen in the detector and nothing else. Data from LHCb run 2 will be used and the analysis will build on previous work. <br />
<br />
''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
<br />
===LHCb: Scintillating Fibre tracker software===<br />
The installation of the scintillating-fibre tracker in LHCb’s underground cavern was recently completed. This detector uses 10000 km of fibres to track particle trajectories in the LHCb detector when the LHC starts up again later this year. The light emitted by the scintillating fibres when a particle interacts with them is measured using photon multiplier tubes. The studies proposed for this project will focus on software, and could include writing a framework to monitor the detector output, improving the detector simulation or working on the data processing.<br />
<br />
''Contact: [mailto:e.gabriel@nikhef.nl Emmy Gabriel]''<br />
<br />
===LHCb: Vertex detector calibration===<br />
In summer 2022 LHCb has started data taking will an almost entirely new detector. At the point closest to the interaction point, the trajectories of charge particles are reconstructed with a so-called silicon pixel detector. The design hit resolution of this detector is about 15 micron. However, to actually reach this resolution a precise calibration of the spatial positions of the silicon sensors needs to be performed. In this project, you will use the first data of the new LHCb detector to perform this calibration and measure the detector performance.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen]''<br />
<br />
<br />
===Neutrinos: Neutrino scattering: the ultimate resolution===<br />
<br />
Neutrino telescopes like IceCube and KM3NeT aim at detecting neutrinos from cosmic sources. The neutrinos are detected with the best resolution when charged current interactions with nucleons produce a muon, which can be detected with high accuracy (depending on the detector). A crucial ingredient in the ultimate achievable pointing accuracy of neutrino telescopes is the scattering angle between the neutrino and the muon. While published computations have investigated the cross-section of the process in great detail, this important scattering angle has not received much attention. The aim of the project is to compute and characterize the distribution of this angle, and that the ultimate resolution of a neutrino telescope. If successful, the results of this project can lead to publication of interest to the neutrino telescope community.<br />
<br />
Depending on your interests, the study could be based on a first-principles calculation (using the deep-inelastic scattering formalism), include state-of-the-art parton distribution functions, and/or exploit existing event-generation software for a more experimental approach. <br />
<br />
''Contacts: [mailto:aart.heijboer@nikhef.nl Aart Heijboer]''<br />
<br />
===Neutrinos: acoustic detection of ultra-high energy neutrinos===<br />
<br />
The study of the cosmic neutrinos of energies above 1017 eV, the so-called ultra-high energy neutrinos, provides a unique view on the universe and may provide insight in the origin of the most violent astrophysical sources, such as gamma ray bursts, supernovae or even dark matter. In addition, the observation of high energy neutrinos may provide a unique tool to study interactions at high energies. The energy deposition of these extreme neutrinos in water induce a thermo-acoustic signal, which can be detected using sensitive hydrophones. The expected neutrino flux is however extremely low and the signal that neutrinos induce is small. TNO is presently developing sensitive hydrophone technology based on fiber optics. Optical fibers form a natural way to create a distributed sensing system. Using this technology a large scale neutrino telescope can be built in the deep sea. TNO is aiming for a prototype hydrophone which will form the building block of a future telescope.<br />
<br />
The work will be executed at the Nikhef institute and/or the TNO laboratories in Delft. In this project master students have the opportunity to contribute in the following ways:<br />
<br />
'''Project 1:''' Hardware development on fiber optics hydrophones technology Goal: characterize existing prototype optical fibre hydrophones in an anechoic basin at TNO laboratory. Data collection, calibration, characterization, analysis of consequences for design future acoustic hydrophone neutrino telescopes;<br />
Keywords: Optical fiber technology, signal processing, electronics, lab.<br />
<br />
'''Project 2:''' Investigation of ultra-high energy neutrinos and their interactions with matter. Goal: Discriminate the neutrino signals from the background noises, in particular clicks from whales and dolphins in the deep sea. Study impact on physics reach for future acoustic hydrophone neutrino telescopes;<br />
Keywords: Monte Carlo simulations, particle physics, neutrino physics, data analysis algorithms.<br />
<br />
Further information: Info on ultra-high energy neutrinos can be found at: http://arxiv.org/abs/1102.3591; Info on acoustic detection of neutrinos can be found at: http://arxiv.org/abs/1311.7588<br />
<br />
''Contact: [mailto:ernst-jan.buis@tno.nl Ernst Jan Buis]'' or ''[mailto:ivo.van.vulpen@nikhef.nl Ivo van Vulpen]''<br />
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===Neutrinos: Oscillation analysis with the first data of KM3NeT===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first few strings with sensitive photodetectors have been deployed at both the Italian and the French detector sites. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In this project the available data will be used together with simulations to best reconstruct the event topologies and optimally identify and reconstruct the first neutrino interactions in the KM3NeT detector. The data will then be used to measure neutrino oscillation parameters, and prepare for a future neutrino mass ordering determination.<br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
''Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn] [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
<br />
===Neutrinos: the Deep Underground Neutrino Experiment (DUNE)===<br />
<br />
The Deep Underground Neutrino Experiment (DUNE) is under construction in the USA, and will consist of a powerful neutrino beam originating at Fermilab, a near detector at Fermilab, and a far detector in the SURF facility in Lead, South Dakota, 1300 km away. During travelling, neutrinos oscillate and a fraction of the neutrino beam changes flavour; DUNE will determine the neutrino oscillation parameters to unrivaled precision, and try and make a first detection of CP-violation in neutrinos. In this project, various elements of DUNE can be studied, including the neutrino oscillation fit, neutrino physics with the near detector, event reconstruction and classification (including machine learning), or elements of data selection and triggering.<br />
<br />
''Contact: [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
===Neutrinos: Searching for Majorana Neutrinos with KamLAND-Zen===<br />
The KamLAND-Zen experiment, located in the Kamioka mine in Japan, is a large liquid scintillator experiment with 750kg of ultra-pure Xe-136 to search for neutrinoless double-beta decay (0n2b). The observation of the 0n2b process would be evidence for lepton number violation and the Majorana nature of neutrinos, i.e. that neutrinos are their own anti-particles. Current limits on this extraordinary rare hypothetical decay process are presented as a half-life, with a lower limit of 10^26 years. KamLAND-Zen, the world’s most sensitive 0n2b experiment, is currently taking data and there is an opportunity to work on the data analysis, analyzing data with the possibility of taking part in a ground-breaking discovery. The main focus will be on developing new techniques to filter the spallation backgrounds, i.e. the production of radioactive isotopes by passing muons. There will be close collaboration with groups in the US (MIT, Berkeley, UW) and Japan (Tohoku Univ). <br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== Cosmic Rays/Neutrinos: Seasonal muon flux variations and the pion/kaon ratio ===<br />
The KM3NeT ARCA and ORCA detectors, located kilometers deep in the Mediterranean Sea, have neutrinos as primary probes. Muons from cosmic ray interactions reach the detectors in relatively large quantities too. These muons, exploiting the capabilities and location of the detectors allow the study of cosmic rays and their interactions. In this way, questions about their origin, type, propagation can be addressed. In particular these muons are tracers of hadronic interactions at energies inaccessible at particle accelerators.<br />
<br />
The muons reaching the depths of the detectors result from decays of mesons, mostly pions and kaons, created in interactions of high-energy cosmic rays with atoms in the upper atmosphere. Seasonal changes of the temperature – and thus density - profile of the atmosphere modulate the balance between the probability for these mesons to decay (producing muons) or to re-interact. Pions and kaons are affected differently, allowing to extract their production ratio by determining how changes in muon rate depend on changes in the effective temperature – an integral over the atmospheric temperature profile weighted by a depth dependent meson production rate.<br />
<br />
In this project, the aim is to measure the rate of muons in the detectors and to calculate the effective temperature above the KM3NeT detectors from atmospheric data, both as function of time. The relation between these two can be used to extract the pion to kaon ratio.<br />
<br />
''Contact: [mailto:rbruijn@nikhef.nl Ronald Bruijn]''<br />
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===Gravitational Waves: Computer modelling to design the laser interferometers for the Einstein telescope===<br />
<br />
A new field of instrument science led to the successful detection of gravitational waves by the LIGO detectors in 2015. We are now preparing the next generation of gravitational wave observatories, such as the Einstein Telescope, with the aim to increase the detector sensitivity by a factor of ten, which would allow, for example, to detect stellar-mass black holes from early in the universe when the first stars began to form. This ambitious goal requires us to find ways to significantly improve the best laser interferometers in the world.<br />
<br />
Gravitational wave detectors, such as LIGO and VIRGO, are complex Michelson-type interferometers enhanced with optical cavities. We develop and use numerical models to study these laser interferometers, to invent new optical techniques and to quantify their performance. For example, we synthesize virtual mirror surfaces to study the effects of higher-order optical modes in the interferometers, and we use opto-mechanical models to test schemes for suppressing quantum fluctuations of the light field. We can offer several projects based on numerical modelling of laser interferometers. All projects will be directly linked to the ongoing design of the Einstein Telescope.<br />
<br />
''Contact: [mailto:a.freise@nikhef.nl Andreas Freise]''<br />
<br />
=== Theory: Effective Field Theories of Particle Physics from low- to high-energies===<br />
Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations” seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature. The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Standard Model Effective Field Theory (SMEFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes with minimal assumptions on the nature of an eventual UV-complete theory that replaces the Standard Model. Specifically, the goal is to connect measurements from ATLAS, CMS, and LHCb experiments at the CERN's LHC among them and to jointly interpret this information with that provided by other experiments including very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
<br />
This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories. Depending on the student profile, sub-projects with a strong computational and/or machine learning component are also possible, for instance to construct new operators with optimal sensitivity to New Physics effects as encoded by the SMEFT higher-dimensional operators. Topics that can be considered in this project include the interpretation of novel physical observables at the LHC and their integration into the global SMEFiT analysis, matching of EFTs to UV-complete theories and their phenomenological analyses, projections for the impact in the SMEFT parameter space of data for future colliders, and the matching to the Weak Effective Field Theory to include data on flavour observables such as B-meson decays.<br />
<br />
References: https://arxiv.org/abs/2105.00006 , https://arxiv.org/abs/2302.06660, https://arxiv.org/abs/2211.02058 , https://arxiv.org/abs/1901.05965 , https://arxiv.org/abs/1906.05296 , https://arxiv.org/abs/1908.05588, https://arxiv.org/abs/1905.05215<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theory: High-energy neutrino-nucleon interactions at the Forward Physics Facility ===<br />
High-energy collisions at the High-Luminosity Large Hadron Collider (HL-LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing experiments. The proposed Forward Physics Facility (FPF) to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe Standard Model (SM) processes and search for physics beyond the Standard Model (BSM). High statistics neutrino detection will provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. The FPF has the promising potential to probe our understanding of the strong interactions as well as of proton and nuclear structure, providing access to both the very low-x and the very high-x regions of the colliding protons. The former regime is sensitive to novel QCD production mechanisms, such as BFKL effects and non-linear dynamics, as well as the gluon parton distribution function (PDF) down to x=1e-7, well beyond the coverage of other experiments and providing key inputs for astroparticle physics. In addition, the FPF acts as a neutrino-induced deep-inelastic scattering (DIS) experiment with TeV-scale neutrino beams. The resulting measurements of neutrino DIS structure functions represent a valuable handle on the partonic structure of nucleons and nuclei, particularly their quark flavour separation, that is fully complementary to the charged-lepton DIS measurements expected at the upcoming Electron-Ion Collider (EIC).<br />
<br />
In this project, the student(s) will carry out updated predictions for the neutrino fluxes expected at the FPF, assess the precision with which neutrino cross-sections will be measured, and quantify their impact on proton and nuclear structure by means of machine learning tools and state-of-the-art calculations in perturbative Quantum Chromodynamics.<br />
<br />
References: arXiv:2109.10905, arXiv:2201.12363 , arXiv:2109.02653<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theory: Probing the origin of the proton spin with machine learning===<br />
At energy-frontier facilities such as the Large Hadron Collider (LHC), scientists study the laws of Nature in their quest for novel phenomena both within and beyond the Standard Model of particle physics. An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions from the nature of the Higgs boson to the origin of cosmic neutrinos. The key to address some of these questions is by carrying out an universal analysis of nucleon structure from the simultaneous determination of the momentum and spin distributions of quarks and gluons and their fragmentation into hadrons. This effort requires combining an extensive experimental dataset and cutting-edge theory calculations within a machine learning framework where neural networks parametrise the underlying physical laws while minimizing ad-hoc model assumptions.<br />
<br />
In this project, the student(s) will carry out a new global analysis of the spin structure of the proton by means of machine learning tools and state-of-the-art calculations in perturbative Quantum Chromodynamics, and integrate it within the corresponding global NNPDF analyses of unpolarised proton and nuclear structure in the framework of a combined integrated global analysis of non-perturbative QCD.<br />
<br />
References: arXiv:2201.12363 , arXiv:2109.02653<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
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== Finished master projects ==<br />
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See: <br />
* https://wiki.nikhef.nl/education/Master_Theses<br />
* https://www.nikhef.nl/master-theses-2021/<br />
* https://www.nikhef.nl/facts-figures-2020/master-theses-2020/<br />
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[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=783Master Projects2022-02-25T12:24:28Z<p>Rojo@nikhef.nl: Added Theory master projects</p>
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<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
== Projects with a 2022 start ==<br />
<br />
=== Dark Matter: Building better Dark Matter Detectors - the XAMS R&D Setup===<br />
The Amsterdam Dark Matter group operates an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 4kg of ultra-pure liquid xenon. We use this detector for the development of new detection techniques - such as utilizing our newly installed silicon photomultipliers - and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENONnT experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory, or for future Dark Matter experiments like DARWIN. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data him/herself. You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
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===Dark Matter: Searching for Dark Matter Particles - XENONnT Data Analysis ===<br />
The XENON collaboration has used the XENON1T detector to achieve the world’s most sensitive direct detection dark matter results and is currently starting the XENONnT successor experiment. The detectors operate at the Gran Sasso underground laboratory and consist of so-called dual-phase xenon time-projection chambers filled with ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the new data coming from the XENONnT detector. The work will consist of understanding the detector signals and applying a deep neural network to improve the (gas-) background discrimination in our Python-based analysis tool to improve the sensitivity for low-mass dark matter particles. The work will continue a study started by a recent graduate. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy.<br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
===Dark Matter: The Ultimate Dark Matter Experiment - DARWIN Sensitivity Studies===<br />
DARWIN is the “ultimate” direct detection dark matter experiment, with the goal to reach the so-called “neutrino floor”, when neutrinos become a hard-to-reduce background. The large and exquisitely clean xenon mass will allow DARWIN to also be sensitive to other physics signals such as solar neutrinos, double-beta decay from Xe-136, axions and axion-like particles etc. While the experiment will only start in 2027, we are in the midst of optimizing the experiment, which is driven by simulations. We have an opening for a student to work on the GEANT4 Monte Carlo simulations for DARWIN, as part of a simulation team together with the University of Freiburg and Zurich. We are also working on a “fast simulation” that could be included in this framework. It is your opportunity to steer the optimization of a large and unique experiment. This project requires good programming skills (Python and C++) and data analysis/physics interpretation skills.<br />
''Contact: [mailto:t.pollmann@nikhef.nl Tina Pollmann], [mailto:decowski@nikhef.nl Patrick Decowski] or [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
<br />
=== Detector R&D: Time resolution of ultrathin monolithic timing detectors ===<br />
For the upgrade of ALICE and LHCb vertex detectors, new silicon pixel detectors are being developed now that can register the passing particles with a time precision of tens of picoseconds. ALICE is the first experiment at the LHC to have installed monolithic sensors where electronics is integrated into the sensor. New prototypes of their sensors have arrived at Nikhef. In this project, you will tackle the challenge to accurately measure their time resolution with our laser setups in the laboratory. You will have the chance to work in an international collaboration where you will report about the performance of these novel sensors. For this project, we are looking for someone who is interested to work with high-tech sensors and equipment in our Nikhef laboratory and with python programming skills.<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
<br />
=== Detector R&D: Performance of monolithic sensors for the ALICE upgrade from test beam data ===<br />
For the upgrade of the ALICE detector, ultrathin picosecond timing integrated sensors are being developed now, of which the first prototypes are now at Nikhef and are being studied in test beams at CERN and DESY in Hamburg. Sensors are studied with the ALPIDE (ALICE PIxel DEtector) telescope that uses the same sensors that have recently installed in the heart of the ALICE experiment at CERN. In this project, you will analyze data from beam tests to measure the efficiency and time resolution of the new prototypes for the ALICE upgrade with the latest data from test beams at CERN. If the travel situation allows, you will have the opportunity to join the ALICE test beam group at CERN or in Hamburg at DESY to take part in the exciting experience of taking real data. We are looking for someone with good programming and data analysis skills.<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
<br />
=== Detector R&D: Modeling radiation damage in silicon sensors ===<br />
In the coming years, the ATLAS experiment at the LHC works on upgrades to prepare for the high-luminosity LHC, where many more collisions will take place than today. Both analysis of data and decisions made in preparation of these detectors and on data taking heavily rely on simulations, especially those that model the damage done to sensors after many collisions. It may sound counterintuitive, but particle detectors do not actually like particles: after many collisions at the LHC, a silicon pixel detector has seen so many particles that its bulk gathers defects. Charge generated by traversing particles can get trapped in defects resulting in less charge induced in the readout electrodes, reducing detector performance in resolution and efficiency. In this project, you will be a member of the international ATLAS collaboration where you will compare different models of radiation damage with measured data. You will learn technology computer aided design (TCAD), widely used in industry, and contribute to the open source program Allpix Squared that is widely used for simulations in many areas of particle physics. Here we are looking for someone with good programming and data analysis skills who would like to contribute to upgrades of collider experiments.<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
<br />
===Neutrinos: Neutrino scattering: the ultimate resolution===<br />
<br />
Neutrino telescopes like IceCube and KM3NeT aim at detecting neutrinos from cosmic sources. The neutrinos are detected with the best resolution when charged current interactions with nucleons produce a muon, which can be detected with high accuracy (depending on the detector). A crucial ingredient in the ultimate achievable pointing accuracy of neutrino telescopes is the scattering angle between the neutrino and the muon. While published computations have investigated the cross-section of the process in great detail, this important scattering angle has not received much attention. The aim of the project is to compute and characterize the distribution of this angle, and that the ultimate resolution of a neutrino telescope. If successful, the results of this project can lead to publication of interest to the neutrino telescope community.<br />
<br />
Depending on your interests, the study could be based on a first-principles calculation (using the deep-inelastic scattering formalism), include state-of-the-art parton distribution functions, and/or exploit existing event-generation software for a more experimental approach. <br />
<br />
''Contacts: [mailto:aart.heijboer@nikhef.nl Aart Heijboer]''<br />
<br />
=== Theory: Effective Field Theories of Particle Physics from low- to high-energies ===<br />
Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations” seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature. Until recently, it was widely assumed that matter particles from each of the three generations interact with the same (“universal”) strength. This hypothesis is being challenged by new measurements at the Large Hadron Collider (LHC) at CERN, which hint towards non-universal interactions. If confirmed, these measurements will be the first signs of new particles and interactions in high-energy colliders. These exciting findings indicate the urgent need to explore such phenomena in depth. The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Effective Field Theory (EFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes. Specifically, the goal is to connect measurements from ATLAS and LHCb among them and to jointly interpret this information with that provided by other experiments, from CMS and Belle-II to very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
<br />
This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories. This project accommodates several students, who would work together in developing the main formalism while each of them focuses on a specific sub-project. Depending on the student profile, sub-projects with a strong computational and/or machine learning component are also possible.<br />
<br />
'''Subproject #1: SMEFT & Flavour symmetries'''. While the power of the Standard Model EFT (named SMEFT) framework is its generality and lack of assumptions, the number of operators is somewhat daunting. A popular way to trim the number of operators is to assume flavour symmetries that relate operators with different quark and lepton flavours. In this project you will investigate the theoretical basis for commonly-used flavour symmetries and what they imply for the connection between high-energy observables involving third-generation particles (top and bottom quarks and tau leptons) and low-energy precision tests involving first- and second-generation particles.<br />
<br />
'''Subproject #2: SMEFT & magnetic moment of the muon'''. The magnetic moment of the muon appears to differ from the Standard Model expectations by a large amount, well beyond the known experimental and theoretical uncertainties. Recent experiments have only strengthened the significance of this anomaly. In this project, the students will investigate the feasibility of implementing the measurement of the magnetic moment of the muon into a global SMEFT analysis, by exploiting recently provided calculations. Special attention will be devoted to the flavour assumptions required to consistently match this measurement with the LHC data. The SMEFiT analysis framework will be used to connect the g-2 data with high-energy LHC measurements.<br />
<br />
References: arXiv:2105.00006, <nowiki>https://arxiv.org/abs/1901.05965</nowiki> , <nowiki>https://arxiv.org/abs/1906.05296</nowiki> , <nowiki>https://arxiv.org/abs/1908.05588</nowiki>, <nowiki>https://arxiv.org/abs/1905.05215</nowiki><br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo], [mailto:K.vos@maastrichtuniversity.nl Keri Vos], [mailto:j.devries4@uva.nl Jordy de Vries]''<br />
<br />
=== Theory: High-energy neutrino-nucleon interactions at the Forward Physics Facility ===<br />
High-energy collisions at the High-Luminosity Large Hadron Collider (HL-LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing experiments. The proposed Forward Physics Facility (FPF) to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe Standard Model (SM) processes and search for physics beyond the Standard Model (BSM). High statistics neutrino detection will provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. The FPF has the promising potential to probe our understanding of the strong interactions as well as of proton and nuclear structure, providing access to both the very low-x and the very high-x regions of the colliding protons. The former regime is sensitive to novel QCD production mechanisms, such as BFKL effects and non-linear dynamics, as well as the gluon parton distribution function (PDF) down to x=1e-7, well beyond the coverage of other experiments and providing key inputs for astroparticle physics. In addition, the FPF acts as a neutrino-induced deep-inelastic scattering (DIS) experiment with TeV-scale neutrino beams. The resulting measurements of neutrino DIS structure functions represent a valuable handle on the partonic structure of nucleons and nuclei, particularly their quark flavour separation, that is fully complementary to the charged-lepton DIS measurements expected at the upcoming Electron-Ion Collider (EIC).<br />
<br />
In this project, the student(s) will carry out updated predictions for the neutrino fluxes expected at the FPF, assess the precision with which neutrino cross-sections will be measured, and quantify their impact on proton and nuclear structure by means of machine learning tools and state-of-the-art calculations in perturbative Quantum Chromodynamics.<br />
<br />
References: arXiv:2109.10905, arXiv:2201.12363 , arXiv:2109.02653<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory: Probing the origin of the proton spin with machine learning ===<br />
At energy-frontier facilities such as the Large Hadron Collider (LHC), scientists study the laws of Nature in their quest for novel phenomena both within and beyond the Standard Model of particle physics. An in-depth understanding of the quark and gluon substructure of protons and heavy nuclei is crucial to address pressing questions from the nature of the Higgs boson to the origin of cosmic neutrinos. The key to address some of these questions is by carrying out an universal analysis of nucleon structure from the simultaneous determination of the momentum and spin distributions of quarks and gluons and their fragmentation into hadrons. This effort requires combining an extensive experimental dataset and cutting-edge theory calculations within a machine learning framework where neural networks parametrise the underlying physical laws while minimizing ad-hoc model assumptions.<br />
<br />
In this project, the student(s) will carry out a new global analysis of the spin structure of the proton by means of machine learning tools and state-of-the-art calculations in perturbative Quantum Chromodynamics, and integrate it within the corresponding global NNPDF analyses of unpolarised proton and nuclear structure in the framework of a combined integrated global analysis of non-perturbative QCD.<br />
<br />
References: arXiv:2201.12363 , arXiv:2109.02653<br />
<br />
''Contacts: [Mailto:j.rojo@vu.nl Juan Rojo]''<br />
------------------------------------------------------------------<br />
<br />
== PREVIOUS PROJECTS! Projects with a 2021 start ==<br />
<br />
=== ALICE: The next-generation multi-purpose detector at the LHC ===<br />
This main goal of this project is to focus on the next-generation multi-purpose detector planned to be built at the LHC. Its core will be a nearly massless barrel detector consisting of truly cylindrical layers based on curved wafer-scale ultra-thin silicon sensors with MAPS technology, featuring an unprecedented low material budget of 0.05% X0 per layer, with the innermost layers possibly positioned inside the beam pipe. The proposed detector is conceived for studies of pp, pA and AA collisions at luminosities a factor of 20 to 50 times higher than possible with the upgraded ALICE detector, enabling a rich physics program ranging from measurements with electromagnetic probes at ultra-low transverse momenta to precision physics in the charm and beauty sector. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli] and [mailto:marco.van.leeuwen@cern.ch Marco van Leeuwen]''<br />
<br />
=== ALICE: Searching for the strongest magnetic field in nature ===<br />
In case of a non-central collision between two Pb ions, with a large value of impact parameter (b), the charged nucleons that do not participate in the interaction (called spectators) create strong magnetic fields. A back of the envelope calculation using the Biot-Savart law brings the magnitude of this filed close to 10^19Gauss in agreement with state of the art theoretical calculation, making it the strongest magnetic field in nature. The presence of this field could have direct implications in the motion of final state particles. The magnetic field, however, decays rapidly. The decay rate depends on the electric conductivity of the medium which is experimentally poorly constrained. Overall, the presence of the magnetic field, the main goal of this project, is so far not confirmed experimentally.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Looking for parity violating effects in strong interactions ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions, in the presence of a deconfined state, gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, what is called the Chiral Magnetic Effect (CME).<br />
The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, however further studies are needed to constrain background effects. These highly anticipated results have the potential to reveal exiting, new physics.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Machine learning techniques as a tool to study the production of heavy flavour particles ===<br />
There was recently a shift in the field of heavy-ion physics triggered by experimental results obtained in collisions between small systems (e.g. protons on protons). These results resemble the ones obtained in collisions between heavy ions. This consequently raises the question of whether we create the smallest QGP droplet in collisions between small systems. The main objective of this project will be to study the production of charm particles such as D-mesons and Λc-baryons in pp collisions at the LHC. This will be done with the help of a new and innovative technique which is based on machine learning (ML). The student will also extend the studies to investigate how this production rate depends on the event activity e.g. on how many particles are created after every collision.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli]''<br />
<br />
=== ALICE: Energy Loss of Energetic Quarks and Gluons in the Quark-Gluon Plasma ===<br />
One of the ways to study the quark-gluon plasma that is formed in high-energy nuclear collisions, is using high-energy partons (quarks or gluons) that are produced early in the collision and interact with the quark-gluon plasma as they propagate through it. There are several current open questions related to this topic, which can be explored in a Master's project. For example, we would like to use the new Monte Carlo generator framework JetScape to simulate collisions to see whether we can extract information about the interaction with the quark-gluon plasma. In the project you will collaborate with one of the PhD students or postdocs in our group to use the model to generate predictions of measurements and compare those to data analysis results. Depending on your interests, the project can focus more on the modeling aspects or on the analysis of experimental data from the ALICE detector at the LHC.<br />
<br />
''Contact: [mailto:marco.van.leeuwen@cern.ch Marco van Leeuwen] and [mailto:marta.verweij@cern.ch Marta Verweij]''<br />
<br />
=== ALICE: Extreme Rare Probes of the Quark-Gluon Plasma ===<br />
The quark-gluon plasma is formed in high-energy nuclear collisions and also existed shortly after the big bang. With the large amount of data collected in recent years at the Large Hadron Collider at CERN, rare processes that previously were not accessible provide now new ways to study how the quark-gluon plasma emerges from the fundamental theory of strong interaction. One of such processes is the heavy W boson which in many cases decays to two quarks. The W boson itself doesn’t interact with the quark-gluon plasma because it doesn’t carry color, but the quark decay products do interact with the plasma and therefore provide an ideal tool to study the space-time evolution of this hot and dense medium. In this project you will use data from the ALICE detector at the LHC and simulated data from generators to study various physics mechanisms that could be happening in the real collisions.<br />
<br />
''Contact: [mailto:marta.verweij@cern.ch Marta Verweij] and [mailto:marco.van.leeuwen@cern.ch Marco van Leeuwen]''<br />
<br />
=== ALICE: Jet Quenching with Machine Learning ===<br />
<br />
Machine learning applications are rising steadily as a vital tool in the field of data science but are relatively new in the particle physics community. In this project machine learning tools will be used to gain insights into the modification of a parton shower in the quark-gluon plasma (QGP). The QGP is created in high-energy nuclear collisions and only lives for a very short period of time. Highly energetic partons created in the same collisions interact with the plasma while they travers it and are observed as a collimated spray of particles, known as jets, in the detector. One of the key recent insights is that the internal structure of jets provides information about the evolution of the QGP. With data recorded by the ALICE experiment, you will use jet substructure techniques in combination with machine learning algorithms to dissect the structure of the QGP. Machine learning will be used to select the regions of radiation phase space that are affected by the presence of the QGP.<br />
<br />
''Contact: [mailto:marta.verweij@cern.ch Marta Verweij] and [mailto:marco.van.leeuwen@cern.ch Marco van Leeuwen]''<br />
<br />
<br />
=== ATLAS: Top Spin and EFTs in the Wtb vertex ===<br />
<br />
The top quark has an exceptional high mass, close to the electroweak symmetry breaking scale and therefore sensitive to new physics effects. Theoretically, new physics is well described in the EFT framework [1]. The (EFT) operators are experimentally well accessible in single top t-channel production where the top quark is produced spin polarized. The focus at Nikhef is the operator O_{tW} with a possible imaginary phase, leading to CP violation. Experimentally, many angular distribution are reconstructed in the top rest frame to hunt for these effects. There are several challenging analysis-topics for master students, which can also be tailored a bit your interests:<br />
1) MC study EFT effects from background substraction.<br />
2) NLO reweighting (as function of EFT parameters) based on Madgraph<br />
3) Kinematic Fitter neural network estimation vs analytic as available<br />
4) Pt dependent analysis of existing analysis<br />
5) Make a combination with a higgs channel? (difficult)<br />
6) Make a combination with other top channels? (difficult)<br />
<br />
More info in this presentation:<br />
www.nikhef.nl/~h73/top_masterstudenten_mrt2021.pptx<br />
and/or in the video:<br />
https://video.uva.nl/media/t/0_0f2fuazf<br />
<br />
<br />
[1] https://arxiv.org/abs/1807.03576<br />
<br />
''Contact: Marcel Vreeswijk [mailto:h73@nikhef.nl] and Jordy Degens [mailto:jdegens@nikhef.nl] ''<br />
<br />
=== ATLAS: The Next Generation ===<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks is very new [1] and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays), advanced analysis techiques (using deep learning methods) and expanding the theory interpretation. Another opportunity would be the development of the first statistical combination of results between the ATLAS and CMS experiment, which could significantly improve the discovery potentional.<br />
<br />
[1] https://arxiv.org/abs/1802.04329<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
=== ATLAS: The Most Energetic Higgs Boson ===<br />
<br />
The production of Higgs bosons at the highest energies could give the first indications for deviations from the standard model of particle physics, but production energies above 500 GeV have not been observed yet [1]. The LHC Run-2 dataset, collected during the last 4 years, might be the first opportunity to observe such processes, and we have various ideas for new studies. Possible developments include the improvement of boosted reconstruction techniques, for example using multivariate deep learning methods. Also, there are various opportunities for unexplored theory interpretations (using the MadGraph event generator), including effective field theory models (with novel ‘morphing’ techniques) and new interpretations of the newly observed boosted VZ(bb) process.<br />
<br />
[1] https://arxiv.org/abs/1709.05543<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree]''<br />
<br />
=== ATLAS: Searching for new particles in very energetic diboson production ===<br />
<br />
The discovery of new phenomena in high-energy proton–proton collisions is one of the main goals of the Large Hadron Collider (LHC). New heavy particles decaying into a pair of vector bosons (WW, WZ, ZZ) are predicted in several extensions to the Standard Model (e.g. extended gauge-symmetry models, Grand Unified theories, theories with warped extra dimensions, etc). In this project we will investigate new ideas to look for these resonances in a region that is yet unexplored in the data. We will focus on the final states where both vector bosons decay into quarks as they are expected to bring the highest sensitivity [1]. We will try to reconstruct and exploit the polarisation of the vector bosons (using machine learning methods) and then tackle the problem of estimating contributions from beyond the Standard Model processes in the tails of the mass distribution.<br />
<br />
[1] https://arxiv.org/abs/1906.08589<br />
<br />
''Contact: [mailto:f.dias@nikhef.nl Flavia de Almeida Dias]''<br />
=== ATLAS R&D: Study of LGAD sensors ===<br />
The Atlas detector has been installed more than a decade ago. Several upgrades of the detector are being worked on that will adapt the ATLAS experiment to the so-called High Luminosity LHC. A new (sub)detector that will be installed and become part of the Atlas detector is the High-Granularity Timing Detector (HGTD) detector. The HGTD will measure very precisely the passage time of particles in the detector and will help identify from which of the plurious proton-proton collisions the particle originates from. The HGTD is partly made of LGAD sensors. These are granulated silicon sensors dedicatedly designed for the HGTD. In this project we will characterise the LGAD sensors. <br />
<br />
''Contact: [mailto:f.dias@nikhef.nl Hella Snoek]''<br />
<br />
===LHCb: Measuring differences between electrons and muons, beyond the Standard Model=== <br />
A current “hot topic” in the field of particle physics is the potential violation of lepton-universality. <br />
At the LHCb experiment, lepton-universality tests are performed by looking at the ratio of decays<br />
into muons and into electrons/taus. Recent measurements in meson modes show hints (2 ? 3?) of lepton non-universality. <br />
Baryonic modes, however, have been less studied and provide an independent test of lepton-universality. <br />
At Nikhef, we study the decay Lambdab->Lambda l+l- , where l can be an electron or a muon. <br />
There are two possible project topics:<br />
<br />
1. Identifying novel analysis techniques in the high di-lepton invariant mass region. Electrons in this region undergo more Bremsstrahlung, and therefore have a worse momentum resolution,<br />
meaning background from the resonant Psi(2S) mode can leak into our signal. Since we expect most of our signal in this region, it is important to improve this, most likely using machine learning techniques.<br />
<br />
2. Identifying, simulating, and setting up a rejection for partially reconstructed Lambdab->Lambda* l+l- backgrounds. By not fully reconstructing the excited Lambda*0, we can mis-reconstruct it as a signal<br />
candidate. Machine learning techniques could be explored.<br />
<br />
''Contact: [mailto:l.greeven@nikhef.nl Lex Greeven] and [mailto:h71@nikhef.nl Niels Tuning]''<br />
<br />
===LHCb: New physics in the angular distributions of B decays to K*ee===<br />
<br />
Lepton flavour violation in B decays can be explained by a variety of non-standard model interactions. Angular distributions in decays of a B meson to a hadron and two leptons are an important source of information to understand which model is correct. Previous analyses at the LHCb experiment have considered final states with a pair of muons. Our LHCb group at Nikhef concentrates on a new measurement of angular distributions in decays with two electrons. The main challenge in this measurement is the calibration of the detection efficiency. In this project you will confront estimates of the detection efficiency derived from simulation with decay distributions in a well known B decay. Once the calibration is understood, the very first analysis of the angular distributions in the electron final state can be performed. <br />
<br />
Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen] and [mailto:m.senghi.soares@nikhef.nl Mara Soares]<br />
<br />
===LHCb: Discovering heavy neutrinos in B decays===<br />
<br />
Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, much heavier, neutral leptons. If the mass of these new neutrinos is below the b-quark mass, they can be observed in B hadron decays.<br />
<br />
In this project we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undisovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The analysis will be performed within the LHCb group at Nikhef using LHCb run-2 data.<br />
<br />
<br />
''Contact: [mailto:v.lukashenko@nikhef.nl Lera Lukashenko] and'' [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
<br />
===LHCb: Searching for dark matter in exotic six-quark particles ===<br />
3/4 of the mass in the Universe is of unknown type. Many hypotheses about this dark matter have been proposed, but none confirmed. Recently it has been proposed that it could be made of particles made of the six quarks uuddss. Such a particle could be produced in decays of heavy baryons. It is proposed to use Xi_b baryons produced at LHCb to search for such a state. The latter would appear as missing 4-momentum in a kinematically constrained decay. The project consists in optimising a selection and applying it to LHCb data. See [https://arxiv.org/abs/1708.08951 arXiv:1708.08951]<br />
<br />
''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
<br />
===With the Dark Matter group: Fine structure constant===<br />
The fine-structure constant has been measured by many experiments in the past and it is one of the most precisely known constants in nature. The goal of this project is to design and build an experiment to do an in-house measurement of the fine structure constant by investigating positron annihilation to two and to three photons. The work within this project encompasses the full breadth of experimental physics: from a conceptual design to the final analysis of the data. In addition, there is a budget of 10kEuro available to purchase the necessary hardware for the project. Supervision will be done by Colijn and the Nikhef director Bentvelsen. <br />
<br />
''Contact: [mailto:colijn@nikhef.nl Auke-Pieter Colijn]''<br />
<br />
===Dark Matter: Sensitive tests of wavelength-shifting properties of materials for dark matter detectors===<br />
Rare event search experiments that look for neutrino and dark matter interactions are performed with highly sensitive detector systems, often relying on scintillators, especially liquid noble gases, to detect particle interactions. Detectors consist of structural materials that are assumed to be optically passive, and light detection systems that use reflectors, light detectors, and sometimes, wavelength-shifting materials. MSc theses are available related to measuring the efficiency of light detection systems that might be used in future detectors. Furthermore, measurements to ensure that presumably passive materials do not fluoresce, at the low level relevant to the detectors, can be done. Part of the thesis work can include Monte Carlo simulations and data analysis for current and upcoming dark matter detectors, to study the effect of different levels of desired and nuisance wavelength shifting. In this project, students will acquire skills in photon detection, wavelength shifting technologies, vacuum systems, UV and extreme-UV optics, detector design, and optionally in C++ programming, data analysis, and Monte Carlo techniques.<br />
<br />
''Contact: [mailto:Tina.Pollmann@tum.de Tina Pollmann] and [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== Dark Matter: Building better Dark Matter Detectors - the XAMS R&D Setup===<br />
The Amsterdam Dark Matter group operates an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 4kg of ultra-pure liquid xenon. We use this detector for the development of new detection techniques - such as utilizing our newly installed silicon photomultipliers - and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENONnT experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory, or for future Dark Matter experiments like DARWIN. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data him/herself. You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
===Dark Matter: Searching for Dark Matter Particles - XENONnT Data Analysis ===<br />
The XENON collaboration has used the XENON1T detector to achieve the world’s most sensitive direct detection dark matter results and is currently starting the XENONnT successor experiment. The detectors operate at the Gran Sasso underground laboratory and consist of so-called dual-phase xenon time-projection chambers filled with ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the new data coming from the XENONnT detector. The work will consist of understanding the detector signals and applying a deep neural network to improve the (gas-) background discrimination in our Python-based analysis tool to improve the sensitivity for low-mass dark matter particles. The work will continue a study started by a recent graduate. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy.<br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
===Dark Matter: The Ultimate Dark Matter Experiment - DARWIN Sensitivity Studies===<br />
DARWIN is the “ultimate” direct detection dark matter experiment, with the goal to reach the so-called “neutrino floor”, when neutrinos become a hard-to-reduce background. The large and exquisitely clean xenon mass will allow DARWIN to also be sensitive to other physics signals such as solar neutrinos, double-beta decay from Xe-136, axions and axion-like particles etc. While the experiment will only start in 2027, we are in the midst of optimizing the experiment, which is driven by simulations. We have an opening for a student to work on the GEANT4 Monte Carlo simulations for DARWIN, as part of a simulation team together with the University of Freiburg and Zurich. We are also working on a “fast simulation” that could be included in this framework. It is your opportunity to steer the optimization of a large and unique experiment. This project requires good programming skills (Python and C++) and data analysis/physics interpretation skills.<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
===Detector R&D: Test beam with a bent ALPIDE monolithic active pixel sensor===<br />
The next ALICE inner tracking system that is to be installed in 2025 at the large hadron collider (LHC) will feature ultrathin silicon monolithic active pixel sensors (MAPS). The current ALICE tracking system that has just been installed already features this new, very thin pixel detectors with low noise and low power consumption, but for the next tracker they will be bent around the beam pipe. In this project, you will be part of the international ALICE collaboration. You will analyze data from beam tests performed at CERN and DESY to characterize bent pixel detectors. You will be part of the Nikhef R&D group and will also have the opportunity to perform your own measurements in the lab on the ALICE pixel detector (ALPIDE) or on an even thinner version thereof. If the travel situation allows, you will have the opportunity to join the ALICE test beam group in Hamburg at DESY to take part in the exciting experience of taking real data.<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
===Detector R&D: Modeling radiation damage for the next generation ATLAS pixel detector===<br />
In 2026 the ATLAS tracker will be upgraded to the largest silicon tracker in the world. This tracker will have to cope with very large data rates foreseen in the upgraded high luminosity large hadron collider (HL-LHC). From then on, this tracker will see very high rates of radiation, particularly in the inner tracker closest to the LHC beam line. In this project you will evaluate the performance of the silicon pixel sensors for the new ATLAS inner tracker. You will learn to use commercial technology computer aided design software (TCAD) for modeling semiconductors widely used in the semiconductor industry and compare your simulation results with data from the beam tests performed on the new modules for ATLAS ITk at CERN. You will also use and develop fast simulation tools like Allpix Squared for which you will use your C++ programming skills. As a member of the international ATLAS collaboration you will present your work in an international environment, and you will be part of the Nikhef detector R&D group where you will learn about the newest fast timing silicon detector technologies for LHC experiments and beyond.<br />
''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
===Detector R&D: Characterisation of Trench Isolated Low Gain Avalanche Detectors (TI-LGAD) ===<br />
The future vertex detector of the LHCb Experiment needs to measure the spatial coordinates and time of the particles originating in the LHC proton-proton collisions with resolutions better than 10 um and 50 ps, respectively. Several technologies are being considered to achieve these resolutions. Among those is a novel sensor technology called Trench Isolated Low Gain Avalanche Detector. <br />
Prototype pixelated sensors have been manufactured recently and have to be characterised. Therefore these new sensors will be bump bonded to a Timepix4 ASIC which provides charge and time measurements in each of 230 thousand pixels. Characterisation will be done using a lab setup at Nikhef, and includes tests with a micro-focused laser beam, radioactive sources, and possibly with particle tracks obtained in a test-beam. This project involves data taking with these new devices and analysing the data to determine the performance parameters such as the spatial and temporal resolution. as function of temperature and other operational conditions. <br />
<br />
''Contacts: [mailto:kazu.akiba@nikhef.nl Kazu Akiba] and [mailto:martinb@nikhef.nl Martin van Beuzekom]''<br />
<br />
=== Detector R&D: Studying fast timing detectors===<br />
Fast timing detectors are the solution for future tracking detectors. In future LHC operation conditions and future colliders, more and more particles are produced per collision. The high particle densities make it increasingly more difficult to separate particle trajectories with the spatial information that current silicon tracking detectors provide. A solution would be to add very precise (in order of 10ps) timestamps to the spatial measurements of the particle trackers. A good understanding of the performance of fast timing detectors is necessary. With the user of a pulsed laser in the lab we study the characteristics of several prototype detectors.<br />
<br />
''Contact: [mailto:hella.snoek@.nl Hella Snoek] or [mailto:kazu.akiba@nikhef.nl Kazu Akiba]''<br />
===Detector R&D: Laser Interferometer Space Antenna (LISA) - Wavefront sensors for gravitational wave detection===<br />
The space-based gravitational wave antenna LISA is one of the most challenging space missions ever proposed. ESA plans to launch around 2030 three spacecraft separated by a few million kilometres. This constellation measures tiny variations in the distances between test-masses located in each satellite to detect gravitational waves from sources such as supermassive black holes. LISA is based on laser interferometry, and the three satellites form a giant Michelson interferometer. LISA measures a relative phase shift between one local laser and one distant laser by light interference. The phase shift measurement requires sensitive wavefront sensors. The Nikhef DR&D group fabricated prototype sensors in 2020 together with the Photonics industry and the Dutch institute for space research SRON. As an MSc student, you will work on various aspects of the wavefront sensor development: study the performance of the epitaxial stacks of Indium-Gallium-Arsenide, setting up test benches to characterize the sensors, and performing the actual tests and data analysis.<br />
<br />
''Contact: [mailto:nielsvb@nikhef.nl Niels van Bakel]''<br />
<br />
===Detector R&D: Time tracking Cosmic rays===<br />
One of the main challenges in particle physics detector technologies is to perform precise time measurements while maintaining, or even improving, the excellent spatial resolution. New sensor prototypes need to be characterised using charged particles in order to determine the actual temporal resolution. Such a characterisation can be done for instance with high energy cosmic rays. In this project you will work on building, commissioning and characterising a compact timing cosmic ray setup, aiming to achieve a resolution better than 100 picoseconds. The work will take place in the R&D labs at Nikhef using a combination of existing detectors and readout electronics as well as new silicon detectors with internal gain (LGADs), and/or fast Micro Channel Plates (MCPs).<br />
<br />
''Contacts: [mailto:kazu.akiba@nikhef.nl Kazu Akiba] and [mailto:martinb@nikhef.nl Martin van Beuzekom]''<br />
<br />
===Neutrinos: Searching for Majorana Neutrinos with KamLAND-Zen===<br />
The KamLAND-Zen experiment, located in the Kamioka mine in Japan, is a large liquid scintillator experiment with 750kg of ultra-pure Xe-136 to search for neutrinoless double-beta decay (0n2b). The observation of the 0n2b process would be evidence for lepton number violation and the Majorana nature of neutrinos, i.e. that neutrinos are their own anti-particles. Current limits on this extraordinary rare hypothetical decay process are presented as a half-life, with a lower limit of 10^26 years. KamLAND-Zen, the world’s most sensitive 0n2b experiment, is currently taking data and there is an opportunity to work on the data analysis, analyzing data with the possibility of taking part in a ground-breaking discovery. The main focus will be on developing new techniques to filter the spallation backgrounds, i.e. the production of radioactive isotopes by passing muons. There will be close collaboration with groups in the US (MIT, Berkeley, UW) and Japan (Tohoku Univ). <br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== Neutrinos: acoustic detection of ultra-high energy neutrinos===<br />
<br />
The study of the cosmic neutrinos of energies above 1017 eV, the so-called ultra-high energy neutrinos, provides a unique view on the universe and may provide insight in the origin of the most violent astrophysical sources, such as gamma ray bursts, supernovae or even dark matter. In addition, the observation of high energy neutrinos may provide a unique tool to study interactions at high energies. The energy deposition of these extreme neutrinos in water induce a thermo-acoustic signal, which can be detected using sensitive hydrophones. The expected neutrino flux is however extremely low and the signal that neutrinos induce is small. TNO is presently developing sensitive hydrophone technology based on fiber optics. Optical fibers form a natural way to create a distributed sensing system. Using this technology a large scale neutrino telescope can be built in the deep sea. TNO is aiming for a prototype hydrophone which will form the building block of a future telescope.<br />
<br />
The work will be executed at the Nikhef institute and/or the TNO laboratories in Delft. In this project master students have the opportunity to contribute in the following ways:<br />
<br />
'''Project 1:''' Hardware development on fiber optics hydrophones technology Goal: characterize existing prototype optical fibre hydrophones in an anechoic basin at TNO laboratory. Data collection, calibration, characterization, analysis of consequences for design future acoustic hydrophone neutrino telescopes;<br />
Keywords: Optical fiber technology, signal processing, electronics, lab.<br />
<br />
'''Project 2:''' Investigation of ultra-high energy neutrinos and their interactions with matter. Goal: Discriminate the neutrino signals from the background noises, in particular clicks from whales and dolphins in the deep sea. Study impact on physics reach for future acoustic hydrophone neutrino telescopes;<br />
Keywords: Monte Carlo simulations, particle physics, neutrino physics, data analysis algorithms.<br />
<br />
Further information: Info on ultra-high energy neutrinos can be found at: http://arxiv.org/abs/1102.3591; Info on acoustic detection of neutrinos can be found at: http://arxiv.org/abs/1311.7588<br />
<br />
''Contact: [mailto:ernst-jan.buis@tno.nl Ernst Jan Buis]'' or ''[mailto:ivo.van.vulpen@nikhef.nl Ivo van Vulpen]''<br />
<br />
=== Neutrinos: Oscillation analysis with the first data of KM3NeT===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first few strings with sensitive photodetectors have been deployed at both the Italian and the French detector sites. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In this project the available data will be used together with simulations to best reconstruct the event topologies and optimally identify and reconstruct the first neutrino interactions in the KM3NeT detector. The data will then be used to measure neutrino oscillation parameters, and prepare for a future neutrino mass ordering determination.<br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
''Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn] [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
===Neutrinos: Searching for New Heavy Neutrinos or Other Exotic Particles in KM3NeT===<br />
<br />
In this project we will be searching for a new heavy neutrino, looking at signatures created by atmospheric neutrinos interacting in the detector volume of KM3NeT-ORCA. The aim of this project is to study a specific event topology which appears as double blobs of signals detected separately by densely instrumented ORCA detector units. We will be exploiting the tau reconstruction algorithms to verify the possibility of ORCA to detect such signals and to estimate the potential sensitivity of the experiment as well. The data also opens up the possibility to search for other exotic new particles, such as magnetic monopoles. Basic knowledge of elementary particle physics and data analysis techniques will be advantageous. The knowledge of programming languages e.g. python (and possibly C++) and ROOT are advantageous but not mandatory. <br />
<br />
''Contact: [mailto:suzanbp@nikhef.nl Suzan B. du Pree] [mailto:dveijk@nikhef.nl Daan van Eijk] [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
===Neutrinos: Dark Matter with KM3NeT-ORCA=== <br />
<br />
Dark Matter is thought to be everywhere (we should be swimming through it), but we have no idea what it is. Using the good energy and angular resolutions of the KM3NeT neutrino telescope, we can search for Dark Matter signatures that originate from the center of our galaxy. In this project, we will search for such signatures using the reconstructed track and shower events with the KM3NeT-ORCA detector to discover relatively light Dark Matter particles. Since this year, the KM3NeT-ORCA experiment has 6 detection lines under the Mediterranean Sea: fully operational and continuously taking data. Using the available data, it is possible to compare data and simulation for different event topologies and to estimate the experiment's sensitivity. The project is suitable for a student who is interested to explore new physics scenarios and willing to develop new skills. Basic knowledge of elementary particle physics and data analysis techniques will be advantageous. The knowledge of programming languages e.g. python (possibly C++) and ROOT data analysis tool are advantageous but not mandatory. <br />
<br />
''Contact: [mailto:suzanbp@nikhef.nl Suzan B. du Pree] [mailto:dveijk@nikhef.nl Daan van Eijk]''<br />
<br />
===Neutrinos: the Deep Underground Neutrino Experiment (DUNE)===<br />
<br />
The Deep Underground Neutrino Experiment (DUNE) is under construction in the USA, and will consist of a powerful neutrino beam originating at Fermilab, a near detector at Fermilab, and a far detector in the SURF facility in Lead, South Dakota, 1300 km away. During travelling, neutrinos oscillate and a fraction of the neutrino beam changes flavour; DUNE will determine the neutrino oscillation parameters to unrivaled precision, and try and make a first detection of CP-violation in neutrinos. In this project, various elements of DUNE can be studied, including the neutrino oscillation fit, neutrino physics with the near detector, event reconstruction and classification (including machine learning), or elements of data selection and triggering.<br />
<br />
''Contact: [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
<br />
===Gravitational Waves: Computer modelling to design the laser interferometers for the Einstein telescope===<br />
<br />
A new field of instrument science led to the successful detection of gravitational waves by the LIGO detectors in 2015. We are now preparing the next generation of gravitational wave observatories, such as the Einstein Telescope, with the aim to increase the detector sensitivity by a factor of ten, which would allow, for example, to detect stellar-mass black holes from early in the universe when the first stars began to form. This ambitious goal requires us to find ways to significantly improve the best laser interferometers in the world.<br />
<br />
Gravitational wave detectors, such as LIGO and VIRGO, are complex Michelson-type interferometers enhanced with optical cavities. We develop and use numerical models to study these laser interferometers, to invent new optical techniques and to quantify their performance. For example, we synthesize virtual mirror surfaces to study the effects of higher-order optical modes in the interferometers, and we use opto-mechanical models to test schemes for suppressing quantum fluctuations of the light field. We can offer several projects based on numerical modelling of laser interferometers. All projects will be directly linked to the ongoing design of the Einstein Telescope.<br />
<br />
''Contact: [mailto:a.freise@nikhef.nl Andreas Freise]''<br />
<br />
<br />
===Gravitational Waves: Digging away the noise to find the signal===<br />
<br />
Gravitational Wave interferometers are extremely sensitive, but suffer <br />
from instrumental issues that produce noise that mimics astrophysical <br />
signals. This needs to be solved as much as possible before the data <br />
analysis. The problem is that instrumentalists don't know about <br />
analysis pipelines, and data analysts don't know about experimental <br />
details. We need your help to bridge the gap. This is a good opportunity <br />
to learn about both sides and contribute directly to a booming <br />
international field. We have several tools and new ideas for correlating <br />
noises with the state of the instrument. These need to be developed <br />
further, used on years of data, and written up. Will require Python, <br />
signal processing and statistics.<br />
<br />
''Contact: [mailto:swinkels@nikhef.nl Bas Swinkels] and [mailto:physarah@gmail.com Sarah Caudill]''<br />
<br />
===Theory: The electroweak phase transition and baryogenesis/gravitational wave production===<br />
<br />
In extensions of the Standard Model the electroweak phase transition can be first order and proceed via the nucleation of bubbles. Colliding bubbles can produce gravitational waves [1] and plasma particles interacting with the bubbles can generate a matter-antimatter asymmetry [2]. A detailed understanding of the dynamics of the phase transitions is needed to accurately describe these processes. One project is to study QFT at finite temperature and compare/apply methods that address the non-perturbative IR dynamics of the thermal processes [3,4]. Another project is to calculate the velocity by which the bubbles expand, which is an important parameter for gravitational waves production and baryogensis. A final option is to study the phase transition in conformal Higgs models, which naturally have a strong 1st order phase transition [5].<br />
<br />
[1]https://arxiv.org/abs/1705.01783<br />
[2]https://arxiv.org/pdf/hep-ph/0609145.pdf<br />
[3]https://arxiv.org/pdf/1609.06230.pdf<br />
[4]https://arxiv.org/pdf/1612.00466.pdf<br />
[5]https://arxiv.org/abs/1910.13460.pdf<br />
<br />
''Contact: [mailto:mpostma@nikhef.nl Marieke Postma]''<br />
<br />
===Theory: Higgs inflation===<br />
<br />
The Higgs boson can drive cosmic inflation provided it has new couplings to gravity [1]. Although classically the model is in excellent agreement with the data, in the full quantum theory there are theoretical consistency issues. One possible project would be to embed Higgs inflation in [2] -- motivated to solve the Strong CP problem and explain the matter-antimatter asymmetry -- as the extended Higgs sector can alleviate the theoretical constraints. Another direction is to consider multiple new couplings to gravity [3], to see whether the ensuing inflationary dynamics allows for the production of primordial black holes. <br />
<br />
[1]https://arxiv.org/pdf/1307.0708.pdf<br />
[2]https://arxiv.org/pdf/2007.12711.pdf<br />
[3]https://arxiv.org/abs/2011.09485.pdf<br />
<br />
''Contact: [mailto:mpostma@nikhef.nl Marieke Postma]''<br />
<br />
===Theory: Neutrinos, hierarchy problem and cosmology===<br />
<br />
The electroweak hierachy is radiatively stable if the quadratic term in the Higgs potential is generated dynamically. This is achieved in 'the neutrino option' [1] where the Higgs potential stems exclusively from quantum effects of heavy right-handed neutrinos, which can also generate the mass pattern of the oberved left-handed neutrinos. The project focusses on model building aspects (e.g. [2]) and the cosmology (e.g. leptogenesis [3]) of these set-ups.<br />
<br />
[1] https://arxiv.org/pdf/1703.10924.pdf<br />
[2] https://arxiv.org/pdf/1807.11490.pdf<br />
[3] https://arxiv.org/pdf/1905.12642.pdf<br />
<br />
''Contact: [mailto:mpostma@nikhef.nl Marieke Postma]''<br />
<br />
<br />
----<br />
<br />
<br />
<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Bachelor_Projects&diff=772Bachelor Projects2022-02-02T08:40:17Z<p>Rojo@nikhef.nl: </p>
<hr />
<div><br />
== Bachelor Projects 2022 ==<br />
<br />
=== Dark Matter ===<br />
<br />
==== Response of materials to scintillation light from liquid noble gasses ====<br />
<br />
The liquid form of the noble gases argon and xenon is a popular target material for neutrino and dark matter detectors. The scintillation light from noble gases is in the vacuum UV spectral region. Air and many materials used for optical studies are not transparent to these photons. Measurements of the optical properties of detector materials, such as their reflectivity for example, thus have to be performed with dedicated VUV optics and in vacuum. Additionally, to reproduce the conditions in the detectors, the samples must be cooled to cryogenic temperatures. In this BSc project, you will calibrate the photon detectors in an experimental setup designed to study the optical response of materials excited with VUV photons. You will learn about material requirements for rare event search detectors, vacuum instrumentation, vacuum UV optics including monochromators and spectrometers, and single-photon sensors.<br />
<br />
Supervisors: T. Pollmann (t.pollmann_at_nikhef.nl)<br />
<br />
=== ATLAS ===<br />
<br />
=== LHCb ===<br />
<br />
<br />
==== Exotic neutrinos in B decays====<br />
<br />
Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, heavier, neutral leptons. In the LHCb group at Nikhef we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undisovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The bachelor project will contribute with the optimization of the selection using state-of-the-art tools for the multi-variate analysis.<br />
<br />
Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
<br />
<br />
=== Gravitational Waves ===<br />
<br />
=== Detector R&D ===<br />
Answering big elementary particle physics questions requires pioneering experiments. The Detector R&D program at Nikhef is aimed at conceptualizing and testing of instrumentation concepts before they are implemented in scientific programs at Nikhef. <br />
<br />
==== Time resolution of monolithic timing detectors ====<br />
For the upgrade of the vertex detectors of the large LHC experiments like LHCb and ALICE, new silicon pixel detectors will developed now that can register the passing particles with a time precision of tens of picoseconds. ALICE is the first experiment at the LHC to have installed monolithic sensors where electronics is integrated into the sensor resulting in ultrathin, low-material detectors. In this project you will measure the time resolution of these promising integrated sensors with a laser setup in our laboratory.<br />
<br />
Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
==== Modeling radiation damage in silicon sensors ====<br />
In the coming years, the ATLAS experiment at the LHC works on upgrades to prepare for the high-luminosity LHC, where many more collisions will take place than today. Analyses of LHC data rely heavily on simulations of the detector. It may sound counterintuitive, but particle detectors do not actually like particles: after many collisions at the LHC, a silicon pixel detector has seen so many particles that its bulk gathers defects. Charge generated by traversing particles can get trapped in defects resulting in less charge induced in the readout electrodes, reducing detector performance in resolution and efficiency. In this project, you will be part of the international ATLAS collaboration and compare different models of radiation damage with measured data and you will contribute to the open source program Allpix Squared that is widely used for simulations in many areas of particle physics.<br />
<br />
Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
==== Time resolution of a new digital pixel test structure from test beam data ====<br />
For the upgrade of the ALICE detector, ultrathin picosecond timing integrated sensors are developed. To reduce power consumption, asynchronous readout is implemented in this prototype sensor in a digital pixel test structure. This structure was studied in test beams with an ALPIDE (ALICE PIxel DEtector) telescope at CERN. You will measure the efficiency and time resolution of this new sensor with the latest data from test beams at CERN.<br />
<br />
Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
<br />
<br />
<br />
=== KM3NeT ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along 200-700m long vertical lines, called detection units.<br />
<br />
==== Neutrino oscillation measurements with the first KM3NeT data ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope is able to measure the oscillations of neutrinos produced in interactions of cosmic rays with the earth atmosphere. Fundamental neutrino properties can be deduced from these oscillations measurements. In this project we will use the first data of ORCA (more than one year with six detection units) to study neutrino oscillations and fit neutrino mixing parameters and mass differences between neutrino mass states. We will study data selection, event reconstruction, and effects of systematic uncertainties on the results. <br />
<br />
Supervisors: Brian O'Fearraigh, Ronald Bruijn, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
==== Search for sterile neutrinos with KM3NeT. ====<br />
A detailed study of neutrino oscillations in the KM3NeT detector is sensitive to the existence of so-called sterile neutrinos: neutrinos that are not part of the Standard Model of particle physics, and have no ordinary interactions with matter. We will use a mixture of data and simulations to estimate KM3NeT sensitivity.<br />
<br />
Supervisors: Alba Domi, Paul de Jong<br />
<br />
==== Machine learning for event classification in KM3NeT ====<br />
The classification of neutrino events recorded in the KM3NeT detector in terms of originating from electron neutrinos, muon neutrinos, or tau neutrinos, is very well suited for machine learning techniques. We will study the performance of a few advanced machine learning techniques on simulated high-energy neutrino events.<br />
<br />
Supervisors: Alba Domi, Paul de Jong<br />
<br />
==== Multi-messenger astronomy with neutrinos and radio signals ====<br />
The main goal of neutrino telescopes, such as ANTARES, KM3NeT and IceCube, is to detect cosmic neutrinos from astrophysical sources. When an interesting neutrino candidate is detected they send out a message to alert the scientific community. Other scientific instruments, like the Murchison Widefield Array (MWA) radio telescope, can then do a follow-up observation, to see if there are other messengers coming from the same source as the neutrinos. In this project you will analyse MWA data that were taken after the reception of neutrino alerts, to search for a radio source that can be associated with a neutrino source.<br />
<br />
Supervisor: Mieke Bouwhuis (mieke.bouwhuis at nikhef.nl)<br />
<br />
=== Theory ===<br />
<br />
==== Symmetries and sterile neutrinos ====<br />
<br />
The fact that neutrinos have masses is problematic for the Standard Model. A plausible solution requires the existence of additional so-called sterile neutrinos. In this project we will study why such neutrinos could exist and describe their mixing with the active neutrinos we have seen in experiments. In particular, we will investigate how large active-sterile mixing can be while accounting for the small neutrino masses and what this tells us about possible lepton number violation. <br />
<br />
Supervisor: Jordy de Vries <br />
<br />
==== Effective Field Theories of Particle Physics from low- to high-energies ====<br />
<br />
Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations<nowiki>''</nowiki> seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature.<br />
<br />
Until recently, it was widely assumed that matter particles from each of the three generations interact with the same (“universal”) strength. This hypothesis is being challenged by new measurements at the Large Hadron Collider (LHC) at CERN, which hint towards non-universal interactions. If confirmed, these measurements will be the first signs of new particles and interactions in high-energy colliders. These exciting findings indicate the urgent need to explore such phenomena in depth.<br />
<br />
The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Effective Field Theory (EFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes. Specifically, the goal is to connect measurements from ATLAS and LHCb among them and to jointly interpret this information with that provided by other experiments, from CMS and Belle-II to very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
<br />
''Methodology and workplan''<br />
<br />
This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories.<br />
<br />
This project accommodates several students, who would work together in developing the main formalism while each of them focuses on a specific sub-project. The maximum capacity of this project is 5 students. <br />
<br />
Depending on the student profile, sub-projects with a strong computational / machine learning component are also possible.<br />
<br />
During the first four weeks of the project, students will learn the required background material on effective field theories, following the guidelines from the supervisors. Afterwards, they will focus on different sub-projects, each covering a different aspect of the same global EFT program.<br />
<br />
Required knowledge<br />
<br />
Quantum Mechanics 2, Particle Physics 1 (required)<br />
<br />
Advanced Quantum Mechanics, Particle Physics 2, Machine Learning (optional)<br />
<br />
Available subprojects<br />
<br />
Here we list the available subprojects, including the corresponding daily supervisor(s) in each case.<br />
<br />
''Subproject #1: SMEFT & Flavour symmetries'' <br />
<br />
Daily supervisors: Jordy de Vries (UvA), Keri Vos (Maastricht University), Jaco ter Hoeve (VU), Giacomo Magni (VU)<br />
<br />
While the power of the Standard Model EFT (named SMEFT) framework is its generality and lack of assumptions, the number of operators is somewhat daunting. A popular way to trim the number of operators is to assume flavour symmetries that relate operators with different quark and lepton flavours. In this project you will investigate the theoretical basis for commonly-used flavour symmetries and what they imply for the connection between high-energy observables involving third-generation particles (top and bottom quarks and tau leptons) and low-energy precision tests involving first- and second-generation particles. The investigations of this project are connected with Subproject #2.<br />
<br />
''Subproject #2: SMEFT & magnetic moment of the muon''<br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU)<br />
<br />
The magnetic moment of the muon appears to differ from the Standard Model expectations by a large amount, well beyond the known experimental and theoretical uncertainties. Recent experiments have only strengthened the significance of this anomaly. In this project, the students will investigate the feasibility of implementing the measurement of the magnetic moment of the muon into a global SMEFT analysis, by exploiting recently provided calculations. Special attention will be devoted to the flavour assumptions required to consistently match this measurement with the LHC data, also at the light of the connection with Subproject #1. The SMEFiT analysis framework will be used to connect the g-2 data with high-energy LHC measurements.<br />
<br />
''Subproject #3: CP Violation and low-energy precision experiments''<br />
<br />
Most analyses of LHC data are performed under the assumption that CP symmetry (charge conjugation + parity, essentially the symmetry between particles and anti-particles) is conserved. More recent analyses attempt to also measure possible new sources of CP violation in SMEFT operators in the Higgs and top sector. <br />
<br />
''Subproject #3a: CP Violation and low-energy precision experiments''<br />
<br />
Daily supervisors: Jordy de Vries (UvA), Juan Rojo (VU)<br />
<br />
Low-energy precision experiments can also set stringent constraints on new mechanisms of CP violation. In this project you will try to combine high- and low-energy data to put CP symmetry to the test. <br />
<br />
''Subproject #3b: CP Violation and flavour physics experiments''<br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU)<br />
<br />
Besides low-energy precision experiments, also B-meson decays are excellent probes of CP violation. Unlike most low-energy experiments, this allows us to probe CP violation in the third generation. In this project you will link constraints on CP violation at high-energy to those from B meson decays. <br />
<br />
''Subproject #4: SMEFT & optimal observables'' <br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU), Tommaso Giani (VU & Nikhef)<br />
<br />
In full generality, the number of operators in SMEFT spans a very large parameter space. These parameters are constrained by experimental inputs from ATLAS and CMS, depending on the precise parameters these constraints may be more or less stringent. In order to fully exploit the whole parameters space in SMEFT, it is necessary to devise statistically optimal observables that have a large constraining power. In this project, we will define such observables. This project has a strong computational / machine learning component and may involve simulations based on tools such as MadGraph and Pythia8.<br />
<br />
Contacts:<br />
<br />
Juan Rojo (VU Amsterdam & Nikhef): j.rojo at vu.nl<br />
<br />
Keri Vos (UM & Nikhef): k.vos at maastrichtuniversity.nl <br />
<br />
Jordy de Vries (UvA & Nikhef): j.devries4 at uva.nl<br />
<br />
== Bachelor Projects 2021 ==<br />
=== Dark Matter ===<br />
<br />
==== XAMS ====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso.<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with recently upgraded hardware to test a novel concept for UV light detection. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complete the first measurements with our upgraded setup.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== XENONnT reconstruction software ====<br />
The XENONnT experiment becomes operational during 2021. While the hwardware is finished we keep on developing and perfecting our reconstruction software. For this project we are looking for a student with a keen interest in and talent for writing physics based event reconstruction software (we use python). Specifically we have an idea to improve the localization of events inside the XENONnT for which proto-type software exists. The proto-type software needs to be implemented in the XENONnT reconstruction framework and subsequently it needs to be validated on the first data from the experiment. The final goal of the project is to deliver the reconstruction software to the collaboration that will be used during teh full lifetime of the experiment.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Backgrounds in Radioactive Decay Measurements ====<br />
At Nikhef, the XENON group has a working setup, continuously monitoring the<br />
radioactive decay of Cobalt-60, Caesium-137 and Titanium-44. This beautiful setup is<br />
however not shielded perfectly; it is still vulnerable to background radioactivity. Our<br />
current way of working around this background radiation is to subtract it from our<br />
waveforms. You as a BSc student could help us hands-on and with analyses:<br />
together, we can disassemble the setup, measure background spectra and<br />
implement this in the data analysis. You can use all the data to validate the<br />
lifetime of our isotopes!<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Detection of scintillation light from liquid noble gasses ====<br />
<br />
The liquid form of the noble gases argon and xenon is a popular target material for neutrino and dark matter detectors. The scintillation light from noble gases is in the vacuum UV spectral region. Air and many materials used for optics studies are not transparent to these photons. Measurements of the optical properties of detector materials, such as their reflectivity for example, thus have to be performed with dedicated VUV optics and in vacuum. Additionally, to reproduce the conditions in the detectors, the samples must be cooled to cryogenic temperatures. In this BSc project, you will design, using professional hardware design software, a vacuum chamber to hold the detector materials whose optical properties are to be investigated, as well as the cooling system and photon detectors. You will learn about material requirements for rare event search detectors, vacuum instrumentation, vacuum UV optics including monochromators and spectrometers, and single-photon sensors.<br />
<br />
Supervisors: T. Pollmann (t.pollmann_at_nikhef.nl)<br />
<br />
=== Detector R&D ===<br />
<br />
==== Characterization of the new ultrathin ALPIDE monolithic active pixel sensor ====<br />
At the Large Hadron Collider at CERN, major upgrades of experiments take place in the long shutdown years where particle collisions are paused. The ALICE inner tracking system (ITS) 2, the part of the ALICE experiment closest to the beam pipe, is currently being installed at CERN. This detector makes use of ultra-lightweight monolithic active pixel sensors, the first to use this technology at particle colliders after the STAR experiment at RHIC in Brookhaven. These very thin pixel detectors have a low power consumption, result in very little material in the detector, and still have optimal timing and resolution -- and are a promising technology for future experiments. To characterize the performance of these sensors, you will learn to set up experiments, carry out measurements, and analyze data using various instruments available in the detector R&D lab at Nikhef. This could lead to novel insights of monolithic active pixel sensors. It is also possible to do measurements from home using data from the first test beams with bent (yes, with a curvature!) ALPIDE sensors. You will work in an international, stimulating research environment in the detector R&D group at Nikhef at the forefront of silicon detector technologies for high energy physics. ''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
==== Simulation of 3D silicon sensors ====<br />
<br />
For the upgrade of the vertex detector of the LHCb experiment novel silicon pixel detectors have to be developed that can register the passing particles with a time precision of tens of picoseconds. Given the harsh radiation environment very close to the LHCb interaction point only a limited number of technologies can be applied. One of the most promising technologies are the so-called 3D sensors whose readout electrodes are pillars that are placed into the sensor perpendicular to the surface; this in contrast to ’standard’ planar silicon sensors where the pixel electrodes are at the surface, similar to the camera in your smartphone. To understand the time response of these 3D sensors, simulations with TCAD software have to be performed and the results will be compared to measured data. These simulations involve the creation/adaptation of the 3D structures of the model, optimising the simulation speed, and analysing the signals as function voltage, track impact point and deposited charge. If time and Covid regulations permit, gaining some hands-on experience with such 3D sensors in the R&D labs at Nikhef is possible. ''Contacts: [mailto:martinb@nikhef.nl Martin van Beuzekom] [mailto:k.heijhoff@cern.ch Kevin Heijhoff] ''<br />
<br />
<br />
=== Theory ===<br />
<br />
==== Standard Model Effective Field Theory analysis of Z+dijet production ====<br />
The goal of this project is to study the effect of higher dimensional operators from the Standard Model Effective Field Theory in Z-boson production measured at LHC. The ATLAS collaboration has just reported in 2020 the measurement of Z production alongside with a pair of jets, based on the full Run II luminosity. In this project we aim to study the effect of dimension six SMEFT operators on the signal (EW-induced) and/or background (QCD-induced), finding which is the kinematic variable that maximises the possible effect of beyond the SM operators and thus may provide the best constraint on New Physics. The outcome of this project may be the first step of the inclusion of Vector production in a global SMEFT fit. <br />
<br />
References: https://arxiv.org/pdf/2006.15458.pdf, https://www.hepdata.net/record/ins1803608<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Maximum precision on new physics through information theory ====<br />
One way to look for physics beyond the standard model is through the framework of effective field theory. In this framework, deviations from the standard model are described by a set of continuous parameters. Finding constraints on these parameters might point to the discovery of new physics. With the large number of LHC experiments we currently face, we want to be able to quantify the maximum knowledge that (future) experiments can provide on new physics parameters. In this project, the student will study and quantify the maximum information that is contained in particle physics experiments through information theory. The central object of study will be the Fisher information matrix. The idea is to work with a simple toy experiment that describes Higgs physics and compute its associated Fisher information matrix to quantify the optimal bounds on new physics. The project will start with studying central objects from statistics and information theory. Later, we will apply these to open problems in particle physics.<br />
<br />
Reference: https://arxiv.org/pdf/1612.05261.pdf<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Seesaw mechanism and neutrino mass ==== <br />
Many unsolved questions in particle physics are related to the nature of the neutrino and its mass generation. The goal of this theoretical project is to understand and review one of the possible candidate theories that describe how neutrinos mix and get massive, namely the Seesaw mechanism. Among the many possible Seesaw mechanisms that can generate new phenomenology including lepton number non-conservation, the student will focus on one minimal model to understand the key processes that are currently used to probe the validity of the given theory. <br />
<br />
References: https://cds.cern.ch/record/408119/files/9911364.pdf, https://arxiv.org/pdf/1711.02180.pdf<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Mixing of sterile neutrinos ====<br />
<br />
Neutrino oscillation experiments demonstrate that neutrinos are massive particles. However, the mass mechanism of neutrinos is unknown. A<br />
minimal solution requires the existence of so-called sterile neutrinos: neutrinos that are even more elusive than ordinary neutrinos. <br />
We will investigate how to parametrize the matrix that describes the mixing between ordinary and sterile neutrinos. We will then use this<br />
to calculate how sterile neutrinos induce rare nuclear decays and determine the sensitivity of ongoing experiments to observe sterile<br />
neutrinos.<br />
<br />
Supervisor: Jordy de Vries (devries.jordy at gmail.com)<br />
<br />
<br />
=== KM3NeT ===<br />
<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
==== Data analysis of the first deployed KM3NeT detection lines ====<br />
<br />
First detection lines of the KM3NeT neutrino telescope have been deployed<br />
in the Mediterranean Sea, and a first data set is available. The lines consist<br />
of light-sensitive detectors that record the time of arrival of photons<br />
produced by relativistic particles in the deep sea, and their number.<br />
In this project we will study the first data to separate various components:<br />
photons from potassium decay, bioluminesence, sparks in the photomultipliers,<br />
downgoing muons from cosmic rays, and first neutrinos.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben (paul.de.jong at nikhef.nl)<br />
<br />
==== Neutrino oscillation measurements with the KM3NeT neutrino telescope ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope currently under construction<br />
will be able to measure the oscillations of neutrinos produced in interactions<br />
of cosmic rays with the earth atmosphere. Fundamental neutrino properties can<br />
be deduced from these oscillations measurements, in particular the so-called<br />
mass hierarchy of neutrinos. In this project we will simulate the ORCA measurements<br />
of neutrino oscillations, and study the dependence of the sensitivity on<br />
experimental uncertainties, such as energy resolution and neutrino flavour<br />
identification, and theoretical uncertainties, such as the atmospheric neutrino<br />
flux and neutrino cross sections. The results will help ORCA to identify<br />
the main sources of uncertainty, and therefore to actively try to reduce these<br />
and improve the final measurement.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
==== Performance Studies of ORCA for Dark Matter Detection ====<br />
<br />
The interactions of neutrinos in KM3NeT-ORCA give different signatures which are categorised as track and shower events. This project involves the studies of muon, electron and tau neutrino interactions for the reconstruction performance of ORCA. Efficient reconstruction of such signals is important for Dark Matter searches in the low-mass regime. We will work on understanding the detector performance, e.g. effective acceptance, energy and angular resolution, with different configurations of the detector setup. The result of this study will be very useful to improve the sensitivity of the experiment for Dark Matter detection and its possible location. The student will have the opportunity to work closely with KM3NeT members at Nikhef and gain skills of analyzing data. <br />
<br />
Supervisors: Suzan Basegmez du Pree, Aart Heijboer (s.basegmez.du.pree at nikhef.nl)<br />
<br />
==== Study of Optical Properties of Sea Water using Hit Coincidences in MC Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
By studying coincidences of L1 hits between neighbouring DOMs, for various Monte Carlo (MC) data sets with different sea water optical properties such as scattering and absorption coefficients, in this project we try to figure out if and how well we can quantify optical sea water properties by studying L1 hit coincidences in real KM3NeT data.<br />
<br />
Supervisor: Daan van Eijk (dveijk at nikhef.nl)<br />
<br />
==== Determination of Inter-DOM Distances using Hit Coincidences in KM3NeT Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
The number of L1 hit coincidences from atmospheric muons between neighbouring DOMs on a DU is expected to decrease exponentially. By fitting the observed number of L1 hit coincidences between neighbouring DOMs in real data to the expected exponential decay, in this project we study how accurately we can determine the distances between DOMs on a single DU. In addition, we try to determine the distances between DUs by looking for L1 hit coincidences between DOMs on neighbouring DUs.<br />
<br />
Supervisor: Daan van Eijk (dveijk at nikhef.nl)<br />
<br />
<br />
=== ATLAS ===<br />
<br />
==== The Higgs boson life-time ====<br />
<br />
The Higgs particle does not have eternal life. The Standard Model (SM) predicts that it decays into other particles and as these couplings are fixed we can predict its life-time with very high precision. Determining this life-time is a crucial test for the Standard Model. If the Higgs boson life-time is shorter that we expect this could mean that the Higgs boson could decay into non-SM particles. In this project we investigate a) how we can identify Higgs particles in the detector and b) how we plan to use quantum-interference to get a handle on the Higgs boson's life-time. <br />
<br />
Supervisor: Wouter Verkerke (verkerke_at_nikhef.nl)<br />
<br />
==== The Higgs boson decaying to photons ====<br />
<br />
One of the main channels used to analyse the properties of the Higgs boson is when the Higgs boson decays into two photons. The crucial building block in this analysis is our ability to reconstruct the energy and the direction of the photons in the ATLAS detector and in this project we will revisit the photon reconstruction. We will start by studying simulations and learning about photon reconstruction in general. Then our goal is to determine the energy and position resolution of photons in the ATLAS detector and see if we can exploit our knowledge on the photon resolution to get an (improved) estimate of the Higgs boson mass. For the analysis we will use the '''real data from the LHC''' - the ATLAS open data project.<br />
<br />
Supervisor: Ashley McDougall and Ivo van Vulpen (Ivo.van.Vulpen_at_nikhef.nl)<br />
<br />
<br />
=== LHCb (1) ===<br />
<br />
One of the most fascinating mysteries in physics today is: how is it possible that universe is filled with matter? If the Big Bang produced equal amounts of matter and antimatter, we still do not understand the mechanism that lead to the excess of matter over antimatter that we observe today.<br />
<br />
One interesting feature of some particles is that they can transform themselves into their antiparticles, then back to particle, and so forth, in an oscillatory way until they finally decay. In particular, beauty mesons (B) can oscillate into their antiparticle (B ̄). The parameters of this oscillation, such as amplitude, frequency and phase, are calculable mathematically: predictions for it are available in the standard model (SM) of particle physics. But the oscillations according to the SM alone would not lead to the imbalance of matter in the universe – we still need to find a new type of physics that may be able to explain it.<br />
<br />
In this context, it is very important to measure B oscillations in the laboratory, and compare these observations with the expectations from the SM. Are the experimental data in good agreement with the SM, as we expect? If the aswer is not, i.e. if there are features of the oscillation that we do not understand well, then we may be observing “new physics”. In other words, the data may reveal a new mechanism that generates a different matter-antimatter balance than predicted by the SM, that may potentially solve the puzzle.<br />
<br />
The LHCb experiment at CERN is dedicated to such studies: LHCb detectors are placed in a region along the LHC collider beamline, where a large number of B mesons are produced, arising from the proton-proton collision data from the LHC collider. Looking at the LHCb data we can obtain large samples of B mesons, and observe their oscillations.<br />
In this project we will learn how to select a sample of B mesons out of the data taken with the LHCb detector, measure the parameters that govern their oscillation and compare them with the SM.<br />
<br />
For more information, please contact Mara Soares (msoares_at_nikhef.nl).<br />
<br />
== Bachelor Projects 2020 ==<br />
<br />
<br />
=== Dark Matter ===<br />
<br />
==== XAMS ====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso.<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source and liquid scintillatorneutron detector we have acquired for the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study of neutron transport in xenon.<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Backgrounds in Radioactive Decay Measurements ====<br />
At Nikhef, the XENON group has a working setup, continuously monitoring the<br />
radioactive decay of Cobalt-60, Caesium-137 and Titanium-44. This beautiful setup is<br />
however not shielded perfectly; it is still vulnerable to background radioactivity. Our<br />
current way of working around this background radiation is to subtract it from our<br />
waveforms. You as a BSc student could help us hands-on and with analyses:<br />
together, we can disassemble the setup, measure background spectra and<br />
implement this in the data analysis. You can use all the data to validate the<br />
lifetime of our isotopes!<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
=== ATLAS ===<br />
<br />
==== Project ATLAS-ITk ====<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
==== The Most Energetic Higgs Boson ====<br />
A common approach to search for physics beyond the standard model is by searching for the direct production of new particles. Alternatively, indirect quantum effects on the production of known particles -such as the Higgs Boson- could reveal the first cracks in the theory. Processes with high energy transfer are of particular potential since possible deviations are expected to increase with the square of the involved energy scale. Using the entire data-set collected by the ATLAS experiment at CERN during the four years of the LHC’s Run 2, a proof-of-principle analysis, targeting transverse momenta of the above 400 GeV, has been developed by Nikhef researchers. The first results of this Higgs boson study are expected to be published this year and this project aims to develop refinements of the analysis techniques. We will investigate the usage of sophisticated machine learning tools such as artificial neural networks, the search for new variables that can help discriminating the signal from its background, revisiting the analysis categorisation and improving the reconstruction techniques at these extreme momenta. Supervisors: Brian Moser and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs: The Next Generation ====<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks has been developed by Nikhef researchers and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays), advanced analysis techiques (using deep learning methods) and expanding the theory interpretation. Another opportunity would be the development of a new statistical combination with various independent searches, which could significantly improve the discovery potential. Supervisors: Marko Stamenkovic and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs interferentie ====<br />
In 2012 hebben het ATLAS en het CMS experiment het Higgs deeltje gevonden. Inmiddels zijn we het Higgs boson aan het bestuderen, hoe gedraagt het zich precies, bestaan er meer soorten Higgs bosonen of is er echt maar eentje van? In dit project leer je hoe we een Higgs boson kunnen herkennen in de detector en gaan we kijken naar hoe de signalen veranderen als er meer Higgs bosonen bestaan of misschien wel andere exotische nieuwe deeltjes. <br />
Dit doen we door gebruik te maken van quantum interferentie wat plaats vindt tussen het Higgs boson en achtergrondprocessen. Hoe dit precies werkt leer je in het project. Supervisor: Hella Snoek (h.snoek_at_nikhef.nl)<br />
<br />
=== B-Physics - LHCb ===<br />
<br />
==== Time dependent CP violation ====<br />
The LHCb experiment studies CP violation withB-meson decays.<br />
The project focusses on the measurement of the unitarity angle gamma using decays of the Bs mesons to Ds K.<br />
Supervisors: Sevda Esen & Michele Veronesi<br />
<br />
==== Machine learning ====<br />
Machine learning has proven to be an indispensable tool in the selection of interesting events in high energy physics. Such technologies will become increasingly important as detector upgrades are introduced and data rates increase by orders of magnitude. HEPDrone is a toolkit to enable the creation of a drone classifier from any machine learning classifier, such that different classifiers may be standardised into a single form and executed in parallel. A detailed evaluation of the performance of different drone models in the real production environment of LHCb will give the collaboration a complete idea of not only the advantages of the drone model, but also the limits of drone complexity given the available computing resources.<br />
Requirements: Advanced python and Advanced C++<br />
Supervisor: Sean Benson<br />
<br />
==== LHCb simulations of physics beyond the Standard Model ====<br />
This project is of relatively theoretical and computing nature and performs simulation studies for physics beyond the Standard Model in the context of long lived particles. It is related to test the sensitivity of the LHCb experiment to detect specific signals of physics beyond the Standard Model.<br />
supervisor: Carlos Vazquez Sierra<br />
<br />
=== Detector R&D ===<br />
<br />
==== Fast timing detectoren ====<br />
Op dit moment maken we veel gebruik van silicon detectoren in onze deeltjes experimenten. Deze zijn gevoelig voor geladen deeltjes en zijn bij uitstek geschikt om de paden vast te leggen die de deeltjes maken die in de botsingen worden gemaakt. Bijvoorbeeld in de Atlas en LHCb experimenten worden tientallen tot honderden deeltjes gemaakt bij elk botsingsgebeurtenis (event) die met 40MHz plaatsvinden. Voor toekomstige deeltjesdetectoren willen we niet alleen het traject vastleggen maar ook met grote precisie een tijdsmeting toevoegen. We hebben hiervoor dus nieuwe detectoren nodig die behalve met een hele hoge snelheid en efficientie de posities van de langsvliegende deeltjes kunnen vastleggen, maar hier ook een zeer nauwkeurige tijdsmeting (in orde van picosecondes) aan kunnen toevoegen. We hebben met verschillende detectoren metingen gedaan, in testbundels op CERN, maar ook in het lab op Nikhef kunnen we metingen doen. In dit project ga je samen met het fast-timing detectoren team op het Nikhef metingen verrichten en de resultaten hiervan bekijken. Contact: Hella Snoek (h.snoek@nikhef.nl)<br />
<br />
==== Muon tomography ====<br />
In this project we are not looking for where cosmic rays come from. We are looking for what we can use them for instead. The muons in cosmic rays can be used to ‘probe’ massive objects. Muons are short lived particles that carry the same charge as electrons, have a high penetrating power and can be detected relatively easy. It is possible to reconstruct a density distribution within an object by measuring muon scattering and absorption. In this context the objects may be freight containers, buildings, melting furnaces, etc… <br />
<br />
Systems that scan objects through the use of muons are often large (objects often need to be enclosed by the system) and complex. The question we want to answer is: Can we develop a smaller, simpler and cheaper system for muon tomography? <br />
<br />
A method to detect muons is by using a material that scintillates (emits light) when hit by an ionising particle. When this light emission is prompt after the passage of the muon, timing information of the light can be used to reconstruct the path of the muon.<br />
In this experiment we make a muon tracker based on two sheets of scintillating material and photo multiplier tubes (PMTs). Photo multiplier tubes are fast responding and very sensitive light detectors (capable of detecting single photons).<br />
<br />
The big question is: How well does this system perform?<br />
<br />
Currently a set-up is being build. You have a lot of freedom to choose a focus in this project (theory, simulation, hardware, or a combination of those).<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Spectral X-ray imaging - Looking at colours the eyes can't see ====<br />
When a conventional X-ray image is made to analyse the composition of a sample, or to perform a medical examination on a patient, one acquires an image that only shows intensities. One obtains a ‘black and white’ image. Most of the information carried by the photon energy is lost. Lacking spectral information can result in an ambiguity between material composition and amount of material in the sample. If the X-ray intensity as a function of the energy can be measured (i.e. a ‘colour’ X-ray image) more information can be obtained from a sample. This translates to less required dose and/or to a better understanding of the sample that is being investigated. For example, two fields that can benefit from spectral X-ray imaging are mammography and real time CT.<br />
<br />
X-ray detectors based on Medipix/Timepix pixel chips have spectral resolving capabilities and can be used to make polychromatic X-ray images. Medipix and Timepix chips have branched from pixel chips developed for detectors for high energy physics collider experiments.<br />
<br />
Some themes that students can work on: <br />
<br />
- Optimising methods to acquire spectral X-ray images.<br />
<br />
- Determining how much existing applications benefit from spectral X-ray imaging and looking for potential new applications.<br />
<br />
- Characterising, calibrating, optimising X-ray imaging detector systems.<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Holographic emitter ====<br />
A difficulty in generating holograms (based on the interference of light) is the required dense spatial light field sampling. One would need pixels of less than 200 nanometer. With larger pixels artefacts occur due to spatial under sampling. A pixel pitch of 200 nm or less is difficult, if not, impossible, to achieve, especially for larger areas. Another challenge is the massive amount of computing power that is required to control such a dense pixel matrix. <br />
<br />
A new holographic projection method has been developed that reduces under sampling artefacts, regardless of spatial sample density. The trick is to create 'pixels' at random but known positions, resulting in an array that lacks any spatial periodicity. As a result a holographic emitter can be built with a significantly lower sample density and less required computing power. This could bring holography in reach for many applications like display, lithography, 3D printing, metrology, etc...<br />
<br />
The big question: How does the performance of the holographic emitter depend on sample density and sample positions?<br />
<br />
The aspects of a holographic image we are interested in are:<br />
<br />
- Noise<br />
<br />
- Contrast<br />
<br />
- Suppression of under sampling artefacts<br />
<br />
- Resolution <br />
<br />
For this project we are building a proof of concept holographic emitter. This set-up will be used to verify simulation results (and to make some cool holograms of course). <br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
=== KM3NeT ===<br />
<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
==== Data analysis of the first deployed KM3NeT detection lines ====<br />
<br />
First detection lines of the KM3NeT neutrino telescope have been deployed<br />
in the Mediterranean Sea, and a first data set is available. The lines consist<br />
of light-sensitive detectors that record the time of arrival of photons<br />
produced by relativistic particles in the deep sea, and their number.<br />
In this project we will study the first data to separate various components:<br />
photons from potassium decay, bioluminesence, sparks in the photomultipliers,<br />
downgoing muons from cosmic rays, and perhaps first neutrinos.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Neutrino oscillation measurements with the KM3NeT neutrino telescope ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope currently under construction<br />
will be able to measure the oscillations of neutrinos produced in interactions<br />
of cosmic rays with the earth atmosphere. Fundamental neutrino properties can<br />
be deduced from these oscillations measurements, in particular the so-called<br />
mass hierarchy of neutrinos. In this project we will simulate the ORCA measurements<br />
of neutrino oscillations, and study the dependence of the sensitivity on<br />
experimental uncertainties, such as energy resolution and neutrino flavour<br />
identification, and theoretical uncertainties, such as the atmospheric neutrino<br />
flux and neutrino cross sections. The results will help ORCA to identify<br />
the main sources of uncertainty, and therefore to actively try to reduce these<br />
and improve the final measurement.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Performance Studies of ORCA for Dark Matter Detection ====<br />
<br />
The interactions of neutrinos in KM3NeT-ORCA give different signatures which are categorised as track and shower events. This project involves the studies of muon, electron and tau neutrino interactions for the reconstruction performance of ORCA. Efficient reconstruction of such signals is important for Dark Matter searches in the low-mass regime. We will work on understanding the detector performance, e.g. effective acceptance, energy and angular resolution, with different configurations of the detector setup. The result of this study will be very useful to improve the sensitivity of the experiment for Dark Matter detection and its possible location. The student will have the opportunity to work closely with KM3NeT members at Nikhef and gain skills of analyzing data. <br />
<br />
Supervisors: Suzan Basegmez du Pree, Aart Heijboer<br />
<br />
==== A search for periodic sources in Antares data ====<br />
<br />
The Antares deep-sea neutrino telescope has been operated for more then ten years. A search for periodic sources is proposed by applying a fast Fourier transformation (FFT) analysis on the available low-level data. This search will be combined with a (literature) study of pulsars which are thought to emit neutrinos.<br />
<br />
Supervisor: Maarten de Jong<br />
<br />
==== Study of Optical Properties of Sea Water using Hit Coincidences in MC Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
By studying coincidences of L1 hits between neighbouring DOMs, for various Monte Carlo (MC) data sets with different sea water optical properties such as scattering and absorption coefficients, in this project we try to figure out if and how well we can quantify optical sea water properties by studying L1 hit coincidences in real KM3NeT data.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
==== Determination of Inter-DOM Distances using Hit Coincidences in KM3NeT Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
The number of L1 hit coincidences from atmospheric muons between neighbouring DOMs on a DU is expected to decrease exponentially. By fitting the observed number of L1 hit coincidences between neighbouring DOMs in real data to the expected exponential decay, in this project we study how accurately we can determine the distances between DOMs on a single DU. In addition, we try to determine the distances between DUs by looking for L1 hit coincidences between DOMs on neighbouring DUs.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
=== VIRGO ===<br />
<br />
The Advanced LIGO and Advanced Virgo interferometers have recently observed gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results.<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Frank Linde (frank.linde_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
<br><br><br><br />
<br />
== Bachelor Projects 2017 ==<br />
<br />
=== Extreme Astronomy – Preparing for CTA, the Next-Generation Gamma-Ray Observatory ===<br />
<br />
The Cherenkov Telescope Array (CTA) is a planned facility for measuring gamma rays from space covering more than four orders of magnitude in energy, up to energies exceeding 100 TeV. CTA employs the imaging atmospheric Cherenkov technique to measure properties of cosmic gamma rays. This technique is based on measuring Cherenkov light emitted during the development of a gamma-ray air shower. CTA will be built at two experimental sites, one in the Northern, one in the Southern hemisphere, and will consist of up to 100 telescopes. It represents a major leap forward in sensitivity and precision for gamma-ray astronomy, and will allow us to explore very-high-energy processes of the extreme Universe at an unprecedented level.<br />
<br />
Two projects for students are available at the CTA group of UvA in the field of optical and photonic R&D contributing to the starting phase of CTA. For the first project the student will conduct measurements to characterise novel kinds of single-photon detectors, referred to as silicon photomultipliers, and evaluate different types of these sensors for their use for CTA. For the second project the student will develop and test an imaging system making use of a liquid crystal display. This flexible light source will be able to mimic images from different light sources of the night sky as seen by cameras of CTA, for instance gamma-ray air showers or stars, and will be used for camera tests and calibration.<br />
<br />
<br />
Supervisors: David Berge, Maurice Stephan (postdoc)<br />
<br />
=== Dark Matter ===<br />
<br />
<!--<br />
==== XENON1T - the world's most sensitive dark matter detector ====<br />
<br />
Finding the mysterious dark matter particles is one of the most challenging enterprises in physics today. Soon we will get first data from the world's most sensitive dark matter detector yet: the XENON1T experiment.<br />
<br />
The first goal of this project is to understand why dak matter is necessary to understand the universe, and how we could detect it with XENON1T. Then, you can contribute to our group's efforts preparing for <br />
and analyzing the XENON1T data by, for example: examining XENON1T's calibration signals to check for problems in the experiment, testing our data analysis software with simulated dark matter signals, or studying the physics behind XENON1T's detection process to learn how to better distinguish dark matter signals from backgrounds. For data analyis, experience with or willingness to learn programming in python is essential.<br />
<br />
<br />
Supervisors: M.P. Decowski & J. Aalbers --><br />
<br />
==== Neutrinoless double beta decay sensitivity study in future dark matter detectors ====<br />
<br />
The discovery of neutrino oscillation (Nobel Physics 2015) means that neutrinos have mass. We already know that their masses are tiny, more than one million times smaller than the next-lightest particle in the standard model, the electron. This raises the question if the mass-generation mechanism is the same for neutrinos as it is for the other subatomic particles. In particular, since neutrinos are electrically neutral, they could be their own anti-particles - we call these types of particles Majorana. The only practical way to discover if neutrinos are Majorana is through the search of an extremely rare radioactive decay called neutrinoless double beta decay (0n2b). A few isotopes are candidates for this process, among them Xe-136. The natural abundance of Xe-136 in natural xenon is about 9%, and this gives the opportunity to look for a 0n2b signal in xenon-based dark matter detectors like XENON1T and the future XENONnT and DARWIN detectors. <br />
<br />
We are looking for a student interested in doing a sensitivity study for 0n2b in XENONnT and the DARWIN experiments. The first goal will be to understand the physics addressed in neutrinoless double beta decay. Then the student will inventory possible backgrounds for the signal, use a (controversial) claim of a 0n2b signal as a benchmark and finally obtain the sensitivity of these future detectors. The work will involve simulations and analysis, building on an existing framework developed in our group. <br />
<br />
Supervisors: M.P. Decowski & A. Tiseni<br />
<br />
==== Shaking Dark Matter detectors ====<br />
<br />
Our XENON1T detector is built in the lab underneath the Gran Sasso mountains in central Italy. The lab is very well suited for low-background experiments due to the 1.5km of rock overburden. <br />
However, as you may know, cental Italy has been plagued by earthqaukes over the past decade, with the most recentones occurring in January 2017. We need a BSc student to investigate the <br />
details of such earthquakes in our underground lab. What are the magnitdues by which stuff is moving underground? What are the accelerations? What is the potential effect on our experimental<br />
setup? What would ahppen if an earthquake happens much closer to our lab? Furthermore we are interested to find out whether Earthquakes can be predicted. Some papers claim that before<br />
an earthquake the radon emanating from rock increases. In our lab we measure the radon concentration as a function of time: can you find a correlation between the measurements and recent <br />
earthquakes?<br />
<br />
If you are interested in finding out more about earthquakes, please contact M.P. Decowski or A.P. Colijn<br />
<br />
==== XAMS - a baby dark matter detector ====<br />
<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso<br />
we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector<br />
are identical to its big sibling in Gran Sasso.<br />
<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source we have acquired<br />
before the start of the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project<br />
will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study<br />
of neutron transport in xenon.<br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
==== Radon is bad for Dark Matter ====<br />
<br />
Radon is the dominant background for xenon based dark matter detectors, like the XENON1T experiment. In our lab at Nikhef we are investigating ways to reduce or eliminate the effect of radon<br />
on our sensitivity. For our lab setup XAMS we have designed and constructed a radon detector, that can be used in xenon systems at high-pressure. This completely new detector<br />
is now waiting for a BSc student to fully chracterize and use it. During this project you will first study the effect that radon contaminations have on dark matter detectors, then you will start working to<br />
understand our new radon detector in detail. You will learn howto use a radioactive source to calibrate the detector: this is something which is not easy and has not been done before in our lab. <br />
If you manage to succesfully calibrate the detector, we then want to incorporate it into our lab xenon system at Nikhef and maybe at some later stage in the real XENON1T detector!<br />
<br />
The profile of the student to work on this project is broad. I expect a good theoretical knowledge in order to quickly get upto speed with understanding dark mater detectors, and in addition I <br />
need 'lab-creativity' in order to develop methods for calibrating the new detector. If a good method is developed, it will be used for many years by the Nikhef dark matter group and beyond. <br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
=== ATLAS ===<br />
<br />
<br />
==== ATLAS (1): Searching for new physics with the Higgs and W bosons ====<br />
<br />
The strength of the Higgs interactions with electroweak bosons are precisely defined in the<br />
Standard Model. Therefore they are sensitive probes of the mechanism of electroweak symmetry<br />
breaking and enable searches for new physics beyond the SM. With the data collected by the ATLAS<br />
experiment in years 2015-2016 we plan to measure separately the Higgs coupling to<br />
longitudinally and transversely polarised W bosons in a process of weak boson fusion. To<br />
maximise experimental sensitivity we are developing techniques to separate the signal from<br />
background processes. You will take part in investigating possible improvements from<br />
reconstructing events in reference frames boosted with respect to the detector. During the<br />
project you will learn modern experimental analysis techniques. This project is a part of Vector<br />
Boson Scattering Coordination and Action Network (VBSCan) which connects researchers studying<br />
this and related topics worldwide.<br />
<br />
Supervisors: Pamela Ferrari, Magdalena Slawinska, Bob van Eijk<br />
<br />
<br />
==== ATLAS (2): Dark-matter-motivated searches for supersymmetric particles at the LHC ====<br />
<br />
Supersymmetry, a symmetry between fermions and bosons in particle physics,<br />
may provide a particle that could be the dark matter in the universe.<br />
The observation of an excess of gamma rays originating from the centre of our<br />
galaxy could be explained in a model where supersymmetric dark matter<br />
particles annihilate each other in the galactic centre, leading to gamma rays.<br />
<br />
Given the model parameters, it should also be possible to produce such<br />
particles at the LHC, at CERN in Geneva. But it is not so easy to observe<br />
them: the signal is small, and the noise (background) is large.<br />
In this project, we will use simulations of signal and background to<br />
optimize experimental searches for such particles with the ATLAS detector,<br />
apply them to the data collected in 2015, and prepare for the new data in<br />
2016 and later.Where possible, we will explore new machine learning techniques.<br />
<br />
Supervisors: Paul de Jong, Broos Vermeulen<br />
<br />
<br />
==== ATLAS (3): Simulations / Quality tests for the ATLAS High-Luminosity LHC Upgrade ====<br />
<br />
One of the key sub-systems of the ATLAS experiment at the Large<br />
Hadron Collider (LHC) is the Inner Detector (ID), designed to provide<br />
excellent charged particles momentum and vertex resolution measurements.<br />
<br />
At Phase-2 of the LHC run, in ~2025, the operating luminosity of<br />
the collider will be increased significantly.<br />
This will imply an upgrade of all ATLAS subsystems. In particular,<br />
the ID will be fully replaced with a tracker completely made of<br />
Silicon, having higher granularity and radiation hardness.<br />
The R&D process for the new ATLAS ID is now ongoing.<br />
Different geometrical layouts are simulated and their performance is<br />
studied under different operating conditions in search for the optimal<br />
detector architecture. Also, the performance of the new<br />
Si-sensors/modules is under investigation with dedicated laboratory tests.<br />
<br />
The focus of the project could be on the simulation of the High-Luminosity LHC<br />
version of the ATLAS Inner Detector. The student will learn how a<br />
high-energy physics experiment is designed and optimized.<br />
Alternatively, if possible at that moment, the student could<br />
work on a project at the Nikhef Silicon laboratory at the test-bench for<br />
new ATLAS Si-strip detectors and participate in the quality<br />
assurance procedure for the new ATLAS Si detectors.<br />
<br />
==== ATLAS (4): Higgs productie in Run-2 van de LHC ====<br />
In de eerste run van de LHC is onder andere bij het ATLAS experiment het Higgs deeltje gevonden. Nu is de tweede run begonnen en kan het Higgs deeltje worden bevestigd. Door de verhoogde energie ziet de achtergrond er echter heel anders uit, dus is de optimalisatie van het wegsnijden van de achtergronden qua fysica anders. Voor je bachelor project kan met behulp van de ATLAS detector het Higgs deeltje in run twee komen vinden. <br />
<br />
Supervisors: Lydia Brenner, Wouter Verkerke<br />
<br />
==== ATLAS (5): De lange staart van het Higgs boson ====<br />
<br />
[[File:HiggsMassa.png |thumb|left|upright=1.25]]<br />
<br />
<br><br />
Na de ontdekking van het Higgs boson in 2012 zijn we druk bezig om te kijken of zijn eigenschappen overeenkomen met de voorspellingen van het Standaard Model. Een van de belangrijkste eigenschappen is de zogenaamde breedte van het Higgs boson. Als het Higgs boson naast de Standaard Model deeltjes ook in exotische nieuwe speeltje uit elkaar kan vallen (bijvoorbeeld donkere materie) dan zal dat ale eerste zichtbaar worden in een afwijking van de breedte tov de verwachting. We gaan in dit project uitzoeken hoe de strategie die nu gebruikt wordt (meten van de hoeveelheid Higgs bosonen met een extreem hoge massa) precies werkt en kijken of we door het toevoegen van nieuwe ideeën een verbetering kunnen aanbrengen. <br />
<br />
<br><br />
Specifiek: We gaan eerst in detail de eigenschappen bekijken van het Higgs signaal en de twee achtergronden die er het meest op lijken. Daarna gaan we op zoek naar de verschillen en een manier waarop we onze kennis daarover kunnen gebruiken om gevoeliger te worden voor het Higgs signaal.<br />
<br />
Supervisors: Hella Snoek, Ivo van Vulpen<br />
<br />
E-mail: H.Snoek_at_nikhef.nl & Ivo.van.Vulpen_at_nikhef.nl<br />
<br><br><br><br><br><br><br />
<br />
=== ATLAS (6): Project ATLAS-ITk ===<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
<br><br />
<br />
=== KM3Net ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierachy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
The first phase of the KM3NeT neutrino telescope is currently under construction, with the first two detection units operational at 3500m depth in the Mediterranean Sea, 100 km off the coast of Sicily.<br />
<br />
<br />
==== KM3NeT (1): Photon counting in KM3NeT ====<br />
<br />
The details of a neutrino interaction, such as its incoming direction and energy, determine the pattern, time and amount, of recorded photons (´hits´) by the photo-multplier tubes. The time of arrival is recorded with nanosecond accuracy and the amount of photons is encoded in the length of the pulse(time-over-threshold, ToT). Currently, only the photon arrival time and the number of photo-multipliers that record a hit are used in reconstructing event properties.<br />
In this project, the distributions of the ToT mainly originating from photons from potassium-40 decays in the sea-water and from atmospheric muons passing through the water will be studied. The goals are to investigate the properties of the ToT distributions obtained from data and simulation, in particular the dependence on the photo-multiplier efficiency and atmospheric muon flux.<br />
In this project we will be extensively using the programming language C++ to analyse the data, so a reasonable proficiency is required.<br />
<br />
Supervisors: Ronald Bruijn & Karel Melis<br />
<br />
Email: rbruijn_at_nikhef.nl<br />
<br />
<br />
<br />
<br><br><br><br />
<br />
=== VIRGO ===<br />
<br />
"It is anticipated that in the next few years, Advanced LIGO and Advanced Virgo will start observing gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results."<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Jo van den Brand (jo_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
=== LHCb ===<br />
<br />
Begeleider: Sean Benson<br />
<br />
Title: <br />
Searching for physics beyond the Standard Model with LHCb<br />
<br />
The LHCb experiment is designed to study the "The Flavour Problem" in particle physics:<br />
Why is the universe dominated by matter over antimatter? Why are there three generations of elementary particles? What is the origin of quark flavour changing interactions.<br />
<br />
To solve these riddles, LHCb performs precision measurements on b-quark particle decays.<br />
An intriguing signal has recently been observed in the decay of a B-meson to a K* and two muons: Bd→K*μμ, which does not seem to behave according to the predictions of the Standard Model<br />
In this project the bachelor student will investigate this further by studying the case where the K* particle decays to a so-called k-short particle and a π0. The observation of such a final state will provide valuable information in the search for physics beyond the Standard Model.<br />
<br />
In this ambitious project the student is expected to study both a theory on the mechanism of CP violation with B mesons, in addition to data analysis with B decays. Programming experience in python is required.<br />
<br />
The LHCb experiment at CERN analyzes the properties of B-hadrons produced in proton-proton collisions at the LHC. For projects in the LHCb group, please contact Marcel Mark (marcel.merk_at_nikhef.nl)<br />
<br />
<br />
=== LHCb (1) ===<br />
<br />
One of the most fascinating mysteries in physics today is: how is it possible that universe is filled with matter? If the Big Bang produced equal amounts of matter and antimatter, we still do not understand the mechanism that lead to the excess of matter over antimatter that we observe today.<br />
<br />
One interesting feature of some particles is that they can transform themselves into their antiparticles, then back to particle, and so forth, in an oscillatory way until they finally decay. In particular, beauty mesons (B) can oscillate into their antiparticle (B ̄). The parameters of this oscillation, such as amplitude, frequency and phase, are calculable mathematically: predictions for it are available in the standard model (SM) of particle physics. But the oscillations according to the SM alone would not lead to the imbalance of matter in the universe – we still need to find a new type of physics that may be able to explain it.<br />
<br />
In this context, it is very important to measure B oscillations in the laboratory, and compare these observations with the expectations from the SM. Are the experimental data in good agreement with the SM, as we expect? If the aswer is not, i.e. if there are features of the oscillation that we do not understand well, then we may be observing “new physics”. In other words, the data may reveal a new mechanism that generates a different matter-antimatter balance than predicted by the SM, that may potentially solve the puzzle.<br />
<br />
The LHCb experiment at CERN is dedicated to such studies: LHCb detectors are placed in a region along the LHC collider beamline, where a large number of B mesons are produced, arising from the proton-proton collision data from the LHC collider. Looking at the LHCb data we can obtain large samples of B mesons, and observe their oscillations.<br />
In this project we will learn how to select a sample of B mesons out of the data taken with the LHCb detector, measure the parameters that govern their oscillation and compare them with the SM.<br />
<br />
For more information, please contact Mara Soares (msoares_at_nikhef.nl).</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Bachelor_Projects&diff=771Bachelor Projects2022-02-02T08:39:09Z<p>Rojo@nikhef.nl: /* Theory */</p>
<hr />
<div><br />
== Bachelor Projects 2022 ==<br />
<br />
=== Dark Matter ===<br />
<br />
==== Response of materials to scintillation light from liquid noble gasses ====<br />
<br />
The liquid form of the noble gases argon and xenon is a popular target material for neutrino and dark matter detectors. The scintillation light from noble gases is in the vacuum UV spectral region. Air and many materials used for optical studies are not transparent to these photons. Measurements of the optical properties of detector materials, such as their reflectivity for example, thus have to be performed with dedicated VUV optics and in vacuum. Additionally, to reproduce the conditions in the detectors, the samples must be cooled to cryogenic temperatures. In this BSc project, you will calibrate the photon detectors in an experimental setup designed to study the optical response of materials excited with VUV photons. You will learn about material requirements for rare event search detectors, vacuum instrumentation, vacuum UV optics including monochromators and spectrometers, and single-photon sensors.<br />
<br />
Supervisors: T. Pollmann (t.pollmann_at_nikhef.nl)<br />
<br />
=== ATLAS ===<br />
<br />
=== LHCb ===<br />
<br />
<br />
==== Exotic neutrinos in B decays====<br />
<br />
Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, heavier, neutral leptons. In the LHCb group at Nikhef we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undisovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The bachelor project will contribute with the optimization of the selection using state-of-the-art tools for the multi-variate analysis.<br />
<br />
Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
<br />
<br />
=== Gravitational Waves ===<br />
<br />
=== Detector R&D ===<br />
Answering big elementary particle physics questions requires pioneering experiments. The Detector R&D program at Nikhef is aimed at conceptualizing and testing of instrumentation concepts before they are implemented in scientific programs at Nikhef. <br />
<br />
==== Time resolution of monolithic timing detectors ====<br />
For the upgrade of the vertex detectors of the large LHC experiments like LHCb and ALICE, new silicon pixel detectors will developed now that can register the passing particles with a time precision of tens of picoseconds. ALICE is the first experiment at the LHC to have installed monolithic sensors where electronics is integrated into the sensor resulting in ultrathin, low-material detectors. In this project you will measure the time resolution of these promising integrated sensors with a laser setup in our laboratory.<br />
<br />
Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
==== Modeling radiation damage in silicon sensors ====<br />
In the coming years, the ATLAS experiment at the LHC works on upgrades to prepare for the high-luminosity LHC, where many more collisions will take place than today. Analyses of LHC data rely heavily on simulations of the detector. It may sound counterintuitive, but particle detectors do not actually like particles: after many collisions at the LHC, a silicon pixel detector has seen so many particles that its bulk gathers defects. Charge generated by traversing particles can get trapped in defects resulting in less charge induced in the readout electrodes, reducing detector performance in resolution and efficiency. In this project, you will be part of the international ATLAS collaboration and compare different models of radiation damage with measured data and you will contribute to the open source program Allpix Squared that is widely used for simulations in many areas of particle physics.<br />
<br />
Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
==== Time resolution of a new digital pixel test structure from test beam data ====<br />
For the upgrade of the ALICE detector, ultrathin picosecond timing integrated sensors are developed. To reduce power consumption, asynchronous readout is implemented in this prototype sensor in a digital pixel test structure. This structure was studied in test beams with an ALPIDE (ALICE PIxel DEtector) telescope at CERN. You will measure the efficiency and time resolution of this new sensor with the latest data from test beams at CERN.<br />
<br />
Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
<br />
<br />
<br />
=== KM3NeT ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along 200-700m long vertical lines, called detection units.<br />
<br />
==== Neutrino oscillation measurements with the first KM3NeT data ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope is able to measure the oscillations of neutrinos produced in interactions of cosmic rays with the earth atmosphere. Fundamental neutrino properties can be deduced from these oscillations measurements. In this project we will use the first data of ORCA (more than one year with six detection units) to study neutrino oscillations and fit neutrino mixing parameters and mass differences between neutrino mass states. We will study data selection, event reconstruction, and effects of systematic uncertainties on the results. <br />
<br />
Supervisors: Brian O'Fearraigh, Ronald Bruijn, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
==== Search for sterile neutrinos with KM3NeT. ====<br />
A detailed study of neutrino oscillations in the KM3NeT detector is sensitive to the existence of so-called sterile neutrinos: neutrinos that are not part of the Standard Model of particle physics, and have no ordinary interactions with matter. We will use a mixture of data and simulations to estimate KM3NeT sensitivity.<br />
<br />
Supervisors: Alba Domi, Paul de Jong<br />
<br />
==== Machine learning for event classification in KM3NeT ====<br />
The classification of neutrino events recorded in the KM3NeT detector in terms of originating from electron neutrinos, muon neutrinos, or tau neutrinos, is very well suited for machine learning techniques. We will study the performance of a few advanced machine learning techniques on simulated high-energy neutrino events.<br />
<br />
Supervisors: Alba Domi, Paul de Jong<br />
<br />
==== Multi-messenger astronomy with neutrinos and radio signals ====<br />
The main goal of neutrino telescopes, such as ANTARES, KM3NeT and IceCube, is to detect cosmic neutrinos from astrophysical sources. When an interesting neutrino candidate is detected they send out a message to alert the scientific community. Other scientific instruments, like the Murchison Widefield Array (MWA) radio telescope, can then do a follow-up observation, to see if there are other messengers coming from the same source as the neutrinos. In this project you will analyse MWA data that were taken after the reception of neutrino alerts, to search for a radio source that can be associated with a neutrino source.<br />
<br />
Supervisor: Mieke Bouwhuis (mieke.bouwhuis at nikhef.nl)<br />
<br />
=== Theory ===<br />
'''Symmetries and sterile neutrinos'''<br />
<br />
The fact that neutrinos have masses is problematic for the Standard Model. A plausible solution requires the existence of additional so-called sterile neutrinos. In this project we will study why such neutrinos could exist and describe their mixing with the active neutrinos we have seen in experiments. In particular, we will investigate how large active-sterile mixing can be while accounting for the small neutrino masses and what this tells us about possible lepton number violation. <br />
<br />
Supervisor: Jordy de Vries <br />
<br />
'''Effective Field Theories of Particle Physics from low- to high-energies'''<br />
<br />
Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations<nowiki>''</nowiki> seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature.<br />
<br />
Until recently, it was widely assumed that matter particles from each of the three generations interact with the same (“universal”) strength. This hypothesis is being challenged by new measurements at the Large Hadron Collider (LHC) at CERN, which hint towards non-universal interactions. If confirmed, these measurements will be the first signs of new particles and interactions in high-energy colliders. These exciting findings indicate the urgent need to explore such phenomena in depth.<br />
<br />
The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Effective Field Theory (EFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes. Specifically, the goal is to connect measurements from ATLAS and LHCb among them and to jointly interpret this information with that provided by other experiments, from CMS and Belle-II to very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
<br />
''Methodology and workplan''<br />
<br />
This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories.<br />
<br />
This project accommodates several students, who would work together in developing the main formalism while each of them focuses on a specific sub-project. The maximum capacity of this project is 5 students. <br />
<br />
Depending on the student profile, sub-projects with a strong computational / machine learning component are also possible.<br />
<br />
During the first four weeks of the project, students will learn the required background material on effective field theories, following the guidelines from the supervisors. Afterwards, they will focus on different sub-projects, each covering a different aspect of the same global EFT program.<br />
<br />
Required knowledge<br />
<br />
Quantum Mechanics 2, Particle Physics 1 (required)<br />
<br />
Advanced Quantum Mechanics, Particle Physics 2, Machine Learning (optional)<br />
<br />
Available subprojects<br />
<br />
Here we list the available subprojects, including the corresponding daily supervisor(s) in each case.<br />
<br />
''Subproject #1: SMEFT & Flavour symmetries'' <br />
<br />
Daily supervisors: Jordy de Vries (UvA), Keri Vos (Maastricht University), Jaco ter Hoeve (VU), Giacomo Magni (VU)<br />
<br />
While the power of the Standard Model EFT (named SMEFT) framework is its generality and lack of assumptions, the number of operators is somewhat daunting. A popular way to trim the number of operators is to assume flavour symmetries that relate operators with different quark and lepton flavours. In this project you will investigate the theoretical basis for commonly-used flavour symmetries and what they imply for the connection between high-energy observables involving third-generation particles (top and bottom quarks and tau leptons) and low-energy precision tests involving first- and second-generation particles. The investigations of this project are connected with Subproject #2.<br />
<br />
''Subproject #2: SMEFT & magnetic moment of the muon''<br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU)<br />
<br />
The magnetic moment of the muon appears to differ from the Standard Model expectations by a large amount, well beyond the known experimental and theoretical uncertainties. Recent experiments have only strengthened the significance of this anomaly. In this project, the students will investigate the feasibility of implementing the measurement of the magnetic moment of the muon into a global SMEFT analysis, by exploiting recently provided calculations. Special attention will be devoted to the flavour assumptions required to consistently match this measurement with the LHC data, also at the light of the connection with Subproject #1. The SMEFiT analysis framework will be used to connect the g-2 data with high-energy LHC measurements.<br />
<br />
''Subproject #3: CP Violation and low-energy precision experiments''<br />
<br />
Most analyses of LHC data are performed under the assumption that CP symmetry (charge conjugation + parity, essentially the symmetry between particles and anti-particles) is conserved. More recent analyses attempt to also measure possible new sources of CP violation in SMEFT operators in the Higgs and top sector. <br />
<br />
''Subproject #3a: CP Violation and low-energy precision experiments''<br />
<br />
Daily supervisors: Jordy de Vries (UvA), Juan Rojo (VU)<br />
<br />
Low-energy precision experiments can also set stringent constraints on new mechanisms of CP violation. In this project you will try to combine high- and low-energy data to put CP symmetry to the test. <br />
<br />
''Subproject #3b: CP Violation and flavour physics experiments''<br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU)<br />
<br />
Besides low-energy precision experiments, also B-meson decays are excellent probes of CP violation. Unlike most low-energy experiments, this allows us to probe CP violation in the third generation. In this project you will link constraints on CP violation at high-energy to those from B meson decays. <br />
<br />
''Subproject #4: SMEFT & optimal observables'' <br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU), Tommaso Giani (VU & Nikhef)<br />
<br />
In full generality, the number of operators in SMEFT spans a very large parameter space. These parameters are constrained by experimental inputs from ATLAS and CMS, depending on the precise parameters these constraints may be more or less stringent. In order to fully exploit the whole parameters space in SMEFT, it is necessary to devise statistically optimal observables that have a large constraining power. In this project, we will define such observables. This project has a strong computational / machine learning component and may involve simulations based on tools such as MadGraph and Pythia8.<br />
<br />
Contacts:<br />
<br />
Juan Rojo (VU Amsterdam & Nikhef): j.rojo at vu.nl<br />
<br />
Keri Vos (UM & Nikhef): k.vos at maastrichtuniversity.nl <br />
<br />
Jordy de Vries (UvA & Nikhef): j.devries4 at uva.nl<br />
<br />
== Bachelor Projects 2021 ==<br />
=== Dark Matter ===<br />
<br />
==== XAMS ====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso.<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with recently upgraded hardware to test a novel concept for UV light detection. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complete the first measurements with our upgraded setup.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== XENONnT reconstruction software ====<br />
The XENONnT experiment becomes operational during 2021. While the hwardware is finished we keep on developing and perfecting our reconstruction software. For this project we are looking for a student with a keen interest in and talent for writing physics based event reconstruction software (we use python). Specifically we have an idea to improve the localization of events inside the XENONnT for which proto-type software exists. The proto-type software needs to be implemented in the XENONnT reconstruction framework and subsequently it needs to be validated on the first data from the experiment. The final goal of the project is to deliver the reconstruction software to the collaboration that will be used during teh full lifetime of the experiment.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Backgrounds in Radioactive Decay Measurements ====<br />
At Nikhef, the XENON group has a working setup, continuously monitoring the<br />
radioactive decay of Cobalt-60, Caesium-137 and Titanium-44. This beautiful setup is<br />
however not shielded perfectly; it is still vulnerable to background radioactivity. Our<br />
current way of working around this background radiation is to subtract it from our<br />
waveforms. You as a BSc student could help us hands-on and with analyses:<br />
together, we can disassemble the setup, measure background spectra and<br />
implement this in the data analysis. You can use all the data to validate the<br />
lifetime of our isotopes!<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Detection of scintillation light from liquid noble gasses ====<br />
<br />
The liquid form of the noble gases argon and xenon is a popular target material for neutrino and dark matter detectors. The scintillation light from noble gases is in the vacuum UV spectral region. Air and many materials used for optics studies are not transparent to these photons. Measurements of the optical properties of detector materials, such as their reflectivity for example, thus have to be performed with dedicated VUV optics and in vacuum. Additionally, to reproduce the conditions in the detectors, the samples must be cooled to cryogenic temperatures. In this BSc project, you will design, using professional hardware design software, a vacuum chamber to hold the detector materials whose optical properties are to be investigated, as well as the cooling system and photon detectors. You will learn about material requirements for rare event search detectors, vacuum instrumentation, vacuum UV optics including monochromators and spectrometers, and single-photon sensors.<br />
<br />
Supervisors: T. Pollmann (t.pollmann_at_nikhef.nl)<br />
<br />
=== Detector R&D ===<br />
<br />
==== Characterization of the new ultrathin ALPIDE monolithic active pixel sensor ====<br />
At the Large Hadron Collider at CERN, major upgrades of experiments take place in the long shutdown years where particle collisions are paused. The ALICE inner tracking system (ITS) 2, the part of the ALICE experiment closest to the beam pipe, is currently being installed at CERN. This detector makes use of ultra-lightweight monolithic active pixel sensors, the first to use this technology at particle colliders after the STAR experiment at RHIC in Brookhaven. These very thin pixel detectors have a low power consumption, result in very little material in the detector, and still have optimal timing and resolution -- and are a promising technology for future experiments. To characterize the performance of these sensors, you will learn to set up experiments, carry out measurements, and analyze data using various instruments available in the detector R&D lab at Nikhef. This could lead to novel insights of monolithic active pixel sensors. It is also possible to do measurements from home using data from the first test beams with bent (yes, with a curvature!) ALPIDE sensors. You will work in an international, stimulating research environment in the detector R&D group at Nikhef at the forefront of silicon detector technologies for high energy physics. ''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
==== Simulation of 3D silicon sensors ====<br />
<br />
For the upgrade of the vertex detector of the LHCb experiment novel silicon pixel detectors have to be developed that can register the passing particles with a time precision of tens of picoseconds. Given the harsh radiation environment very close to the LHCb interaction point only a limited number of technologies can be applied. One of the most promising technologies are the so-called 3D sensors whose readout electrodes are pillars that are placed into the sensor perpendicular to the surface; this in contrast to ’standard’ planar silicon sensors where the pixel electrodes are at the surface, similar to the camera in your smartphone. To understand the time response of these 3D sensors, simulations with TCAD software have to be performed and the results will be compared to measured data. These simulations involve the creation/adaptation of the 3D structures of the model, optimising the simulation speed, and analysing the signals as function voltage, track impact point and deposited charge. If time and Covid regulations permit, gaining some hands-on experience with such 3D sensors in the R&D labs at Nikhef is possible. ''Contacts: [mailto:martinb@nikhef.nl Martin van Beuzekom] [mailto:k.heijhoff@cern.ch Kevin Heijhoff] ''<br />
<br />
<br />
=== Theory ===<br />
<br />
==== Standard Model Effective Field Theory analysis of Z+dijet production ====<br />
The goal of this project is to study the effect of higher dimensional operators from the Standard Model Effective Field Theory in Z-boson production measured at LHC. The ATLAS collaboration has just reported in 2020 the measurement of Z production alongside with a pair of jets, based on the full Run II luminosity. In this project we aim to study the effect of dimension six SMEFT operators on the signal (EW-induced) and/or background (QCD-induced), finding which is the kinematic variable that maximises the possible effect of beyond the SM operators and thus may provide the best constraint on New Physics. The outcome of this project may be the first step of the inclusion of Vector production in a global SMEFT fit. <br />
<br />
References: https://arxiv.org/pdf/2006.15458.pdf, https://www.hepdata.net/record/ins1803608<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Maximum precision on new physics through information theory ====<br />
One way to look for physics beyond the standard model is through the framework of effective field theory. In this framework, deviations from the standard model are described by a set of continuous parameters. Finding constraints on these parameters might point to the discovery of new physics. With the large number of LHC experiments we currently face, we want to be able to quantify the maximum knowledge that (future) experiments can provide on new physics parameters. In this project, the student will study and quantify the maximum information that is contained in particle physics experiments through information theory. The central object of study will be the Fisher information matrix. The idea is to work with a simple toy experiment that describes Higgs physics and compute its associated Fisher information matrix to quantify the optimal bounds on new physics. The project will start with studying central objects from statistics and information theory. Later, we will apply these to open problems in particle physics.<br />
<br />
Reference: https://arxiv.org/pdf/1612.05261.pdf<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Seesaw mechanism and neutrino mass ==== <br />
Many unsolved questions in particle physics are related to the nature of the neutrino and its mass generation. The goal of this theoretical project is to understand and review one of the possible candidate theories that describe how neutrinos mix and get massive, namely the Seesaw mechanism. Among the many possible Seesaw mechanisms that can generate new phenomenology including lepton number non-conservation, the student will focus on one minimal model to understand the key processes that are currently used to probe the validity of the given theory. <br />
<br />
References: https://cds.cern.ch/record/408119/files/9911364.pdf, https://arxiv.org/pdf/1711.02180.pdf<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Mixing of sterile neutrinos ====<br />
<br />
Neutrino oscillation experiments demonstrate that neutrinos are massive particles. However, the mass mechanism of neutrinos is unknown. A<br />
minimal solution requires the existence of so-called sterile neutrinos: neutrinos that are even more elusive than ordinary neutrinos. <br />
We will investigate how to parametrize the matrix that describes the mixing between ordinary and sterile neutrinos. We will then use this<br />
to calculate how sterile neutrinos induce rare nuclear decays and determine the sensitivity of ongoing experiments to observe sterile<br />
neutrinos.<br />
<br />
Supervisor: Jordy de Vries (devries.jordy at gmail.com)<br />
<br />
<br />
=== KM3NeT ===<br />
<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
==== Data analysis of the first deployed KM3NeT detection lines ====<br />
<br />
First detection lines of the KM3NeT neutrino telescope have been deployed<br />
in the Mediterranean Sea, and a first data set is available. The lines consist<br />
of light-sensitive detectors that record the time of arrival of photons<br />
produced by relativistic particles in the deep sea, and their number.<br />
In this project we will study the first data to separate various components:<br />
photons from potassium decay, bioluminesence, sparks in the photomultipliers,<br />
downgoing muons from cosmic rays, and first neutrinos.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben (paul.de.jong at nikhef.nl)<br />
<br />
==== Neutrino oscillation measurements with the KM3NeT neutrino telescope ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope currently under construction<br />
will be able to measure the oscillations of neutrinos produced in interactions<br />
of cosmic rays with the earth atmosphere. Fundamental neutrino properties can<br />
be deduced from these oscillations measurements, in particular the so-called<br />
mass hierarchy of neutrinos. In this project we will simulate the ORCA measurements<br />
of neutrino oscillations, and study the dependence of the sensitivity on<br />
experimental uncertainties, such as energy resolution and neutrino flavour<br />
identification, and theoretical uncertainties, such as the atmospheric neutrino<br />
flux and neutrino cross sections. The results will help ORCA to identify<br />
the main sources of uncertainty, and therefore to actively try to reduce these<br />
and improve the final measurement.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
==== Performance Studies of ORCA for Dark Matter Detection ====<br />
<br />
The interactions of neutrinos in KM3NeT-ORCA give different signatures which are categorised as track and shower events. This project involves the studies of muon, electron and tau neutrino interactions for the reconstruction performance of ORCA. Efficient reconstruction of such signals is important for Dark Matter searches in the low-mass regime. We will work on understanding the detector performance, e.g. effective acceptance, energy and angular resolution, with different configurations of the detector setup. The result of this study will be very useful to improve the sensitivity of the experiment for Dark Matter detection and its possible location. The student will have the opportunity to work closely with KM3NeT members at Nikhef and gain skills of analyzing data. <br />
<br />
Supervisors: Suzan Basegmez du Pree, Aart Heijboer (s.basegmez.du.pree at nikhef.nl)<br />
<br />
==== Study of Optical Properties of Sea Water using Hit Coincidences in MC Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
By studying coincidences of L1 hits between neighbouring DOMs, for various Monte Carlo (MC) data sets with different sea water optical properties such as scattering and absorption coefficients, in this project we try to figure out if and how well we can quantify optical sea water properties by studying L1 hit coincidences in real KM3NeT data.<br />
<br />
Supervisor: Daan van Eijk (dveijk at nikhef.nl)<br />
<br />
==== Determination of Inter-DOM Distances using Hit Coincidences in KM3NeT Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
The number of L1 hit coincidences from atmospheric muons between neighbouring DOMs on a DU is expected to decrease exponentially. By fitting the observed number of L1 hit coincidences between neighbouring DOMs in real data to the expected exponential decay, in this project we study how accurately we can determine the distances between DOMs on a single DU. In addition, we try to determine the distances between DUs by looking for L1 hit coincidences between DOMs on neighbouring DUs.<br />
<br />
Supervisor: Daan van Eijk (dveijk at nikhef.nl)<br />
<br />
<br />
=== ATLAS ===<br />
<br />
==== The Higgs boson life-time ====<br />
<br />
The Higgs particle does not have eternal life. The Standard Model (SM) predicts that it decays into other particles and as these couplings are fixed we can predict its life-time with very high precision. Determining this life-time is a crucial test for the Standard Model. If the Higgs boson life-time is shorter that we expect this could mean that the Higgs boson could decay into non-SM particles. In this project we investigate a) how we can identify Higgs particles in the detector and b) how we plan to use quantum-interference to get a handle on the Higgs boson's life-time. <br />
<br />
Supervisor: Wouter Verkerke (verkerke_at_nikhef.nl)<br />
<br />
==== The Higgs boson decaying to photons ====<br />
<br />
One of the main channels used to analyse the properties of the Higgs boson is when the Higgs boson decays into two photons. The crucial building block in this analysis is our ability to reconstruct the energy and the direction of the photons in the ATLAS detector and in this project we will revisit the photon reconstruction. We will start by studying simulations and learning about photon reconstruction in general. Then our goal is to determine the energy and position resolution of photons in the ATLAS detector and see if we can exploit our knowledge on the photon resolution to get an (improved) estimate of the Higgs boson mass. For the analysis we will use the '''real data from the LHC''' - the ATLAS open data project.<br />
<br />
Supervisor: Ashley McDougall and Ivo van Vulpen (Ivo.van.Vulpen_at_nikhef.nl)<br />
<br />
<br />
=== LHCb (1) ===<br />
<br />
One of the most fascinating mysteries in physics today is: how is it possible that universe is filled with matter? If the Big Bang produced equal amounts of matter and antimatter, we still do not understand the mechanism that lead to the excess of matter over antimatter that we observe today.<br />
<br />
One interesting feature of some particles is that they can transform themselves into their antiparticles, then back to particle, and so forth, in an oscillatory way until they finally decay. In particular, beauty mesons (B) can oscillate into their antiparticle (B ̄). The parameters of this oscillation, such as amplitude, frequency and phase, are calculable mathematically: predictions for it are available in the standard model (SM) of particle physics. But the oscillations according to the SM alone would not lead to the imbalance of matter in the universe – we still need to find a new type of physics that may be able to explain it.<br />
<br />
In this context, it is very important to measure B oscillations in the laboratory, and compare these observations with the expectations from the SM. Are the experimental data in good agreement with the SM, as we expect? If the aswer is not, i.e. if there are features of the oscillation that we do not understand well, then we may be observing “new physics”. In other words, the data may reveal a new mechanism that generates a different matter-antimatter balance than predicted by the SM, that may potentially solve the puzzle.<br />
<br />
The LHCb experiment at CERN is dedicated to such studies: LHCb detectors are placed in a region along the LHC collider beamline, where a large number of B mesons are produced, arising from the proton-proton collision data from the LHC collider. Looking at the LHCb data we can obtain large samples of B mesons, and observe their oscillations.<br />
In this project we will learn how to select a sample of B mesons out of the data taken with the LHCb detector, measure the parameters that govern their oscillation and compare them with the SM.<br />
<br />
For more information, please contact Mara Soares (msoares_at_nikhef.nl).<br />
<br />
== Bachelor Projects 2020 ==<br />
<br />
<br />
=== Dark Matter ===<br />
<br />
==== XAMS ====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso.<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source and liquid scintillatorneutron detector we have acquired for the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study of neutron transport in xenon.<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Backgrounds in Radioactive Decay Measurements ====<br />
At Nikhef, the XENON group has a working setup, continuously monitoring the<br />
radioactive decay of Cobalt-60, Caesium-137 and Titanium-44. This beautiful setup is<br />
however not shielded perfectly; it is still vulnerable to background radioactivity. Our<br />
current way of working around this background radiation is to subtract it from our<br />
waveforms. You as a BSc student could help us hands-on and with analyses:<br />
together, we can disassemble the setup, measure background spectra and<br />
implement this in the data analysis. You can use all the data to validate the<br />
lifetime of our isotopes!<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
=== ATLAS ===<br />
<br />
==== Project ATLAS-ITk ====<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
==== The Most Energetic Higgs Boson ====<br />
A common approach to search for physics beyond the standard model is by searching for the direct production of new particles. Alternatively, indirect quantum effects on the production of known particles -such as the Higgs Boson- could reveal the first cracks in the theory. Processes with high energy transfer are of particular potential since possible deviations are expected to increase with the square of the involved energy scale. Using the entire data-set collected by the ATLAS experiment at CERN during the four years of the LHC’s Run 2, a proof-of-principle analysis, targeting transverse momenta of the above 400 GeV, has been developed by Nikhef researchers. The first results of this Higgs boson study are expected to be published this year and this project aims to develop refinements of the analysis techniques. We will investigate the usage of sophisticated machine learning tools such as artificial neural networks, the search for new variables that can help discriminating the signal from its background, revisiting the analysis categorisation and improving the reconstruction techniques at these extreme momenta. Supervisors: Brian Moser and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs: The Next Generation ====<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks has been developed by Nikhef researchers and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays), advanced analysis techiques (using deep learning methods) and expanding the theory interpretation. Another opportunity would be the development of a new statistical combination with various independent searches, which could significantly improve the discovery potential. Supervisors: Marko Stamenkovic and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs interferentie ====<br />
In 2012 hebben het ATLAS en het CMS experiment het Higgs deeltje gevonden. Inmiddels zijn we het Higgs boson aan het bestuderen, hoe gedraagt het zich precies, bestaan er meer soorten Higgs bosonen of is er echt maar eentje van? In dit project leer je hoe we een Higgs boson kunnen herkennen in de detector en gaan we kijken naar hoe de signalen veranderen als er meer Higgs bosonen bestaan of misschien wel andere exotische nieuwe deeltjes. <br />
Dit doen we door gebruik te maken van quantum interferentie wat plaats vindt tussen het Higgs boson en achtergrondprocessen. Hoe dit precies werkt leer je in het project. Supervisor: Hella Snoek (h.snoek_at_nikhef.nl)<br />
<br />
=== B-Physics - LHCb ===<br />
<br />
==== Time dependent CP violation ====<br />
The LHCb experiment studies CP violation withB-meson decays.<br />
The project focusses on the measurement of the unitarity angle gamma using decays of the Bs mesons to Ds K.<br />
Supervisors: Sevda Esen & Michele Veronesi<br />
<br />
==== Machine learning ====<br />
Machine learning has proven to be an indispensable tool in the selection of interesting events in high energy physics. Such technologies will become increasingly important as detector upgrades are introduced and data rates increase by orders of magnitude. HEPDrone is a toolkit to enable the creation of a drone classifier from any machine learning classifier, such that different classifiers may be standardised into a single form and executed in parallel. A detailed evaluation of the performance of different drone models in the real production environment of LHCb will give the collaboration a complete idea of not only the advantages of the drone model, but also the limits of drone complexity given the available computing resources.<br />
Requirements: Advanced python and Advanced C++<br />
Supervisor: Sean Benson<br />
<br />
==== LHCb simulations of physics beyond the Standard Model ====<br />
This project is of relatively theoretical and computing nature and performs simulation studies for physics beyond the Standard Model in the context of long lived particles. It is related to test the sensitivity of the LHCb experiment to detect specific signals of physics beyond the Standard Model.<br />
supervisor: Carlos Vazquez Sierra<br />
<br />
=== Detector R&D ===<br />
<br />
==== Fast timing detectoren ====<br />
Op dit moment maken we veel gebruik van silicon detectoren in onze deeltjes experimenten. Deze zijn gevoelig voor geladen deeltjes en zijn bij uitstek geschikt om de paden vast te leggen die de deeltjes maken die in de botsingen worden gemaakt. Bijvoorbeeld in de Atlas en LHCb experimenten worden tientallen tot honderden deeltjes gemaakt bij elk botsingsgebeurtenis (event) die met 40MHz plaatsvinden. Voor toekomstige deeltjesdetectoren willen we niet alleen het traject vastleggen maar ook met grote precisie een tijdsmeting toevoegen. We hebben hiervoor dus nieuwe detectoren nodig die behalve met een hele hoge snelheid en efficientie de posities van de langsvliegende deeltjes kunnen vastleggen, maar hier ook een zeer nauwkeurige tijdsmeting (in orde van picosecondes) aan kunnen toevoegen. We hebben met verschillende detectoren metingen gedaan, in testbundels op CERN, maar ook in het lab op Nikhef kunnen we metingen doen. In dit project ga je samen met het fast-timing detectoren team op het Nikhef metingen verrichten en de resultaten hiervan bekijken. Contact: Hella Snoek (h.snoek@nikhef.nl)<br />
<br />
==== Muon tomography ====<br />
In this project we are not looking for where cosmic rays come from. We are looking for what we can use them for instead. The muons in cosmic rays can be used to ‘probe’ massive objects. Muons are short lived particles that carry the same charge as electrons, have a high penetrating power and can be detected relatively easy. It is possible to reconstruct a density distribution within an object by measuring muon scattering and absorption. In this context the objects may be freight containers, buildings, melting furnaces, etc… <br />
<br />
Systems that scan objects through the use of muons are often large (objects often need to be enclosed by the system) and complex. The question we want to answer is: Can we develop a smaller, simpler and cheaper system for muon tomography? <br />
<br />
A method to detect muons is by using a material that scintillates (emits light) when hit by an ionising particle. When this light emission is prompt after the passage of the muon, timing information of the light can be used to reconstruct the path of the muon.<br />
In this experiment we make a muon tracker based on two sheets of scintillating material and photo multiplier tubes (PMTs). Photo multiplier tubes are fast responding and very sensitive light detectors (capable of detecting single photons).<br />
<br />
The big question is: How well does this system perform?<br />
<br />
Currently a set-up is being build. You have a lot of freedom to choose a focus in this project (theory, simulation, hardware, or a combination of those).<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Spectral X-ray imaging - Looking at colours the eyes can't see ====<br />
When a conventional X-ray image is made to analyse the composition of a sample, or to perform a medical examination on a patient, one acquires an image that only shows intensities. One obtains a ‘black and white’ image. Most of the information carried by the photon energy is lost. Lacking spectral information can result in an ambiguity between material composition and amount of material in the sample. If the X-ray intensity as a function of the energy can be measured (i.e. a ‘colour’ X-ray image) more information can be obtained from a sample. This translates to less required dose and/or to a better understanding of the sample that is being investigated. For example, two fields that can benefit from spectral X-ray imaging are mammography and real time CT.<br />
<br />
X-ray detectors based on Medipix/Timepix pixel chips have spectral resolving capabilities and can be used to make polychromatic X-ray images. Medipix and Timepix chips have branched from pixel chips developed for detectors for high energy physics collider experiments.<br />
<br />
Some themes that students can work on: <br />
<br />
- Optimising methods to acquire spectral X-ray images.<br />
<br />
- Determining how much existing applications benefit from spectral X-ray imaging and looking for potential new applications.<br />
<br />
- Characterising, calibrating, optimising X-ray imaging detector systems.<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Holographic emitter ====<br />
A difficulty in generating holograms (based on the interference of light) is the required dense spatial light field sampling. One would need pixels of less than 200 nanometer. With larger pixels artefacts occur due to spatial under sampling. A pixel pitch of 200 nm or less is difficult, if not, impossible, to achieve, especially for larger areas. Another challenge is the massive amount of computing power that is required to control such a dense pixel matrix. <br />
<br />
A new holographic projection method has been developed that reduces under sampling artefacts, regardless of spatial sample density. The trick is to create 'pixels' at random but known positions, resulting in an array that lacks any spatial periodicity. As a result a holographic emitter can be built with a significantly lower sample density and less required computing power. This could bring holography in reach for many applications like display, lithography, 3D printing, metrology, etc...<br />
<br />
The big question: How does the performance of the holographic emitter depend on sample density and sample positions?<br />
<br />
The aspects of a holographic image we are interested in are:<br />
<br />
- Noise<br />
<br />
- Contrast<br />
<br />
- Suppression of under sampling artefacts<br />
<br />
- Resolution <br />
<br />
For this project we are building a proof of concept holographic emitter. This set-up will be used to verify simulation results (and to make some cool holograms of course). <br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
=== KM3NeT ===<br />
<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
==== Data analysis of the first deployed KM3NeT detection lines ====<br />
<br />
First detection lines of the KM3NeT neutrino telescope have been deployed<br />
in the Mediterranean Sea, and a first data set is available. The lines consist<br />
of light-sensitive detectors that record the time of arrival of photons<br />
produced by relativistic particles in the deep sea, and their number.<br />
In this project we will study the first data to separate various components:<br />
photons from potassium decay, bioluminesence, sparks in the photomultipliers,<br />
downgoing muons from cosmic rays, and perhaps first neutrinos.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Neutrino oscillation measurements with the KM3NeT neutrino telescope ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope currently under construction<br />
will be able to measure the oscillations of neutrinos produced in interactions<br />
of cosmic rays with the earth atmosphere. Fundamental neutrino properties can<br />
be deduced from these oscillations measurements, in particular the so-called<br />
mass hierarchy of neutrinos. In this project we will simulate the ORCA measurements<br />
of neutrino oscillations, and study the dependence of the sensitivity on<br />
experimental uncertainties, such as energy resolution and neutrino flavour<br />
identification, and theoretical uncertainties, such as the atmospheric neutrino<br />
flux and neutrino cross sections. The results will help ORCA to identify<br />
the main sources of uncertainty, and therefore to actively try to reduce these<br />
and improve the final measurement.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Performance Studies of ORCA for Dark Matter Detection ====<br />
<br />
The interactions of neutrinos in KM3NeT-ORCA give different signatures which are categorised as track and shower events. This project involves the studies of muon, electron and tau neutrino interactions for the reconstruction performance of ORCA. Efficient reconstruction of such signals is important for Dark Matter searches in the low-mass regime. We will work on understanding the detector performance, e.g. effective acceptance, energy and angular resolution, with different configurations of the detector setup. The result of this study will be very useful to improve the sensitivity of the experiment for Dark Matter detection and its possible location. The student will have the opportunity to work closely with KM3NeT members at Nikhef and gain skills of analyzing data. <br />
<br />
Supervisors: Suzan Basegmez du Pree, Aart Heijboer<br />
<br />
==== A search for periodic sources in Antares data ====<br />
<br />
The Antares deep-sea neutrino telescope has been operated for more then ten years. A search for periodic sources is proposed by applying a fast Fourier transformation (FFT) analysis on the available low-level data. This search will be combined with a (literature) study of pulsars which are thought to emit neutrinos.<br />
<br />
Supervisor: Maarten de Jong<br />
<br />
==== Study of Optical Properties of Sea Water using Hit Coincidences in MC Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
By studying coincidences of L1 hits between neighbouring DOMs, for various Monte Carlo (MC) data sets with different sea water optical properties such as scattering and absorption coefficients, in this project we try to figure out if and how well we can quantify optical sea water properties by studying L1 hit coincidences in real KM3NeT data.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
==== Determination of Inter-DOM Distances using Hit Coincidences in KM3NeT Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
The number of L1 hit coincidences from atmospheric muons between neighbouring DOMs on a DU is expected to decrease exponentially. By fitting the observed number of L1 hit coincidences between neighbouring DOMs in real data to the expected exponential decay, in this project we study how accurately we can determine the distances between DOMs on a single DU. In addition, we try to determine the distances between DUs by looking for L1 hit coincidences between DOMs on neighbouring DUs.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
=== VIRGO ===<br />
<br />
The Advanced LIGO and Advanced Virgo interferometers have recently observed gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results.<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Frank Linde (frank.linde_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
<br><br><br><br />
<br />
== Bachelor Projects 2017 ==<br />
<br />
=== Extreme Astronomy – Preparing for CTA, the Next-Generation Gamma-Ray Observatory ===<br />
<br />
The Cherenkov Telescope Array (CTA) is a planned facility for measuring gamma rays from space covering more than four orders of magnitude in energy, up to energies exceeding 100 TeV. CTA employs the imaging atmospheric Cherenkov technique to measure properties of cosmic gamma rays. This technique is based on measuring Cherenkov light emitted during the development of a gamma-ray air shower. CTA will be built at two experimental sites, one in the Northern, one in the Southern hemisphere, and will consist of up to 100 telescopes. It represents a major leap forward in sensitivity and precision for gamma-ray astronomy, and will allow us to explore very-high-energy processes of the extreme Universe at an unprecedented level.<br />
<br />
Two projects for students are available at the CTA group of UvA in the field of optical and photonic R&D contributing to the starting phase of CTA. For the first project the student will conduct measurements to characterise novel kinds of single-photon detectors, referred to as silicon photomultipliers, and evaluate different types of these sensors for their use for CTA. For the second project the student will develop and test an imaging system making use of a liquid crystal display. This flexible light source will be able to mimic images from different light sources of the night sky as seen by cameras of CTA, for instance gamma-ray air showers or stars, and will be used for camera tests and calibration.<br />
<br />
<br />
Supervisors: David Berge, Maurice Stephan (postdoc)<br />
<br />
=== Dark Matter ===<br />
<br />
<!--<br />
==== XENON1T - the world's most sensitive dark matter detector ====<br />
<br />
Finding the mysterious dark matter particles is one of the most challenging enterprises in physics today. Soon we will get first data from the world's most sensitive dark matter detector yet: the XENON1T experiment.<br />
<br />
The first goal of this project is to understand why dak matter is necessary to understand the universe, and how we could detect it with XENON1T. Then, you can contribute to our group's efforts preparing for <br />
and analyzing the XENON1T data by, for example: examining XENON1T's calibration signals to check for problems in the experiment, testing our data analysis software with simulated dark matter signals, or studying the physics behind XENON1T's detection process to learn how to better distinguish dark matter signals from backgrounds. For data analyis, experience with or willingness to learn programming in python is essential.<br />
<br />
<br />
Supervisors: M.P. Decowski & J. Aalbers --><br />
<br />
==== Neutrinoless double beta decay sensitivity study in future dark matter detectors ====<br />
<br />
The discovery of neutrino oscillation (Nobel Physics 2015) means that neutrinos have mass. We already know that their masses are tiny, more than one million times smaller than the next-lightest particle in the standard model, the electron. This raises the question if the mass-generation mechanism is the same for neutrinos as it is for the other subatomic particles. In particular, since neutrinos are electrically neutral, they could be their own anti-particles - we call these types of particles Majorana. The only practical way to discover if neutrinos are Majorana is through the search of an extremely rare radioactive decay called neutrinoless double beta decay (0n2b). A few isotopes are candidates for this process, among them Xe-136. The natural abundance of Xe-136 in natural xenon is about 9%, and this gives the opportunity to look for a 0n2b signal in xenon-based dark matter detectors like XENON1T and the future XENONnT and DARWIN detectors. <br />
<br />
We are looking for a student interested in doing a sensitivity study for 0n2b in XENONnT and the DARWIN experiments. The first goal will be to understand the physics addressed in neutrinoless double beta decay. Then the student will inventory possible backgrounds for the signal, use a (controversial) claim of a 0n2b signal as a benchmark and finally obtain the sensitivity of these future detectors. The work will involve simulations and analysis, building on an existing framework developed in our group. <br />
<br />
Supervisors: M.P. Decowski & A. Tiseni<br />
<br />
==== Shaking Dark Matter detectors ====<br />
<br />
Our XENON1T detector is built in the lab underneath the Gran Sasso mountains in central Italy. The lab is very well suited for low-background experiments due to the 1.5km of rock overburden. <br />
However, as you may know, cental Italy has been plagued by earthqaukes over the past decade, with the most recentones occurring in January 2017. We need a BSc student to investigate the <br />
details of such earthquakes in our underground lab. What are the magnitdues by which stuff is moving underground? What are the accelerations? What is the potential effect on our experimental<br />
setup? What would ahppen if an earthquake happens much closer to our lab? Furthermore we are interested to find out whether Earthquakes can be predicted. Some papers claim that before<br />
an earthquake the radon emanating from rock increases. In our lab we measure the radon concentration as a function of time: can you find a correlation between the measurements and recent <br />
earthquakes?<br />
<br />
If you are interested in finding out more about earthquakes, please contact M.P. Decowski or A.P. Colijn<br />
<br />
==== XAMS - a baby dark matter detector ====<br />
<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso<br />
we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector<br />
are identical to its big sibling in Gran Sasso.<br />
<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source we have acquired<br />
before the start of the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project<br />
will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study<br />
of neutron transport in xenon.<br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
==== Radon is bad for Dark Matter ====<br />
<br />
Radon is the dominant background for xenon based dark matter detectors, like the XENON1T experiment. In our lab at Nikhef we are investigating ways to reduce or eliminate the effect of radon<br />
on our sensitivity. For our lab setup XAMS we have designed and constructed a radon detector, that can be used in xenon systems at high-pressure. This completely new detector<br />
is now waiting for a BSc student to fully chracterize and use it. During this project you will first study the effect that radon contaminations have on dark matter detectors, then you will start working to<br />
understand our new radon detector in detail. You will learn howto use a radioactive source to calibrate the detector: this is something which is not easy and has not been done before in our lab. <br />
If you manage to succesfully calibrate the detector, we then want to incorporate it into our lab xenon system at Nikhef and maybe at some later stage in the real XENON1T detector!<br />
<br />
The profile of the student to work on this project is broad. I expect a good theoretical knowledge in order to quickly get upto speed with understanding dark mater detectors, and in addition I <br />
need 'lab-creativity' in order to develop methods for calibrating the new detector. If a good method is developed, it will be used for many years by the Nikhef dark matter group and beyond. <br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
=== ATLAS ===<br />
<br />
<br />
==== ATLAS (1): Searching for new physics with the Higgs and W bosons ====<br />
<br />
The strength of the Higgs interactions with electroweak bosons are precisely defined in the<br />
Standard Model. Therefore they are sensitive probes of the mechanism of electroweak symmetry<br />
breaking and enable searches for new physics beyond the SM. With the data collected by the ATLAS<br />
experiment in years 2015-2016 we plan to measure separately the Higgs coupling to<br />
longitudinally and transversely polarised W bosons in a process of weak boson fusion. To<br />
maximise experimental sensitivity we are developing techniques to separate the signal from<br />
background processes. You will take part in investigating possible improvements from<br />
reconstructing events in reference frames boosted with respect to the detector. During the<br />
project you will learn modern experimental analysis techniques. This project is a part of Vector<br />
Boson Scattering Coordination and Action Network (VBSCan) which connects researchers studying<br />
this and related topics worldwide.<br />
<br />
Supervisors: Pamela Ferrari, Magdalena Slawinska, Bob van Eijk<br />
<br />
<br />
==== ATLAS (2): Dark-matter-motivated searches for supersymmetric particles at the LHC ====<br />
<br />
Supersymmetry, a symmetry between fermions and bosons in particle physics,<br />
may provide a particle that could be the dark matter in the universe.<br />
The observation of an excess of gamma rays originating from the centre of our<br />
galaxy could be explained in a model where supersymmetric dark matter<br />
particles annihilate each other in the galactic centre, leading to gamma rays.<br />
<br />
Given the model parameters, it should also be possible to produce such<br />
particles at the LHC, at CERN in Geneva. But it is not so easy to observe<br />
them: the signal is small, and the noise (background) is large.<br />
In this project, we will use simulations of signal and background to<br />
optimize experimental searches for such particles with the ATLAS detector,<br />
apply them to the data collected in 2015, and prepare for the new data in<br />
2016 and later.Where possible, we will explore new machine learning techniques.<br />
<br />
Supervisors: Paul de Jong, Broos Vermeulen<br />
<br />
<br />
==== ATLAS (3): Simulations / Quality tests for the ATLAS High-Luminosity LHC Upgrade ====<br />
<br />
One of the key sub-systems of the ATLAS experiment at the Large<br />
Hadron Collider (LHC) is the Inner Detector (ID), designed to provide<br />
excellent charged particles momentum and vertex resolution measurements.<br />
<br />
At Phase-2 of the LHC run, in ~2025, the operating luminosity of<br />
the collider will be increased significantly.<br />
This will imply an upgrade of all ATLAS subsystems. In particular,<br />
the ID will be fully replaced with a tracker completely made of<br />
Silicon, having higher granularity and radiation hardness.<br />
The R&D process for the new ATLAS ID is now ongoing.<br />
Different geometrical layouts are simulated and their performance is<br />
studied under different operating conditions in search for the optimal<br />
detector architecture. Also, the performance of the new<br />
Si-sensors/modules is under investigation with dedicated laboratory tests.<br />
<br />
The focus of the project could be on the simulation of the High-Luminosity LHC<br />
version of the ATLAS Inner Detector. The student will learn how a<br />
high-energy physics experiment is designed and optimized.<br />
Alternatively, if possible at that moment, the student could<br />
work on a project at the Nikhef Silicon laboratory at the test-bench for<br />
new ATLAS Si-strip detectors and participate in the quality<br />
assurance procedure for the new ATLAS Si detectors.<br />
<br />
==== ATLAS (4): Higgs productie in Run-2 van de LHC ====<br />
In de eerste run van de LHC is onder andere bij het ATLAS experiment het Higgs deeltje gevonden. Nu is de tweede run begonnen en kan het Higgs deeltje worden bevestigd. Door de verhoogde energie ziet de achtergrond er echter heel anders uit, dus is de optimalisatie van het wegsnijden van de achtergronden qua fysica anders. Voor je bachelor project kan met behulp van de ATLAS detector het Higgs deeltje in run twee komen vinden. <br />
<br />
Supervisors: Lydia Brenner, Wouter Verkerke<br />
<br />
==== ATLAS (5): De lange staart van het Higgs boson ====<br />
<br />
[[File:HiggsMassa.png |thumb|left|upright=1.25]]<br />
<br />
<br><br />
Na de ontdekking van het Higgs boson in 2012 zijn we druk bezig om te kijken of zijn eigenschappen overeenkomen met de voorspellingen van het Standaard Model. Een van de belangrijkste eigenschappen is de zogenaamde breedte van het Higgs boson. Als het Higgs boson naast de Standaard Model deeltjes ook in exotische nieuwe speeltje uit elkaar kan vallen (bijvoorbeeld donkere materie) dan zal dat ale eerste zichtbaar worden in een afwijking van de breedte tov de verwachting. We gaan in dit project uitzoeken hoe de strategie die nu gebruikt wordt (meten van de hoeveelheid Higgs bosonen met een extreem hoge massa) precies werkt en kijken of we door het toevoegen van nieuwe ideeën een verbetering kunnen aanbrengen. <br />
<br />
<br><br />
Specifiek: We gaan eerst in detail de eigenschappen bekijken van het Higgs signaal en de twee achtergronden die er het meest op lijken. Daarna gaan we op zoek naar de verschillen en een manier waarop we onze kennis daarover kunnen gebruiken om gevoeliger te worden voor het Higgs signaal.<br />
<br />
Supervisors: Hella Snoek, Ivo van Vulpen<br />
<br />
E-mail: H.Snoek_at_nikhef.nl & Ivo.van.Vulpen_at_nikhef.nl<br />
<br><br><br><br><br><br><br />
<br />
=== ATLAS (6): Project ATLAS-ITk ===<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
<br><br />
<br />
=== KM3Net ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierachy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
The first phase of the KM3NeT neutrino telescope is currently under construction, with the first two detection units operational at 3500m depth in the Mediterranean Sea, 100 km off the coast of Sicily.<br />
<br />
<br />
==== KM3NeT (1): Photon counting in KM3NeT ====<br />
<br />
The details of a neutrino interaction, such as its incoming direction and energy, determine the pattern, time and amount, of recorded photons (´hits´) by the photo-multplier tubes. The time of arrival is recorded with nanosecond accuracy and the amount of photons is encoded in the length of the pulse(time-over-threshold, ToT). Currently, only the photon arrival time and the number of photo-multipliers that record a hit are used in reconstructing event properties.<br />
In this project, the distributions of the ToT mainly originating from photons from potassium-40 decays in the sea-water and from atmospheric muons passing through the water will be studied. The goals are to investigate the properties of the ToT distributions obtained from data and simulation, in particular the dependence on the photo-multiplier efficiency and atmospheric muon flux.<br />
In this project we will be extensively using the programming language C++ to analyse the data, so a reasonable proficiency is required.<br />
<br />
Supervisors: Ronald Bruijn & Karel Melis<br />
<br />
Email: rbruijn_at_nikhef.nl<br />
<br />
<br />
<br />
<br><br><br><br />
<br />
=== VIRGO ===<br />
<br />
"It is anticipated that in the next few years, Advanced LIGO and Advanced Virgo will start observing gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results."<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Jo van den Brand (jo_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
=== LHCb ===<br />
<br />
Begeleider: Sean Benson<br />
<br />
Title: <br />
Searching for physics beyond the Standard Model with LHCb<br />
<br />
The LHCb experiment is designed to study the "The Flavour Problem" in particle physics:<br />
Why is the universe dominated by matter over antimatter? Why are there three generations of elementary particles? What is the origin of quark flavour changing interactions.<br />
<br />
To solve these riddles, LHCb performs precision measurements on b-quark particle decays.<br />
An intriguing signal has recently been observed in the decay of a B-meson to a K* and two muons: Bd→K*μμ, which does not seem to behave according to the predictions of the Standard Model<br />
In this project the bachelor student will investigate this further by studying the case where the K* particle decays to a so-called k-short particle and a π0. The observation of such a final state will provide valuable information in the search for physics beyond the Standard Model.<br />
<br />
In this ambitious project the student is expected to study both a theory on the mechanism of CP violation with B mesons, in addition to data analysis with B decays. Programming experience in python is required.<br />
<br />
The LHCb experiment at CERN analyzes the properties of B-hadrons produced in proton-proton collisions at the LHC. For projects in the LHCb group, please contact Marcel Mark (marcel.merk_at_nikhef.nl)<br />
<br />
<br />
=== LHCb (1) ===<br />
<br />
One of the most fascinating mysteries in physics today is: how is it possible that universe is filled with matter? If the Big Bang produced equal amounts of matter and antimatter, we still do not understand the mechanism that lead to the excess of matter over antimatter that we observe today.<br />
<br />
One interesting feature of some particles is that they can transform themselves into their antiparticles, then back to particle, and so forth, in an oscillatory way until they finally decay. In particular, beauty mesons (B) can oscillate into their antiparticle (B ̄). The parameters of this oscillation, such as amplitude, frequency and phase, are calculable mathematically: predictions for it are available in the standard model (SM) of particle physics. But the oscillations according to the SM alone would not lead to the imbalance of matter in the universe – we still need to find a new type of physics that may be able to explain it.<br />
<br />
In this context, it is very important to measure B oscillations in the laboratory, and compare these observations with the expectations from the SM. Are the experimental data in good agreement with the SM, as we expect? If the aswer is not, i.e. if there are features of the oscillation that we do not understand well, then we may be observing “new physics”. In other words, the data may reveal a new mechanism that generates a different matter-antimatter balance than predicted by the SM, that may potentially solve the puzzle.<br />
<br />
The LHCb experiment at CERN is dedicated to such studies: LHCb detectors are placed in a region along the LHC collider beamline, where a large number of B mesons are produced, arising from the proton-proton collision data from the LHC collider. Looking at the LHCb data we can obtain large samples of B mesons, and observe their oscillations.<br />
In this project we will learn how to select a sample of B mesons out of the data taken with the LHCb detector, measure the parameters that govern their oscillation and compare them with the SM.<br />
<br />
For more information, please contact Mara Soares (msoares_at_nikhef.nl).</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Bachelor_Projects&diff=770Bachelor Projects2022-02-02T08:38:40Z<p>Rojo@nikhef.nl: </p>
<hr />
<div><br />
== Bachelor Projects 2022 ==<br />
<br />
=== Dark Matter ===<br />
<br />
==== Response of materials to scintillation light from liquid noble gasses ====<br />
<br />
The liquid form of the noble gases argon and xenon is a popular target material for neutrino and dark matter detectors. The scintillation light from noble gases is in the vacuum UV spectral region. Air and many materials used for optical studies are not transparent to these photons. Measurements of the optical properties of detector materials, such as their reflectivity for example, thus have to be performed with dedicated VUV optics and in vacuum. Additionally, to reproduce the conditions in the detectors, the samples must be cooled to cryogenic temperatures. In this BSc project, you will calibrate the photon detectors in an experimental setup designed to study the optical response of materials excited with VUV photons. You will learn about material requirements for rare event search detectors, vacuum instrumentation, vacuum UV optics including monochromators and spectrometers, and single-photon sensors.<br />
<br />
Supervisors: T. Pollmann (t.pollmann_at_nikhef.nl)<br />
<br />
=== ATLAS ===<br />
<br />
=== LHCb ===<br />
<br />
<br />
==== Exotic neutrinos in B decays====<br />
<br />
Neutrinos are the lightest of all fermions in the standard model. Mechanisms to explain their small mass rely on the introduction of new, heavier, neutral leptons. In the LHCb group at Nikhef we search for the decay of B+ mesons in into an ordinary electron or muon and the yet undisovered heavy neutrino. The heavy neutrino is expected to be unstable and in turn decay quickly into a charged pion and another electron or muon. The final state in which the two leptons differ in flavour, "B+ to e mu pi", is particularly interesting: It is forbidden in the standard model, such that backgrounds are small. The bachelor project will contribute with the optimization of the selection using state-of-the-art tools for the multi-variate analysis.<br />
<br />
Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen]<br />
<br />
<br />
=== Gravitational Waves ===<br />
<br />
=== Detector R&D ===<br />
Answering big elementary particle physics questions requires pioneering experiments. The Detector R&D program at Nikhef is aimed at conceptualizing and testing of instrumentation concepts before they are implemented in scientific programs at Nikhef. <br />
<br />
==== Time resolution of monolithic timing detectors ====<br />
For the upgrade of the vertex detectors of the large LHC experiments like LHCb and ALICE, new silicon pixel detectors will developed now that can register the passing particles with a time precision of tens of picoseconds. ALICE is the first experiment at the LHC to have installed monolithic sensors where electronics is integrated into the sensor resulting in ultrathin, low-material detectors. In this project you will measure the time resolution of these promising integrated sensors with a laser setup in our laboratory.<br />
<br />
Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
==== Modeling radiation damage in silicon sensors ====<br />
In the coming years, the ATLAS experiment at the LHC works on upgrades to prepare for the high-luminosity LHC, where many more collisions will take place than today. Analyses of LHC data rely heavily on simulations of the detector. It may sound counterintuitive, but particle detectors do not actually like particles: after many collisions at the LHC, a silicon pixel detector has seen so many particles that its bulk gathers defects. Charge generated by traversing particles can get trapped in defects resulting in less charge induced in the readout electrodes, reducing detector performance in resolution and efficiency. In this project, you will be part of the international ATLAS collaboration and compare different models of radiation damage with measured data and you will contribute to the open source program Allpix Squared that is widely used for simulations in many areas of particle physics.<br />
<br />
Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
==== Time resolution of a new digital pixel test structure from test beam data ====<br />
For the upgrade of the ALICE detector, ultrathin picosecond timing integrated sensors are developed. To reduce power consumption, asynchronous readout is implemented in this prototype sensor in a digital pixel test structure. This structure was studied in test beams with an ALPIDE (ALICE PIxel DEtector) telescope at CERN. You will measure the efficiency and time resolution of this new sensor with the latest data from test beams at CERN.<br />
<br />
Supervisor: Jory Sonneveld -- jory.sonneveld@nikhef.nl<br />
<br />
<br />
<br />
<br />
=== KM3NeT ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along 200-700m long vertical lines, called detection units.<br />
<br />
==== Neutrino oscillation measurements with the first KM3NeT data ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope is able to measure the oscillations of neutrinos produced in interactions of cosmic rays with the earth atmosphere. Fundamental neutrino properties can be deduced from these oscillations measurements. In this project we will use the first data of ORCA (more than one year with six detection units) to study neutrino oscillations and fit neutrino mixing parameters and mass differences between neutrino mass states. We will study data selection, event reconstruction, and effects of systematic uncertainties on the results. <br />
<br />
Supervisors: Brian O'Fearraigh, Ronald Bruijn, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
==== Search for sterile neutrinos with KM3NeT. ====<br />
A detailed study of neutrino oscillations in the KM3NeT detector is sensitive to the existence of so-called sterile neutrinos: neutrinos that are not part of the Standard Model of particle physics, and have no ordinary interactions with matter. We will use a mixture of data and simulations to estimate KM3NeT sensitivity.<br />
<br />
Supervisors: Alba Domi, Paul de Jong<br />
<br />
==== Machine learning for event classification in KM3NeT ====<br />
The classification of neutrino events recorded in the KM3NeT detector in terms of originating from electron neutrinos, muon neutrinos, or tau neutrinos, is very well suited for machine learning techniques. We will study the performance of a few advanced machine learning techniques on simulated high-energy neutrino events.<br />
<br />
Supervisors: Alba Domi, Paul de Jong<br />
<br />
==== Multi-messenger astronomy with neutrinos and radio signals ====<br />
The main goal of neutrino telescopes, such as ANTARES, KM3NeT and IceCube, is to detect cosmic neutrinos from astrophysical sources. When an interesting neutrino candidate is detected they send out a message to alert the scientific community. Other scientific instruments, like the Murchison Widefield Array (MWA) radio telescope, can then do a follow-up observation, to see if there are other messengers coming from the same source as the neutrinos. In this project you will analyse MWA data that were taken after the reception of neutrino alerts, to search for a radio source that can be associated with a neutrino source.<br />
<br />
Supervisor: Mieke Bouwhuis (mieke.bouwhuis at nikhef.nl)<br />
<br />
=== Theory ===<br />
'''Symmetries and sterile neutrinos'''<br />
<br />
The fact that neutrinos have masses is problematic for the Standard Model. A plausible solution requires the existence of additional so-called sterile neutrinos. In this project we will study why such neutrinos could exist and describe their mixing with the active neutrinos we have seen in experiments. In particular, we will investigate how large active-sterile mixing can be while accounting for the small neutrino masses and what this tells us about possible lepton number violation. <br />
<br />
Supervisor: Jordy de Vries <br />
<br />
<br />
<br />
'''Effective Field Theories of Particle Physics from low- to high-energies'''<br />
<br />
Known elementary matter particles exhibit a surprising three-fold structure. The particles belonging to each of these three “generations<nowiki>''</nowiki> seem to display a remarkable pattern of identical properties, yet have vastly different masses. This puzzling pattern is unexplained. Equally unexplained is the bewildering imbalance between matter and anti-matter observed in the universe, despite minimal differences in the properties of particles and anti-particles. These two mystifying phenomena may originate from a deeper, still unknown, fundamental structure characterised by novel types of particles and interactions, whose unveiling would revolutionise our understanding of nature.<br />
<br />
Until recently, it was widely assumed that matter particles from each of the three generations interact with the same (“universal”) strength. This hypothesis is being challenged by new measurements at the Large Hadron Collider (LHC) at CERN, which hint towards non-universal interactions. If confirmed, these measurements will be the first signs of new particles and interactions in high-energy colliders. These exciting findings indicate the urgent need to explore such phenomena in depth.<br />
<br />
The ultimate goal of particle physics is uncovering a fundamental theory which allows the coherent interpretation of phenomena taking place at all energy and distance scales. In this project, the students will exploit the Effective Field Theory (EFT) formalism, which allows the theoretical interpretation of particle physics data in terms of new fundamental quantum interactions which relate seemingly disconnected processes. Specifically, the goal is to connect measurements from ATLAS and LHCb among them and to jointly interpret this information with that provided by other experiments, from CMS and Belle-II to very low-energy probes such as the anomalous magnetic moment of the muon or electric dipole moments of the electron and neutron.<br />
<br />
''Methodology and workplan''<br />
<br />
This project will be based on theoretical calculations in particle physics, numerical simulations in Python, analysis of existing data from the LHC and other experiments, as well as formal developments in understanding the operator structure of effective field theories.<br />
<br />
This project accommodates several students, who would work together in developing the main formalism while each of them focuses on a specific sub-project. The maximum capacity of this project is 5 students. <br />
<br />
Depending on the student profile, sub-projects with a strong computational / machine learning component are also possible.<br />
<br />
During the first four weeks of the project, students will learn the required background material on effective field theories, following the guidelines from the supervisors. Afterwards, they will focus on different sub-projects, each covering a different aspect of the same global EFT program.<br />
<br />
Required knowledge<br />
<br />
Quantum Mechanics 2, Particle Physics 1 (required)<br />
<br />
Advanced Quantum Mechanics, Particle Physics 2, Machine Learning (optional)<br />
<br />
Available subprojects<br />
<br />
Here we list the available subprojects, including the corresponding daily supervisor(s) in each case.<br />
<br />
''Subproject #1: SMEFT & Flavour symmetries'' <br />
<br />
Daily supervisors: Jordy de Vries (UvA), Keri Vos (Maastricht University), Jaco ter Hoeve (VU), Giacomo Magni (VU)<br />
<br />
While the power of the Standard Model EFT (named SMEFT) framework is its generality and lack of assumptions, the number of operators is somewhat daunting. A popular way to trim the number of operators is to assume flavour symmetries that relate operators with different quark and lepton flavours. In this project you will investigate the theoretical basis for commonly-used flavour symmetries and what they imply for the connection between high-energy observables involving third-generation particles (top and bottom quarks and tau leptons) and low-energy precision tests involving first- and second-generation particles. The investigations of this project are connected with Subproject #2.<br />
<br />
''Subproject #2: SMEFT & magnetic moment of the muon''<br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU)<br />
<br />
The magnetic moment of the muon appears to differ from the Standard Model expectations by a large amount, well beyond the known experimental and theoretical uncertainties. Recent experiments have only strengthened the significance of this anomaly. In this project, the students will investigate the feasibility of implementing the measurement of the magnetic moment of the muon into a global SMEFT analysis, by exploiting recently provided calculations. Special attention will be devoted to the flavour assumptions required to consistently match this measurement with the LHC data, also at the light of the connection with Subproject #1. The SMEFiT analysis framework will be used to connect the g-2 data with high-energy LHC measurements.<br />
<br />
''Subproject #3: CP Violation and low-energy precision experiments''<br />
<br />
Most analyses of LHC data are performed under the assumption that CP symmetry (charge conjugation + parity, essentially the symmetry between particles and anti-particles) is conserved. More recent analyses attempt to also measure possible new sources of CP violation in SMEFT operators in the Higgs and top sector. <br />
<br />
''Subproject #3a: CP Violation and low-energy precision experiments''<br />
<br />
Daily supervisors: Jordy de Vries (UvA), Juan Rojo (VU)<br />
<br />
Low-energy precision experiments can also set stringent constraints on new mechanisms of CP violation. In this project you will try to combine high- and low-energy data to put CP symmetry to the test. <br />
<br />
''Subproject #3b: CP Violation and flavour physics experiments''<br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU)<br />
<br />
Besides low-energy precision experiments, also B-meson decays are excellent probes of CP violation. Unlike most low-energy experiments, this allows us to probe CP violation in the third generation. In this project you will link constraints on CP violation at high-energy to those from B meson decays. <br />
<br />
''Subproject #4: SMEFT & optimal observables'' <br />
<br />
Daily supervisors: Keri Vos (Maastricht University), Juan Rojo (VU), Tommaso Giani (VU & Nikhef)<br />
<br />
In full generality, the number of operators in SMEFT spans a very large parameter space. These parameters are constrained by experimental inputs from ATLAS and CMS, depending on the precise parameters these constraints may be more or less stringent. In order to fully exploit the whole parameters space in SMEFT, it is necessary to devise statistically optimal observables that have a large constraining power. In this project, we will define such observables. This project has a strong computational / machine learning component and may involve simulations based on tools such as MadGraph and Pythia8.<br />
<br />
Contacts:<br />
<br />
Juan Rojo (VU Amsterdam & Nikhef): j.rojo at vu.nl<br />
<br />
Keri Vos (UM & Nikhef): k.vos at maastrichtuniversity.nl <br />
<br />
Jordy de Vries (UvA & Nikhef): j.devries4 at uva.nl<br />
<br />
== Bachelor Projects 2021 ==<br />
=== Dark Matter ===<br />
<br />
==== XAMS ====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso.<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with recently upgraded hardware to test a novel concept for UV light detection. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complete the first measurements with our upgraded setup.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== XENONnT reconstruction software ====<br />
The XENONnT experiment becomes operational during 2021. While the hwardware is finished we keep on developing and perfecting our reconstruction software. For this project we are looking for a student with a keen interest in and talent for writing physics based event reconstruction software (we use python). Specifically we have an idea to improve the localization of events inside the XENONnT for which proto-type software exists. The proto-type software needs to be implemented in the XENONnT reconstruction framework and subsequently it needs to be validated on the first data from the experiment. The final goal of the project is to deliver the reconstruction software to the collaboration that will be used during teh full lifetime of the experiment.<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Backgrounds in Radioactive Decay Measurements ====<br />
At Nikhef, the XENON group has a working setup, continuously monitoring the<br />
radioactive decay of Cobalt-60, Caesium-137 and Titanium-44. This beautiful setup is<br />
however not shielded perfectly; it is still vulnerable to background radioactivity. Our<br />
current way of working around this background radiation is to subtract it from our<br />
waveforms. You as a BSc student could help us hands-on and with analyses:<br />
together, we can disassemble the setup, measure background spectra and<br />
implement this in the data analysis. You can use all the data to validate the<br />
lifetime of our isotopes!<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Detection of scintillation light from liquid noble gasses ====<br />
<br />
The liquid form of the noble gases argon and xenon is a popular target material for neutrino and dark matter detectors. The scintillation light from noble gases is in the vacuum UV spectral region. Air and many materials used for optics studies are not transparent to these photons. Measurements of the optical properties of detector materials, such as their reflectivity for example, thus have to be performed with dedicated VUV optics and in vacuum. Additionally, to reproduce the conditions in the detectors, the samples must be cooled to cryogenic temperatures. In this BSc project, you will design, using professional hardware design software, a vacuum chamber to hold the detector materials whose optical properties are to be investigated, as well as the cooling system and photon detectors. You will learn about material requirements for rare event search detectors, vacuum instrumentation, vacuum UV optics including monochromators and spectrometers, and single-photon sensors.<br />
<br />
Supervisors: T. Pollmann (t.pollmann_at_nikhef.nl)<br />
<br />
=== Detector R&D ===<br />
<br />
==== Characterization of the new ultrathin ALPIDE monolithic active pixel sensor ====<br />
At the Large Hadron Collider at CERN, major upgrades of experiments take place in the long shutdown years where particle collisions are paused. The ALICE inner tracking system (ITS) 2, the part of the ALICE experiment closest to the beam pipe, is currently being installed at CERN. This detector makes use of ultra-lightweight monolithic active pixel sensors, the first to use this technology at particle colliders after the STAR experiment at RHIC in Brookhaven. These very thin pixel detectors have a low power consumption, result in very little material in the detector, and still have optimal timing and resolution -- and are a promising technology for future experiments. To characterize the performance of these sensors, you will learn to set up experiments, carry out measurements, and analyze data using various instruments available in the detector R&D lab at Nikhef. This could lead to novel insights of monolithic active pixel sensors. It is also possible to do measurements from home using data from the first test beams with bent (yes, with a curvature!) ALPIDE sensors. You will work in an international, stimulating research environment in the detector R&D group at Nikhef at the forefront of silicon detector technologies for high energy physics. ''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
==== Simulation of 3D silicon sensors ====<br />
<br />
For the upgrade of the vertex detector of the LHCb experiment novel silicon pixel detectors have to be developed that can register the passing particles with a time precision of tens of picoseconds. Given the harsh radiation environment very close to the LHCb interaction point only a limited number of technologies can be applied. One of the most promising technologies are the so-called 3D sensors whose readout electrodes are pillars that are placed into the sensor perpendicular to the surface; this in contrast to ’standard’ planar silicon sensors where the pixel electrodes are at the surface, similar to the camera in your smartphone. To understand the time response of these 3D sensors, simulations with TCAD software have to be performed and the results will be compared to measured data. These simulations involve the creation/adaptation of the 3D structures of the model, optimising the simulation speed, and analysing the signals as function voltage, track impact point and deposited charge. If time and Covid regulations permit, gaining some hands-on experience with such 3D sensors in the R&D labs at Nikhef is possible. ''Contacts: [mailto:martinb@nikhef.nl Martin van Beuzekom] [mailto:k.heijhoff@cern.ch Kevin Heijhoff] ''<br />
<br />
<br />
=== Theory ===<br />
<br />
==== Standard Model Effective Field Theory analysis of Z+dijet production ====<br />
The goal of this project is to study the effect of higher dimensional operators from the Standard Model Effective Field Theory in Z-boson production measured at LHC. The ATLAS collaboration has just reported in 2020 the measurement of Z production alongside with a pair of jets, based on the full Run II luminosity. In this project we aim to study the effect of dimension six SMEFT operators on the signal (EW-induced) and/or background (QCD-induced), finding which is the kinematic variable that maximises the possible effect of beyond the SM operators and thus may provide the best constraint on New Physics. The outcome of this project may be the first step of the inclusion of Vector production in a global SMEFT fit. <br />
<br />
References: https://arxiv.org/pdf/2006.15458.pdf, https://www.hepdata.net/record/ins1803608<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Maximum precision on new physics through information theory ====<br />
One way to look for physics beyond the standard model is through the framework of effective field theory. In this framework, deviations from the standard model are described by a set of continuous parameters. Finding constraints on these parameters might point to the discovery of new physics. With the large number of LHC experiments we currently face, we want to be able to quantify the maximum knowledge that (future) experiments can provide on new physics parameters. In this project, the student will study and quantify the maximum information that is contained in particle physics experiments through information theory. The central object of study will be the Fisher information matrix. The idea is to work with a simple toy experiment that describes Higgs physics and compute its associated Fisher information matrix to quantify the optimal bounds on new physics. The project will start with studying central objects from statistics and information theory. Later, we will apply these to open problems in particle physics.<br />
<br />
Reference: https://arxiv.org/pdf/1612.05261.pdf<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Seesaw mechanism and neutrino mass ==== <br />
Many unsolved questions in particle physics are related to the nature of the neutrino and its mass generation. The goal of this theoretical project is to understand and review one of the possible candidate theories that describe how neutrinos mix and get massive, namely the Seesaw mechanism. Among the many possible Seesaw mechanisms that can generate new phenomenology including lepton number non-conservation, the student will focus on one minimal model to understand the key processes that are currently used to probe the validity of the given theory. <br />
<br />
References: https://cds.cern.ch/record/408119/files/9911364.pdf, https://arxiv.org/pdf/1711.02180.pdf<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Mixing of sterile neutrinos ====<br />
<br />
Neutrino oscillation experiments demonstrate that neutrinos are massive particles. However, the mass mechanism of neutrinos is unknown. A<br />
minimal solution requires the existence of so-called sterile neutrinos: neutrinos that are even more elusive than ordinary neutrinos. <br />
We will investigate how to parametrize the matrix that describes the mixing between ordinary and sterile neutrinos. We will then use this<br />
to calculate how sterile neutrinos induce rare nuclear decays and determine the sensitivity of ongoing experiments to observe sterile<br />
neutrinos.<br />
<br />
Supervisor: Jordy de Vries (devries.jordy at gmail.com)<br />
<br />
<br />
=== KM3NeT ===<br />
<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
==== Data analysis of the first deployed KM3NeT detection lines ====<br />
<br />
First detection lines of the KM3NeT neutrino telescope have been deployed<br />
in the Mediterranean Sea, and a first data set is available. The lines consist<br />
of light-sensitive detectors that record the time of arrival of photons<br />
produced by relativistic particles in the deep sea, and their number.<br />
In this project we will study the first data to separate various components:<br />
photons from potassium decay, bioluminesence, sparks in the photomultipliers,<br />
downgoing muons from cosmic rays, and first neutrinos.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben (paul.de.jong at nikhef.nl)<br />
<br />
==== Neutrino oscillation measurements with the KM3NeT neutrino telescope ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope currently under construction<br />
will be able to measure the oscillations of neutrinos produced in interactions<br />
of cosmic rays with the earth atmosphere. Fundamental neutrino properties can<br />
be deduced from these oscillations measurements, in particular the so-called<br />
mass hierarchy of neutrinos. In this project we will simulate the ORCA measurements<br />
of neutrino oscillations, and study the dependence of the sensitivity on<br />
experimental uncertainties, such as energy resolution and neutrino flavour<br />
identification, and theoretical uncertainties, such as the atmospheric neutrino<br />
flux and neutrino cross sections. The results will help ORCA to identify<br />
the main sources of uncertainty, and therefore to actively try to reduce these<br />
and improve the final measurement.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong (paul.de.jong at nikhef.nl)<br />
<br />
==== Performance Studies of ORCA for Dark Matter Detection ====<br />
<br />
The interactions of neutrinos in KM3NeT-ORCA give different signatures which are categorised as track and shower events. This project involves the studies of muon, electron and tau neutrino interactions for the reconstruction performance of ORCA. Efficient reconstruction of such signals is important for Dark Matter searches in the low-mass regime. We will work on understanding the detector performance, e.g. effective acceptance, energy and angular resolution, with different configurations of the detector setup. The result of this study will be very useful to improve the sensitivity of the experiment for Dark Matter detection and its possible location. The student will have the opportunity to work closely with KM3NeT members at Nikhef and gain skills of analyzing data. <br />
<br />
Supervisors: Suzan Basegmez du Pree, Aart Heijboer (s.basegmez.du.pree at nikhef.nl)<br />
<br />
==== Study of Optical Properties of Sea Water using Hit Coincidences in MC Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
By studying coincidences of L1 hits between neighbouring DOMs, for various Monte Carlo (MC) data sets with different sea water optical properties such as scattering and absorption coefficients, in this project we try to figure out if and how well we can quantify optical sea water properties by studying L1 hit coincidences in real KM3NeT data.<br />
<br />
Supervisor: Daan van Eijk (dveijk at nikhef.nl)<br />
<br />
==== Determination of Inter-DOM Distances using Hit Coincidences in KM3NeT Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
The number of L1 hit coincidences from atmospheric muons between neighbouring DOMs on a DU is expected to decrease exponentially. By fitting the observed number of L1 hit coincidences between neighbouring DOMs in real data to the expected exponential decay, in this project we study how accurately we can determine the distances between DOMs on a single DU. In addition, we try to determine the distances between DUs by looking for L1 hit coincidences between DOMs on neighbouring DUs.<br />
<br />
Supervisor: Daan van Eijk (dveijk at nikhef.nl)<br />
<br />
<br />
=== ATLAS ===<br />
<br />
==== The Higgs boson life-time ====<br />
<br />
The Higgs particle does not have eternal life. The Standard Model (SM) predicts that it decays into other particles and as these couplings are fixed we can predict its life-time with very high precision. Determining this life-time is a crucial test for the Standard Model. If the Higgs boson life-time is shorter that we expect this could mean that the Higgs boson could decay into non-SM particles. In this project we investigate a) how we can identify Higgs particles in the detector and b) how we plan to use quantum-interference to get a handle on the Higgs boson's life-time. <br />
<br />
Supervisor: Wouter Verkerke (verkerke_at_nikhef.nl)<br />
<br />
==== The Higgs boson decaying to photons ====<br />
<br />
One of the main channels used to analyse the properties of the Higgs boson is when the Higgs boson decays into two photons. The crucial building block in this analysis is our ability to reconstruct the energy and the direction of the photons in the ATLAS detector and in this project we will revisit the photon reconstruction. We will start by studying simulations and learning about photon reconstruction in general. Then our goal is to determine the energy and position resolution of photons in the ATLAS detector and see if we can exploit our knowledge on the photon resolution to get an (improved) estimate of the Higgs boson mass. For the analysis we will use the '''real data from the LHC''' - the ATLAS open data project.<br />
<br />
Supervisor: Ashley McDougall and Ivo van Vulpen (Ivo.van.Vulpen_at_nikhef.nl)<br />
<br />
<br />
=== LHCb (1) ===<br />
<br />
One of the most fascinating mysteries in physics today is: how is it possible that universe is filled with matter? If the Big Bang produced equal amounts of matter and antimatter, we still do not understand the mechanism that lead to the excess of matter over antimatter that we observe today.<br />
<br />
One interesting feature of some particles is that they can transform themselves into their antiparticles, then back to particle, and so forth, in an oscillatory way until they finally decay. In particular, beauty mesons (B) can oscillate into their antiparticle (B ̄). The parameters of this oscillation, such as amplitude, frequency and phase, are calculable mathematically: predictions for it are available in the standard model (SM) of particle physics. But the oscillations according to the SM alone would not lead to the imbalance of matter in the universe – we still need to find a new type of physics that may be able to explain it.<br />
<br />
In this context, it is very important to measure B oscillations in the laboratory, and compare these observations with the expectations from the SM. Are the experimental data in good agreement with the SM, as we expect? If the aswer is not, i.e. if there are features of the oscillation that we do not understand well, then we may be observing “new physics”. In other words, the data may reveal a new mechanism that generates a different matter-antimatter balance than predicted by the SM, that may potentially solve the puzzle.<br />
<br />
The LHCb experiment at CERN is dedicated to such studies: LHCb detectors are placed in a region along the LHC collider beamline, where a large number of B mesons are produced, arising from the proton-proton collision data from the LHC collider. Looking at the LHCb data we can obtain large samples of B mesons, and observe their oscillations.<br />
In this project we will learn how to select a sample of B mesons out of the data taken with the LHCb detector, measure the parameters that govern their oscillation and compare them with the SM.<br />
<br />
For more information, please contact Mara Soares (msoares_at_nikhef.nl).<br />
<br />
== Bachelor Projects 2020 ==<br />
<br />
<br />
=== Dark Matter ===<br />
<br />
==== XAMS ====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso.<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source and liquid scintillatorneutron detector we have acquired for the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study of neutron transport in xenon.<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Backgrounds in Radioactive Decay Measurements ====<br />
At Nikhef, the XENON group has a working setup, continuously monitoring the<br />
radioactive decay of Cobalt-60, Caesium-137 and Titanium-44. This beautiful setup is<br />
however not shielded perfectly; it is still vulnerable to background radioactivity. Our<br />
current way of working around this background radiation is to subtract it from our<br />
waveforms. You as a BSc student could help us hands-on and with analyses:<br />
together, we can disassemble the setup, measure background spectra and<br />
implement this in the data analysis. You can use all the data to validate the<br />
lifetime of our isotopes!<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
=== ATLAS ===<br />
<br />
==== Project ATLAS-ITk ====<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
==== The Most Energetic Higgs Boson ====<br />
A common approach to search for physics beyond the standard model is by searching for the direct production of new particles. Alternatively, indirect quantum effects on the production of known particles -such as the Higgs Boson- could reveal the first cracks in the theory. Processes with high energy transfer are of particular potential since possible deviations are expected to increase with the square of the involved energy scale. Using the entire data-set collected by the ATLAS experiment at CERN during the four years of the LHC’s Run 2, a proof-of-principle analysis, targeting transverse momenta of the above 400 GeV, has been developed by Nikhef researchers. The first results of this Higgs boson study are expected to be published this year and this project aims to develop refinements of the analysis techniques. We will investigate the usage of sophisticated machine learning tools such as artificial neural networks, the search for new variables that can help discriminating the signal from its background, revisiting the analysis categorisation and improving the reconstruction techniques at these extreme momenta. Supervisors: Brian Moser and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs: The Next Generation ====<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks has been developed by Nikhef researchers and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays), advanced analysis techiques (using deep learning methods) and expanding the theory interpretation. Another opportunity would be the development of a new statistical combination with various independent searches, which could significantly improve the discovery potential. Supervisors: Marko Stamenkovic and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs interferentie ====<br />
In 2012 hebben het ATLAS en het CMS experiment het Higgs deeltje gevonden. Inmiddels zijn we het Higgs boson aan het bestuderen, hoe gedraagt het zich precies, bestaan er meer soorten Higgs bosonen of is er echt maar eentje van? In dit project leer je hoe we een Higgs boson kunnen herkennen in de detector en gaan we kijken naar hoe de signalen veranderen als er meer Higgs bosonen bestaan of misschien wel andere exotische nieuwe deeltjes. <br />
Dit doen we door gebruik te maken van quantum interferentie wat plaats vindt tussen het Higgs boson en achtergrondprocessen. Hoe dit precies werkt leer je in het project. Supervisor: Hella Snoek (h.snoek_at_nikhef.nl)<br />
<br />
=== B-Physics - LHCb ===<br />
<br />
==== Time dependent CP violation ====<br />
The LHCb experiment studies CP violation withB-meson decays.<br />
The project focusses on the measurement of the unitarity angle gamma using decays of the Bs mesons to Ds K.<br />
Supervisors: Sevda Esen & Michele Veronesi<br />
<br />
==== Machine learning ====<br />
Machine learning has proven to be an indispensable tool in the selection of interesting events in high energy physics. Such technologies will become increasingly important as detector upgrades are introduced and data rates increase by orders of magnitude. HEPDrone is a toolkit to enable the creation of a drone classifier from any machine learning classifier, such that different classifiers may be standardised into a single form and executed in parallel. A detailed evaluation of the performance of different drone models in the real production environment of LHCb will give the collaboration a complete idea of not only the advantages of the drone model, but also the limits of drone complexity given the available computing resources.<br />
Requirements: Advanced python and Advanced C++<br />
Supervisor: Sean Benson<br />
<br />
==== LHCb simulations of physics beyond the Standard Model ====<br />
This project is of relatively theoretical and computing nature and performs simulation studies for physics beyond the Standard Model in the context of long lived particles. It is related to test the sensitivity of the LHCb experiment to detect specific signals of physics beyond the Standard Model.<br />
supervisor: Carlos Vazquez Sierra<br />
<br />
=== Detector R&D ===<br />
<br />
==== Fast timing detectoren ====<br />
Op dit moment maken we veel gebruik van silicon detectoren in onze deeltjes experimenten. Deze zijn gevoelig voor geladen deeltjes en zijn bij uitstek geschikt om de paden vast te leggen die de deeltjes maken die in de botsingen worden gemaakt. Bijvoorbeeld in de Atlas en LHCb experimenten worden tientallen tot honderden deeltjes gemaakt bij elk botsingsgebeurtenis (event) die met 40MHz plaatsvinden. Voor toekomstige deeltjesdetectoren willen we niet alleen het traject vastleggen maar ook met grote precisie een tijdsmeting toevoegen. We hebben hiervoor dus nieuwe detectoren nodig die behalve met een hele hoge snelheid en efficientie de posities van de langsvliegende deeltjes kunnen vastleggen, maar hier ook een zeer nauwkeurige tijdsmeting (in orde van picosecondes) aan kunnen toevoegen. We hebben met verschillende detectoren metingen gedaan, in testbundels op CERN, maar ook in het lab op Nikhef kunnen we metingen doen. In dit project ga je samen met het fast-timing detectoren team op het Nikhef metingen verrichten en de resultaten hiervan bekijken. Contact: Hella Snoek (h.snoek@nikhef.nl)<br />
<br />
==== Muon tomography ====<br />
In this project we are not looking for where cosmic rays come from. We are looking for what we can use them for instead. The muons in cosmic rays can be used to ‘probe’ massive objects. Muons are short lived particles that carry the same charge as electrons, have a high penetrating power and can be detected relatively easy. It is possible to reconstruct a density distribution within an object by measuring muon scattering and absorption. In this context the objects may be freight containers, buildings, melting furnaces, etc… <br />
<br />
Systems that scan objects through the use of muons are often large (objects often need to be enclosed by the system) and complex. The question we want to answer is: Can we develop a smaller, simpler and cheaper system for muon tomography? <br />
<br />
A method to detect muons is by using a material that scintillates (emits light) when hit by an ionising particle. When this light emission is prompt after the passage of the muon, timing information of the light can be used to reconstruct the path of the muon.<br />
In this experiment we make a muon tracker based on two sheets of scintillating material and photo multiplier tubes (PMTs). Photo multiplier tubes are fast responding and very sensitive light detectors (capable of detecting single photons).<br />
<br />
The big question is: How well does this system perform?<br />
<br />
Currently a set-up is being build. You have a lot of freedom to choose a focus in this project (theory, simulation, hardware, or a combination of those).<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Spectral X-ray imaging - Looking at colours the eyes can't see ====<br />
When a conventional X-ray image is made to analyse the composition of a sample, or to perform a medical examination on a patient, one acquires an image that only shows intensities. One obtains a ‘black and white’ image. Most of the information carried by the photon energy is lost. Lacking spectral information can result in an ambiguity between material composition and amount of material in the sample. If the X-ray intensity as a function of the energy can be measured (i.e. a ‘colour’ X-ray image) more information can be obtained from a sample. This translates to less required dose and/or to a better understanding of the sample that is being investigated. For example, two fields that can benefit from spectral X-ray imaging are mammography and real time CT.<br />
<br />
X-ray detectors based on Medipix/Timepix pixel chips have spectral resolving capabilities and can be used to make polychromatic X-ray images. Medipix and Timepix chips have branched from pixel chips developed for detectors for high energy physics collider experiments.<br />
<br />
Some themes that students can work on: <br />
<br />
- Optimising methods to acquire spectral X-ray images.<br />
<br />
- Determining how much existing applications benefit from spectral X-ray imaging and looking for potential new applications.<br />
<br />
- Characterising, calibrating, optimising X-ray imaging detector systems.<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Holographic emitter ====<br />
A difficulty in generating holograms (based on the interference of light) is the required dense spatial light field sampling. One would need pixels of less than 200 nanometer. With larger pixels artefacts occur due to spatial under sampling. A pixel pitch of 200 nm or less is difficult, if not, impossible, to achieve, especially for larger areas. Another challenge is the massive amount of computing power that is required to control such a dense pixel matrix. <br />
<br />
A new holographic projection method has been developed that reduces under sampling artefacts, regardless of spatial sample density. The trick is to create 'pixels' at random but known positions, resulting in an array that lacks any spatial periodicity. As a result a holographic emitter can be built with a significantly lower sample density and less required computing power. This could bring holography in reach for many applications like display, lithography, 3D printing, metrology, etc...<br />
<br />
The big question: How does the performance of the holographic emitter depend on sample density and sample positions?<br />
<br />
The aspects of a holographic image we are interested in are:<br />
<br />
- Noise<br />
<br />
- Contrast<br />
<br />
- Suppression of under sampling artefacts<br />
<br />
- Resolution <br />
<br />
For this project we are building a proof of concept holographic emitter. This set-up will be used to verify simulation results (and to make some cool holograms of course). <br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
=== KM3NeT ===<br />
<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
==== Data analysis of the first deployed KM3NeT detection lines ====<br />
<br />
First detection lines of the KM3NeT neutrino telescope have been deployed<br />
in the Mediterranean Sea, and a first data set is available. The lines consist<br />
of light-sensitive detectors that record the time of arrival of photons<br />
produced by relativistic particles in the deep sea, and their number.<br />
In this project we will study the first data to separate various components:<br />
photons from potassium decay, bioluminesence, sparks in the photomultipliers,<br />
downgoing muons from cosmic rays, and perhaps first neutrinos.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Neutrino oscillation measurements with the KM3NeT neutrino telescope ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope currently under construction<br />
will be able to measure the oscillations of neutrinos produced in interactions<br />
of cosmic rays with the earth atmosphere. Fundamental neutrino properties can<br />
be deduced from these oscillations measurements, in particular the so-called<br />
mass hierarchy of neutrinos. In this project we will simulate the ORCA measurements<br />
of neutrino oscillations, and study the dependence of the sensitivity on<br />
experimental uncertainties, such as energy resolution and neutrino flavour<br />
identification, and theoretical uncertainties, such as the atmospheric neutrino<br />
flux and neutrino cross sections. The results will help ORCA to identify<br />
the main sources of uncertainty, and therefore to actively try to reduce these<br />
and improve the final measurement.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Performance Studies of ORCA for Dark Matter Detection ====<br />
<br />
The interactions of neutrinos in KM3NeT-ORCA give different signatures which are categorised as track and shower events. This project involves the studies of muon, electron and tau neutrino interactions for the reconstruction performance of ORCA. Efficient reconstruction of such signals is important for Dark Matter searches in the low-mass regime. We will work on understanding the detector performance, e.g. effective acceptance, energy and angular resolution, with different configurations of the detector setup. The result of this study will be very useful to improve the sensitivity of the experiment for Dark Matter detection and its possible location. The student will have the opportunity to work closely with KM3NeT members at Nikhef and gain skills of analyzing data. <br />
<br />
Supervisors: Suzan Basegmez du Pree, Aart Heijboer<br />
<br />
==== A search for periodic sources in Antares data ====<br />
<br />
The Antares deep-sea neutrino telescope has been operated for more then ten years. A search for periodic sources is proposed by applying a fast Fourier transformation (FFT) analysis on the available low-level data. This search will be combined with a (literature) study of pulsars which are thought to emit neutrinos.<br />
<br />
Supervisor: Maarten de Jong<br />
<br />
==== Study of Optical Properties of Sea Water using Hit Coincidences in MC Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
By studying coincidences of L1 hits between neighbouring DOMs, for various Monte Carlo (MC) data sets with different sea water optical properties such as scattering and absorption coefficients, in this project we try to figure out if and how well we can quantify optical sea water properties by studying L1 hit coincidences in real KM3NeT data.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
==== Determination of Inter-DOM Distances using Hit Coincidences in KM3NeT Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
The number of L1 hit coincidences from atmospheric muons between neighbouring DOMs on a DU is expected to decrease exponentially. By fitting the observed number of L1 hit coincidences between neighbouring DOMs in real data to the expected exponential decay, in this project we study how accurately we can determine the distances between DOMs on a single DU. In addition, we try to determine the distances between DUs by looking for L1 hit coincidences between DOMs on neighbouring DUs.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
=== VIRGO ===<br />
<br />
The Advanced LIGO and Advanced Virgo interferometers have recently observed gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results.<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Frank Linde (frank.linde_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
<br><br><br><br />
<br />
== Bachelor Projects 2017 ==<br />
<br />
=== Extreme Astronomy – Preparing for CTA, the Next-Generation Gamma-Ray Observatory ===<br />
<br />
The Cherenkov Telescope Array (CTA) is a planned facility for measuring gamma rays from space covering more than four orders of magnitude in energy, up to energies exceeding 100 TeV. CTA employs the imaging atmospheric Cherenkov technique to measure properties of cosmic gamma rays. This technique is based on measuring Cherenkov light emitted during the development of a gamma-ray air shower. CTA will be built at two experimental sites, one in the Northern, one in the Southern hemisphere, and will consist of up to 100 telescopes. It represents a major leap forward in sensitivity and precision for gamma-ray astronomy, and will allow us to explore very-high-energy processes of the extreme Universe at an unprecedented level.<br />
<br />
Two projects for students are available at the CTA group of UvA in the field of optical and photonic R&D contributing to the starting phase of CTA. For the first project the student will conduct measurements to characterise novel kinds of single-photon detectors, referred to as silicon photomultipliers, and evaluate different types of these sensors for their use for CTA. For the second project the student will develop and test an imaging system making use of a liquid crystal display. This flexible light source will be able to mimic images from different light sources of the night sky as seen by cameras of CTA, for instance gamma-ray air showers or stars, and will be used for camera tests and calibration.<br />
<br />
<br />
Supervisors: David Berge, Maurice Stephan (postdoc)<br />
<br />
=== Dark Matter ===<br />
<br />
<!--<br />
==== XENON1T - the world's most sensitive dark matter detector ====<br />
<br />
Finding the mysterious dark matter particles is one of the most challenging enterprises in physics today. Soon we will get first data from the world's most sensitive dark matter detector yet: the XENON1T experiment.<br />
<br />
The first goal of this project is to understand why dak matter is necessary to understand the universe, and how we could detect it with XENON1T. Then, you can contribute to our group's efforts preparing for <br />
and analyzing the XENON1T data by, for example: examining XENON1T's calibration signals to check for problems in the experiment, testing our data analysis software with simulated dark matter signals, or studying the physics behind XENON1T's detection process to learn how to better distinguish dark matter signals from backgrounds. For data analyis, experience with or willingness to learn programming in python is essential.<br />
<br />
<br />
Supervisors: M.P. Decowski & J. Aalbers --><br />
<br />
==== Neutrinoless double beta decay sensitivity study in future dark matter detectors ====<br />
<br />
The discovery of neutrino oscillation (Nobel Physics 2015) means that neutrinos have mass. We already know that their masses are tiny, more than one million times smaller than the next-lightest particle in the standard model, the electron. This raises the question if the mass-generation mechanism is the same for neutrinos as it is for the other subatomic particles. In particular, since neutrinos are electrically neutral, they could be their own anti-particles - we call these types of particles Majorana. The only practical way to discover if neutrinos are Majorana is through the search of an extremely rare radioactive decay called neutrinoless double beta decay (0n2b). A few isotopes are candidates for this process, among them Xe-136. The natural abundance of Xe-136 in natural xenon is about 9%, and this gives the opportunity to look for a 0n2b signal in xenon-based dark matter detectors like XENON1T and the future XENONnT and DARWIN detectors. <br />
<br />
We are looking for a student interested in doing a sensitivity study for 0n2b in XENONnT and the DARWIN experiments. The first goal will be to understand the physics addressed in neutrinoless double beta decay. Then the student will inventory possible backgrounds for the signal, use a (controversial) claim of a 0n2b signal as a benchmark and finally obtain the sensitivity of these future detectors. The work will involve simulations and analysis, building on an existing framework developed in our group. <br />
<br />
Supervisors: M.P. Decowski & A. Tiseni<br />
<br />
==== Shaking Dark Matter detectors ====<br />
<br />
Our XENON1T detector is built in the lab underneath the Gran Sasso mountains in central Italy. The lab is very well suited for low-background experiments due to the 1.5km of rock overburden. <br />
However, as you may know, cental Italy has been plagued by earthqaukes over the past decade, with the most recentones occurring in January 2017. We need a BSc student to investigate the <br />
details of such earthquakes in our underground lab. What are the magnitdues by which stuff is moving underground? What are the accelerations? What is the potential effect on our experimental<br />
setup? What would ahppen if an earthquake happens much closer to our lab? Furthermore we are interested to find out whether Earthquakes can be predicted. Some papers claim that before<br />
an earthquake the radon emanating from rock increases. In our lab we measure the radon concentration as a function of time: can you find a correlation between the measurements and recent <br />
earthquakes?<br />
<br />
If you are interested in finding out more about earthquakes, please contact M.P. Decowski or A.P. Colijn<br />
<br />
==== XAMS - a baby dark matter detector ====<br />
<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso<br />
we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector<br />
are identical to its big sibling in Gran Sasso.<br />
<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source we have acquired<br />
before the start of the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project<br />
will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study<br />
of neutron transport in xenon.<br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
==== Radon is bad for Dark Matter ====<br />
<br />
Radon is the dominant background for xenon based dark matter detectors, like the XENON1T experiment. In our lab at Nikhef we are investigating ways to reduce or eliminate the effect of radon<br />
on our sensitivity. For our lab setup XAMS we have designed and constructed a radon detector, that can be used in xenon systems at high-pressure. This completely new detector<br />
is now waiting for a BSc student to fully chracterize and use it. During this project you will first study the effect that radon contaminations have on dark matter detectors, then you will start working to<br />
understand our new radon detector in detail. You will learn howto use a radioactive source to calibrate the detector: this is something which is not easy and has not been done before in our lab. <br />
If you manage to succesfully calibrate the detector, we then want to incorporate it into our lab xenon system at Nikhef and maybe at some later stage in the real XENON1T detector!<br />
<br />
The profile of the student to work on this project is broad. I expect a good theoretical knowledge in order to quickly get upto speed with understanding dark mater detectors, and in addition I <br />
need 'lab-creativity' in order to develop methods for calibrating the new detector. If a good method is developed, it will be used for many years by the Nikhef dark matter group and beyond. <br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
=== ATLAS ===<br />
<br />
<br />
==== ATLAS (1): Searching for new physics with the Higgs and W bosons ====<br />
<br />
The strength of the Higgs interactions with electroweak bosons are precisely defined in the<br />
Standard Model. Therefore they are sensitive probes of the mechanism of electroweak symmetry<br />
breaking and enable searches for new physics beyond the SM. With the data collected by the ATLAS<br />
experiment in years 2015-2016 we plan to measure separately the Higgs coupling to<br />
longitudinally and transversely polarised W bosons in a process of weak boson fusion. To<br />
maximise experimental sensitivity we are developing techniques to separate the signal from<br />
background processes. You will take part in investigating possible improvements from<br />
reconstructing events in reference frames boosted with respect to the detector. During the<br />
project you will learn modern experimental analysis techniques. This project is a part of Vector<br />
Boson Scattering Coordination and Action Network (VBSCan) which connects researchers studying<br />
this and related topics worldwide.<br />
<br />
Supervisors: Pamela Ferrari, Magdalena Slawinska, Bob van Eijk<br />
<br />
<br />
==== ATLAS (2): Dark-matter-motivated searches for supersymmetric particles at the LHC ====<br />
<br />
Supersymmetry, a symmetry between fermions and bosons in particle physics,<br />
may provide a particle that could be the dark matter in the universe.<br />
The observation of an excess of gamma rays originating from the centre of our<br />
galaxy could be explained in a model where supersymmetric dark matter<br />
particles annihilate each other in the galactic centre, leading to gamma rays.<br />
<br />
Given the model parameters, it should also be possible to produce such<br />
particles at the LHC, at CERN in Geneva. But it is not so easy to observe<br />
them: the signal is small, and the noise (background) is large.<br />
In this project, we will use simulations of signal and background to<br />
optimize experimental searches for such particles with the ATLAS detector,<br />
apply them to the data collected in 2015, and prepare for the new data in<br />
2016 and later.Where possible, we will explore new machine learning techniques.<br />
<br />
Supervisors: Paul de Jong, Broos Vermeulen<br />
<br />
<br />
==== ATLAS (3): Simulations / Quality tests for the ATLAS High-Luminosity LHC Upgrade ====<br />
<br />
One of the key sub-systems of the ATLAS experiment at the Large<br />
Hadron Collider (LHC) is the Inner Detector (ID), designed to provide<br />
excellent charged particles momentum and vertex resolution measurements.<br />
<br />
At Phase-2 of the LHC run, in ~2025, the operating luminosity of<br />
the collider will be increased significantly.<br />
This will imply an upgrade of all ATLAS subsystems. In particular,<br />
the ID will be fully replaced with a tracker completely made of<br />
Silicon, having higher granularity and radiation hardness.<br />
The R&D process for the new ATLAS ID is now ongoing.<br />
Different geometrical layouts are simulated and their performance is<br />
studied under different operating conditions in search for the optimal<br />
detector architecture. Also, the performance of the new<br />
Si-sensors/modules is under investigation with dedicated laboratory tests.<br />
<br />
The focus of the project could be on the simulation of the High-Luminosity LHC<br />
version of the ATLAS Inner Detector. The student will learn how a<br />
high-energy physics experiment is designed and optimized.<br />
Alternatively, if possible at that moment, the student could<br />
work on a project at the Nikhef Silicon laboratory at the test-bench for<br />
new ATLAS Si-strip detectors and participate in the quality<br />
assurance procedure for the new ATLAS Si detectors.<br />
<br />
==== ATLAS (4): Higgs productie in Run-2 van de LHC ====<br />
In de eerste run van de LHC is onder andere bij het ATLAS experiment het Higgs deeltje gevonden. Nu is de tweede run begonnen en kan het Higgs deeltje worden bevestigd. Door de verhoogde energie ziet de achtergrond er echter heel anders uit, dus is de optimalisatie van het wegsnijden van de achtergronden qua fysica anders. Voor je bachelor project kan met behulp van de ATLAS detector het Higgs deeltje in run twee komen vinden. <br />
<br />
Supervisors: Lydia Brenner, Wouter Verkerke<br />
<br />
==== ATLAS (5): De lange staart van het Higgs boson ====<br />
<br />
[[File:HiggsMassa.png |thumb|left|upright=1.25]]<br />
<br />
<br><br />
Na de ontdekking van het Higgs boson in 2012 zijn we druk bezig om te kijken of zijn eigenschappen overeenkomen met de voorspellingen van het Standaard Model. Een van de belangrijkste eigenschappen is de zogenaamde breedte van het Higgs boson. Als het Higgs boson naast de Standaard Model deeltjes ook in exotische nieuwe speeltje uit elkaar kan vallen (bijvoorbeeld donkere materie) dan zal dat ale eerste zichtbaar worden in een afwijking van de breedte tov de verwachting. We gaan in dit project uitzoeken hoe de strategie die nu gebruikt wordt (meten van de hoeveelheid Higgs bosonen met een extreem hoge massa) precies werkt en kijken of we door het toevoegen van nieuwe ideeën een verbetering kunnen aanbrengen. <br />
<br />
<br><br />
Specifiek: We gaan eerst in detail de eigenschappen bekijken van het Higgs signaal en de twee achtergronden die er het meest op lijken. Daarna gaan we op zoek naar de verschillen en een manier waarop we onze kennis daarover kunnen gebruiken om gevoeliger te worden voor het Higgs signaal.<br />
<br />
Supervisors: Hella Snoek, Ivo van Vulpen<br />
<br />
E-mail: H.Snoek_at_nikhef.nl & Ivo.van.Vulpen_at_nikhef.nl<br />
<br><br><br><br><br><br><br />
<br />
=== ATLAS (6): Project ATLAS-ITk ===<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
<br><br />
<br />
=== KM3Net ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierachy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
The first phase of the KM3NeT neutrino telescope is currently under construction, with the first two detection units operational at 3500m depth in the Mediterranean Sea, 100 km off the coast of Sicily.<br />
<br />
<br />
==== KM3NeT (1): Photon counting in KM3NeT ====<br />
<br />
The details of a neutrino interaction, such as its incoming direction and energy, determine the pattern, time and amount, of recorded photons (´hits´) by the photo-multplier tubes. The time of arrival is recorded with nanosecond accuracy and the amount of photons is encoded in the length of the pulse(time-over-threshold, ToT). Currently, only the photon arrival time and the number of photo-multipliers that record a hit are used in reconstructing event properties.<br />
In this project, the distributions of the ToT mainly originating from photons from potassium-40 decays in the sea-water and from atmospheric muons passing through the water will be studied. The goals are to investigate the properties of the ToT distributions obtained from data and simulation, in particular the dependence on the photo-multiplier efficiency and atmospheric muon flux.<br />
In this project we will be extensively using the programming language C++ to analyse the data, so a reasonable proficiency is required.<br />
<br />
Supervisors: Ronald Bruijn & Karel Melis<br />
<br />
Email: rbruijn_at_nikhef.nl<br />
<br />
<br />
<br />
<br><br><br><br />
<br />
=== VIRGO ===<br />
<br />
"It is anticipated that in the next few years, Advanced LIGO and Advanced Virgo will start observing gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results."<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Jo van den Brand (jo_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
=== LHCb ===<br />
<br />
Begeleider: Sean Benson<br />
<br />
Title: <br />
Searching for physics beyond the Standard Model with LHCb<br />
<br />
The LHCb experiment is designed to study the "The Flavour Problem" in particle physics:<br />
Why is the universe dominated by matter over antimatter? Why are there three generations of elementary particles? What is the origin of quark flavour changing interactions.<br />
<br />
To solve these riddles, LHCb performs precision measurements on b-quark particle decays.<br />
An intriguing signal has recently been observed in the decay of a B-meson to a K* and two muons: Bd→K*μμ, which does not seem to behave according to the predictions of the Standard Model<br />
In this project the bachelor student will investigate this further by studying the case where the K* particle decays to a so-called k-short particle and a π0. The observation of such a final state will provide valuable information in the search for physics beyond the Standard Model.<br />
<br />
In this ambitious project the student is expected to study both a theory on the mechanism of CP violation with B mesons, in addition to data analysis with B decays. Programming experience in python is required.<br />
<br />
The LHCb experiment at CERN analyzes the properties of B-hadrons produced in proton-proton collisions at the LHC. For projects in the LHCb group, please contact Marcel Mark (marcel.merk_at_nikhef.nl)<br />
<br />
<br />
=== LHCb (1) ===<br />
<br />
One of the most fascinating mysteries in physics today is: how is it possible that universe is filled with matter? If the Big Bang produced equal amounts of matter and antimatter, we still do not understand the mechanism that lead to the excess of matter over antimatter that we observe today.<br />
<br />
One interesting feature of some particles is that they can transform themselves into their antiparticles, then back to particle, and so forth, in an oscillatory way until they finally decay. In particular, beauty mesons (B) can oscillate into their antiparticle (B ̄). The parameters of this oscillation, such as amplitude, frequency and phase, are calculable mathematically: predictions for it are available in the standard model (SM) of particle physics. But the oscillations according to the SM alone would not lead to the imbalance of matter in the universe – we still need to find a new type of physics that may be able to explain it.<br />
<br />
In this context, it is very important to measure B oscillations in the laboratory, and compare these observations with the expectations from the SM. Are the experimental data in good agreement with the SM, as we expect? If the aswer is not, i.e. if there are features of the oscillation that we do not understand well, then we may be observing “new physics”. In other words, the data may reveal a new mechanism that generates a different matter-antimatter balance than predicted by the SM, that may potentially solve the puzzle.<br />
<br />
The LHCb experiment at CERN is dedicated to such studies: LHCb detectors are placed in a region along the LHC collider beamline, where a large number of B mesons are produced, arising from the proton-proton collision data from the LHC collider. Looking at the LHCb data we can obtain large samples of B mesons, and observe their oscillations.<br />
In this project we will learn how to select a sample of B mesons out of the data taken with the LHCb detector, measure the parameters that govern their oscillation and compare them with the SM.<br />
<br />
For more information, please contact Mara Soares (msoares_at_nikhef.nl).</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Bachelor_Projects&diff=667Bachelor Projects2021-01-14T05:16:01Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>== Bachelor Projects 2021 ==<br />
<br />
=== Theory ===<br />
<br />
==== Standard Model Effective Field Theory analysis of Z+dijet production ====<br />
The goal of this project is to study the effect of higher dimensional operators from the Standard Model Effective Field Theory in Z-boson production measured at LHC. The ATLAS collaboration has just reported in 2020 the measurement of Z production alongside with a pair of jets, based on the full Run II luminosity. In this project we aim to study the effect of dimension six SMEFT operators on the signal (EW-induced) and/or background (QCD-induced), finding which is the kinematic variable that maximises the possible effect of beyond the SM operators and thus may provide the best constraint on New Physics. The outcome of this project may be the first step of the inclusion of Vector production in a global SMEFT fit. <br />
<br />
References: https://arxiv.org/pdf/2006.15458.pdf, https://www.hepdata.net/record/ins1803608<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
==== Maximum precision on new physics through information theory ====<br />
One way to look for physics beyond the standard model is through the framework of effective field theory. In this framework, deviations from the standard model are described by a set of continuous parameters. Finding constraints on these parameters might point to the discovery of new physics. With the large number of LHC experiments we currently face, we want to be able to quantify the maximum knowledge that (future) experiments can provide on new physics parameters. In this project, the student will study and quantify the maximum information that is contained in particle physics experiments through information theory. The central object of study will be the Fisher information matrix. The idea is to work with a simple toy experiment that describes Higgs physics and compute its associated Fisher information matrix to quantify the optimal bounds on new physics. The project will start with studying central objects from statistics and information theory. Later, we will apply these to open problems in particle physics.<br />
<br />
Reference: https://arxiv.org/pdf/1612.05261.pdf<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
<br />
==== Seesaw mechanism and neutrino mass ==== <br />
Many unsolved questions in particle physics are related to the nature of the neutrino and its mass generation. The goal of this theoretical project is to understand and review one of the possible candidate theories that describe how neutrinos mix and get massive, namely the Seesaw mechanism. Among the many possible Seesaw mechanisms that can generate new phenomenology including lepton number non-conservation, the student will focus on one minimal model to understand the key processes that are currently used to probe the validity of the given theory. <br />
<br />
References: https://cds.cern.ch/record/408119/files/9911364.pdf, https://arxiv.org/pdf/1711.02180.pdf<br />
<br />
Supervisor: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
<br />
== Bachelor Projects 2020 ==<br />
<br />
<br />
=== Dark Matter ===<br />
<br />
==== XAMS ====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso.<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source and liquid scintillatorneutron detector we have acquired for the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study of neutron transport in xenon.<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Backgrounds in Radioactive Decay Measurements ====<br />
At Nikhef, the XENON group has a working setup, continuously monitoring the<br />
radioactive decay of Cobalt-60, Caesium-137 and Titanium-44. This beautiful setup is<br />
however not shielded perfectly; it is still vulnerable to background radioactivity. Our<br />
current way of working around this background radiation is to subtract it from our<br />
waveforms. You as a BSc student could help us hands-on and with analyses:<br />
together, we can disassemble the setup, measure background spectra and<br />
implement this in the data analysis. You can use all the data to validate the<br />
lifetime of our isotopes!<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
=== ATLAS ===<br />
<br />
==== Project ATLAS-ITk ====<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
==== The Most Energetic Higgs Boson ====<br />
A common approach to search for physics beyond the standard model is by searching for the direct production of new particles. Alternatively, indirect quantum effects on the production of known particles -such as the Higgs Boson- could reveal the first cracks in the theory. Processes with high energy transfer are of particular potential since possible deviations are expected to increase with the square of the involved energy scale. Using the entire data-set collected by the ATLAS experiment at CERN during the four years of the LHC’s Run 2, a proof-of-principle analysis, targeting transverse momenta of the above 400 GeV, has been developed by Nikhef researchers. The first results of this Higgs boson study are expected to be published this year and this project aims to develop refinements of the analysis techniques. We will investigate the usage of sophisticated machine learning tools such as artificial neural networks, the search for new variables that can help discriminating the signal from its background, revisiting the analysis categorisation and improving the reconstruction techniques at these extreme momenta. Supervisors: Brian Moser and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs: The Next Generation ====<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks has been developed by Nikhef researchers and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays), advanced analysis techiques (using deep learning methods) and expanding the theory interpretation. Another opportunity would be the development of a new statistical combination with various independent searches, which could significantly improve the discovery potential. Supervisors: Marko Stamenkovic and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs interferentie ====<br />
In 2012 hebben het ATLAS en het CMS experiment het Higgs deeltje gevonden. Inmiddels zijn we het Higgs boson aan het bestuderen, hoe gedraagt het zich precies, bestaan er meer soorten Higgs bosonen of is er echt maar eentje van? In dit project leer je hoe we een Higgs boson kunnen herkennen in de detector en gaan we kijken naar hoe de signalen veranderen als er meer Higgs bosonen bestaan of misschien wel andere exotische nieuwe deeltjes. <br />
Dit doen we door gebruik te maken van quantum interferentie wat plaats vindt tussen het Higgs boson en achtergrondprocessen. Hoe dit precies werkt leer je in het project. Supervisor: Hella Snoek (h.snoek_at_nikhef.nl)<br />
<br />
=== B-Physics - LHCb ===<br />
<br />
==== Time dependent CP violation ====<br />
The LHCb experiment studies CP violation withB-meson decays.<br />
The project focusses on the measurement of the unitarity angle gamma using decays of the Bs mesons to Ds K.<br />
Supervisors: Sevda Esen & Michele Veronesi<br />
<br />
==== Machine learning ====<br />
Machine learning has proven to be an indispensable tool in the selection of interesting events in high energy physics. Such technologies will become increasingly important as detector upgrades are introduced and data rates increase by orders of magnitude. HEPDrone is a toolkit to enable the creation of a drone classifier from any machine learning classifier, such that different classifiers may be standardised into a single form and executed in parallel. A detailed evaluation of the performance of different drone models in the real production environment of LHCb will give the collaboration a complete idea of not only the advantages of the drone model, but also the limits of drone complexity given the available computing resources.<br />
Requirements: Advanced python and Advanced C++<br />
Supervisor: Sean Benson<br />
<br />
==== LHCb simulations of physics beyond the Standard Model ====<br />
This project is of relatively theoretical and computing nature and performs simulation studies for physics beyond the Standard Model in the context of long lived particles. It is related to test the sensitivity of the LHCb experiment to detect specific signals of physics beyond the Standard Model.<br />
supervisor: Carlos Vazquez Sierra<br />
<br />
=== Detector R&D ===<br />
<br />
==== Characterization of the new ultrathin ALPIDE monolithic active pixel sensor ====<br />
At the Large Hadron Collider at CERN, major upgrades of experiments take place in the long shutdown years where particle collisions are paused. The ALICE inner tracking system (ITS) 2, the part of the ALICE experiment closest to the beam pipe, is currently being installed at CERN. This detector makes use of ultra-lightweight monolithic active pixel sensors, the first to use this technology at particle colliders after the STAR experiment at RHIC in Brookhaven. These very thin pixel detectors have a low power consumption, result in very little material in the detector, and still have optimal timing and resolution -- and are a promising technology for future experiments. To characterize the performance of these sensors, you will learn to set up experiments, carry out measurements, and analyze data using various instruments available in the detector R&D lab at Nikhef. This could lead to novel insights of monolithic active pixel sensors. It is also possible to do measurements from home using data from the first test beams with bent (yes, with a curvature!) ALPIDE sensors. You will work in an international, stimulating research environment in the detector R&D group at Nikhef at the forefront of silicon detector technologies for high energy physics. ''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
==== Fast timing detectoren ====<br />
Op dit moment maken we veel gebruik van silicon detectoren in onze deeltjes experimenten. Deze zijn gevoelig voor geladen deeltjes en zijn bij uitstek geschikt om de paden vast te leggen die de deeltjes maken die in de botsingen worden gemaakt. Bijvoorbeeld in de Atlas en LHCb experimenten worden tientallen tot honderden deeltjes gemaakt bij elk botsingsgebeurtenis (event) die met 40MHz plaatsvinden. Voor toekomstige deeltjesdetectoren willen we niet alleen het traject vastleggen maar ook met grote precisie een tijdsmeting toevoegen. We hebben hiervoor dus nieuwe detectoren nodig die behalve met een hele hoge snelheid en efficientie de posities van de langsvliegende deeltjes kunnen vastleggen, maar hier ook een zeer nauwkeurige tijdsmeting (in orde van picosecondes) aan kunnen toevoegen. We hebben met verschillende detectoren metingen gedaan, in testbundels op CERN, maar ook in het lab op Nikhef kunnen we metingen doen. In dit project ga je samen met het fast-timing detectoren team op het Nikhef metingen verrichten en de resultaten hiervan bekijken. Contact: Hella Snoek (h.snoek@nikhef.nl)<br />
<br />
==== Muon tomography ====<br />
In this project we are not looking for where cosmic rays come from. We are looking for what we can use them for instead. The muons in cosmic rays can be used to ‘probe’ massive objects. Muons are short lived particles that carry the same charge as electrons, have a high penetrating power and can be detected relatively easy. It is possible to reconstruct a density distribution within an object by measuring muon scattering and absorption. In this context the objects may be freight containers, buildings, melting furnaces, etc… <br />
<br />
Systems that scan objects through the use of muons are often large (objects often need to be enclosed by the system) and complex. The question we want to answer is: Can we develop a smaller, simpler and cheaper system for muon tomography? <br />
<br />
A method to detect muons is by using a material that scintillates (emits light) when hit by an ionising particle. When this light emission is prompt after the passage of the muon, timing information of the light can be used to reconstruct the path of the muon.<br />
In this experiment we make a muon tracker based on two sheets of scintillating material and photo multiplier tubes (PMTs). Photo multiplier tubes are fast responding and very sensitive light detectors (capable of detecting single photons).<br />
<br />
The big question is: How well does this system perform?<br />
<br />
Currently a set-up is being build. You have a lot of freedom to choose a focus in this project (theory, simulation, hardware, or a combination of those).<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Spectral X-ray imaging - Looking at colours the eyes can't see ====<br />
When a conventional X-ray image is made to analyse the composition of a sample, or to perform a medical examination on a patient, one acquires an image that only shows intensities. One obtains a ‘black and white’ image. Most of the information carried by the photon energy is lost. Lacking spectral information can result in an ambiguity between material composition and amount of material in the sample. If the X-ray intensity as a function of the energy can be measured (i.e. a ‘colour’ X-ray image) more information can be obtained from a sample. This translates to less required dose and/or to a better understanding of the sample that is being investigated. For example, two fields that can benefit from spectral X-ray imaging are mammography and real time CT.<br />
<br />
X-ray detectors based on Medipix/Timepix pixel chips have spectral resolving capabilities and can be used to make polychromatic X-ray images. Medipix and Timepix chips have branched from pixel chips developed for detectors for high energy physics collider experiments.<br />
<br />
Some themes that students can work on: <br />
<br />
- Optimising methods to acquire spectral X-ray images.<br />
<br />
- Determining how much existing applications benefit from spectral X-ray imaging and looking for potential new applications.<br />
<br />
- Characterising, calibrating, optimising X-ray imaging detector systems.<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Holographic emitter ====<br />
A difficulty in generating holograms (based on the interference of light) is the required dense spatial light field sampling. One would need pixels of less than 200 nanometer. With larger pixels artefacts occur due to spatial under sampling. A pixel pitch of 200 nm or less is difficult, if not, impossible, to achieve, especially for larger areas. Another challenge is the massive amount of computing power that is required to control such a dense pixel matrix. <br />
<br />
A new holographic projection method has been developed that reduces under sampling artefacts, regardless of spatial sample density. The trick is to create 'pixels' at random but known positions, resulting in an array that lacks any spatial periodicity. As a result a holographic emitter can be built with a significantly lower sample density and less required computing power. This could bring holography in reach for many applications like display, lithography, 3D printing, metrology, etc...<br />
<br />
The big question: How does the performance of the holographic emitter depend on sample density and sample positions?<br />
<br />
The aspects of a holographic image we are interested in are:<br />
<br />
- Noise<br />
<br />
- Contrast<br />
<br />
- Suppression of under sampling artefacts<br />
<br />
- Resolution <br />
<br />
For this project we are building a proof of concept holographic emitter. This set-up will be used to verify simulation results (and to make some cool holograms of course). <br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
=== KM3NeT ===<br />
<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
==== Data analysis of the first deployed KM3NeT detection lines ====<br />
<br />
First detection lines of the KM3NeT neutrino telescope have been deployed<br />
in the Mediterranean Sea, and a first data set is available. The lines consist<br />
of light-sensitive detectors that record the time of arrival of photons<br />
produced by relativistic particles in the deep sea, and their number.<br />
In this project we will study the first data to separate various components:<br />
photons from potassium decay, bioluminesence, sparks in the photomultipliers,<br />
downgoing muons from cosmic rays, and perhaps first neutrinos.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Neutrino oscillation measurements with the KM3NeT neutrino telescope ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope currently under construction<br />
will be able to measure the oscillations of neutrinos produced in interactions<br />
of cosmic rays with the earth atmosphere. Fundamental neutrino properties can<br />
be deduced from these oscillations measurements, in particular the so-called<br />
mass hierarchy of neutrinos. In this project we will simulate the ORCA measurements<br />
of neutrino oscillations, and study the dependence of the sensitivity on<br />
experimental uncertainties, such as energy resolution and neutrino flavour<br />
identification, and theoretical uncertainties, such as the atmospheric neutrino<br />
flux and neutrino cross sections. The results will help ORCA to identify<br />
the main sources of uncertainty, and therefore to actively try to reduce these<br />
and improve the final measurement.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Performance Studies of ORCA for Dark Matter Detection ====<br />
<br />
The interactions of neutrinos in KM3NeT-ORCA give different signatures which are categorised as track and shower events. This project involves the studies of muon, electron and tau neutrino interactions for the reconstruction performance of ORCA. Efficient reconstruction of such signals is important for Dark Matter searches in the low-mass regime. We will work on understanding the detector performance, e.g. effective acceptance, energy and angular resolution, with different configurations of the detector setup. The result of this study will be very useful to improve the sensitivity of the experiment for Dark Matter detection and its possible location. The student will have the opportunity to work closely with KM3NeT members at Nikhef and gain skills of analyzing data. <br />
<br />
Supervisors: Suzan Basegmez du Pree, Aart Heijboer<br />
<br />
==== A search for periodic sources in Antares data ====<br />
<br />
The Antares deep-sea neutrino telescope has been operated for more then ten years. A search for periodic sources is proposed by applying a fast Fourier transformation (FFT) analysis on the available low-level data. This search will be combined with a (literature) study of pulsars which are thought to emit neutrinos.<br />
<br />
Supervisor: Maarten de Jong<br />
<br />
==== Study of Optical Properties of Sea Water using Hit Coincidences in MC Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
By studying coincidences of L1 hits between neighbouring DOMs, for various Monte Carlo (MC) data sets with different sea water optical properties such as scattering and absorption coefficients, in this project we try to figure out if and how well we can quantify optical sea water properties by studying L1 hit coincidences in real KM3NeT data.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
==== Determination of Inter-DOM Distances using Hit Coincidences in KM3NeT Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
The number of L1 hit coincidences from atmospheric muons between neighbouring DOMs on a DU is expected to decrease exponentially. By fitting the observed number of L1 hit coincidences between neighbouring DOMs in real data to the expected exponential decay, in this project we study how accurately we can determine the distances between DOMs on a single DU. In addition, we try to determine the distances between DUs by looking for L1 hit coincidences between DOMs on neighbouring DUs.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
=== VIRGO ===<br />
<br />
The Advanced LIGO and Advanced Virgo interferometers have recently observed gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results.<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Frank Linde (frank.linde_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
<br><br><br><br />
<br />
== Bachelor Projects 2017 ==<br />
<br />
=== Extreme Astronomy – Preparing for CTA, the Next-Generation Gamma-Ray Observatory ===<br />
<br />
The Cherenkov Telescope Array (CTA) is a planned facility for measuring gamma rays from space covering more than four orders of magnitude in energy, up to energies exceeding 100 TeV. CTA employs the imaging atmospheric Cherenkov technique to measure properties of cosmic gamma rays. This technique is based on measuring Cherenkov light emitted during the development of a gamma-ray air shower. CTA will be built at two experimental sites, one in the Northern, one in the Southern hemisphere, and will consist of up to 100 telescopes. It represents a major leap forward in sensitivity and precision for gamma-ray astronomy, and will allow us to explore very-high-energy processes of the extreme Universe at an unprecedented level.<br />
<br />
Two projects for students are available at the CTA group of UvA in the field of optical and photonic R&D contributing to the starting phase of CTA. For the first project the student will conduct measurements to characterise novel kinds of single-photon detectors, referred to as silicon photomultipliers, and evaluate different types of these sensors for their use for CTA. For the second project the student will develop and test an imaging system making use of a liquid crystal display. This flexible light source will be able to mimic images from different light sources of the night sky as seen by cameras of CTA, for instance gamma-ray air showers or stars, and will be used for camera tests and calibration.<br />
<br />
<br />
Supervisors: David Berge, Maurice Stephan (postdoc)<br />
<br />
=== Dark Matter ===<br />
<br />
<!--<br />
==== XENON1T - the world's most sensitive dark matter detector ====<br />
<br />
Finding the mysterious dark matter particles is one of the most challenging enterprises in physics today. Soon we will get first data from the world's most sensitive dark matter detector yet: the XENON1T experiment.<br />
<br />
The first goal of this project is to understand why dak matter is necessary to understand the universe, and how we could detect it with XENON1T. Then, you can contribute to our group's efforts preparing for <br />
and analyzing the XENON1T data by, for example: examining XENON1T's calibration signals to check for problems in the experiment, testing our data analysis software with simulated dark matter signals, or studying the physics behind XENON1T's detection process to learn how to better distinguish dark matter signals from backgrounds. For data analyis, experience with or willingness to learn programming in python is essential.<br />
<br />
<br />
Supervisors: M.P. Decowski & J. Aalbers --><br />
<br />
==== Neutrinoless double beta decay sensitivity study in future dark matter detectors ====<br />
<br />
The discovery of neutrino oscillation (Nobel Physics 2015) means that neutrinos have mass. We already know that their masses are tiny, more than one million times smaller than the next-lightest particle in the standard model, the electron. This raises the question if the mass-generation mechanism is the same for neutrinos as it is for the other subatomic particles. In particular, since neutrinos are electrically neutral, they could be their own anti-particles - we call these types of particles Majorana. The only practical way to discover if neutrinos are Majorana is through the search of an extremely rare radioactive decay called neutrinoless double beta decay (0n2b). A few isotopes are candidates for this process, among them Xe-136. The natural abundance of Xe-136 in natural xenon is about 9%, and this gives the opportunity to look for a 0n2b signal in xenon-based dark matter detectors like XENON1T and the future XENONnT and DARWIN detectors. <br />
<br />
We are looking for a student interested in doing a sensitivity study for 0n2b in XENONnT and the DARWIN experiments. The first goal will be to understand the physics addressed in neutrinoless double beta decay. Then the student will inventory possible backgrounds for the signal, use a (controversial) claim of a 0n2b signal as a benchmark and finally obtain the sensitivity of these future detectors. The work will involve simulations and analysis, building on an existing framework developed in our group. <br />
<br />
Supervisors: M.P. Decowski & A. Tiseni<br />
<br />
==== Shaking Dark Matter detectors ====<br />
<br />
Our XENON1T detector is built in the lab underneath the Gran Sasso mountains in central Italy. The lab is very well suited for low-background experiments due to the 1.5km of rock overburden. <br />
However, as you may know, cental Italy has been plagued by earthqaukes over the past decade, with the most recentones occurring in January 2017. We need a BSc student to investigate the <br />
details of such earthquakes in our underground lab. What are the magnitdues by which stuff is moving underground? What are the accelerations? What is the potential effect on our experimental<br />
setup? What would ahppen if an earthquake happens much closer to our lab? Furthermore we are interested to find out whether Earthquakes can be predicted. Some papers claim that before<br />
an earthquake the radon emanating from rock increases. In our lab we measure the radon concentration as a function of time: can you find a correlation between the measurements and recent <br />
earthquakes?<br />
<br />
If you are interested in finding out more about earthquakes, please contact M.P. Decowski or A.P. Colijn<br />
<br />
==== XAMS - a baby dark matter detector ====<br />
<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso<br />
we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector<br />
are identical to its big sibling in Gran Sasso.<br />
<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source we have acquired<br />
before the start of the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project<br />
will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study<br />
of neutron transport in xenon.<br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
==== Radon is bad for Dark Matter ====<br />
<br />
Radon is the dominant background for xenon based dark matter detectors, like the XENON1T experiment. In our lab at Nikhef we are investigating ways to reduce or eliminate the effect of radon<br />
on our sensitivity. For our lab setup XAMS we have designed and constructed a radon detector, that can be used in xenon systems at high-pressure. This completely new detector<br />
is now waiting for a BSc student to fully chracterize and use it. During this project you will first study the effect that radon contaminations have on dark matter detectors, then you will start working to<br />
understand our new radon detector in detail. You will learn howto use a radioactive source to calibrate the detector: this is something which is not easy and has not been done before in our lab. <br />
If you manage to succesfully calibrate the detector, we then want to incorporate it into our lab xenon system at Nikhef and maybe at some later stage in the real XENON1T detector!<br />
<br />
The profile of the student to work on this project is broad. I expect a good theoretical knowledge in order to quickly get upto speed with understanding dark mater detectors, and in addition I <br />
need 'lab-creativity' in order to develop methods for calibrating the new detector. If a good method is developed, it will be used for many years by the Nikhef dark matter group and beyond. <br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
=== ATLAS ===<br />
<br />
<br />
==== ATLAS (1): Searching for new physics with the Higgs and W bosons ====<br />
<br />
The strength of the Higgs interactions with electroweak bosons are precisely defined in the<br />
Standard Model. Therefore they are sensitive probes of the mechanism of electroweak symmetry<br />
breaking and enable searches for new physics beyond the SM. With the data collected by the ATLAS<br />
experiment in years 2015-2016 we plan to measure separately the Higgs coupling to<br />
longitudinally and transversely polarised W bosons in a process of weak boson fusion. To<br />
maximise experimental sensitivity we are developing techniques to separate the signal from<br />
background processes. You will take part in investigating possible improvements from<br />
reconstructing events in reference frames boosted with respect to the detector. During the<br />
project you will learn modern experimental analysis techniques. This project is a part of Vector<br />
Boson Scattering Coordination and Action Network (VBSCan) which connects researchers studying<br />
this and related topics worldwide.<br />
<br />
Supervisors: Pamela Ferrari, Magdalena Slawinska, Bob van Eijk<br />
<br />
<br />
==== ATLAS (2): Dark-matter-motivated searches for supersymmetric particles at the LHC ====<br />
<br />
Supersymmetry, a symmetry between fermions and bosons in particle physics,<br />
may provide a particle that could be the dark matter in the universe.<br />
The observation of an excess of gamma rays originating from the centre of our<br />
galaxy could be explained in a model where supersymmetric dark matter<br />
particles annihilate each other in the galactic centre, leading to gamma rays.<br />
<br />
Given the model parameters, it should also be possible to produce such<br />
particles at the LHC, at CERN in Geneva. But it is not so easy to observe<br />
them: the signal is small, and the noise (background) is large.<br />
In this project, we will use simulations of signal and background to<br />
optimize experimental searches for such particles with the ATLAS detector,<br />
apply them to the data collected in 2015, and prepare for the new data in<br />
2016 and later.Where possible, we will explore new machine learning techniques.<br />
<br />
Supervisors: Paul de Jong, Broos Vermeulen<br />
<br />
<br />
==== ATLAS (3): Simulations / Quality tests for the ATLAS High-Luminosity LHC Upgrade ====<br />
<br />
One of the key sub-systems of the ATLAS experiment at the Large<br />
Hadron Collider (LHC) is the Inner Detector (ID), designed to provide<br />
excellent charged particles momentum and vertex resolution measurements.<br />
<br />
At Phase-2 of the LHC run, in ~2025, the operating luminosity of<br />
the collider will be increased significantly.<br />
This will imply an upgrade of all ATLAS subsystems. In particular,<br />
the ID will be fully replaced with a tracker completely made of<br />
Silicon, having higher granularity and radiation hardness.<br />
The R&D process for the new ATLAS ID is now ongoing.<br />
Different geometrical layouts are simulated and their performance is<br />
studied under different operating conditions in search for the optimal<br />
detector architecture. Also, the performance of the new<br />
Si-sensors/modules is under investigation with dedicated laboratory tests.<br />
<br />
The focus of the project could be on the simulation of the High-Luminosity LHC<br />
version of the ATLAS Inner Detector. The student will learn how a<br />
high-energy physics experiment is designed and optimized.<br />
Alternatively, if possible at that moment, the student could<br />
work on a project at the Nikhef Silicon laboratory at the test-bench for<br />
new ATLAS Si-strip detectors and participate in the quality<br />
assurance procedure for the new ATLAS Si detectors.<br />
<br />
==== ATLAS (4): Higgs productie in Run-2 van de LHC ====<br />
In de eerste run van de LHC is onder andere bij het ATLAS experiment het Higgs deeltje gevonden. Nu is de tweede run begonnen en kan het Higgs deeltje worden bevestigd. Door de verhoogde energie ziet de achtergrond er echter heel anders uit, dus is de optimalisatie van het wegsnijden van de achtergronden qua fysica anders. Voor je bachelor project kan met behulp van de ATLAS detector het Higgs deeltje in run twee komen vinden. <br />
<br />
Supervisors: Lydia Brenner, Wouter Verkerke<br />
<br />
==== ATLAS (5): De lange staart van het Higgs boson ====<br />
<br />
[[File:HiggsMassa.png |thumb|left|upright=1.25]]<br />
<br />
<br><br />
Na de ontdekking van het Higgs boson in 2012 zijn we druk bezig om te kijken of zijn eigenschappen overeenkomen met de voorspellingen van het Standaard Model. Een van de belangrijkste eigenschappen is de zogenaamde breedte van het Higgs boson. Als het Higgs boson naast de Standaard Model deeltjes ook in exotische nieuwe speeltje uit elkaar kan vallen (bijvoorbeeld donkere materie) dan zal dat ale eerste zichtbaar worden in een afwijking van de breedte tov de verwachting. We gaan in dit project uitzoeken hoe de strategie die nu gebruikt wordt (meten van de hoeveelheid Higgs bosonen met een extreem hoge massa) precies werkt en kijken of we door het toevoegen van nieuwe ideeën een verbetering kunnen aanbrengen. <br />
<br />
<br><br />
Specifiek: We gaan eerst in detail de eigenschappen bekijken van het Higgs signaal en de twee achtergronden die er het meest op lijken. Daarna gaan we op zoek naar de verschillen en een manier waarop we onze kennis daarover kunnen gebruiken om gevoeliger te worden voor het Higgs signaal.<br />
<br />
Supervisors: Hella Snoek, Ivo van Vulpen<br />
<br />
E-mail: H.Snoek_at_nikhef.nl & Ivo.van.Vulpen_at_nikhef.nl<br />
<br><br><br><br><br><br><br />
<br />
=== ATLAS (6): Project ATLAS-ITk ===<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
<br><br />
<br />
=== KM3Net ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierachy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
The first phase of the KM3NeT neutrino telescope is currently under construction, with the first two detection units operational at 3500m depth in the Mediterranean Sea, 100 km off the coast of Sicily.<br />
<br />
<br />
==== KM3NeT (1): Photon counting in KM3NeT ====<br />
<br />
The details of a neutrino interaction, such as its incoming direction and energy, determine the pattern, time and amount, of recorded photons (´hits´) by the photo-multplier tubes. The time of arrival is recorded with nanosecond accuracy and the amount of photons is encoded in the length of the pulse(time-over-threshold, ToT). Currently, only the photon arrival time and the number of photo-multipliers that record a hit are used in reconstructing event properties.<br />
In this project, the distributions of the ToT mainly originating from photons from potassium-40 decays in the sea-water and from atmospheric muons passing through the water will be studied. The goals are to investigate the properties of the ToT distributions obtained from data and simulation, in particular the dependence on the photo-multiplier efficiency and atmospheric muon flux.<br />
In this project we will be extensively using the programming language C++ to analyse the data, so a reasonable proficiency is required.<br />
<br />
Supervisors: Ronald Bruijn & Karel Melis<br />
<br />
Email: rbruijn_at_nikhef.nl<br />
<br />
<br />
<br />
<br><br><br><br />
<br />
=== VIRGO ===<br />
<br />
"It is anticipated that in the next few years, Advanced LIGO and Advanced Virgo will start observing gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results."<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Jo van den Brand (jo_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
=== LHCb ===<br />
<br />
Begeleider: Sean Benson<br />
<br />
Title: <br />
Searching for physics beyond the Standard Model with LHCb<br />
<br />
The LHCb experiment is designed to study the "The Flavour Problem" in particle physics:<br />
Why is the universe dominated by matter over antimatter? Why are there three generations of elementary particles? What is the origin of quark flavour changing interactions.<br />
<br />
To solve these riddles, LHCb performs precision measurements on b-quark particle decays.<br />
An intriguing signal has recently been observed in the decay of a B-meson to a K* and two muons: Bd→K*μμ, which does not seem to behave according to the predictions of the Standard Model<br />
In this project the bachelor student will investigate this further by studying the case where the K* particle decays to a so-called k-short particle and a π0. The observation of such a final state will provide valuable information in the search for physics beyond the Standard Model.<br />
<br />
In this ambitious project the student is expected to study both a theory on the mechanism of CP violation with B mesons, in addition to data analysis with B decays. Programming experience in python is required.<br />
<br />
The LHCb experiment at CERN analyzes the properties of B-hadrons produced in proton-proton collisions at the LHC. For projects in the LHCb group, please contact Marcel Mark (marcel.merk_at_nikhef.nl)</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Bachelor_Projects&diff=666Bachelor Projects2021-01-14T05:14:35Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>== Bachelor Projects 2021 ==<br />
<br />
=== Theory ===<br />
<br />
==== Standard Model Effective Field Theory analysis of Z+dijet production ====<br />
The goal of this project is to study the effect of higher dimensional operators from the Standard Model Effective Field Theory in Z-boson production measured at LHC. The ATLAS collaboration has just reported in 2020 the measurement of Z production alongside with a pair of jets, based on the full Run II luminosity. In this project we aim to study the effect of dimension six SMEFT operators on the signal (EW-induced) and/or background (QCD-induced), finding which is the kinematic variable that maximises the possible effect of beyond the SM operators and thus may provide the best constraint on New Physics. The outcome of this project may be the first step of the inclusion of Vector production in a global SMEFT fit. <br />
<br />
References: https://arxiv.org/pdf/2006.15458.pdf, https://www.hepdata.net/record/ins1803608<br />
<br />
Supervisors: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
<br />
== Bachelor Projects 2020 ==<br />
<br />
<br />
=== Dark Matter ===<br />
<br />
==== XAMS ====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso.<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source and liquid scintillatorneutron detector we have acquired for the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study of neutron transport in xenon.<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Backgrounds in Radioactive Decay Measurements ====<br />
At Nikhef, the XENON group has a working setup, continuously monitoring the<br />
radioactive decay of Cobalt-60, Caesium-137 and Titanium-44. This beautiful setup is<br />
however not shielded perfectly; it is still vulnerable to background radioactivity. Our<br />
current way of working around this background radiation is to subtract it from our<br />
waveforms. You as a BSc student could help us hands-on and with analyses:<br />
together, we can disassemble the setup, measure background spectra and<br />
implement this in the data analysis. You can use all the data to validate the<br />
lifetime of our isotopes!<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
=== ATLAS ===<br />
<br />
==== Project ATLAS-ITk ====<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
==== The Most Energetic Higgs Boson ====<br />
A common approach to search for physics beyond the standard model is by searching for the direct production of new particles. Alternatively, indirect quantum effects on the production of known particles -such as the Higgs Boson- could reveal the first cracks in the theory. Processes with high energy transfer are of particular potential since possible deviations are expected to increase with the square of the involved energy scale. Using the entire data-set collected by the ATLAS experiment at CERN during the four years of the LHC’s Run 2, a proof-of-principle analysis, targeting transverse momenta of the above 400 GeV, has been developed by Nikhef researchers. The first results of this Higgs boson study are expected to be published this year and this project aims to develop refinements of the analysis techniques. We will investigate the usage of sophisticated machine learning tools such as artificial neural networks, the search for new variables that can help discriminating the signal from its background, revisiting the analysis categorisation and improving the reconstruction techniques at these extreme momenta. Supervisors: Brian Moser and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs: The Next Generation ====<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks has been developed by Nikhef researchers and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays), advanced analysis techiques (using deep learning methods) and expanding the theory interpretation. Another opportunity would be the development of a new statistical combination with various independent searches, which could significantly improve the discovery potential. Supervisors: Marko Stamenkovic and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs interferentie ====<br />
In 2012 hebben het ATLAS en het CMS experiment het Higgs deeltje gevonden. Inmiddels zijn we het Higgs boson aan het bestuderen, hoe gedraagt het zich precies, bestaan er meer soorten Higgs bosonen of is er echt maar eentje van? In dit project leer je hoe we een Higgs boson kunnen herkennen in de detector en gaan we kijken naar hoe de signalen veranderen als er meer Higgs bosonen bestaan of misschien wel andere exotische nieuwe deeltjes. <br />
Dit doen we door gebruik te maken van quantum interferentie wat plaats vindt tussen het Higgs boson en achtergrondprocessen. Hoe dit precies werkt leer je in het project. Supervisor: Hella Snoek (h.snoek_at_nikhef.nl)<br />
<br />
=== B-Physics - LHCb ===<br />
<br />
==== Time dependent CP violation ====<br />
The LHCb experiment studies CP violation withB-meson decays.<br />
The project focusses on the measurement of the unitarity angle gamma using decays of the Bs mesons to Ds K.<br />
Supervisors: Sevda Esen & Michele Veronesi<br />
<br />
==== Machine learning ====<br />
Machine learning has proven to be an indispensable tool in the selection of interesting events in high energy physics. Such technologies will become increasingly important as detector upgrades are introduced and data rates increase by orders of magnitude. HEPDrone is a toolkit to enable the creation of a drone classifier from any machine learning classifier, such that different classifiers may be standardised into a single form and executed in parallel. A detailed evaluation of the performance of different drone models in the real production environment of LHCb will give the collaboration a complete idea of not only the advantages of the drone model, but also the limits of drone complexity given the available computing resources.<br />
Requirements: Advanced python and Advanced C++<br />
Supervisor: Sean Benson<br />
<br />
==== LHCb simulations of physics beyond the Standard Model ====<br />
This project is of relatively theoretical and computing nature and performs simulation studies for physics beyond the Standard Model in the context of long lived particles. It is related to test the sensitivity of the LHCb experiment to detect specific signals of physics beyond the Standard Model.<br />
supervisor: Carlos Vazquez Sierra<br />
<br />
=== Detector R&D ===<br />
<br />
==== Characterization of the new ultrathin ALPIDE monolithic active pixel sensor ====<br />
At the Large Hadron Collider at CERN, major upgrades of experiments take place in the long shutdown years where particle collisions are paused. The ALICE inner tracking system (ITS) 2, the part of the ALICE experiment closest to the beam pipe, is currently being installed at CERN. This detector makes use of ultra-lightweight monolithic active pixel sensors, the first to use this technology at particle colliders after the STAR experiment at RHIC in Brookhaven. These very thin pixel detectors have a low power consumption, result in very little material in the detector, and still have optimal timing and resolution -- and are a promising technology for future experiments. To characterize the performance of these sensors, you will learn to set up experiments, carry out measurements, and analyze data using various instruments available in the detector R&D lab at Nikhef. This could lead to novel insights of monolithic active pixel sensors. It is also possible to do measurements from home using data from the first test beams with bent (yes, with a curvature!) ALPIDE sensors. You will work in an international, stimulating research environment in the detector R&D group at Nikhef at the forefront of silicon detector technologies for high energy physics. ''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
==== Fast timing detectoren ====<br />
Op dit moment maken we veel gebruik van silicon detectoren in onze deeltjes experimenten. Deze zijn gevoelig voor geladen deeltjes en zijn bij uitstek geschikt om de paden vast te leggen die de deeltjes maken die in de botsingen worden gemaakt. Bijvoorbeeld in de Atlas en LHCb experimenten worden tientallen tot honderden deeltjes gemaakt bij elk botsingsgebeurtenis (event) die met 40MHz plaatsvinden. Voor toekomstige deeltjesdetectoren willen we niet alleen het traject vastleggen maar ook met grote precisie een tijdsmeting toevoegen. We hebben hiervoor dus nieuwe detectoren nodig die behalve met een hele hoge snelheid en efficientie de posities van de langsvliegende deeltjes kunnen vastleggen, maar hier ook een zeer nauwkeurige tijdsmeting (in orde van picosecondes) aan kunnen toevoegen. We hebben met verschillende detectoren metingen gedaan, in testbundels op CERN, maar ook in het lab op Nikhef kunnen we metingen doen. In dit project ga je samen met het fast-timing detectoren team op het Nikhef metingen verrichten en de resultaten hiervan bekijken. Contact: Hella Snoek (h.snoek@nikhef.nl)<br />
<br />
==== Muon tomography ====<br />
In this project we are not looking for where cosmic rays come from. We are looking for what we can use them for instead. The muons in cosmic rays can be used to ‘probe’ massive objects. Muons are short lived particles that carry the same charge as electrons, have a high penetrating power and can be detected relatively easy. It is possible to reconstruct a density distribution within an object by measuring muon scattering and absorption. In this context the objects may be freight containers, buildings, melting furnaces, etc… <br />
<br />
Systems that scan objects through the use of muons are often large (objects often need to be enclosed by the system) and complex. The question we want to answer is: Can we develop a smaller, simpler and cheaper system for muon tomography? <br />
<br />
A method to detect muons is by using a material that scintillates (emits light) when hit by an ionising particle. When this light emission is prompt after the passage of the muon, timing information of the light can be used to reconstruct the path of the muon.<br />
In this experiment we make a muon tracker based on two sheets of scintillating material and photo multiplier tubes (PMTs). Photo multiplier tubes are fast responding and very sensitive light detectors (capable of detecting single photons).<br />
<br />
The big question is: How well does this system perform?<br />
<br />
Currently a set-up is being build. You have a lot of freedom to choose a focus in this project (theory, simulation, hardware, or a combination of those).<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Spectral X-ray imaging - Looking at colours the eyes can't see ====<br />
When a conventional X-ray image is made to analyse the composition of a sample, or to perform a medical examination on a patient, one acquires an image that only shows intensities. One obtains a ‘black and white’ image. Most of the information carried by the photon energy is lost. Lacking spectral information can result in an ambiguity between material composition and amount of material in the sample. If the X-ray intensity as a function of the energy can be measured (i.e. a ‘colour’ X-ray image) more information can be obtained from a sample. This translates to less required dose and/or to a better understanding of the sample that is being investigated. For example, two fields that can benefit from spectral X-ray imaging are mammography and real time CT.<br />
<br />
X-ray detectors based on Medipix/Timepix pixel chips have spectral resolving capabilities and can be used to make polychromatic X-ray images. Medipix and Timepix chips have branched from pixel chips developed for detectors for high energy physics collider experiments.<br />
<br />
Some themes that students can work on: <br />
<br />
- Optimising methods to acquire spectral X-ray images.<br />
<br />
- Determining how much existing applications benefit from spectral X-ray imaging and looking for potential new applications.<br />
<br />
- Characterising, calibrating, optimising X-ray imaging detector systems.<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Holographic emitter ====<br />
A difficulty in generating holograms (based on the interference of light) is the required dense spatial light field sampling. One would need pixels of less than 200 nanometer. With larger pixels artefacts occur due to spatial under sampling. A pixel pitch of 200 nm or less is difficult, if not, impossible, to achieve, especially for larger areas. Another challenge is the massive amount of computing power that is required to control such a dense pixel matrix. <br />
<br />
A new holographic projection method has been developed that reduces under sampling artefacts, regardless of spatial sample density. The trick is to create 'pixels' at random but known positions, resulting in an array that lacks any spatial periodicity. As a result a holographic emitter can be built with a significantly lower sample density and less required computing power. This could bring holography in reach for many applications like display, lithography, 3D printing, metrology, etc...<br />
<br />
The big question: How does the performance of the holographic emitter depend on sample density and sample positions?<br />
<br />
The aspects of a holographic image we are interested in are:<br />
<br />
- Noise<br />
<br />
- Contrast<br />
<br />
- Suppression of under sampling artefacts<br />
<br />
- Resolution <br />
<br />
For this project we are building a proof of concept holographic emitter. This set-up will be used to verify simulation results (and to make some cool holograms of course). <br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
=== KM3NeT ===<br />
<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
==== Data analysis of the first deployed KM3NeT detection lines ====<br />
<br />
First detection lines of the KM3NeT neutrino telescope have been deployed<br />
in the Mediterranean Sea, and a first data set is available. The lines consist<br />
of light-sensitive detectors that record the time of arrival of photons<br />
produced by relativistic particles in the deep sea, and their number.<br />
In this project we will study the first data to separate various components:<br />
photons from potassium decay, bioluminesence, sparks in the photomultipliers,<br />
downgoing muons from cosmic rays, and perhaps first neutrinos.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Neutrino oscillation measurements with the KM3NeT neutrino telescope ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope currently under construction<br />
will be able to measure the oscillations of neutrinos produced in interactions<br />
of cosmic rays with the earth atmosphere. Fundamental neutrino properties can<br />
be deduced from these oscillations measurements, in particular the so-called<br />
mass hierarchy of neutrinos. In this project we will simulate the ORCA measurements<br />
of neutrino oscillations, and study the dependence of the sensitivity on<br />
experimental uncertainties, such as energy resolution and neutrino flavour<br />
identification, and theoretical uncertainties, such as the atmospheric neutrino<br />
flux and neutrino cross sections. The results will help ORCA to identify<br />
the main sources of uncertainty, and therefore to actively try to reduce these<br />
and improve the final measurement.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Performance Studies of ORCA for Dark Matter Detection ====<br />
<br />
The interactions of neutrinos in KM3NeT-ORCA give different signatures which are categorised as track and shower events. This project involves the studies of muon, electron and tau neutrino interactions for the reconstruction performance of ORCA. Efficient reconstruction of such signals is important for Dark Matter searches in the low-mass regime. We will work on understanding the detector performance, e.g. effective acceptance, energy and angular resolution, with different configurations of the detector setup. The result of this study will be very useful to improve the sensitivity of the experiment for Dark Matter detection and its possible location. The student will have the opportunity to work closely with KM3NeT members at Nikhef and gain skills of analyzing data. <br />
<br />
Supervisors: Suzan Basegmez du Pree, Aart Heijboer<br />
<br />
==== A search for periodic sources in Antares data ====<br />
<br />
The Antares deep-sea neutrino telescope has been operated for more then ten years. A search for periodic sources is proposed by applying a fast Fourier transformation (FFT) analysis on the available low-level data. This search will be combined with a (literature) study of pulsars which are thought to emit neutrinos.<br />
<br />
Supervisor: Maarten de Jong<br />
<br />
==== Study of Optical Properties of Sea Water using Hit Coincidences in MC Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
By studying coincidences of L1 hits between neighbouring DOMs, for various Monte Carlo (MC) data sets with different sea water optical properties such as scattering and absorption coefficients, in this project we try to figure out if and how well we can quantify optical sea water properties by studying L1 hit coincidences in real KM3NeT data.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
==== Determination of Inter-DOM Distances using Hit Coincidences in KM3NeT Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
The number of L1 hit coincidences from atmospheric muons between neighbouring DOMs on a DU is expected to decrease exponentially. By fitting the observed number of L1 hit coincidences between neighbouring DOMs in real data to the expected exponential decay, in this project we study how accurately we can determine the distances between DOMs on a single DU. In addition, we try to determine the distances between DUs by looking for L1 hit coincidences between DOMs on neighbouring DUs.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
=== VIRGO ===<br />
<br />
The Advanced LIGO and Advanced Virgo interferometers have recently observed gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results.<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Frank Linde (frank.linde_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
<br><br><br><br />
<br />
== Bachelor Projects 2017 ==<br />
<br />
=== Extreme Astronomy – Preparing for CTA, the Next-Generation Gamma-Ray Observatory ===<br />
<br />
The Cherenkov Telescope Array (CTA) is a planned facility for measuring gamma rays from space covering more than four orders of magnitude in energy, up to energies exceeding 100 TeV. CTA employs the imaging atmospheric Cherenkov technique to measure properties of cosmic gamma rays. This technique is based on measuring Cherenkov light emitted during the development of a gamma-ray air shower. CTA will be built at two experimental sites, one in the Northern, one in the Southern hemisphere, and will consist of up to 100 telescopes. It represents a major leap forward in sensitivity and precision for gamma-ray astronomy, and will allow us to explore very-high-energy processes of the extreme Universe at an unprecedented level.<br />
<br />
Two projects for students are available at the CTA group of UvA in the field of optical and photonic R&D contributing to the starting phase of CTA. For the first project the student will conduct measurements to characterise novel kinds of single-photon detectors, referred to as silicon photomultipliers, and evaluate different types of these sensors for their use for CTA. For the second project the student will develop and test an imaging system making use of a liquid crystal display. This flexible light source will be able to mimic images from different light sources of the night sky as seen by cameras of CTA, for instance gamma-ray air showers or stars, and will be used for camera tests and calibration.<br />
<br />
<br />
Supervisors: David Berge, Maurice Stephan (postdoc)<br />
<br />
=== Dark Matter ===<br />
<br />
<!--<br />
==== XENON1T - the world's most sensitive dark matter detector ====<br />
<br />
Finding the mysterious dark matter particles is one of the most challenging enterprises in physics today. Soon we will get first data from the world's most sensitive dark matter detector yet: the XENON1T experiment.<br />
<br />
The first goal of this project is to understand why dak matter is necessary to understand the universe, and how we could detect it with XENON1T. Then, you can contribute to our group's efforts preparing for <br />
and analyzing the XENON1T data by, for example: examining XENON1T's calibration signals to check for problems in the experiment, testing our data analysis software with simulated dark matter signals, or studying the physics behind XENON1T's detection process to learn how to better distinguish dark matter signals from backgrounds. For data analyis, experience with or willingness to learn programming in python is essential.<br />
<br />
<br />
Supervisors: M.P. Decowski & J. Aalbers --><br />
<br />
==== Neutrinoless double beta decay sensitivity study in future dark matter detectors ====<br />
<br />
The discovery of neutrino oscillation (Nobel Physics 2015) means that neutrinos have mass. We already know that their masses are tiny, more than one million times smaller than the next-lightest particle in the standard model, the electron. This raises the question if the mass-generation mechanism is the same for neutrinos as it is for the other subatomic particles. In particular, since neutrinos are electrically neutral, they could be their own anti-particles - we call these types of particles Majorana. The only practical way to discover if neutrinos are Majorana is through the search of an extremely rare radioactive decay called neutrinoless double beta decay (0n2b). A few isotopes are candidates for this process, among them Xe-136. The natural abundance of Xe-136 in natural xenon is about 9%, and this gives the opportunity to look for a 0n2b signal in xenon-based dark matter detectors like XENON1T and the future XENONnT and DARWIN detectors. <br />
<br />
We are looking for a student interested in doing a sensitivity study for 0n2b in XENONnT and the DARWIN experiments. The first goal will be to understand the physics addressed in neutrinoless double beta decay. Then the student will inventory possible backgrounds for the signal, use a (controversial) claim of a 0n2b signal as a benchmark and finally obtain the sensitivity of these future detectors. The work will involve simulations and analysis, building on an existing framework developed in our group. <br />
<br />
Supervisors: M.P. Decowski & A. Tiseni<br />
<br />
==== Shaking Dark Matter detectors ====<br />
<br />
Our XENON1T detector is built in the lab underneath the Gran Sasso mountains in central Italy. The lab is very well suited for low-background experiments due to the 1.5km of rock overburden. <br />
However, as you may know, cental Italy has been plagued by earthqaukes over the past decade, with the most recentones occurring in January 2017. We need a BSc student to investigate the <br />
details of such earthquakes in our underground lab. What are the magnitdues by which stuff is moving underground? What are the accelerations? What is the potential effect on our experimental<br />
setup? What would ahppen if an earthquake happens much closer to our lab? Furthermore we are interested to find out whether Earthquakes can be predicted. Some papers claim that before<br />
an earthquake the radon emanating from rock increases. In our lab we measure the radon concentration as a function of time: can you find a correlation between the measurements and recent <br />
earthquakes?<br />
<br />
If you are interested in finding out more about earthquakes, please contact M.P. Decowski or A.P. Colijn<br />
<br />
==== XAMS - a baby dark matter detector ====<br />
<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso<br />
we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector<br />
are identical to its big sibling in Gran Sasso.<br />
<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source we have acquired<br />
before the start of the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project<br />
will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study<br />
of neutron transport in xenon.<br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
==== Radon is bad for Dark Matter ====<br />
<br />
Radon is the dominant background for xenon based dark matter detectors, like the XENON1T experiment. In our lab at Nikhef we are investigating ways to reduce or eliminate the effect of radon<br />
on our sensitivity. For our lab setup XAMS we have designed and constructed a radon detector, that can be used in xenon systems at high-pressure. This completely new detector<br />
is now waiting for a BSc student to fully chracterize and use it. During this project you will first study the effect that radon contaminations have on dark matter detectors, then you will start working to<br />
understand our new radon detector in detail. You will learn howto use a radioactive source to calibrate the detector: this is something which is not easy and has not been done before in our lab. <br />
If you manage to succesfully calibrate the detector, we then want to incorporate it into our lab xenon system at Nikhef and maybe at some later stage in the real XENON1T detector!<br />
<br />
The profile of the student to work on this project is broad. I expect a good theoretical knowledge in order to quickly get upto speed with understanding dark mater detectors, and in addition I <br />
need 'lab-creativity' in order to develop methods for calibrating the new detector. If a good method is developed, it will be used for many years by the Nikhef dark matter group and beyond. <br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
=== ATLAS ===<br />
<br />
<br />
==== ATLAS (1): Searching for new physics with the Higgs and W bosons ====<br />
<br />
The strength of the Higgs interactions with electroweak bosons are precisely defined in the<br />
Standard Model. Therefore they are sensitive probes of the mechanism of electroweak symmetry<br />
breaking and enable searches for new physics beyond the SM. With the data collected by the ATLAS<br />
experiment in years 2015-2016 we plan to measure separately the Higgs coupling to<br />
longitudinally and transversely polarised W bosons in a process of weak boson fusion. To<br />
maximise experimental sensitivity we are developing techniques to separate the signal from<br />
background processes. You will take part in investigating possible improvements from<br />
reconstructing events in reference frames boosted with respect to the detector. During the<br />
project you will learn modern experimental analysis techniques. This project is a part of Vector<br />
Boson Scattering Coordination and Action Network (VBSCan) which connects researchers studying<br />
this and related topics worldwide.<br />
<br />
Supervisors: Pamela Ferrari, Magdalena Slawinska, Bob van Eijk<br />
<br />
<br />
==== ATLAS (2): Dark-matter-motivated searches for supersymmetric particles at the LHC ====<br />
<br />
Supersymmetry, a symmetry between fermions and bosons in particle physics,<br />
may provide a particle that could be the dark matter in the universe.<br />
The observation of an excess of gamma rays originating from the centre of our<br />
galaxy could be explained in a model where supersymmetric dark matter<br />
particles annihilate each other in the galactic centre, leading to gamma rays.<br />
<br />
Given the model parameters, it should also be possible to produce such<br />
particles at the LHC, at CERN in Geneva. But it is not so easy to observe<br />
them: the signal is small, and the noise (background) is large.<br />
In this project, we will use simulations of signal and background to<br />
optimize experimental searches for such particles with the ATLAS detector,<br />
apply them to the data collected in 2015, and prepare for the new data in<br />
2016 and later.Where possible, we will explore new machine learning techniques.<br />
<br />
Supervisors: Paul de Jong, Broos Vermeulen<br />
<br />
<br />
==== ATLAS (3): Simulations / Quality tests for the ATLAS High-Luminosity LHC Upgrade ====<br />
<br />
One of the key sub-systems of the ATLAS experiment at the Large<br />
Hadron Collider (LHC) is the Inner Detector (ID), designed to provide<br />
excellent charged particles momentum and vertex resolution measurements.<br />
<br />
At Phase-2 of the LHC run, in ~2025, the operating luminosity of<br />
the collider will be increased significantly.<br />
This will imply an upgrade of all ATLAS subsystems. In particular,<br />
the ID will be fully replaced with a tracker completely made of<br />
Silicon, having higher granularity and radiation hardness.<br />
The R&D process for the new ATLAS ID is now ongoing.<br />
Different geometrical layouts are simulated and their performance is<br />
studied under different operating conditions in search for the optimal<br />
detector architecture. Also, the performance of the new<br />
Si-sensors/modules is under investigation with dedicated laboratory tests.<br />
<br />
The focus of the project could be on the simulation of the High-Luminosity LHC<br />
version of the ATLAS Inner Detector. The student will learn how a<br />
high-energy physics experiment is designed and optimized.<br />
Alternatively, if possible at that moment, the student could<br />
work on a project at the Nikhef Silicon laboratory at the test-bench for<br />
new ATLAS Si-strip detectors and participate in the quality<br />
assurance procedure for the new ATLAS Si detectors.<br />
<br />
==== ATLAS (4): Higgs productie in Run-2 van de LHC ====<br />
In de eerste run van de LHC is onder andere bij het ATLAS experiment het Higgs deeltje gevonden. Nu is de tweede run begonnen en kan het Higgs deeltje worden bevestigd. Door de verhoogde energie ziet de achtergrond er echter heel anders uit, dus is de optimalisatie van het wegsnijden van de achtergronden qua fysica anders. Voor je bachelor project kan met behulp van de ATLAS detector het Higgs deeltje in run twee komen vinden. <br />
<br />
Supervisors: Lydia Brenner, Wouter Verkerke<br />
<br />
==== ATLAS (5): De lange staart van het Higgs boson ====<br />
<br />
[[File:HiggsMassa.png |thumb|left|upright=1.25]]<br />
<br />
<br><br />
Na de ontdekking van het Higgs boson in 2012 zijn we druk bezig om te kijken of zijn eigenschappen overeenkomen met de voorspellingen van het Standaard Model. Een van de belangrijkste eigenschappen is de zogenaamde breedte van het Higgs boson. Als het Higgs boson naast de Standaard Model deeltjes ook in exotische nieuwe speeltje uit elkaar kan vallen (bijvoorbeeld donkere materie) dan zal dat ale eerste zichtbaar worden in een afwijking van de breedte tov de verwachting. We gaan in dit project uitzoeken hoe de strategie die nu gebruikt wordt (meten van de hoeveelheid Higgs bosonen met een extreem hoge massa) precies werkt en kijken of we door het toevoegen van nieuwe ideeën een verbetering kunnen aanbrengen. <br />
<br />
<br><br />
Specifiek: We gaan eerst in detail de eigenschappen bekijken van het Higgs signaal en de twee achtergronden die er het meest op lijken. Daarna gaan we op zoek naar de verschillen en een manier waarop we onze kennis daarover kunnen gebruiken om gevoeliger te worden voor het Higgs signaal.<br />
<br />
Supervisors: Hella Snoek, Ivo van Vulpen<br />
<br />
E-mail: H.Snoek_at_nikhef.nl & Ivo.van.Vulpen_at_nikhef.nl<br />
<br><br><br><br><br><br><br />
<br />
=== ATLAS (6): Project ATLAS-ITk ===<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
<br><br />
<br />
=== KM3Net ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierachy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
The first phase of the KM3NeT neutrino telescope is currently under construction, with the first two detection units operational at 3500m depth in the Mediterranean Sea, 100 km off the coast of Sicily.<br />
<br />
<br />
==== KM3NeT (1): Photon counting in KM3NeT ====<br />
<br />
The details of a neutrino interaction, such as its incoming direction and energy, determine the pattern, time and amount, of recorded photons (´hits´) by the photo-multplier tubes. The time of arrival is recorded with nanosecond accuracy and the amount of photons is encoded in the length of the pulse(time-over-threshold, ToT). Currently, only the photon arrival time and the number of photo-multipliers that record a hit are used in reconstructing event properties.<br />
In this project, the distributions of the ToT mainly originating from photons from potassium-40 decays in the sea-water and from atmospheric muons passing through the water will be studied. The goals are to investigate the properties of the ToT distributions obtained from data and simulation, in particular the dependence on the photo-multiplier efficiency and atmospheric muon flux.<br />
In this project we will be extensively using the programming language C++ to analyse the data, so a reasonable proficiency is required.<br />
<br />
Supervisors: Ronald Bruijn & Karel Melis<br />
<br />
Email: rbruijn_at_nikhef.nl<br />
<br />
<br />
<br />
<br><br><br><br />
<br />
=== VIRGO ===<br />
<br />
"It is anticipated that in the next few years, Advanced LIGO and Advanced Virgo will start observing gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results."<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Jo van den Brand (jo_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
=== LHCb ===<br />
<br />
Begeleider: Sean Benson<br />
<br />
Title: <br />
Searching for physics beyond the Standard Model with LHCb<br />
<br />
The LHCb experiment is designed to study the "The Flavour Problem" in particle physics:<br />
Why is the universe dominated by matter over antimatter? Why are there three generations of elementary particles? What is the origin of quark flavour changing interactions.<br />
<br />
To solve these riddles, LHCb performs precision measurements on b-quark particle decays.<br />
An intriguing signal has recently been observed in the decay of a B-meson to a K* and two muons: Bd→K*μμ, which does not seem to behave according to the predictions of the Standard Model<br />
In this project the bachelor student will investigate this further by studying the case where the K* particle decays to a so-called k-short particle and a π0. The observation of such a final state will provide valuable information in the search for physics beyond the Standard Model.<br />
<br />
In this ambitious project the student is expected to study both a theory on the mechanism of CP violation with B mesons, in addition to data analysis with B decays. Programming experience in python is required.<br />
<br />
The LHCb experiment at CERN analyzes the properties of B-hadrons produced in proton-proton collisions at the LHC. For projects in the LHCb group, please contact Marcel Mark (marcel.merk_at_nikhef.nl)</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Bachelor_Projects&diff=665Bachelor Projects2021-01-14T05:14:15Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>== Bachelor Projects 2021 ==<br />
<br />
=== Theory ===<br />
<br />
==== Standard Model Effective Field Theory analysis of Z+dijet production ====<br />
The goal of this project is to study the effect of higher dimensional operators from the Standard Model Effective Field Theory in Z-boson production measured at LHC. The ATLAS collaboration has just reported in 2020 the measurement of Z production alongside with a pair of jets, based on the full Run II luminosity. In this project we aim to study the effect of dimension six SMEFT operators on the signal (EW-induced) and/or background (QCD-induced), finding which is the kinematic variable that maximises the possible effect of beyond the SM operators and thus may provide the best constraint on New Physics. The outcome of this project may be the first step of the inclusion of Vector production in a global SMEFT fit. <br />
References: https://arxiv.org/pdf/2006.15458.pdf, https://www.hepdata.net/record/ins1803608<br />
Supervisors: J. Rojo (j.rojo_at_vu.nl)<br />
<br />
<br />
== Bachelor Projects 2020 ==<br />
<br />
<br />
=== Dark Matter ===<br />
<br />
==== XAMS ====<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso.<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source and liquid scintillatorneutron detector we have acquired for the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study of neutron transport in xenon.<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
==== Backgrounds in Radioactive Decay Measurements ====<br />
At Nikhef, the XENON group has a working setup, continuously monitoring the<br />
radioactive decay of Cobalt-60, Caesium-137 and Titanium-44. This beautiful setup is<br />
however not shielded perfectly; it is still vulnerable to background radioactivity. Our<br />
current way of working around this background radiation is to subtract it from our<br />
waveforms. You as a BSc student could help us hands-on and with analyses:<br />
together, we can disassemble the setup, measure background spectra and<br />
implement this in the data analysis. You can use all the data to validate the<br />
lifetime of our isotopes!<br />
<br />
Supervisors: A.P. Colijn (colijn_at_nikhef.nl)<br />
<br />
=== ATLAS ===<br />
<br />
==== Project ATLAS-ITk ====<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
==== The Most Energetic Higgs Boson ====<br />
A common approach to search for physics beyond the standard model is by searching for the direct production of new particles. Alternatively, indirect quantum effects on the production of known particles -such as the Higgs Boson- could reveal the first cracks in the theory. Processes with high energy transfer are of particular potential since possible deviations are expected to increase with the square of the involved energy scale. Using the entire data-set collected by the ATLAS experiment at CERN during the four years of the LHC’s Run 2, a proof-of-principle analysis, targeting transverse momenta of the above 400 GeV, has been developed by Nikhef researchers. The first results of this Higgs boson study are expected to be published this year and this project aims to develop refinements of the analysis techniques. We will investigate the usage of sophisticated machine learning tools such as artificial neural networks, the search for new variables that can help discriminating the signal from its background, revisiting the analysis categorisation and improving the reconstruction techniques at these extreme momenta. Supervisors: Brian Moser and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs: The Next Generation ====<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks has been developed by Nikhef researchers and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays), advanced analysis techiques (using deep learning methods) and expanding the theory interpretation. Another opportunity would be the development of a new statistical combination with various independent searches, which could significantly improve the discovery potential. Supervisors: Marko Stamenkovic and Tristan du Pree (tdupree_at_nikhef.nl)<br />
<br />
==== Higgs interferentie ====<br />
In 2012 hebben het ATLAS en het CMS experiment het Higgs deeltje gevonden. Inmiddels zijn we het Higgs boson aan het bestuderen, hoe gedraagt het zich precies, bestaan er meer soorten Higgs bosonen of is er echt maar eentje van? In dit project leer je hoe we een Higgs boson kunnen herkennen in de detector en gaan we kijken naar hoe de signalen veranderen als er meer Higgs bosonen bestaan of misschien wel andere exotische nieuwe deeltjes. <br />
Dit doen we door gebruik te maken van quantum interferentie wat plaats vindt tussen het Higgs boson en achtergrondprocessen. Hoe dit precies werkt leer je in het project. Supervisor: Hella Snoek (h.snoek_at_nikhef.nl)<br />
<br />
=== B-Physics - LHCb ===<br />
<br />
==== Time dependent CP violation ====<br />
The LHCb experiment studies CP violation withB-meson decays.<br />
The project focusses on the measurement of the unitarity angle gamma using decays of the Bs mesons to Ds K.<br />
Supervisors: Sevda Esen & Michele Veronesi<br />
<br />
==== Machine learning ====<br />
Machine learning has proven to be an indispensable tool in the selection of interesting events in high energy physics. Such technologies will become increasingly important as detector upgrades are introduced and data rates increase by orders of magnitude. HEPDrone is a toolkit to enable the creation of a drone classifier from any machine learning classifier, such that different classifiers may be standardised into a single form and executed in parallel. A detailed evaluation of the performance of different drone models in the real production environment of LHCb will give the collaboration a complete idea of not only the advantages of the drone model, but also the limits of drone complexity given the available computing resources.<br />
Requirements: Advanced python and Advanced C++<br />
Supervisor: Sean Benson<br />
<br />
==== LHCb simulations of physics beyond the Standard Model ====<br />
This project is of relatively theoretical and computing nature and performs simulation studies for physics beyond the Standard Model in the context of long lived particles. It is related to test the sensitivity of the LHCb experiment to detect specific signals of physics beyond the Standard Model.<br />
supervisor: Carlos Vazquez Sierra<br />
<br />
=== Detector R&D ===<br />
<br />
==== Characterization of the new ultrathin ALPIDE monolithic active pixel sensor ====<br />
At the Large Hadron Collider at CERN, major upgrades of experiments take place in the long shutdown years where particle collisions are paused. The ALICE inner tracking system (ITS) 2, the part of the ALICE experiment closest to the beam pipe, is currently being installed at CERN. This detector makes use of ultra-lightweight monolithic active pixel sensors, the first to use this technology at particle colliders after the STAR experiment at RHIC in Brookhaven. These very thin pixel detectors have a low power consumption, result in very little material in the detector, and still have optimal timing and resolution -- and are a promising technology for future experiments. To characterize the performance of these sensors, you will learn to set up experiments, carry out measurements, and analyze data using various instruments available in the detector R&D lab at Nikhef. This could lead to novel insights of monolithic active pixel sensors. It is also possible to do measurements from home using data from the first test beams with bent (yes, with a curvature!) ALPIDE sensors. You will work in an international, stimulating research environment in the detector R&D group at Nikhef at the forefront of silicon detector technologies for high energy physics. ''Contact: [mailto:jory.sonneveld@nikhef.nl Jory Sonneveld]''<br />
<br />
==== Fast timing detectoren ====<br />
Op dit moment maken we veel gebruik van silicon detectoren in onze deeltjes experimenten. Deze zijn gevoelig voor geladen deeltjes en zijn bij uitstek geschikt om de paden vast te leggen die de deeltjes maken die in de botsingen worden gemaakt. Bijvoorbeeld in de Atlas en LHCb experimenten worden tientallen tot honderden deeltjes gemaakt bij elk botsingsgebeurtenis (event) die met 40MHz plaatsvinden. Voor toekomstige deeltjesdetectoren willen we niet alleen het traject vastleggen maar ook met grote precisie een tijdsmeting toevoegen. We hebben hiervoor dus nieuwe detectoren nodig die behalve met een hele hoge snelheid en efficientie de posities van de langsvliegende deeltjes kunnen vastleggen, maar hier ook een zeer nauwkeurige tijdsmeting (in orde van picosecondes) aan kunnen toevoegen. We hebben met verschillende detectoren metingen gedaan, in testbundels op CERN, maar ook in het lab op Nikhef kunnen we metingen doen. In dit project ga je samen met het fast-timing detectoren team op het Nikhef metingen verrichten en de resultaten hiervan bekijken. Contact: Hella Snoek (h.snoek@nikhef.nl)<br />
<br />
==== Muon tomography ====<br />
In this project we are not looking for where cosmic rays come from. We are looking for what we can use them for instead. The muons in cosmic rays can be used to ‘probe’ massive objects. Muons are short lived particles that carry the same charge as electrons, have a high penetrating power and can be detected relatively easy. It is possible to reconstruct a density distribution within an object by measuring muon scattering and absorption. In this context the objects may be freight containers, buildings, melting furnaces, etc… <br />
<br />
Systems that scan objects through the use of muons are often large (objects often need to be enclosed by the system) and complex. The question we want to answer is: Can we develop a smaller, simpler and cheaper system for muon tomography? <br />
<br />
A method to detect muons is by using a material that scintillates (emits light) when hit by an ionising particle. When this light emission is prompt after the passage of the muon, timing information of the light can be used to reconstruct the path of the muon.<br />
In this experiment we make a muon tracker based on two sheets of scintillating material and photo multiplier tubes (PMTs). Photo multiplier tubes are fast responding and very sensitive light detectors (capable of detecting single photons).<br />
<br />
The big question is: How well does this system perform?<br />
<br />
Currently a set-up is being build. You have a lot of freedom to choose a focus in this project (theory, simulation, hardware, or a combination of those).<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Spectral X-ray imaging - Looking at colours the eyes can't see ====<br />
When a conventional X-ray image is made to analyse the composition of a sample, or to perform a medical examination on a patient, one acquires an image that only shows intensities. One obtains a ‘black and white’ image. Most of the information carried by the photon energy is lost. Lacking spectral information can result in an ambiguity between material composition and amount of material in the sample. If the X-ray intensity as a function of the energy can be measured (i.e. a ‘colour’ X-ray image) more information can be obtained from a sample. This translates to less required dose and/or to a better understanding of the sample that is being investigated. For example, two fields that can benefit from spectral X-ray imaging are mammography and real time CT.<br />
<br />
X-ray detectors based on Medipix/Timepix pixel chips have spectral resolving capabilities and can be used to make polychromatic X-ray images. Medipix and Timepix chips have branched from pixel chips developed for detectors for high energy physics collider experiments.<br />
<br />
Some themes that students can work on: <br />
<br />
- Optimising methods to acquire spectral X-ray images.<br />
<br />
- Determining how much existing applications benefit from spectral X-ray imaging and looking for potential new applications.<br />
<br />
- Characterising, calibrating, optimising X-ray imaging detector systems.<br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
==== Holographic emitter ====<br />
A difficulty in generating holograms (based on the interference of light) is the required dense spatial light field sampling. One would need pixels of less than 200 nanometer. With larger pixels artefacts occur due to spatial under sampling. A pixel pitch of 200 nm or less is difficult, if not, impossible, to achieve, especially for larger areas. Another challenge is the massive amount of computing power that is required to control such a dense pixel matrix. <br />
<br />
A new holographic projection method has been developed that reduces under sampling artefacts, regardless of spatial sample density. The trick is to create 'pixels' at random but known positions, resulting in an array that lacks any spatial periodicity. As a result a holographic emitter can be built with a significantly lower sample density and less required computing power. This could bring holography in reach for many applications like display, lithography, 3D printing, metrology, etc...<br />
<br />
The big question: How does the performance of the holographic emitter depend on sample density and sample positions?<br />
<br />
The aspects of a holographic image we are interested in are:<br />
<br />
- Noise<br />
<br />
- Contrast<br />
<br />
- Suppression of under sampling artefacts<br />
<br />
- Resolution <br />
<br />
For this project we are building a proof of concept holographic emitter. This set-up will be used to verify simulation results (and to make some cool holograms of course). <br />
<br />
Supervisor: Martin Fransen (martinfr-at-nikhef.nl)<br />
<br />
=== KM3NeT ===<br />
<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierarchy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
==== Data analysis of the first deployed KM3NeT detection lines ====<br />
<br />
First detection lines of the KM3NeT neutrino telescope have been deployed<br />
in the Mediterranean Sea, and a first data set is available. The lines consist<br />
of light-sensitive detectors that record the time of arrival of photons<br />
produced by relativistic particles in the deep sea, and their number.<br />
In this project we will study the first data to separate various components:<br />
photons from potassium decay, bioluminesence, sparks in the photomultipliers,<br />
downgoing muons from cosmic rays, and perhaps first neutrinos.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Neutrino oscillation measurements with the KM3NeT neutrino telescope ====<br />
<br />
The ORCA block of the KM3NeT neutrino telescope currently under construction<br />
will be able to measure the oscillations of neutrinos produced in interactions<br />
of cosmic rays with the earth atmosphere. Fundamental neutrino properties can<br />
be deduced from these oscillations measurements, in particular the so-called<br />
mass hierarchy of neutrinos. In this project we will simulate the ORCA measurements<br />
of neutrino oscillations, and study the dependence of the sensitivity on<br />
experimental uncertainties, such as energy resolution and neutrino flavour<br />
identification, and theoretical uncertainties, such as the atmospheric neutrino<br />
flux and neutrino cross sections. The results will help ORCA to identify<br />
the main sources of uncertainty, and therefore to actively try to reduce these<br />
and improve the final measurement.<br />
<br />
Supervisors: Ronald Bruijn, Paul de Jong and Dorothea Samtleben<br />
<br />
==== Performance Studies of ORCA for Dark Matter Detection ====<br />
<br />
The interactions of neutrinos in KM3NeT-ORCA give different signatures which are categorised as track and shower events. This project involves the studies of muon, electron and tau neutrino interactions for the reconstruction performance of ORCA. Efficient reconstruction of such signals is important for Dark Matter searches in the low-mass regime. We will work on understanding the detector performance, e.g. effective acceptance, energy and angular resolution, with different configurations of the detector setup. The result of this study will be very useful to improve the sensitivity of the experiment for Dark Matter detection and its possible location. The student will have the opportunity to work closely with KM3NeT members at Nikhef and gain skills of analyzing data. <br />
<br />
Supervisors: Suzan Basegmez du Pree, Aart Heijboer<br />
<br />
==== A search for periodic sources in Antares data ====<br />
<br />
The Antares deep-sea neutrino telescope has been operated for more then ten years. A search for periodic sources is proposed by applying a fast Fourier transformation (FFT) analysis on the available low-level data. This search will be combined with a (literature) study of pulsars which are thought to emit neutrinos.<br />
<br />
Supervisor: Maarten de Jong<br />
<br />
==== Study of Optical Properties of Sea Water using Hit Coincidences in MC Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
By studying coincidences of L1 hits between neighbouring DOMs, for various Monte Carlo (MC) data sets with different sea water optical properties such as scattering and absorption coefficients, in this project we try to figure out if and how well we can quantify optical sea water properties by studying L1 hit coincidences in real KM3NeT data.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
==== Determination of Inter-DOM Distances using Hit Coincidences in KM3NeT Data ====<br />
<br />
Data from the KM3NeT detector is coming from so-called Digital Optical Modules (DOMs) that are attached to long vertical ropes, which are anchored to the bottom of the Mediterranean Sea at depths down to 3.5 km. There are 18 DOMs in one Detection Unit (i.e. one line), vertically spaced along the length of the DU. Ultimately, hundreds of KM3NeT DUs will be deployed. Every DOM contains 31 photomultiplier tubes (PMTs). A so-called L1 hit is defined as a certain number of single PMT hits in one DOM in a certain time window. <br />
<br />
The number of L1 hit coincidences from atmospheric muons between neighbouring DOMs on a DU is expected to decrease exponentially. By fitting the observed number of L1 hit coincidences between neighbouring DOMs in real data to the expected exponential decay, in this project we study how accurately we can determine the distances between DOMs on a single DU. In addition, we try to determine the distances between DUs by looking for L1 hit coincidences between DOMs on neighbouring DUs.<br />
<br />
Supervisor: Daan van Eijk<br />
<br />
=== VIRGO ===<br />
<br />
The Advanced LIGO and Advanced Virgo interferometers have recently observed gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results.<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Frank Linde (frank.linde_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
<br><br><br><br />
<br />
== Bachelor Projects 2017 ==<br />
<br />
=== Extreme Astronomy – Preparing for CTA, the Next-Generation Gamma-Ray Observatory ===<br />
<br />
The Cherenkov Telescope Array (CTA) is a planned facility for measuring gamma rays from space covering more than four orders of magnitude in energy, up to energies exceeding 100 TeV. CTA employs the imaging atmospheric Cherenkov technique to measure properties of cosmic gamma rays. This technique is based on measuring Cherenkov light emitted during the development of a gamma-ray air shower. CTA will be built at two experimental sites, one in the Northern, one in the Southern hemisphere, and will consist of up to 100 telescopes. It represents a major leap forward in sensitivity and precision for gamma-ray astronomy, and will allow us to explore very-high-energy processes of the extreme Universe at an unprecedented level.<br />
<br />
Two projects for students are available at the CTA group of UvA in the field of optical and photonic R&D contributing to the starting phase of CTA. For the first project the student will conduct measurements to characterise novel kinds of single-photon detectors, referred to as silicon photomultipliers, and evaluate different types of these sensors for their use for CTA. For the second project the student will develop and test an imaging system making use of a liquid crystal display. This flexible light source will be able to mimic images from different light sources of the night sky as seen by cameras of CTA, for instance gamma-ray air showers or stars, and will be used for camera tests and calibration.<br />
<br />
<br />
Supervisors: David Berge, Maurice Stephan (postdoc)<br />
<br />
=== Dark Matter ===<br />
<br />
<!--<br />
==== XENON1T - the world's most sensitive dark matter detector ====<br />
<br />
Finding the mysterious dark matter particles is one of the most challenging enterprises in physics today. Soon we will get first data from the world's most sensitive dark matter detector yet: the XENON1T experiment.<br />
<br />
The first goal of this project is to understand why dak matter is necessary to understand the universe, and how we could detect it with XENON1T. Then, you can contribute to our group's efforts preparing for <br />
and analyzing the XENON1T data by, for example: examining XENON1T's calibration signals to check for problems in the experiment, testing our data analysis software with simulated dark matter signals, or studying the physics behind XENON1T's detection process to learn how to better distinguish dark matter signals from backgrounds. For data analyis, experience with or willingness to learn programming in python is essential.<br />
<br />
<br />
Supervisors: M.P. Decowski & J. Aalbers --><br />
<br />
==== Neutrinoless double beta decay sensitivity study in future dark matter detectors ====<br />
<br />
The discovery of neutrino oscillation (Nobel Physics 2015) means that neutrinos have mass. We already know that their masses are tiny, more than one million times smaller than the next-lightest particle in the standard model, the electron. This raises the question if the mass-generation mechanism is the same for neutrinos as it is for the other subatomic particles. In particular, since neutrinos are electrically neutral, they could be their own anti-particles - we call these types of particles Majorana. The only practical way to discover if neutrinos are Majorana is through the search of an extremely rare radioactive decay called neutrinoless double beta decay (0n2b). A few isotopes are candidates for this process, among them Xe-136. The natural abundance of Xe-136 in natural xenon is about 9%, and this gives the opportunity to look for a 0n2b signal in xenon-based dark matter detectors like XENON1T and the future XENONnT and DARWIN detectors. <br />
<br />
We are looking for a student interested in doing a sensitivity study for 0n2b in XENONnT and the DARWIN experiments. The first goal will be to understand the physics addressed in neutrinoless double beta decay. Then the student will inventory possible backgrounds for the signal, use a (controversial) claim of a 0n2b signal as a benchmark and finally obtain the sensitivity of these future detectors. The work will involve simulations and analysis, building on an existing framework developed in our group. <br />
<br />
Supervisors: M.P. Decowski & A. Tiseni<br />
<br />
==== Shaking Dark Matter detectors ====<br />
<br />
Our XENON1T detector is built in the lab underneath the Gran Sasso mountains in central Italy. The lab is very well suited for low-background experiments due to the 1.5km of rock overburden. <br />
However, as you may know, cental Italy has been plagued by earthqaukes over the past decade, with the most recentones occurring in January 2017. We need a BSc student to investigate the <br />
details of such earthquakes in our underground lab. What are the magnitdues by which stuff is moving underground? What are the accelerations? What is the potential effect on our experimental<br />
setup? What would ahppen if an earthquake happens much closer to our lab? Furthermore we are interested to find out whether Earthquakes can be predicted. Some papers claim that before<br />
an earthquake the radon emanating from rock increases. In our lab we measure the radon concentration as a function of time: can you find a correlation between the measurements and recent <br />
earthquakes?<br />
<br />
If you are interested in finding out more about earthquakes, please contact M.P. Decowski or A.P. Colijn<br />
<br />
==== XAMS - a baby dark matter detector ====<br />
<br />
The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso<br />
we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector<br />
are identical to its big sibling in Gran Sasso.<br />
<br />
We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source we have acquired<br />
before the start of the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project<br />
will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study<br />
of neutron transport in xenon.<br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
==== Radon is bad for Dark Matter ====<br />
<br />
Radon is the dominant background for xenon based dark matter detectors, like the XENON1T experiment. In our lab at Nikhef we are investigating ways to reduce or eliminate the effect of radon<br />
on our sensitivity. For our lab setup XAMS we have designed and constructed a radon detector, that can be used in xenon systems at high-pressure. This completely new detector<br />
is now waiting for a BSc student to fully chracterize and use it. During this project you will first study the effect that radon contaminations have on dark matter detectors, then you will start working to<br />
understand our new radon detector in detail. You will learn howto use a radioactive source to calibrate the detector: this is something which is not easy and has not been done before in our lab. <br />
If you manage to succesfully calibrate the detector, we then want to incorporate it into our lab xenon system at Nikhef and maybe at some later stage in the real XENON1T detector!<br />
<br />
The profile of the student to work on this project is broad. I expect a good theoretical knowledge in order to quickly get upto speed with understanding dark mater detectors, and in addition I <br />
need 'lab-creativity' in order to develop methods for calibrating the new detector. If a good method is developed, it will be used for many years by the Nikhef dark matter group and beyond. <br />
<br />
Supervisors: A.P. Colijn & E. Hogenbirk<br />
<br />
=== ATLAS ===<br />
<br />
<br />
==== ATLAS (1): Searching for new physics with the Higgs and W bosons ====<br />
<br />
The strength of the Higgs interactions with electroweak bosons are precisely defined in the<br />
Standard Model. Therefore they are sensitive probes of the mechanism of electroweak symmetry<br />
breaking and enable searches for new physics beyond the SM. With the data collected by the ATLAS<br />
experiment in years 2015-2016 we plan to measure separately the Higgs coupling to<br />
longitudinally and transversely polarised W bosons in a process of weak boson fusion. To<br />
maximise experimental sensitivity we are developing techniques to separate the signal from<br />
background processes. You will take part in investigating possible improvements from<br />
reconstructing events in reference frames boosted with respect to the detector. During the<br />
project you will learn modern experimental analysis techniques. This project is a part of Vector<br />
Boson Scattering Coordination and Action Network (VBSCan) which connects researchers studying<br />
this and related topics worldwide.<br />
<br />
Supervisors: Pamela Ferrari, Magdalena Slawinska, Bob van Eijk<br />
<br />
<br />
==== ATLAS (2): Dark-matter-motivated searches for supersymmetric particles at the LHC ====<br />
<br />
Supersymmetry, a symmetry between fermions and bosons in particle physics,<br />
may provide a particle that could be the dark matter in the universe.<br />
The observation of an excess of gamma rays originating from the centre of our<br />
galaxy could be explained in a model where supersymmetric dark matter<br />
particles annihilate each other in the galactic centre, leading to gamma rays.<br />
<br />
Given the model parameters, it should also be possible to produce such<br />
particles at the LHC, at CERN in Geneva. But it is not so easy to observe<br />
them: the signal is small, and the noise (background) is large.<br />
In this project, we will use simulations of signal and background to<br />
optimize experimental searches for such particles with the ATLAS detector,<br />
apply them to the data collected in 2015, and prepare for the new data in<br />
2016 and later.Where possible, we will explore new machine learning techniques.<br />
<br />
Supervisors: Paul de Jong, Broos Vermeulen<br />
<br />
<br />
==== ATLAS (3): Simulations / Quality tests for the ATLAS High-Luminosity LHC Upgrade ====<br />
<br />
One of the key sub-systems of the ATLAS experiment at the Large<br />
Hadron Collider (LHC) is the Inner Detector (ID), designed to provide<br />
excellent charged particles momentum and vertex resolution measurements.<br />
<br />
At Phase-2 of the LHC run, in ~2025, the operating luminosity of<br />
the collider will be increased significantly.<br />
This will imply an upgrade of all ATLAS subsystems. In particular,<br />
the ID will be fully replaced with a tracker completely made of<br />
Silicon, having higher granularity and radiation hardness.<br />
The R&D process for the new ATLAS ID is now ongoing.<br />
Different geometrical layouts are simulated and their performance is<br />
studied under different operating conditions in search for the optimal<br />
detector architecture. Also, the performance of the new<br />
Si-sensors/modules is under investigation with dedicated laboratory tests.<br />
<br />
The focus of the project could be on the simulation of the High-Luminosity LHC<br />
version of the ATLAS Inner Detector. The student will learn how a<br />
high-energy physics experiment is designed and optimized.<br />
Alternatively, if possible at that moment, the student could<br />
work on a project at the Nikhef Silicon laboratory at the test-bench for<br />
new ATLAS Si-strip detectors and participate in the quality<br />
assurance procedure for the new ATLAS Si detectors.<br />
<br />
==== ATLAS (4): Higgs productie in Run-2 van de LHC ====<br />
In de eerste run van de LHC is onder andere bij het ATLAS experiment het Higgs deeltje gevonden. Nu is de tweede run begonnen en kan het Higgs deeltje worden bevestigd. Door de verhoogde energie ziet de achtergrond er echter heel anders uit, dus is de optimalisatie van het wegsnijden van de achtergronden qua fysica anders. Voor je bachelor project kan met behulp van de ATLAS detector het Higgs deeltje in run twee komen vinden. <br />
<br />
Supervisors: Lydia Brenner, Wouter Verkerke<br />
<br />
==== ATLAS (5): De lange staart van het Higgs boson ====<br />
<br />
[[File:HiggsMassa.png |thumb|left|upright=1.25]]<br />
<br />
<br><br />
Na de ontdekking van het Higgs boson in 2012 zijn we druk bezig om te kijken of zijn eigenschappen overeenkomen met de voorspellingen van het Standaard Model. Een van de belangrijkste eigenschappen is de zogenaamde breedte van het Higgs boson. Als het Higgs boson naast de Standaard Model deeltjes ook in exotische nieuwe speeltje uit elkaar kan vallen (bijvoorbeeld donkere materie) dan zal dat ale eerste zichtbaar worden in een afwijking van de breedte tov de verwachting. We gaan in dit project uitzoeken hoe de strategie die nu gebruikt wordt (meten van de hoeveelheid Higgs bosonen met een extreem hoge massa) precies werkt en kijken of we door het toevoegen van nieuwe ideeën een verbetering kunnen aanbrengen. <br />
<br />
<br><br />
Specifiek: We gaan eerst in detail de eigenschappen bekijken van het Higgs signaal en de twee achtergronden die er het meest op lijken. Daarna gaan we op zoek naar de verschillen en een manier waarop we onze kennis daarover kunnen gebruiken om gevoeliger te worden voor het Higgs signaal.<br />
<br />
Supervisors: Hella Snoek, Ivo van Vulpen<br />
<br />
E-mail: H.Snoek_at_nikhef.nl & Ivo.van.Vulpen_at_nikhef.nl<br />
<br><br><br><br><br><br><br />
<br />
=== ATLAS (6): Project ATLAS-ITk ===<br />
Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)<br />
<br />
<br><br />
<br />
=== KM3Net ===<br />
The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of<br />
several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, <br />
scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray <br />
bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown <br />
neutrino mass hierachy.<br />
<br />
The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino <br />
interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure <br />
resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along <br />
700m long vertical lines, called detection units.<br />
<br />
The first phase of the KM3NeT neutrino telescope is currently under construction, with the first two detection units operational at 3500m depth in the Mediterranean Sea, 100 km off the coast of Sicily.<br />
<br />
<br />
==== KM3NeT (1): Photon counting in KM3NeT ====<br />
<br />
The details of a neutrino interaction, such as its incoming direction and energy, determine the pattern, time and amount, of recorded photons (´hits´) by the photo-multplier tubes. The time of arrival is recorded with nanosecond accuracy and the amount of photons is encoded in the length of the pulse(time-over-threshold, ToT). Currently, only the photon arrival time and the number of photo-multipliers that record a hit are used in reconstructing event properties.<br />
In this project, the distributions of the ToT mainly originating from photons from potassium-40 decays in the sea-water and from atmospheric muons passing through the water will be studied. The goals are to investigate the properties of the ToT distributions obtained from data and simulation, in particular the dependence on the photo-multiplier efficiency and atmospheric muon flux.<br />
In this project we will be extensively using the programming language C++ to analyse the data, so a reasonable proficiency is required.<br />
<br />
Supervisors: Ronald Bruijn & Karel Melis<br />
<br />
Email: rbruijn_at_nikhef.nl<br />
<br />
<br />
<br />
<br><br><br><br />
<br />
=== VIRGO ===<br />
<br />
"It is anticipated that in the next few years, Advanced LIGO and Advanced Virgo will start observing gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.<br />
<br />
To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.<br />
<br />
In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results."<br />
<br />
The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Jo van den Brand (jo_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)<br />
<br />
=== LHCb ===<br />
<br />
Begeleider: Sean Benson<br />
<br />
Title: <br />
Searching for physics beyond the Standard Model with LHCb<br />
<br />
The LHCb experiment is designed to study the "The Flavour Problem" in particle physics:<br />
Why is the universe dominated by matter over antimatter? Why are there three generations of elementary particles? What is the origin of quark flavour changing interactions.<br />
<br />
To solve these riddles, LHCb performs precision measurements on b-quark particle decays.<br />
An intriguing signal has recently been observed in the decay of a B-meson to a K* and two muons: Bd→K*μμ, which does not seem to behave according to the predictions of the Standard Model<br />
In this project the bachelor student will investigate this further by studying the case where the K* particle decays to a so-called k-short particle and a π0. The observation of such a final state will provide valuable information in the search for physics beyond the Standard Model.<br />
<br />
In this ambitious project the student is expected to study both a theory on the mechanism of CP violation with B mesons, in addition to data analysis with B decays. Programming experience in python is required.<br />
<br />
The LHCb experiment at CERN analyzes the properties of B-hadrons produced in proton-proton collisions at the LHC. For projects in the LHCb group, please contact Marcel Mark (marcel.merk_at_nikhef.nl)</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=584Master Projects2020-05-01T13:00:34Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
== Projects with September 2020 start ==<br />
<br />
=== ATLAS: Top Spin optimal observables using Artificial Intelligence ===<br />
<br />
The top quark has an exceptional high mass, close to the electroweak symmetry breaking scale and therefore sensitive to new physics effects. Theoretically, new physics is well described in the EFT framework [1]. The (EFT) operators are experimentally well accessible in single top t-channel production where the top quark is produced spin polarized. The focus at Nikhef is the operator O_{tW} with a possible imaginary phase, leading to CP violation. Experimentally, many angular distribution are reconstructed in the top rest frame to hunt for these effects. We are looking for a limited set of optimal observables. The objective of your Master project would be to find optimal observables using simulated events including the detector effects and possible systematic deviations. All techniques are allowed, but promising new developments are methods which involve artifical intelligence. This work could lead to an ATLAS note. <br />
<br />
[1] https://arxiv.org/abs/1807.03576<br />
<br />
''Contact: Marcel Vreeswijk [mailto:h73@nikhef.nl] and Jordy Degens [mailto:jdegens@nikhef.nl] ''<br />
<br />
=== ATLAS: The Next Generation ===<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks is very new [1] and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays), advanced analysis techiques (using deep learning methods) and expanding the theory interpretation. Another opportunity would be the development of the first statistical combination of results between the ATLAS and CMS experiment, which could significantly improve the discovery potentional.<br />
<br />
[1] https://arxiv.org/abs/1802.04329<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree and Marko Stamenkovic]''<br />
<br />
=== ATLAS: The Most Energetic Higgs Boson ===<br />
<br />
The production of Higgs bosons at the highest energies could give the first indications for deviations from the standard model of particle physics, but production energies above 500 GeV have not been observed yet [1]. The LHC Run-2 dataset, collected during the last 4 years, might be the first opportunity to observe such processes, and we have various ideas for new studies. Possible developments include the improvement of boosted reconstruction techniques, for example using multivariate deep learning methods. Also, there are various opportunities for unexplored theory interpretations (using the MadGraph event generator), including effective field theory models (with novel ‘morphing’ techniques) and new interpretations of the newly observed boosted VZ(bb) process.<br />
<br />
[1] https://arxiv.org/abs/1709.05543<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree and Brian Moser]''<br />
<br />
=== LHCb: Measurement of delta md === <br />
The decay B0->D-pi+ is very abundant in LHCb, and therefore ideal to study the oscillation frequency<br />
delta md, with which B0 mesons oscillate into anti-B0 mesons, and vice versa.<br />
This process proceeds through a so-called box diagram which might hide new yet-undiscovered particles.<br />
Recently, it has been realized that value of delta md is in tension with the valu of CKM-angle gamma,<br />
triggering renewed interest in this measurement.<br />
<br />
''Contact: [mailto:Marcel.Merk@nikhef.nl Marcel Merk]''<br />
<br />
=== LHCb: Searching for CPT violation === <br />
CPT symmetry is closely linked to Lorentz symmetry, and any violation<br />
would revolutionize science. There are possibilities though that supergravity could<br />
cause CPT violating effects in the system of neutral mesons.<br />
The precise study of B0s oscillations in the abundant Bs->Dspi decays can <br />
give the most stringent limits on Im(z) to date.<br />
<br />
''Contact: [mailto:Marcel.Merk@nikhef.nl Marcel Merk]''<br />
<br />
=== LHCb: BR(B0->D-pi+) and fd/fu with B+->D0pi+ === <br />
The abundant decay B0->D-pi+ is often used as normalization channel, given its<br />
clean signal, and well-known branching fraction, as measured by the B-factories.<br />
However, this branching fraction can be determined more precisely, when comparing<br />
to the decay B+->D0pi+ , which has a twice better precision.<br />
In addition, the production of B0 and B+ mesons is often assumed to be equal,<br />
based on isospin symmetry. The study of B+->D0pi+ and B0->D-pi+ allows for the <br />
first measurement of this ratio, fd/fu.<br />
<br />
''Contact: [mailto:Marcel.Merk@nikhef.nl Marcel Merk]''<br />
<br />
=== LHCb: Isospin asymmetry in B->K(*)mumu decays ===<br />
The family of B->Kmumu decays has drawn enormous attention in the last few years.<br />
Many anomalous measurements in these decays could be hints of the existence of new particles.<br />
A particular measurement is the ratio of decays with either up or down quarks, hence<br />
yielding a measurement of the isospin asymmetry.<br />
This is not expected to deviate from zero, but early measurements have shown small deviations.<br />
New data is available which can yield a twice more precise determination of the isospin asymmetry.<br />
<br />
''Contact: [mailto:Marcel.Merk@nikhef.nl Marcel Merk]''<br />
<br />
=== LHCb: Optimization studies for Vertex detector at the High Lumi LHCb ===<br />
The LHCb experiment is dedicated to measure tiny differences between matter and antimatter through the precise study of rare processes involving b or c quarks. The LHCb detector will undergo a major modification in order to dramatically increase the luminosity and be able to measure indirect effects of physics beyond the standard model. In this environment, over 42 simultaneous collisions are expected to happen at a time interval of 200 ps where the two proton bunches overlap. The particles of interest have a relatively long lifetime and therefore the best way to distinguish them from the background collisions is through the precise reconstruction of displaced vertices and pointing directions. The new detector considers using extremely recent or even future technologies to measure space (with resolutions below 10 um) and time (100 ps or better) to efficiently reconstruct the events of interest for physics. The project involves changing completely the LHCb Vertex Locator (VELO) design in simulation and determine what can be the best performance for the upgraded detector, considering different spatial and temporal resolutions.<br />
<br />
''Contact: [mailto:kazu.akiba@nikhef.nl Kazu Akiba]''<br />
<br />
=== LHCb: Measurement of charge multiplication in heavily irradiated sensors ===<br />
During the R&D phase for the LHCb VELO Upgrade detector a few sensor prototypes were irradiated to the extreme fluence expected to be achieved during the detector lifetime. These samples were tested using high energy particles at the SPS facility at CERN with their trajectories reconstructed by the Timepix3 telescope. A preliminary analysis revealed that at the highest irradiation levels the amount of signal observed is higher than expected, and even larger than the signal obtained at lower doses. At the Device Under Test (DUT) position inside the telescope, the spatial resolution attained by this system is below 2 um. This means that a detailed analysis can be performed in order to study where and how this signal amplification happens within the 55x55 um^2 pixel cell. This project involves analysing the telescope and DUT data to investigate the charge multiplication mechanism at the microscopic level.<br />
<br />
''Contact: [mailto:kazu.akiba@nikhef.nl Kazu Akiba]''<br />
<br />
=== ALICE: Searching for the strongest magnetic field in nature ===<br />
In case of a non-central collision between two Pb ions, with a large value of impact parameter (b), the charged nucleons that do not participate in the interaction (called spectators) create strong magnetic fields. A back of the envelope calculation using the Biot-Savart law brings the magnitude of this filed close to 10^19Gauss in agreement with state of the art theoretical calculation, making it the strongest magnetic field in nature. The presence of this field could have direct implications in the motion of final state particles. The magnetic field, however, decays rapidly. The decay rate depends on the electric conductivity of the medium which is experimentally poorly constrained. Overall, the presence of the magnetic field, the main goal of this project, is so far not confirmed experimentally.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Looking for parity violating effects in strong interactions ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions, in the presence of a deconfined state, gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, what is called the Chiral Magnetic Effect (CME).<br />
The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, however further studies are needed to constrain background effects. These highly anticipated results have the potential to reveal exiting, new physics.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: Machine learning techniques as a tool to study the production of heavy flavour particles ===<br />
There was recently a shift in the field of heavy-ion physics triggered by experimental results obtained in collisions between small systems (e.g. protons on protons). These results resemble the ones obtained in collisions between heavy ions. This consequently raises the question of whether we create the smallest QGP droplet in collisions between small systems. The main objective of this project will be to study the production of charm particles such as D-mesons and Λc-baryons in pp collisions at the LHC. This will be done with the help of a new and innovative technique which is based on machine learning (ML). The student will also extend the studies to investigate how this production rate depends on the event activity e.g. on how many particles are created after every collision.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou] and [mailto:Alessandro.Grelli@cern.ch Alessandro Grelli]''<br />
<br />
=== ALICE: Energy Loss of Energetic Quarks and Gluons in the Quark-Gluon Plasma ===<br />
One of the ways to study the quark-gluon plasma that is formed in high-energy nuclear collisions, is using high-energy partons (quarks or gluons) that are produced early in the collision and interact with the quark-gluon plasma as they propagate through it. There are several current open questions related to this topic, which can be explored in a Master's project. For example, we would like to use the new Monte Carlo generator framework JetScape to simulate collisions to see whether we can extract information about the interaction with the quark-gluon plasma. In the project you will collaborate with one of the PhD students or postdocs in our group to use the model to generate predictions of measurements and compare those to data analysis results. Depending on your interests, the project can focus more on the modeling aspects or on the analysis of experimental data from the ALICE detector at the LHC.<br />
<br />
''Contact: [mailto:marco.van.leeuwen@cern.ch Marco van Leeuwen] and [mailto:marta.verweij@cern.ch Marta Verweij]''<br />
<br />
=== ALICE: Extreme Rare Probes of the Quark-Gluon Plasma ===<br />
The quark-gluon plasma is formed in high-energy nuclear collisions and also existed shortly after the big bang. With the large amount of data collected in recent years at the Large Hadron Collider at CERN, rare processes that previously were not accessible provide now new ways to study how the quark-gluon plasma emerges from the fundamental theory of strong interaction. One of such processes is the heavy W boson which in many cases decays to two quarks. The W boson itself doesn’t interact with the quark-gluon plasma because it doesn’t carry color, but the quark decay products do interact with the plasma and therefore provide an ideal tool to study the space-time evolution of this hot and dense medium. In this project you will use data from the ALICE detector at the LHC and simulated data from generators to study various physics mechanisms that could be happening in the real collisions.<br />
<br />
''Contact: [mailto:marta.verweij@cern.ch Marta Verweij] and [mailto:marco.van.leeuwen@cern.ch Marco van Leeuwen]''<br />
<br />
=== ALICE: Jet Quenching with Machine Learning ===<br />
<br />
Machine learning applications are rising steadily as a vital tool in the field of data science but are relatively new in the particle physics community. In this project machine learning tools will be used to gain insights into the modification of a parton shower in the quark-gluon plasma (QGP). The QGP is created in high-energy nuclear collisions and only lives for a very short period of time. Highly energetic partons created in the same collisions interact with the plasma while they travers it and are observed as a collimated spray of particles, known as jets, in the detector. One of the key recent insights is that the internal structure of jets provides information about the evolution of the QGP. With data recorded by the ALICE experiment, you will use jet substructure techniques in combination with machine learning algorithms to dissect the structure of the QGP. Machine learning will be used to select the regions of radiation phase space that are affected by the presence of the QGP.<br />
<br />
''Contact: [mailto:marta.verweij@cern.ch Marta Verweij] and [mailto:marco.van.leeuwen@cern.ch Marco van Leeuwen]''<br />
<br />
=== Lepton Collider: Pixel TPC testbeam ===<br />
In the Lepton Collider group at Nikhef we work on a tracking detector for a future Collider (e.g. the ILC in Japan). We are developing a gaseous Time Projection Chamber with a pixel readout. At Nikhef we have built an 8-quad GridPix module based on the Timepix3 chip, which is a detector of about 20 cm x 40 cm x 10 cm in size. In August 2020 we will test the device at the DESY particle accelerator in Hamburg. For the project you could work on preparations for the test beam (e.g. running the data acquisition, perform data monitoring using our set up in the lab). The next topics will be the participation in the data taking during the test beam at DESY, the analysis of the data using C++ and ROOT and - finally - publication of the results in a scientific journal.<br />
<br />
Our latest paper can be found in https://www.nikhef.nl/~s01/quad_paper.pdf [www.nikhef.nl].<br />
<br />
''Contact: [mailto:Peter.Kluit@nikhef.nl Peter Kluit] and Kees Ligtenberg''<br />
<br />
=== Dark Matter: Signal reconstruction in XENONnT ===<br />
The next generation direct detection dark matter experiment - XENONnT - comprises close to 500 photomultiplier tubes (PMTs) in the main detector volume. These PMTs are configured to be able to detect even single photons. When a single photoelectron (PE) signal is detected the detected signal (a pulse) is convoluted with the detector response of the PMT. Due to this detector response the pulse shape of a single PE is spread out in time. For XENONnT we would like to explore the possibility to implement a digital (software) filter to deconvolve the detected pulse back to the “true” instantaneous shape (without the detector spread). This is a virtually unexplored new step in the Xenon analysis framework. Later in the analysis framework these pulses from all the PMTs are combined into a signal referred to as a ‘peak’. For XENONnT it is of essence to be extremely good in discriminating between two types of peaks caused by interactions in the detector; a prompt primary scintillation signal (S1) and a secondary ionization signal (S2). The parameters in the software haven’t - as of the time of writing - been optimized for the XENONnT-detector conditions. <br />
The student would investigate how a deconvolution filter would benefit the XENONnT analysis framework and develop such a filter. Furthermore, the student will work on the classification of these signals to fully exploit the XENONnT-detector to optimize the classification. This will be done with simulated data at first but may later even be performed on actual XENONnT-data. As an extension, the possibility of applying machine learning to correctly distinguish between the two signals could be explored. This is a data-analysis oriented project where Python skills are paramount.<br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:j.angevaare@nikhef.nl Joran Angevaare]''<br />
<br />
=== Dark Matter: XAMS R&D Setup ===<br />
The Amsterdam Dark Matter group operates an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 4kg of ultra-pure liquid xenon. We use this detector for the development of new detection techniques - such as utilizing our newly installed silicon photomultipliers - and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENONnT experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory, or for future Dark Matter experiments like DARWIN. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data him/herself. You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter: DARWIN Sensitivity Studies ===<br />
DARWIN is the "ultimate" direct detection dark matter experiment, with the goal to reach the so-called "neutrino floor", when neutrinos become a hard-to-reduce background. The large and exquisitely clean xenon mass will allow DARWIN to also be sensitive to other physics signals such as solar neutrinos, double-beta decay from Xe-136, axions and axion-like particles etc. While the experiment will only start in 2025, we are in the midst of optimizing the experiment, which is driven by simulations. We have an opening for a student to work on the GEANT4 Monte Carlo simulations for DARWIN, as part of a simulation team together with the University of Freiburg and Zurich. We are also working on a "fast simulation" that could be included in this framework. It is your opportunity to steer the optimization of a large and unique experiment. This project requires good programming skills (Python and C++) and data analysis/physics interpretation skills. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter: Fast simulation studies ===<br />
For Dark Matter experiments it is crucial to understand sources of backgrounds in great detail. The most common way to study the effect of backgrounds to the Dark Matter sensitivity is by the<br />
use of Monte Carlo simulations. Unfortunately, the standard Monte Carlo techniques are extremely inefficient. One needs to sometimes simulate millions of events before one background event appears in the Dark Matter search area. We have developed a Monte Carlo technique that accelerates this process by up to 1000x. The method has been validated on very simple and unrealistic detector models. In goal of this project is to make a realistic detector model for the fast detector simulations. For this we are looking for a student with good programming skills, an interest in a software project, and the desire to deeply understand analysis of Dark Matter experimental data. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter & Amsterdam Scientific Instruments: Simulations for Industry ===<br />
In the Nikhef Dark Matter group we have built up an extensive expertise with Monte Carlo simulations of ionizing radiation. Although these simulations have the aim to estimate background levels in our XENON experiments, the same techniques can be applied to study radiation transport in industrial devices. Amsterdam Scientific Instruments (ASI) is a company at Science Park that develops and sells radiation imaging equipment that is used amongst others in electron microscopy. For this application ASI needs a detailed study of gamma ray backgrounds to optimize shielding for their products. The project aims at optimizing a shielding design based on GEANT4 simulations. The results may be implemented in next generation products of ASI. We are looking for a student with preferably strong computing skills, and with an interest in science-industrial collaboration.<br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== The Modulation experiment: Data Analysis ===<br />
For years there have been controversial claims of potential new-physics on the basis of time-varying decay rates of radioactive sources on top of ordinary exponential decay. While some of these claims have been refuted, others have still to be confirmed or falsified. To this end, a dedicated experiment - the modulation experiment - has been designed and operational for the past four years. Using four identical and independent setups the experiment is almost ready for a final analysis to conclude on these claims. In this project the student will perform this analysis, preferably resulting in a conclusive paper. This will require combining the data of the four setups and close collaboration with a small group constituting a collaboration of the four different involved institutes (Purdue University (USA), Universität Zürich (Switzerland), Centro Brasileiro de Pesquisas Fisicas (Brasil) and Nikhef). This project is data-analysis oriented. Additionally, lab-skills can be required as one of the setups is situated at Nikhef.<br />
<br />
''Contact: [mailto:z37@nikhef.nl Auke Colijn] and [mailto:j.angevaare@nikhef.nl Joran Angevaare]''<br />
<br />
=== Detector R&D: Laser Interferometer Space Antenna (LISA) ===<br />
The space-based gravitational wave antenna LISA is, without a doubt, one of the most challenging space missions ever proposed. ESA plans to launch around 2030 three spacecraft that are separated by a few million kilometers to measure tiny variations in the distances between test-masses located in each satellite to detect the gravitational waves from sources such as supermassive black holes. The triangular constellation of the LISA mission is dynamic, requiring a constant fine-tuning related to the pointing of the laser links between the spacecraft and a simultaneous refocusing of the telescope. The noise sources related to the laser links expect to provide a dominant contribution to the LISA performance.<br />
An update and extension of the LISA science simulation software are needed to assess the hardware development for LISA at Nikhef, TNO, and SRON. A position is therefore available for a master student to study the impact of instrumental noise on the performance of LISA. Realistic simulations based on hardware (noise) characterization measurements performed at TNO will be carried out and compared to the expected tantalizing gravitational wave sources.<br />
<br />
''Contact: [mailto:nielsvb@nikhef.nl Niels van Bakel],[mailto:ernst-jan.buis@tno.nl Ernst-Jan Buis]''<br />
<br />
=== Detector R&D: Spectral X-ray imaging - Looking at colours the eyes can't see ===<br />
When a conventional X-ray image is taken, one acquires an image that only shows intensities. a ‘black and white’ image. Most of the information carried by the photon energy is lost. Lacking spectral information can result in an ambiguity between material composition and amount of material in the sample. If the X-ray intensity as a function of the energy can be measured (i.e. a ‘colour’ X-ray image) more information can be obtained from a sample. This translates to less required dose and/or to a better understanding of the sample that is being investigated. For example, two fields that can benefit from spectral X-ray imaging are mammography and real time CT.<br />
<br />
Detectors using Medipix3 chips are used for X-ray imaging. Such a detector is composed of a pixel chip with a semiconductor sensor bonded on top of it. Photoelectric absorption of X-rays in the sensor results in an amount of charge being released that is proportional to the X-ray energy. This charge is registered by a pixel. Depending on configuration, in each pixel 1, 2, 4 or 8 detection thresholds can be set and so, a number of energy bins can be defined. One of the challenges is to maximise X-ray image quality by minimising effects caused by dispersion in the sensitivity of the pixels. The effects of this dispersion can partly be compensated by applying a specific measurement method in combination with image post processing. <br />
<br />
You can work on improving measurement methods and on improving post processing methods. There is flexibility of the planned work depending on the skillset you have. The aim is to get the best X-ray energy resolution over the entire pixel chip. This in turn improves image quality and therefore X-ray CT reconstruction quality.<br />
<br />
Important note: Much of this work is to be performed in the laboratory. For as long as corona safety measures are active, the labs at Nikhef are not accessible for students and this project cannot be worked on except for post-processing in software. Currently we hope that the situation will have improved by August. <br />
Please see the following videos for examples of our work:<br />
<br />
https://youtu.be/cgwQvjfUYns <br />
<br />
https://youtu.be/tf9ZLALPVNY <br />
<br />
https://youtu.be/vjPX7SxvSUk <br />
<br />
https://youtu.be/LqjNVSm7Hoo <br />
<br />
''Contact: [mailto:martinfr@nikhef.nl Martin Fransen],[mailto:navritb@nikhef.nl Navrit Bal]''<br />
<br />
=== Detector R&D: Holographic projector ===<br />
<br />
A difficulty in projecting holograms (based on the interference of light) is the required dense pixel pitch of a projector. One would need a pixel pitch of less than 200 nanometer. With larger pixels artefacts occur due to spatial under sampling. A pixel pitch of 200 nanometer is difficult, if not, impossible, to achieve, especially for larger areas. Another challenge is the massive amount of computing power that would be required to control such a dense pixel matrix. <br />
<br />
A new holographic projection method has been developed that reduces under sampling artefacts for projectors with a ‘low’ pixel density. It uses 'pixels' at random but known positions, resulting in an array of (coherent) light points that lacks (or has suppressed) spatial periodicity. As a result a holographic projector can be built with a significantly lower pixel density and correspondingly less required computing power. This could bring holography in reach for many applications like display, lithography, 3D printing, metrology, etc... <br />
<br />
Of course, nothing comes for free: With less pixels, holograms become noisier and the contrast will be reduced (not all light ends up in the hologram). The questions: How does the quality of a hologram depend on pixel density? How do we determine projector requirements based on requirements for hologram quality?<br />
<br />
Requirements for a hologram can be expressed in terms of: Noise, contrast, resolution, suppression of under sampling artefacts, etc.. <br />
<br />
For this project we have built a proof of concept holographic emitter. This set-up will be used to verify simulation results (and also to project some cool holograms of course ;-). <br />
<br />
Examples of what you could be working on:<br />
<br />
a. Calibration/characterisation of the current projector and compensation of systematic errors.<br />
<br />
b. To realize a phased array of randomly placed light sources the pixel matrix of the projector must be ‘relayed’ onto a mask with apertures at random but precisely known positions. Determine the best possible relaying optics and design an optimized mask accordingly. Factors like deformation of the projected pixel matrix and limitations in resolving power of the lens system must be taken into account for mask design.<br />
<br />
Important note: Much of this work is to be performed in the laboratory. For as long as corona safety measures are active, the labs at Nikhef are not accessible for students and this project cannot be worked on. Currently we hope that the situation will have improved by august. <br />
<br />
''Contact: [mailto:martinfr@nikhef.nl Martin Fransen]''<br />
<br />
=== Theory: The Effective Field Theory Pathway to New Physics at the LHC ===<br />
A promising framework to parametrise in a robust and model-independent way deviations from the Standard Model (SM) induced by new heavy particles is the Standard Model Effective Field Theory (SMEFT). In this formalism, beyond the SM effects are encapsulated in higher-dimensional operators constructed from SM fields respecting their symmetry properties. In this project, we aim to carry out a global analysis of the SMEFT from high-precision LHC data, including Higgs boson production, flavour observables, and low-energy measurements. This analysis will be carried out in the context of the recently developed SMEFiT approach [1] based on Machine Learning techniques to efficiently explore the complex theory parameter space. The ultimate goal is either to uncover glimpses of new particles or interactions at the LHC, or to derive the most stringent model-independent bounds to date on general theories of New Physics. Of particular interest are novel methods for charting the parameter space [2], the matching to UV-complete theories in explicit BSM scenarios [3], and the interplay between EFT-based model-independent searches for new physics and determinations of the proton structure from LHC data [4].<br />
<br />
[1] https://arxiv.org/abs/1901.05965<br />
[2] https://arxiv.org/abs/1906.05296<br />
[3] https://arxiv.org/abs/1908.05588<br />
[4] https://arxiv.org/abs/1905.05215<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory: Charting the quark and gluon structure of protons and nuclei with Machine Learning ===<br />
Deepening our knowledge of the partonic content of nucleons and nuclei [1] represents a central endeavour of modern high-energy and nuclear physics, with ramifications in related disciplines such as astroparticle physics. There are two main scientific drivers motivating these investigations of the partonic structure of hadrons. On the one hand, addressing fundamental open issues in our understanding in the strong interactions such as the origin of the nucleon mass, spin, and transverse structure; the presence of heavy quarks in the nucleon wave function; and the possible onset of novel gluon-dominated dynamical regimes. On the other hand, pinning down with the highest possible precision the substructure of nucleons and nuclei is a central component for theoretical predictions in a wide range of experiments, from proton and heavy ion collisions at the Large Hadron Collider to ultra-high energy neutrino interactions at neutrino telescopes. The goal of this project is to exploit Machine Learning and Artificial Intelligence tools [2,3] (neural networks trained by stochastic gradient descent) to pin down the quark and gluon substructure of protons and nuclei by using recent measurements from proton-proton and proton-lead collisions at the LHC. Topics of special interest are i) the strange content of protons and nuclei, ii) parton distributions at higher-orders in the QCD couplings for precision Higgs physics, iii) the interplay between jet, photon, and top quark production data to pin down the large-x gluon, and iv) charm quarks as a probe of gluon shadowing at small-x. The project also involves developing projects for the Electron-Ion Collider (EIC), a new lepton-nucleus experiment to start operations in the next years.<br />
<br />
[1] https://arxiv.org/abs/1910.03408<br />
[2] https://arxiv.org/abs/1904.00018 <br />
[3] https://arxiv.org/abs/1706.00428<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory: Machine learning for Electron Microscopy for next-generation materials ===<br />
Machine Learning tools developed and applied for particle physics hold great potential for applications in material science, in particular concerning faithful uncertainty estimation and model training for large parameter spaces. In this project, carried out in collaboration with the group of Dr. Sonia Conesa-Boj from the Kavli Institute Nanoscience Delft, http://www.conesabojlab.tudelft.nl, we will develop and deploy ML tools for data analysis in Electron Microscopy. We will focus on pinning down the properties of novel quantum materials such as topological insulators and van der Waals materials. Examples of possible applications include model-independent background subtraction in electron-energy loss spectroscopy, automatic classification of crystalline structures, and enhancing spatial and spectral resolution using convolutional networks.<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
===Theory: The electroweak phase transition and baryogenesis/gravitational wave production ===<br />
<br />
In extensions of the Standard Model the electroweak phase transition can be first order and proceed via the nucleation of bubbles. Colliding bubbles can produce gravitational waves [1] and plasma particles interacting with the bubbles can generate a matter-antimatter asymmetry [2]. A detailed understanding of the dynamics of the phase transitions is needed to accurately describe these processes. One project is to study QFT at finite temperature and compare/apply methods that address the non-perturbative IR dynamics of the thermal processes [3,4]. Another project is to calculate the velocity by which the bubbles expand, which is an important parameter for gravitational waves production and baryogensis. This entails among other things tunneling dymamics, (thermal) scattering rates and Boltzmann equations [5].<br />
<br />
[1]https://arxiv.org/abs/1705.01783<br />
[2]https://arxiv.org/pdf/hep-ph/0609145.pdf<br />
[3]https://arxiv.org/pdf/1609.06230.pdf<br />
[4]https://arxiv.org/pdf/1612.00466.pdf<br />
[5]https://arxiv.org/pdf/1809.04907.pdf<br />
<br />
''Contact: [mailto:mpostma@nikhef.nl Marieke Postma]''<br />
<br />
===Theory: Cosmology of the QCD axion ===<br />
<br />
The QCD axion provides an elegant solution to the strong CP problem in QCD[1]. This project focus on the cosmological dynamics of this hypothesized axion field, and in particular the possibility that it can both produce the observed matter-antimatter asymmetry and dark matter abundance in our universe [2,3].<br />
<br />
[1]https://arxiv.org/abs/1812.02669<br />
[2]https://arxiv.org/pdf/hep-ph/0609145.pdf<br />
[3]https://arxiv.org/pdf/1910.02080.pdf<br />
<br />
''Contact: [mailto:mpostma@nikhef.nl Marieke Postma]''<br />
<br />
===Theory: Neutrinos, hierarchy problem and cosmology ===<br />
<br />
The electroweak hierachy problem is absent if the quadratic term in the Higgs potential is generated dynamically. This is achieved in 'the neutrino option' [1] where the Higgs potential stems exclusively from quantum effects of heavy right-handed neutrinos, which can also generate the mass pattern of the oberved left-handed neutrinos. The project focusses on model building aspects (e.g. [2]) and the cosmology (e.g. leptogenesis [3]) of these set-ups.<br />
<br />
[1] https://arxiv.org/pdf/1703.10924.pdf<br />
[2] https://arxiv.org/pdf/1807.11490.pdf<br />
[3] https://arxiv.org/pdf/1905.12642.pdf<br />
<br />
''Contact: [mailto:mpostma@nikhef.nl Marieke Postma]''<br />
<br />
=== KM3NeT: Reconstruction of first neutrino interactions in KM3NeT ===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first few strings with sensitive photodetectors have been deployed at both the Italian and the French detector sites. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In this project the available data will be used together with simulations to best reconstruct the event topologies and optimally identify and reconstruct the first neutrino interactions in the KM3NeT detector and with this pave the path towards accurate neutrino oscillation measurements and neutrino astronomy. <br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
''Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn] [mailto:dosamtnikhef.nl Dorothea Samtleben]'''<br />
<br />
=== KM3NeT: Searching for New Heavy Neutrinos ===<br />
<br />
In this project we will be searching for a new heavy neutrino, looking at signatures created by atmospheric neutrinos interacting in the detector volume of KM3NeT-ORCA. The aim of this project is to study a specific event topology which appears as double blobs of signals detected separately by densely instrumented ORCA detector units. We will be exploiting the tau reconstruction algorithms to verify the possibility of ORCA to detect such signals and to estimate the potential sensitivity of the experiment as well. Basic knowledge of elementary particle physics and data analysis techniques will be advantageous. The knowledge of programming languages e.g. python (and possibly C++) and ROOT are advantageous but not mandatory. <br />
<br />
''Contact: [mailto:suzanbp@nikhef.nl Suzan B. du Pree] [mailto:dveijk@nikhef.nl Daan van Eijk]''<br />
<br />
=== KM3NeT: Dark Matter with KM3NeT-ORCA === <br />
<br />
Dark Matter is thought to be everywhere (we should be swimming through it), but we have no idea what it is. Using the good energy and angular resolutions of the KM3NeT neutrino telescope, we can search for Dark Matter signatures that originate from the center of our galaxy. In this project, we will search for such signatures using the reconstructed track and shower events with the KM3NeT-ORCA detector to discover relatively light Dark Matter particles. Since this year, the KM3NeT-ORCA experiment has 6 detection lines under the Mediterranean Sea: fully operational and continuously taking data. Using the available data, it is possible to compare data and simulation for different event topologies and to estimate the experiment's sensitivity. The project is suitable for a student who is interested to explore new physics scenarios and willing to develop new skills. Basic knowledge of elementary particle physics and data analysis techniques will be advantageous. The knowledge of programming languages e.g. python (possibly C++) and ROOT data analysis tool are advantageous but not mandatory. <br />
<br />
''Contact: [mailto:suzanbp@nikhef.nl Suzan B. du Pree] [mailto:dveijk@nikhef.nl Daan van Eijk]''<br />
<br />
<br />
=== Gravitational Waves: Unraveling the structure of neutron stars with gravitational wave observations ===<br />
<br />
Neutron stars were first discovered more than half a century ago, yet their detailed internal structure largely remains a mystery. A range of theoretical models have been put forward for the neutron star "equation of state", but until recently there was no real way to test them. The direct detection of gravitational waves with LIGO and Virgo has the potential to remedy the situation. When two neutron stars spiral towards each other, they get tidally deformed in a way that is determined by the equation of state, and these deformations get imprinted upon the shape of the gravitational wave that gets emitted. After the first gravitational wave observation of such an event in 2017, several equation of state models could already be ruled out. With expected upgrades of the detectors, we will at some point have access not only to the "inspiral" of binary neutron stars, but to the merger itself, and what happens afterwards. The project will consist of using results from large-scale numerical simulations to come up with a heuristic model for the waveform that describes the inspiral-merger-postmerger process with sufficient accuracy given expected detector sensitivities, and to develop data analysis techniques to efficiently use this model to extract information about the neutron star equation of state.<br />
<br />
''Contact: [mailto:vdbroeck@nikhef.nl Chris Van Den Broeck]''<br />
<br />
<br />
=== Gravitational Waves: Searches for gravitational waves from compact binary coalescence ===<br />
Searches for gravitational waves from the mergers of black holes and neutron stars have been extraordinarily successful in the last four years. We are now beginning to study a population of heavy stellar-mass black holes in detail, including understanding how these systems came to form and whether they are consistent with general relativity. Additionally, the detection of binary neutron star mergers is allowing us to probe their extreme matter. However, we’ve only just scratched the surface of possible signals and the new physics they’d allow us to study. The detection of highly spinning and precessing systems would allow us to perform black hole population statistics to an extraordinary degree of accuracy. Detection of sub-solar mass systems would provide evidence of dark matter. However, these searches are difficult because they require us to work in high-dimensional spaces and develop new statistical methods. There are possibilities for several projects that involve the development and implementation of these new searches as well as the interpretation of the results, particularly in terms of the physics describing compact binary mergers.<br />
<br />
''Contact: [mailto:physarah@gmail.com Sarah Caudill]''<br />
<br />
=== VU LaserLaB: Measuring the electric dipole moment (EDM) of the electron ===<br />
<br />
In collaboration with Nikhef and the Van Swinderen Institute for Particle Physics and Gravity at the University of Groningen, we have recently started an exciting project to measure the electric dipole moment (EDM) of the electron in cold beams of barium-fluoride molecules. The eEDM, which is predicted by the Standard Model of particle physics to be extremely small, is a powerful probe to explore physics beyond this Standard Model. All extensions to the Standard Model, most prominently supersymmetry, naturally predict an electron EDM that is just below the current experimental limits. We aim to improve on the best current measurement by at least an order of magnitude. To do so we will perform a precision measurement on a slow beam of laser-cooled BaF molecules. With this low-energy precision experiment, we test physics at energies comparable to those of LHC! <br />
<br />
At LaserLaB VU, we are responsible for building and testing a cryogenic source of BaF molecules. The main parts of this source are currently being constructed in the workshop. We are looking for enthusiastic master students to help setup the laser system that will be used to detect BaF. Furthermore, projects are available to perform simulations of trajectory simulations to design a lens system that guides the BaF molecules from the exit of the cryogenic source to the experiment.<br />
<br />
''Contact: [mailto:H.L.Bethlem@vu.nl Rick Bethlem]''<br />
<br />
=== VU LaserLaB: Physics beyond the Standard model from molecules ===<br />
<br />
Our team, with a number of staff members (Ubachs, Eikema, Salumbides, Bethlem, Koelemeij) focuses on precision measurements in the hydrogen molecule, and its isotopomers. The work aims at testing the QED calculations of energy levels in H2, D2, T2, HD, etc. with the most precise measurements, where all kind of experimental laser techniques play a role (cw and pulsed lasers, atomic clocks, frequency combs, molecular beams). Also a target of studies is the connection to the "Proton size puzzle", which may be solved through studies in the hydrogen molecular isotopes.<br />
<br />
In the past half year we have produced a number of important results that are described in<br />
the following papers:<br />
* Frequency comb (Ramsey type) electronic excitations in the H2 molecule:<br />
see: Deep-ultraviolet frequency metrology of H2 for tests of molecular quantum theory<br />
http://www.nat.vu.nl/~wimu/Publications/Altmann-PRL-2018.pdf<br />
* ''Precision measurement of an infrared transition in the HD molecule''<br />
see: Sub-Doppler frequency metrology in HD for tests of fundamental physics: https://arxiv.org/abs/1712.08438<br />
* ''The first precision study in molecular tritium T2''<br />
see: Relativistic and QED effects in the fundamental vibration of T2: http://arxiv.org/abs/1803.03161<br />
* ''Dissociation energy of the hydrogen molecule at 10^-9 accuracy'' paper submitted to Phys. Rev. Lett.<br />
* ''Probing QED and fundamental constants through laser spectroscopy of vibrational transitions in HD+'' <br />
This is also a study of the hydrogen molecular ion HD+, where important results were obtained not so long ago, and where we have a strong activity: http://www.nat.vu.nl/~wimu/Publications/ncomms10385.pdf<br />
<br />
These five results mark the various directions we are pursuing, and in all directions we aim at obtaining improvements. Specific projects with students can be defined; those are mostly experimental, although there might be some theoretical tasks, like performing calculations of hyperfine structures. <br />
''Contact: [mailto:w.m.g.ubachs@vu.nl Wim Ubachs] [mailto:k.s.e.eikema@vu.nl Kjeld Eikema] [mailto:h.l.bethlem@vu.nl Rick Bethlem]''<br />
<br />
<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=469Master Projects2020-03-17T14:10:30Z<p>Rojo@nikhef.nl: /* Theory: Pinning down the initial state of heavy-ion collisions with Machine Learning */</p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
== Projects with September 2020 start ==<br />
<br />
=== Lepton Collider: Pixel TPC testbeam ===<br />
In the Lepton Collider group at Nikhef we work on a tracking detector for a future Collider (e.g. the ILC in Japan). We are developing a gaseous Time Projection Chamber with a pixel readout. At Nikhef we have built an 8-quad GridPix module based on the Timepix3 chip, which is a detector of about 20 cm x 40 cm x 10 cm in size. In August 2020 we will test the device at the DESY particle accelerator in Hamburg. For the project you could work on preparations for the test beam (e.g. running the data acquisition, perform data monitoring using our set up in the lab). The next topics will be the participation in the data taking during the test beam at DESY, the analysis of the data using C++ and ROOT and - finally - publication of the results in a scientific journal.<br />
<br />
Our latest paper can be found in https://www.nikhef.nl/~s01/quad_paper.pdf [www.nikhef.nl].<br />
<br />
''Contact: [mailto:Peter.Kluit@nikhef.nl Peter Kluit] and Kees Ligtenberg''<br />
<br />
<br />
=== ATLAS: The Next Generation ===<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks is very new [1] and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays), advanced analysis techiques (using deep learning methods) and expanding the theory interpretation. Another opportunity would be the development of the first statistical combination of results between the ATLAS and CMS experiment, which could significantly improve the discovery potentional.<br />
<br />
[1] https://arxiv.org/abs/1802.04329<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree and Marko Stamenkovic]''<br />
<br />
=== ATLAS: The Most Energetic Higgs Boson ===<br />
<br />
The production of Higgs bosons at the highest energies could give the first indications for deviations from the standard model of particle physics, but production energies above 500 GeV have not been observed yet [1]. The LHC Run-2 dataset, collected during the last 4 years, might be the first opportunity to observe such processes, and we have various ideas for new studies. Possible developments include the improvement of boosted reconstruction techniques, for example using multivariate deep learning methods. Also, there are various opportunities for unexplored theory interpretations (using the MadGraph event generator), including effective field theory models (with novel ‘morphing’ techniques) and new interpretations of the newly observed boosted VZ(bb) process.<br />
<br />
[1] https://arxiv.org/abs/1709.05543<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree and Brian Moser]''<br />
<br />
=== Dark Matter: XENON1T Data Analysis ===<br />
The XENON collaboration has used the XENON1T detector to achieve the world’s most sensitive direct detection dark matter results and is currently building the XENONnT successor experiment. The detectors operate at the Gran Sasso underground laboratory and consist of so-called dual-phase xenon time-projection chambers filled with ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the data from the XENON1T detector. The work will consist of understanding the detector signals and applying machine learning tools such as deep neutral networks to improve the reconstruction performance in our Python-based analysis tool, following the approach described in arXiv:1804.09641. The final goal is to improve the energy and position reconstruction uncertainties for the dark matter search. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter: XAMS R&D Setup ===<br />
The Amsterdam Dark Matter group operates an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 4kg of ultra-pure liquid xenon. We plan to use this detector for the development of new detection techniques (such as utilizing new photosensors) and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENON experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data him/herself. You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter: DARWIN Sensitivity Studies ===<br />
DARWIN is the "ultimate" direct detection dark matter experiment, with the goal to reach the so-called "neutrino floor", when neutrinos become a hard-to-reduce background. The large and exquisitely clean xenon mass will allow DARWIN to also be sensitive to other physics signals such as solar neutrinos, double-beta decay from Xe-136, axions and axion-like particles etc. While the experiment will only start in 2025, we are in the midst of optimizing the experiment, which is driven by simulations. We have an opening for a student to work on the GEANT4 Monte Carlo simulations for DARWIN, as part of a simulation team together with the University of Freiburg and Zurich. We are also working on a "fast simulation" that could be included in this framework. It is your opportunity to steer the optimization of a large and unique experiment. This project requires good programming skills (Python and C++) and data analysis/physics interpretation skills. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== The Modulation Experiment: Data Analysis ===<br />
There exist a few measurements that suggest an annual modulation in the activity of radioactive sources. With a few groups from the XENON collaboration we have developed four sets of table-top experiments to investigate this effect on a few well known radioactive sources. The experiments are under construction in Purdue University (USA), a mountain top in Switzerland, a beach in Rio de Janeiro and the last one at Nikhef in Amsterdam. We urgently need a master student to (1) analyze the first big data set, and (2) contribute to the first physics paper from the experiment. We are looking for all-round physicists with interest in both lab-work and data-analysis. The student(s) will directly collaborate with the other groups in this small collaboration (around 10 people), and the goal is to have the first physics publication ready by the end of the project. During the 2018-2019 season there are positions for two MSc students.<br />
<br />
''Contact: [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Detector R&D: Laser Interferometer Space Antenna (LISA) ===<br />
The space-based gravitational wave antenna LISA is, without a doubt, one of the most challenging space missions ever proposed. ESA plans to launch around 2030 three spacecraft that are separated by a few million kilometers to measure tiny variations in the distances between test-masses located in each satellite to detect the gravitational waves from sources such as supermassive black holes. The triangular constellation of the LISA mission is dynamic, requiring a constant fine-tuning related to the pointing of the laser links between the spacecraft and a simultaneous refocusing of the telescope. The noise sources related to the laser links expect to provide a dominant contribution to the LISA performance.<br />
An update and extension of the LISA science simulation software are needed to assess the hardware development for LISA at Nikhef, TNO, and SRON. A position is therefore available for a master student to study the impact of instrumental noise on the performance of LISA. Realistic simulations based on hardware (noise) characterization measurements performed at TNO will be carried out and compared to the expected tantalizing gravitational wave sources.<br />
<br />
''Contact: [mailto:nielsvb@nikhef.nl Niels van Bakel],[mailto:ernst-jan.buis@tno.nl Ernst-Jan Buis]''<br />
<br />
=== Theory: The Effective Field Theory Pathway to New Physics at the LHC ===<br />
A promising framework to parametrise in a robust and model-independent way deviations from the Standard Model (SM) induced by new heavy particles is the Standard Model Effective Field Theory (SMEFT). In this formalism, beyond the SM effects are encapsulated in higher-dimensional operators constructed from SM fields respecting their symmetry properties. In this project, we aim to carry out a global analysis of the SMEFT from high-precision LHC data, including Higgs boson production, flavour observables, and low-energy measurements. This analysis will be carried out in the context of the recently developed SMEFiT approach [1] based on Machine Learning techniques to efficiently explore the complex theory parameter space. The ultimate goal is either to uncover glimpses of new particles or interactions at the LHC, or to derive the most stringent model-independent bounds to date on general theories of New Physics. Of particular interest are novel methods for charting the parameter space [2], the matching to UV-complete theories in explicit BSM scenarios [3], and the interplay between EFT-based model-independent searches for new physics and determinations of the proton structure from LHC data [4].<br />
<br />
[1] https://arxiv.org/abs/1901.05965<br />
[2] https://arxiv.org/abs/1906.05296<br />
[3] https://arxiv.org/abs/1908.05588<br />
[4] https://arxiv.org/abs/1905.05215<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory: Charting the quark and gluon structure of protons and nuclei with Machine Learning ===<br />
Deepening our knowledge of the partonic content of nucleons and nuclei [1] represents a central endeavour of modern high-energy and nuclear physics, with ramifications in related disciplines such as astroparticle physics. There are two main scientific drivers motivating these investigations of the partonic structure of hadrons. On the one hand, addressing fundamental open issues in our understanding in the strong interactions such as the origin of the nucleon mass, spin, and transverse structure; the presence of heavy quarks in the nucleon wave function; and the possible onset of novel gluon-dominated dynamical regimes. On the other hand, pinning down with the highest possible precision the substructure of nucleons and nuclei is a central component for theoretical predictions in a wide range of experiments, from proton and heavy ion collisions at the Large Hadron Collider to ultra-high energy neutrino interactions at neutrino telescopes. The goal of this project is to exploit Machine Learning and Artificial Intelligence tools [2,3] (neural networks trained by stochastic gradient descent) to pin down the quark and gluon substructure of protons and nuclei by using recent measurements from proton-proton and proton-lead collisions at the LHC. Topics of special interest are i) the strange content of protons and nuclei, ii) parton distributions at higher-orders in the QCD couplings for precision Higgs physics, iii) the interplay between jet, photon, and top quark production data to pin down the large-x gluon, and iv) charm quarks as a probe of gluon shadowing at small-x. The project also involves developing projects for the Electron-Ion Collider (EIC), a new lepton-nucleus experiment to start operations in the next years.<br />
<br />
[1] https://arxiv.org/abs/1910.03408<br />
[2] https://arxiv.org/abs/1904.00018 <br />
[3] https://arxiv.org/abs/1706.00428<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=468Master Projects2020-03-17T14:02:15Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
== Projects with September 2020 start ==<br />
<br />
=== Lepton Collider: Pixel TPC testbeam ===<br />
In the Lepton Collider group at Nikhef we work on a tracking detector for a future Collider (e.g. the ILC in Japan). We are developing a gaseous Time Projection Chamber with a pixel readout. At Nikhef we have built an 8-quad GridPix module based on the Timepix3 chip, which is a detector of about 20 cm x 40 cm x 10 cm in size. In August 2020 we will test the device at the DESY particle accelerator in Hamburg. For the project you could work on preparations for the test beam (e.g. running the data acquisition, perform data monitoring using our set up in the lab). The next topics will be the participation in the data taking during the test beam at DESY, the analysis of the data using C++ and ROOT and - finally - publication of the results in a scientific journal.<br />
<br />
Our latest paper can be found in https://www.nikhef.nl/~s01/quad_paper.pdf [www.nikhef.nl].<br />
<br />
''Contact: [mailto:Peter.Kluit@nikhef.nl Peter Kluit] and Kees Ligtenberg''<br />
<br />
<br />
=== ATLAS: The Next Generation ===<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks is very new [1] and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays), advanced analysis techiques (using deep learning methods) and expanding the theory interpretation. Another opportunity would be the development of the first statistical combination of results between the ATLAS and CMS experiment, which could significantly improve the discovery potentional.<br />
<br />
[1] https://arxiv.org/abs/1802.04329<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree and Marko Stamenkovic]''<br />
<br />
=== ATLAS: The Most Energetic Higgs Boson ===<br />
<br />
The production of Higgs bosons at the highest energies could give the first indications for deviations from the standard model of particle physics, but production energies above 500 GeV have not been observed yet [1]. The LHC Run-2 dataset, collected during the last 4 years, might be the first opportunity to observe such processes, and we have various ideas for new studies. Possible developments include the improvement of boosted reconstruction techniques, for example using multivariate deep learning methods. Also, there are various opportunities for unexplored theory interpretations (using the MadGraph event generator), including effective field theory models (with novel ‘morphing’ techniques) and new interpretations of the newly observed boosted VZ(bb) process.<br />
<br />
[1] https://arxiv.org/abs/1709.05543<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree and Brian Moser]''<br />
<br />
=== Dark Matter: XENON1T Data Analysis ===<br />
The XENON collaboration has used the XENON1T detector to achieve the world’s most sensitive direct detection dark matter results and is currently building the XENONnT successor experiment. The detectors operate at the Gran Sasso underground laboratory and consist of so-called dual-phase xenon time-projection chambers filled with ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the data from the XENON1T detector. The work will consist of understanding the detector signals and applying machine learning tools such as deep neutral networks to improve the reconstruction performance in our Python-based analysis tool, following the approach described in arXiv:1804.09641. The final goal is to improve the energy and position reconstruction uncertainties for the dark matter search. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter: XAMS R&D Setup ===<br />
The Amsterdam Dark Matter group operates an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 4kg of ultra-pure liquid xenon. We plan to use this detector for the development of new detection techniques (such as utilizing new photosensors) and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENON experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data him/herself. You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter: DARWIN Sensitivity Studies ===<br />
DARWIN is the "ultimate" direct detection dark matter experiment, with the goal to reach the so-called "neutrino floor", when neutrinos become a hard-to-reduce background. The large and exquisitely clean xenon mass will allow DARWIN to also be sensitive to other physics signals such as solar neutrinos, double-beta decay from Xe-136, axions and axion-like particles etc. While the experiment will only start in 2025, we are in the midst of optimizing the experiment, which is driven by simulations. We have an opening for a student to work on the GEANT4 Monte Carlo simulations for DARWIN, as part of a simulation team together with the University of Freiburg and Zurich. We are also working on a "fast simulation" that could be included in this framework. It is your opportunity to steer the optimization of a large and unique experiment. This project requires good programming skills (Python and C++) and data analysis/physics interpretation skills. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== The Modulation Experiment: Data Analysis ===<br />
There exist a few measurements that suggest an annual modulation in the activity of radioactive sources. With a few groups from the XENON collaboration we have developed four sets of table-top experiments to investigate this effect on a few well known radioactive sources. The experiments are under construction in Purdue University (USA), a mountain top in Switzerland, a beach in Rio de Janeiro and the last one at Nikhef in Amsterdam. We urgently need a master student to (1) analyze the first big data set, and (2) contribute to the first physics paper from the experiment. We are looking for all-round physicists with interest in both lab-work and data-analysis. The student(s) will directly collaborate with the other groups in this small collaboration (around 10 people), and the goal is to have the first physics publication ready by the end of the project. During the 2018-2019 season there are positions for two MSc students.<br />
<br />
''Contact: [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Detector R&D: Laser Interferometer Space Antenna (LISA) ===<br />
The space-based gravitational wave antenna LISA is, without a doubt, one of the most challenging space missions ever proposed. ESA plans to launch around 2030 three spacecraft that are separated by a few million kilometers to measure tiny variations in the distances between test-masses located in each satellite to detect the gravitational waves from sources such as supermassive black holes. The triangular constellation of the LISA mission is dynamic, requiring a constant fine-tuning related to the pointing of the laser links between the spacecraft and a simultaneous refocusing of the telescope. The noise sources related to the laser links expect to provide a dominant contribution to the LISA performance.<br />
An update and extension of the LISA science simulation software are needed to assess the hardware development for LISA at Nikhef, TNO, and SRON. A position is therefore available for a master student to study the impact of instrumental noise on the performance of LISA. Realistic simulations based on hardware (noise) characterization measurements performed at TNO will be carried out and compared to the expected tantalizing gravitational wave sources.<br />
<br />
''Contact: [mailto:nielsvb@nikhef.nl Niels van Bakel],[mailto:ernst-jan.buis@tno.nl Ernst-Jan Buis]''<br />
<br />
=== Theory: The Effective Field Theory Pathway to New Physics at the LHC ===<br />
A promising framework to parametrise in a robust and model-independent way deviations from the Standard Model (SM) induced by new heavy particles is the Standard Model Effective Field Theory (SMEFT). In this formalism, beyond the SM effects are encapsulated in higher-dimensional operators constructed from SM fields respecting their symmetry properties. In this project, we aim to carry out a global analysis of the SMEFT from high-precision LHC data, including Higgs boson production, flavour observables, and low-energy measurements. This analysis will be carried out in the context of the recently developed SMEFiT approach [1] based on Machine Learning techniques to efficiently explore the complex theory parameter space. The ultimate goal is either to uncover glimpses of new particles or interactions at the LHC, or to derive the most stringent model-independent bounds to date on general theories of New Physics. Of particular interest are novel methods for charting the parameter space [2], the matching to UV-complete theories in explicit BSM scenarios [3], and the interplay between EFT-based model-independent searches for new physics and determinations of the proton structure from LHC data [4].<br />
<br />
[1] https://arxiv.org/abs/1901.05965<br />
[2] https://arxiv.org/abs/1906.05296<br />
[3] https://arxiv.org/abs/1908.05588<br />
[4] https://arxiv.org/abs/1905.05215<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory: Pinning down the initial state of heavy-ion collisions with Machine Learning ===<br />
It has been known for more than three decades that the parton distribution functions (PDFs) of nucleons bound within heavy nuclei are modified with respect to their free-nucleon counterparts. Despite active experimental and theoretical investigations, the underlying mechanisms that drive these in-medium modifications of nucleon substructure have yet to be fully understood. The determination of nuclear PDFs is a topic of high relevance in order both to improve our fundamental understanding of the strong interactions in the nuclear environment, as well as and for the interpretation of heavy ion collisions at RHIC and the LHC, in particular for the characterization of the Quark-Gluon Plasma. The goal of this project is to exploit Machine Learning and Artificial Intelligence tools [1,2] (neural networks trained by stochastic gradient descent) to pin down the initial state of heavy ion collisions by using recent measurements from proton-lead collisions at the LHC. Emphasis will be put on the poorly-known nuclear modifications of the gluon PDFs, which are still mostly terra incognita and highly relevant for phenomenological applications. In addition to theory calculations, the project will also involve code development using modern AI/ML tools such as TensorFlow and Keras.<br />
<br />
[1] https://arxiv.org/abs/1904.00018 <br />
[2] https://arxiv.org/abs/1706.00428<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=467Master Projects2020-03-17T13:58:11Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
== Projects with September 2020 start ==<br />
<br />
=== Lepton Collider: Pixel TPC testbeam ===<br />
In the Lepton Collider group at Nikhef we work on a tracking detector for a future Collider (e.g. the ILC in Japan). We are developing a gaseous Time Projection Chamber with a pixel readout. At Nikhef we have built an 8-quad GridPix module based on the Timepix3 chip, which is a detector of about 20 cm x 40 cm x 10 cm in size. In August 2020 we will test the device at the DESY particle accelerator in Hamburg. For the project you could work on preparations for the test beam (e.g. running the data acquisition, perform data monitoring using our set up in the lab). The next topics will be the participation in the data taking during the test beam at DESY, the analysis of the data using C++ and ROOT and - finally - publication of the results in a scientific journal.<br />
<br />
Our latest paper can be found in https://www.nikhef.nl/~s01/quad_paper.pdf [www.nikhef.nl].<br />
<br />
''Contact: [mailto:Peter.Kluit@nikhef.nl Peter Kluit] and Kees Ligtenberg''<br />
<br />
<br />
=== ATLAS: The Next Generation ===<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks is very new [1] and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays), advanced analysis techiques (using deep learning methods) and expanding the theory interpretation. Another opportunity would be the development of the first statistical combination of results between the ATLAS and CMS experiment, which could significantly improve the discovery potentional.<br />
<br />
[1] https://arxiv.org/abs/1802.04329<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree and Marko Stamenkovic]''<br />
<br />
=== ATLAS: The Most Energetic Higgs Boson ===<br />
<br />
The production of Higgs bosons at the highest energies could give the first indications for deviations from the standard model of particle physics, but production energies above 500 GeV have not been observed yet [1]. The LHC Run-2 dataset, collected during the last 4 years, might be the first opportunity to observe such processes, and we have various ideas for new studies. Possible developments include the improvement of boosted reconstruction techniques, for example using multivariate deep learning methods. Also, there are various opportunities for unexplored theory interpretations (using the MadGraph event generator), including effective field theory models (with novel ‘morphing’ techniques) and new interpretations of the newly observed boosted VZ(bb) process.<br />
<br />
[1] https://arxiv.org/abs/1709.05543<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree and Brian Moser]''<br />
<br />
=== Dark Matter: XENON1T Data Analysis ===<br />
The XENON collaboration has used the XENON1T detector to achieve the world’s most sensitive direct detection dark matter results and is currently building the XENONnT successor experiment. The detectors operate at the Gran Sasso underground laboratory and consist of so-called dual-phase xenon time-projection chambers filled with ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the data from the XENON1T detector. The work will consist of understanding the detector signals and applying machine learning tools such as deep neutral networks to improve the reconstruction performance in our Python-based analysis tool, following the approach described in arXiv:1804.09641. The final goal is to improve the energy and position reconstruction uncertainties for the dark matter search. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter: XAMS R&D Setup ===<br />
The Amsterdam Dark Matter group operates an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 4kg of ultra-pure liquid xenon. We plan to use this detector for the development of new detection techniques (such as utilizing new photosensors) and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENON experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data him/herself. You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter: DARWIN Sensitivity Studies ===<br />
DARWIN is the "ultimate" direct detection dark matter experiment, with the goal to reach the so-called "neutrino floor", when neutrinos become a hard-to-reduce background. The large and exquisitely clean xenon mass will allow DARWIN to also be sensitive to other physics signals such as solar neutrinos, double-beta decay from Xe-136, axions and axion-like particles etc. While the experiment will only start in 2025, we are in the midst of optimizing the experiment, which is driven by simulations. We have an opening for a student to work on the GEANT4 Monte Carlo simulations for DARWIN, as part of a simulation team together with the University of Freiburg and Zurich. We are also working on a "fast simulation" that could be included in this framework. It is your opportunity to steer the optimization of a large and unique experiment. This project requires good programming skills (Python and C++) and data analysis/physics interpretation skills. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== The Modulation Experiment: Data Analysis ===<br />
There exist a few measurements that suggest an annual modulation in the activity of radioactive sources. With a few groups from the XENON collaboration we have developed four sets of table-top experiments to investigate this effect on a few well known radioactive sources. The experiments are under construction in Purdue University (USA), a mountain top in Switzerland, a beach in Rio de Janeiro and the last one at Nikhef in Amsterdam. We urgently need a master student to (1) analyze the first big data set, and (2) contribute to the first physics paper from the experiment. We are looking for all-round physicists with interest in both lab-work and data-analysis. The student(s) will directly collaborate with the other groups in this small collaboration (around 10 people), and the goal is to have the first physics publication ready by the end of the project. During the 2018-2019 season there are positions for two MSc students.<br />
<br />
''Contact: [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Detector R&D: Laser Interferometer Space Antenna (LISA) ===<br />
The space-based gravitational wave antenna LISA is, without a doubt, one of the most challenging space missions ever proposed. ESA plans to launch around 2030 three spacecraft that are separated by a few million kilometers to measure tiny variations in the distances between test-masses located in each satellite to detect the gravitational waves from sources such as supermassive black holes. The triangular constellation of the LISA mission is dynamic, requiring a constant fine-tuning related to the pointing of the laser links between the spacecraft and a simultaneous refocusing of the telescope. The noise sources related to the laser links expect to provide a dominant contribution to the LISA performance.<br />
An update and extension of the LISA science simulation software are needed to assess the hardware development for LISA at Nikhef, TNO, and SRON. A position is therefore available for a master student to study the impact of instrumental noise on the performance of LISA. Realistic simulations based on hardware (noise) characterization measurements performed at TNO will be carried out and compared to the expected tantalizing gravitational wave sources.<br />
<br />
''Contact: [mailto:nielsvb@nikhef.nl Niels van Bakel],[mailto:ernst-jan.buis@tno.nl Ernst-Jan Buis]''<br />
<br />
=== Theory: The Effective Field Theory Pathway to New Physics at the LHC ===<br />
A very promising framework to parametrise in a robust and model-independent way deviations from the Standard Model (SM) induced by new heavy particles is the Standard Model Effective Field Theory (SMEFT). In this formalism, Beyond the SM effects are encapsulated in higher-dimensional operators constructed from SM fields respecting their symmetry properties. In this project, we aim to carry out a global analysis of the SMEFT from high-precision LHC data, including Higgs boson production, flavour observables, and low-energy measurements. This analysis will be carried out in the context of the recently developed SMEFiT approach [1] based on Machine Learning techniques to efficiently explore the complex theory parameter space. The ultimate goal is either to uncover glimpses of new particles or interactions at the LHC, or to derive the most stringent model-independent bounds to date on general theories of New Physics.<br />
<br />
[1] https://arxiv.org/abs/1901.05965<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory: Pinning down the initial state of heavy-ion collisions with Machine Learning ===<br />
It has been known for more than three decades that the parton distribution functions (PDFs) of nucleons bound within heavy nuclei are modified with respect to their free-nucleon counterparts. Despite active experimental and theoretical investigations, the underlying mechanisms that drive these in-medium modifications of nucleon substructure have yet to be fully understood. The determination of nuclear PDFs is a topic of high relevance in order both to improve our fundamental understanding of the strong interactions in the nuclear environment, as well as and for the interpretation of heavy ion collisions at RHIC and the LHC, in particular for the characterization of the Quark-Gluon Plasma. The goal of this project is to exploit Machine Learning and Artificial Intelligence tools [1,2] (neural networks trained by stochastic gradient descent) to pin down the initial state of heavy ion collisions by using recent measurements from proton-lead collisions at the LHC. Emphasis will be put on the poorly-known nuclear modifications of the gluon PDFs, which are still mostly terra incognita and highly relevant for phenomenological applications. In addition to theory calculations, the project will also involve code development using modern AI/ML tools such as TensorFlow and Keras.<br />
<br />
[1] https://arxiv.org/abs/1904.00018 <br />
[2] https://arxiv.org/abs/1706.00428<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=403Master Projects2019-05-02T12:01:34Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
== Projects with September 2019 start ==<br />
<br />
=== Theory: The Effective Field Theory Pathway to New Physics at the LHC ===<br />
<br />
A very promising framework to parametrise in a robust and model-independent way deviations from the Standard Model (SM) induced by new heavy particles is the Standard Model Effective Field Theory (SMEFT). In this formalism, Beyond the SM effects are encapsulated in higher-dimensional operators constructed from SM fields respecting their symmetry properties. In this project, we aim to carry out a global analysis of the SMEFT from high-precision LHC data, including Higgs boson production, flavour observables, and low-energy measurements. This analysis will be carried out in the context of the recently developed SMEFiT approach [1] based on Machine Learning techniques to efficiently explore the complex theory parameter space. The ultimate goal is either to uncover glimpses of new particles or interactions at the LHC, or to derive the most stringent model-independent bounds to date on general theories of New Physics.<br />
<br />
[1] https://arxiv.org/abs/1901.05965<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory: Pinning down the initial state of heavy-ion collisions with Machine Learning ===<br />
<br />
It has been known for more than three decades that the parton distribution functions (PDFs) of nucleons bound within heavy nuclei are modified with respect to their free-nucleon counterparts. Despite active experimental and theoretical investigations, the underlying mechanisms that drive these in-medium modifications of nucleon substructure have yet to be fully understood. The determination of nuclear PDFs is a topic of high relevance in order both to improve our fundamental understanding of the strong interactions in the nuclear environment, as well as and for the interpretation of heavy ion collisions at RHIC and the LHC, in particular for the characterization of the Quark-Gluon Plasma. The goal of this project is to exploit Machine Learning and Artificial Intelligence tools [1,2] (neural networks trained by stochastic gradient descent) to pin down the initial state of heavy ion collisions by using recent measurements from proton-lead collisions at the LHC. Emphasis will be put on the poorly-known nuclear modifications of the gluon PDFs, which are still mostly ''terra incognita'' and highly relevant for phenomenological applications. In addition to theory calculations, the project will also involve code development using modern AI/ML tools such as TensorFlow and Keras.<br />
<br />
[1] https://arxiv.org/abs/1811.05858<br />
[2] https://arxiv.org/abs/1410.8849<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory: The High-Energy Muon Crisis and Perturbative QCD ===<br />
<br />
The production of charmed meson from the collision of high-energy cosmic rays with air nucleons in the upper atmosphere provides an important component of the flux of high-energy muons and neutrinos that can be detected at cosmic ray experiments such as AUGER and neutrino telescopes such as KM3NET or IceCube. The production of forward muons from charmed meson decays is usually predicted from QCD models tuned to the data, rather than from first principles QCD calculation. Interestingly, the number of such high-energy muons observed by AUGER seems to differ markedly from current theory predictions. In this project we aim to exploit state-of-the-art perturbative and non-perturbative QCD techniques to compute the flux of high-energy muons from charm decays and make predictions for a number of experiments sensitive to them<br />
<br />
<br />
[1] https://arxiv.org/abs/1904.12547<br />
[2] https://arxiv.org/abs/1808.02034<br />
[3] https://arxiv.org/abs/1511.06346 <br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Dark Matter: XENON1T Data Analysis ===<br />
The XENON collaboration has used the XENON1T detector to achieve the world’s most sensitive direct detection dark matter results and is currently building the XENONnT successor experiment. The detectors operate at the Gran Sasso underground laboratory and consist of so-called dual-phase xenon time-projection chambers filled with ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the data from the XENON1T detector. The work will consist of understanding the detector signals and applying machine learning tools such as deep neutral networks to improve the reconstruction performance in our Python-based analysis tool, following the approach described in arXiv:1804.09641. The final goal is to improve the energy and position reconstruction uncertainties for the dark matter search. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter: XAMS R&D Setup ===<br />
The Amsterdam Dark Matter group operates an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 4kg of ultra-pure liquid xenon. We plan to use this detector for the development of new detection techniques (such as utilizing new photosensors) and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENON experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data him/herself. You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter: DARWIN Sensitivity Studies ===<br />
DARWIN is the "ultimate" direct detection dark matter experiment, with the goal to reach the so-called "neutrino floor", when neutrinos become a hard-to-reduce background. The large and exquisitely clean xenon mass will allow DARWIN to also be sensitive to other physics signals such as solar neutrinos, double-beta decay from Xe-136, axions and axion-like particles etc. While the experiment will only start in 2025, we are in the midst of optimizing the experiment, which is driven by simulations. We have an opening for a student to work on the GEANT4 Monte Carlo simulations for DARWIN, as part of a simulation team together with the University of Freiburg and Zurich. We are also working on a "fast simulation" that could be included in this framework. It is your opportunity to steer the optimization of a large and unique experiment. This project requires good programming skills (Python and C++) and data analysis/physics interpretation skills. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== The Modulation Experiment: Data Analysis ===<br />
There exist a few measurements that suggest an annual modulation in the activity of radioactive sources. With a few groups from the XENON collaboration we have developed four sets of table-top experiments to investigate this effect on a few well known radioactive sources. The experiments are under construction in Purdue University (USA), a mountain top in Switzerland, a beach in Rio de Janeiro and the last one at Nikhef in Amsterdam. We urgently need a master student to (1) analyze the first big data set, and (2) contribute to the first physics paper from the experiment. We are looking for all-round physicists with interest in both lab-work and data-analysis. The student(s) will directly collaborate with the other groups in this small collaboration (around 10 people), and the goal is to have the first physics publication ready by the end of the project. During the 2018-2019 season there are positions for two MSc students.<br />
<br />
''Contact: [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== ATLAS: Excited lepton searches with multiple leptons ===<br />
<br />
The Standard Model of particle physics (SM) is extremely successful, but would it hold against check with data containing multiple leptons? Although very rare process, the production of leptons is calculated in SM with high precision. On detector side the leptons (electrons and muons) are easy to reconstruct and such a sample contains very little "non-lepton" background. This analysis has an ambitious goal to find beyond Standard Model processes like Excited leptons using events with 4 leptons. With this project, the student would gain close familiarity with modern experimental techniques (statistical analysis, SM predictions, search for rare signals), with Monte Carlo generators and the standard HEP analysis tools (ROOT, C++, python).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and Marcus Morgenstern and Pepijn Bakker]''<br />
<br />
=== ATLAS: A search for lepton non-universality in Bc meson decays ===<br />
<br />
Recently, LHCb experiment has reported a number of intriguing deviations from SM in leptonic decays of B mesons. With this project we would like to probe if ATLAS also observes the same kind of deviation, e.g. in Bc->Jpsi+tau+nu channel w.r.t BC->Jpsi+mu+nu. Success of project will be essential to understand if we finally observe beyond SM process or if LHCb has some detector bias. The student would gain close familiarity with modern experimental techniques (statistical analysis, SM predictions, search for rare signals), background suppression techniques and the standard HEP analysis tools (ROOT, C++, python).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and JJ Teoh]''<br />
<br />
=== ATLAS: The lifetime of the Higgs boson ===<br />
<br />
While the Higgs boson was discovered in 2012, many of its properties still remain unconstrained. This master student project revolves around one such property, the lifetime of the Higgs boson. The lifetime can be obtained by measuring the width of the boson, but because the width is a few hundred times smaller than the detector resolution, a direct measurement is impossible at the moment. But there is an idea to overcome that limitation. By utilizing the interference between the Higgs boson decay and background processes we can perform an indirect measurement. This measurement potentially has the sensitivity that will allow us to perform a measurement of the width (or lifetime) as predicted by the Standard Model. Specifically, the master project will be about predicting the sensitivity of this measurement for different predictions of the Higgs width. The project is on the interface of theory and experiment, making use of Monte Carlo generators and the standard HEP analysis tools (ROOT, C++, python). <br />
<br />
''Contact: [mailto:mveen@nikhef.nl Michiel Veen] or [mailto:Ivo.van.Vulpen@nikhef.nl Hella Snoek & Ivo van Vulpen]''<br />
<br />
=== ATLAS: The Next Generation ===<br />
<br />
After the observation of the coupling of Higgs bosons to fermions of the third generation, the search for the coupling to fermions of the second generation is one of the next priorities for research at CERN's Large Hadron Collider. The search for the decay of the Higgs boson to two charm quarks is very new [1] and we see various opportunities for interesting developments. For this project we propose improvements in reconstruction (using exclusive decays), advanced analysis techiques (using deep learning methods) and expanding the new physics models (e.g. including a search for off-diagonal H->uc couplings). Another opportunity would be the development of the first statistical combination of results between the ATLAS and CMS experiment, which could significantly improve the discovery potentional.<br />
<br />
[1] https://arxiv.org/abs/1802.04329<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree and Marko Stamenkovic]''<br />
<br />
=== ATLAS: The Most Energetic Higgs Boson ===<br />
<br />
The production of Higgs bosons at the highest energies could give the first indications for deviations from the standard model of particle physics, but production energies above 500 GeV have not been observed yet [1]. The LHC Run-2 dataset, collected during the last 4 years, might be the first opportunity to observe such processes, and we have various ideas for new studies. Possible developments include the improvement of boosted reconstruction techniques, for example using multivariate deep learning methods. Also, there are various opportunities for unexplored theory interpretations (using the MadGraph event generator), including effective field theory models (with novel ‘morphing’ techniques) and the study of the Higgs boson’s self coupling.<br />
<br />
[1] https://arxiv.org/abs/1709.05543<br />
<br />
''Contact: [mailto:tdupree@nikhef.nl Tristan du Pree and Brian Moser]''<br />
<br />
=== LHCb: Measurement of Central Exclusive Production Rates of Chi_c using converted photons in LHCb ===<br />
<br />
Central exclusive production (CEP) of particles at the LHC is characterised by a extremely clean signature. Differently from the typical inelastic collisions where many particles are created resulting in a so-called Primary Vertex, CEP events have only the final state particles of interest. In this project the particle of interest is a pair of charmed quarks creating a chi_c particle. In theory this process is generated by a long range gluon exchange and can elucidate the nature of the strong force, described by the quantum chromodynamics in the the standard model. The proposed work involves analysing a pre-existing dataset with reconstructed chi_c and simulating events at the LHCb in order to obtain the relative occurrence rate of each chi_c species (spins 0, 1, 2), a quantity that can be easily compared to theoretical predictions.<br />
<br />
''Contact: [mailto:K.Akiba@nikhef.nl Kazu Akiba]''<br />
<br />
=== LHCb: Optimization studies for Vertex detector at the High Lumi LHCb ===<br />
<br />
The LHCb experiment is dedicated to measure tiny differences between matter and antimatter through the precise study of rare processes involving b or c quarks. The LHCb detector will undergo a major modification in order to dramatically increase the luminosity and be able to measure indirect effects of physics beyond the standard model. In this environment, over 42 simultaneous collisions are expected to happen at a time interval of 200 ps where the two proton bunches overlap. The particles of interest have a relatively long lifetime and therefore the best way to distinguish them from the background collisions is through the precise reconstruction of displaced vertices and pointing directions. The new detector considers using extremely recent or even future technologies to measure space (with resolutions below 10 um) and time (100 ps or better) to efficiently reconstruct the events of interest for physics. The project involves changing completely the LHCb Vertex Locator (VELO) design in simulation and determine what can be the best performance for the upgraded detector, considering different spatial and temporal resolutions.<br />
<br />
''Contact: [mailto:K.Akiba@nikhef.nl Kazu Akiba]''<br />
<br />
=== LHCb: Measurement of charge multiplication in heavily irradiated sensors ===<br />
<br />
During the R&D phase for the LHCb VELO Upgrade detector a few sensor prototypes were irradiated to the extreme fluence expected to be achieved during the detector lifetime. These samples were tested using high energy particles at the SPS facility at CERN with their trajectories reconstructed by the Timepix3 telescope. A preliminary analysis revealed that at the highest irradiation levels the amount of signal observed is higher than expected, and even larger than the signal obtained at lower doses. At the Device Under Test (DUT) position inside the telescope, the spatial resolution attained by this system is below 2 um. This means that a detailed analysis can be performed in order to study where and how this signal amplification happens within the 55x55 um^2 pixel cell. This project involves analysing the telescope and DUT data to investigate the charge multiplication mechanism at the microscopic level.<br />
<br />
''Contact: [mailto:K.Akiba@nikhef.nl Kazu Akiba]''<br />
<br />
=== Detector R&D: Studying fast timing detectors ===<br />
<br />
Fast timing detectors are the solution for future tracking detectors. In future LHC operation conditions and future colliders, more and more particles are produced per collision. The high particle densities make it increasingly more difficult to separate particle trajectories with the spatial information that current silicon tracking detectors provide. A solution would be to add very precise (in order of 10ps) timestamps to the spatial measurements of the particle trackers. A good understanding of the performance of fast timing detectors is necessary. With the user of a pulsed laser in the lab we study the characteristics of several prototype detectors.<br />
<br />
''Contact: [mailto:H.Snoek@nikhef.nl Hella Snoek, Martin van Beuzekom, Kazu Akiba, Daniel Hynds]''<br />
<br />
=== KM3NeT: Reconstruction of first neutrino interactions in KM3NeT ===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first few strings with sensitive photodetectors have been deployed at both the Italian and the French detector sites. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In order to identify neutrinos an accurate reconstruction and optimal understanding of the backgrounds are crucial. In this project we will use the available data together with simulations to optimally identify and reconstruct the first neutrino interactions in the KM3NeT detector (applying also machine learning for background suppression) and with this pave the path towards accurate neutrino oscillation measurements and neutrino astronomy.<br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
<br />
''Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn] [mailto:dosamtnikhef.nl Dorothea Samtleben]'''<br />
<br />
=== KM3NeT: Acoustic detection of ultra-high energy cosmic-ray neutrinos (2 projects) ===<br />
<br />
The study of the cosmic neutrinos of energies above 1017 eV, the so-called ultra-high<br />
energy neutrinos, provides a unique view on the universe and may provide insight<br />
in the origin of the most violent astrophysical sources, such as gamma ray bursts,<br />
supernovae or even dark matter. In addition, the observation of high energy neutrinos<br />
may provide a unique tool to study interactions at high energies.<br />
The energy deposition of these extreme neutrinos in water induce a thermo-<br />
acoustic signal, which can be detected using sensitive hydrophones. The expected<br />
neutrino flux is however extremely low and the signal that neutrinos induce is small.<br />
TNO is presently developing sensitive hydrophone technology based on fiber optics.<br />
Optical fibers form a natural way to create a distributed sensing system. Using this<br />
technology a large scale neutrino telescope can be built in the deep sea. TNO is aiming<br />
for a prototype hydrophone which will form the building block of a future telescope.<br />
<br />
The work will be executed at the Nikhef institute and/or the TNO laboratories in Delft. In this project there are two opportunities for master students to participate:<br><br />
<b>student project 1: </b> Hardware development on fiber optics hydrophones technology Goal: characterise existing proto-type optical fibre hydrophones in an anechoic basin at TNO laboratory. Data collection, calibration, characterisation, analysis of consequences for design future acoustic hydrophone neutrino telescopes; Keywords: Optical fiber technology, signal processing, electronics, lab. <b>student project 2:</b> Investigation of ultra-high energy neutrinos and their interactions with matter. Goal: simulate (currently imperfectly modelled) interaction for extremely high energy interactions, characterise differences with currently available physics models and impact on physics reach for future acoustic hydrophone neutrino telescopes; Keywords: Monte Carlo simulations, particle physics, cosmology. <br><br />
<br />
Further information: Info on ultra-high energy neutrinos can be found at: http://arxiv.org/abs/1102.3591; Info on acoustic detection of neutrinos can be found at: http://arxiv.org/abs/1311.7588<br />
<br />
''Contact: [mailto:ernst-jan.buis@tno.nl Ernst-Jan Buis] and [mailto:ivo.van.vulpen@nikhef.nl Ivo van Vulpen]'''<br />
<br />
=== KM3NeT: Applying state-of-the-art reconstruction software to 10-years of Antares data ===<br />
<br />
While the KM3NeT neutrino telescope is being constructed in<br />
the deep waters of the Mediterranean Sea,<br />
data from its precursor (Antares) have been accumulated for more than 10 years.<br />
The main objective of these neutrino telescopes is to determine the origin of (cosmic) neutrinos.<br />
The accuracy of the determination of the origin of neutrinos critically depends on<br />
the probability density function (PDF) of the arrival time of Cherenkov light<br />
produced by relativistic charged particles emerging from a neutrino interaction in the sea.<br />
It has been shown that these PDFs can be calculated from first principles and<br />
that the obtained values can efficiently be interpolated in 4 and 5 dimensions,<br />
without compromising the functional dependencies.<br />
The reconstruction software based on this input yields indeed for KM3NeT the best resolution.<br />
This project is aimed at applying the KM3NeT software to available Antares data.<br />
<br />
''Contact: [mailto:mjg@nikhef.nl Maarten de Jong]''<br />
<br />
=== HiSPARC: Extensive Air Shower Reconstruction using Machine Learning === <br />
<br />
An important aspect of high energy cosmic ray research is the reconstruction of the direction and energy of the primary cosmic ray. This is done by measuring the footprint of the extensive air shower initiated by the cosmic ray. The goal of this project is to advance the creation of a reconstruction algorithm based on machine learning (ML) techniques.<br />
<br />
A previous master student has made great progress in the creation of a ML algorithm for the direction reconstruction. The algorithm was trained on simulations and applied to real data. The method works quite well but we expect that better results can be achieved by improving the simulated data set. In this project you will implement a more accurate description of the photomultiplier tube in the simulation pipeline and check if the reconstruction will improve. The next step would be to advance the algorithm towards energy reconstruction. This means upscaling the current method and will involve the creation and manipulation of large simulated data sets.<br />
<br />
The HiSPARC group is small. As a student you can have a big impact and there is freedom to tailor your own project. The proposed project is for students with a particular interest in computational (astro)physics. Advanced programming skills (mainly Python) and Linux knowledge are desirable.<br />
<br />
''Contact: [mailto:kaspervd@nikhef.nl Kasper van Dam] en [mailto:vaneijk@nikhef.nl Bob van Eijk]''<br />
<br />
=== VU LaserLaB: Measuring the electric dipole moment (EDM) of the electron ===<br />
<br />
In collaboration with Nikhef and the Van Swinderen Institute for Particle Physics and Gravity at the University of Groningen, we have recently started an exciting project to measure the electric dipole moment (EDM) of the electron in cold beams of barium-fluoride molecules. The eEDM, which is predicted by the Standard Model of particle physics to be extremely small, is a powerful probe to explore physics beyond this Standard Model. All extensions to the Standard Model, most prominently supersymmetry, naturally predict an electron EDM that is just below the current experimental limits. We aim to improve on the best current measurement by at least an order of magnitude. To do so we will perform a precision measurement on a slow beam of laser-cooled BaF molecules. With this low-energy precision experiment, we test physics at energies comparable to those of LHC! <br />
<br />
At LaserLaB VU, we are responsible for building and testing a cryogenic source of BaF molecules. The main parts of this source are currently being constructed in the workshop. We are looking for enthusiastic master students to help setup the laser system that will be used to detect BaF. Furthermore, projects are available to perform simulations of trajectory simulations to design a lens system that guides the BaF molecules from the exit of the cryogenic source to the experiment.<br />
<br />
''Contact: [mailto:H.L.Bethlem@vu.nl Rick Bethlem]''<br />
<br />
=== VU LaserLab: Physics beyond the Standard model from molecules ===<br />
<br />
Our team, with a number of staff members (Ubachs, Eikema, Salumbides, Bethlem, Koelemeij) focuses on precision measurements in the hydrogen molecule, and its isotopomers. The work aims at testing the QED calculations of energy levels in H2, D2, T2, HD, etc. with the most precise measurements, where all kind of experimental laser techniques play a role (cw and pulsed lasers, atomic clocks, frequency combs, molecular beams). Also a target of studies is the connection to the "Proton size puzzle", which may be solved through studies in the hydrogen molecular isotopes.<br />
<br />
In the past half year we have produced a number of important results that are described in<br />
the following papers:<br />
* Frequency comb (Ramsey type) electronic excitations in the H2 molecule:<br />
see: Deep-ultraviolet frequency metrology of H2 for tests of molecular quantum theory<br />
http://www.nat.vu.nl/~wimu/Publications/Altmann-PRL-2018.pdf<br />
* ''Precision measurement of an infrared transition in the HD molecule''<br />
see: Sub-Doppler frequency metrology in HD for tests of fundamental physics: https://arxiv.org/abs/1712.08438<br />
* ''The first precision study in molecular tritium T2''<br />
see: Relativistic and QED effects in the fundamental vibration of T2: http://arxiv.org/abs/1803.03161<br />
* ''Dissociation energy of the hydrogen molecule at 10^-9 accuracy'' paper submitted to Phys. Rev. Lett.<br />
* ''Probing QED and fundamental constants through laser spectroscopy of vibrational transitions in HD+'' <br />
This is also a study of the hydrogen molecular ion HD+, where important results were obtained not so long ago, and where we have a strong activity: http://www.nat.vu.nl/~wimu/Publications/ncomms10385.pdf<br />
<br />
These five results mark the various directions we are pursuing, and in all directions we aim at obtaining improvements. Specific projects with students can be defined; those are mostly experimental, although there might be some theoretical tasks, like:<br />
* Performing calculations of hyperfine structures<br />
<br />
As for the theory there might also be an international connection for specifically bright theory students: we collaborate closely with prof. Krzystof Pachucki; we might find an opportunity<br />
for a student to perform (the best !) QED calculations in molecules, when working in Warsaw and partly in Amsterdam. Prof Frederic Merkt from the ETH Zurich, an expert in the field, will come to work with us on "hydrogen"<br />
during August - Dec 2018 while on sabbatical.<br />
<br />
''Contact: [mailto:w.m.g.ubachs@vu.nl Wim Ubachs] [mailto:k.s.e.eikema@vu.nl Kjeld Eikema] [mailto:h.l.bethlem@vu.nl Rick Bethlem]''<br />
<br />
== Projects with September 2018 start ==<br />
<br />
<br />
<br />
=== Theory: Stress-testing the Standard Model at the high-energy frontier ===<br />
<br />
A suitable framework to parametrise in a model-independent way deviations from the SM induced by new heavy particles is the Standard Model Effective Field Theory (SMEFT). In this formalism, bSM effects are encapsulated in higher-dimensional operators constructed from SM fields respecting their symmetry properties. Here we aim to perform a global analysis of the SMEFT from high-precision LHC data. This will be achieved by extending the NNPDF fitting framework to constrain the SMEFT coefficients, with the ultimate aim of identifying possible bSM signals.<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory: The quark and gluon internal structure of heavy nuclei in the LHC era ===<br />
<br />
A precise knowledge of the parton distribution functions (PDFs) of the proton is essential in order to make predictions for the Standard Model and beyond at hadron colliders. The presence of nuclear medium and collective phenomena which involve several nucleons modifies the parton distribution functions of nuclei (nPDFs) compared to those of a free nucleon. These modifications have been investigated by different groups using global analyses of high energy nuclear reaction world data. It is important to determine the nPDFs not only for establishing perturbative QCD factorisation in nuclei but also for applications to heavy-ion physics and neutrino physics. In this project the student will join an ongoing effort towards the determination of a data-driven model of nPDFs, and will learn how to construct tailored Artificial Neural Networks (ANNs). <br />
<br />
"Further information [[http://pcteserver.mi.infn.it/~nnpdf/VU/2018-MasterProject-nPDFs.pdf here]]<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory: Combined QCD analysis of parton distribution and fragmentation functions ===<br />
<br />
The formation of hadrons from quarks and gluons, or collectively partons, is a fundamental QCD process that has yet to be fully understood. Since parton-to-hadron fragmentation occurs over long-distance scales, such information can only be extracted from experimental observables that identify mesons and baryons in the final state. Recent progress has been made to determine these fragmentation functions (FFs) from charged pion and kaon production in single inclusive e+e−-annihilation (SIA) and additionally pp-collisions and semi-inclusive deep inelastic scattering (SIDIS). However, charged hadron production in unpolarized pp and inelastic lepton-proton scattering also require information about the momentum distributions of the quarks and gluons in the proton, which is encoded in non-perturbative parton distribution functions (PDFs). In this project, a simultaneous treatment of both PDFs and FFs in a global QCD analysis of single inclusive hadron production processes will be made to determine the individual parton-to-hadron FFs. Furthermore, a robust statistical methodology with an artificial neural network learning algorithm will be used to obtain a precise estimation of the FF uncertainties. This work will emphasis in particular the impact of pp-collision and SIDIS data on the gluon and separated quark/anti-quark FFs, respectively.<br />
<br />
"Further information [[http://pcteserver.mi.infn.it/~nnpdf/VU/2018-MasterProject-FFpPDFs.pdf here]]<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
<br />
=== ALICE: Charm is in the Quark Gluon Plasma ===<br />
The goal of heavy-ion physics is to study the Quark Gluon Plasma (QGP), a hot and dense medium where quarks and gluons move freely over large distances, larger than the typical size of a hadron. Hydrodynamic simulations expect that the QGP will expand under its own pressure, and cool while expanding. These simulations are particularly successful in describing some of the key observables measured experimentally, such as particle spectra and various orders of flow harmonics. Charm quarks are produced very early during the evolution of a heavy-ion collision and can thus serve as an idea probe of the properties of the QGP. The goal of the project is to study higher order flow harmonics (e.g. triangular flow - v3) that are more sensitive to the transport properties of the QGP for charm-mesons, such as D0, D*, Ds. This will be the first ever measurement of this kind. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== ALICE: Probing the time evolution of particle production in the Quark-Gluon Plasma ===<br />
Particle production is governed by conservation laws, such as local charge conservation. The latter ensures that each charged particle is balanced by an oppositely-charged partner, created at the same location in space and time. The charge-dependent angular correlations, traditionally studied with the balance function, have emerged as a powerful tool to probe the properties of the Quark-Gluon Plasma (QGP) created in high energy collisions. The goal of this project is to take full advantage of the unique, among all LHC experiments, capabilities of the ALICE detector that is able to identify particles to extend the studies to different particle species (e.g. pions, kaons, protons…). These studies are highly anticipated by both the experimental and theoretical communities.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: CP violating effects in QCD: looking for the chiral magnetic effect with ALICE at the LHC ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, which is called Chiral Magnetic Effect (CME). The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, but background effects have not yet been properly disentangled. In this project you will develop and test new observables of the CME, trying to understand and discriminate the background sources that affects such a measurement. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== LHCb: Searching for dark matter in exotic six-quark particles ===<br />
3/4 of the mass in the Universe is of unknown type. Many hypotheses about this dark matter have been proposed, but none confirmed. Recently it has been proposed that it could be made of particles made of the six quarks uuddss. Such a particle could be produced in decays of heavy baryons. It is proposed to use Xi_b baryons produced at LHCb to search for such a state. The latter would appear as missing 4-momentum in a kinematically constrained decay. The project consists in optimising a selection and applying it to LHCb data. See [https://arxiv.org/abs/1708.08951 arXiv:1708.08951]<br />
<br />
''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
<br />
<br />
=== LHCb: Measurement of BR(B0 → Ds+ Ds-) ===<br />
<br />
This project aims to discover the branching fraction of the decay B0->Ds- Ds+. The decay B0->Ds- Ds+ is quite rare, because it occurs through the exchange of a W-boson between the b and the d-quark of the B0-meson. This decay proceeds via Cabibbo-suppressed W-exchange and has not yet been observed; theoretical calculations predict a branching fraction at the order of 10^-5 with a best experimental upper limit of 3.6x10^-5.<br />
A measurement of the decay rate of B0 -> Ds+Ds- relative to that of B0 -> D+D- can provide an estimate of the W-exchange contribution to the latter decay, a crucial piece of information for extracting the CKM angle gamma from B0 -> D(*)D(*).<br />
The aim is to determine the relative branching fraction of B0->Ds+Ds- with respect to B0->Ds+D- decays (which has the best known branching ratio at present, (7.2 +- 0.8)x10^-3), in close collaboration with the PhD. The aim is that this project results in a journal publication on behalf of the LHCb collaboration. For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. This is a project that is closely related to previous analyses in the group. Weekly video meetings with CERN coordinate the efforts with in the LHCb collaboration.<br />
Relevant information: <br />
[1] M.Jung and S.Schacht, "Standard Model Predictions and New Physics Sensitivity in B -> DD Decays" https://arxiv.org/pdf/1410.8396.pdf<br />
[2] L.Bel, K.de Bruyn, R. Fleischer, M.Mulder, N.Tuning, "Anatomy of B -> DD Decays" https://arxiv.org/pdf/1505.01361.pdf<br />
[3] A.Zupanc et al [Belle Collaboration] "Improved measurement of B0 -> DsD+ and search for B0 -> Ds+Ds at Belle" https://arxiv.org/pdf/hep-ex/0703040.pdf<br />
[4] B.Aubert et al. [Babar Collaboration] "Search for the W-exchange decays B0 -> DD+" https://arxiv.org/pdf/hep-ex/0510051.pdf<br />
[5] R.Aaij et al. [LHCb Collaboration], "First observations of B0s -> D+D, Ds+D and D0D0 decays" https://arxiv.org/pdf/1302.5854.pdf<br />
<br />
''Contact: [mailto:niels.tuning@nikhef.nl Niels Tuning], [mailto:m.veronesi@nikhef.nl Michele Veronesi (PhD)], [mailto:s.esen@nikhef.nl Sevda Esen (postdoc)]''<br />
<br />
=== LHCb: Measurement of relative ratio of B+ → D0D+ and B+ → D0Ds decays ===<br />
<br />
This decay is closely related to B0->Ds- Ds+ (see above), and close collaboration between the two master projects is foreseen. The decay mode B+->D0D+ is expected to be dominated by tree diagrams with some additional contributions from penguin diagrams. Assuming SU(3) symmetry, measurement of its branching fraction relative to Cabibbo-favored B+->D0D will enable better understanding of penguin contributions to the CP violating mixing phase.<br />
Relevant information: <br />
[1] L.Bel, K.de Bruyn, R. Fleischer, M.Mulder, N.Tuning, "Anatomy of B -> DD Decays" https://arxiv.org/pdf/1505.01361.pdf<br />
[2] R.Aaij et al. [LHCb Collaboration], "First observations of B0s -> D+D, Ds+D and D0D0 decays" https://arxiv.org/pdf/1302.5854.pdf<br />
[3] PDG: http://pdglive.lbl.gov/BranchingRatio.action?desig=261&parCode=S041<br />
<br />
''Contact: [mailto:niels.tuning@nikhef.nl Niels Tuning], [mailto:m.veronesi@nikhef.nl Michele Veronesi (PhD)], [mailto:s.esen@nikhef.nl Sevda Esen (postdoc)]''<br />
<br />
<br />
<br />
=== Virgo: Fast determination of gravitational wave properties ===<br />
<br />
In the era of multi-messenger astronomy, the development of fast, accurate and computationally cheap methods for inference of properties of gravitational wave signal is of paramount importance. In this work, we will work on the development of rapid bayesian parameter estimation method for binary neutron stars as well as precessing black hole binaries. Bayesian parameter estimation methods require the evaluation of a likelihood that describe the probability of obtaining data for a given set of model parameters, which are parameters of gravitational wave signals in this particular problem. Bayesian inference for gravitational wave parameter estimation may require millions of these evaluation making them computationally costly. This work will combine the benefits of machine learning/ deep learning methods and order reduction methods of gravitational wave source modelling to speed up Bayesian inference of gravitational waves.<br />
<br />
''Contact: [mailto:caudills@nikhef.nl Sarah Caudill]''<br />
<br />
=== Virgo: Simulations of Binary Neutron Star Mergers and applications for multimessenger astronomy ===<br />
<br />
With the detection of the binary neutron star merger in August 2017 (GW170817) a new era of multi-messenger astronomy started. GW170817 proved that neutron star mergers are ideal laboratories to constrain the equation of state of cold supranuclear matter, to study the central engines of short GRBs, and to understand the origin and production of heavy elements.<br />
The fundamental tool to understand the last stages of the binary dynamics are numerical relativity simulations. In this project the student will be introduced to the basics of numerical relativity simulations of binary neutron star simulations and will be able to perform simulations on its own. Based on these simulations and the first experience it will be possible to focus on one of the following aspects: <br />
<br />
- the estimation of the ejected material released from the merger and the development of models for the electromagnetic signals<br />
<br />
- further improvement of gravitational waveform models including numerical relativity information<br />
<br />
- further improvement of the construction of the initial conditions of binary neutron star simulations<br />
<br />
- code improvements of the evolution code incorporating additional microphysical aspects as magnetic fields, tabulated equation of states, or neutrino leakage schemes.<br />
<br />
- studying the merger properties of neutron stars with exotic objects as boson or axion stars. <br />
<br />
''Contact: [mailto:diettim@nikhef.nl Tim Dietrich]''<br />
<br />
=== Virgo: Measuring cosmological parameters from gravitational-wave observations of compact binaries ===<br />
<br />
Gravitational wave observation of the binary neutron star merger GW170817 with its coincident optical counterpart led to a first "standard siren" measurement of the Hubble parameter independent of the cosmological distance ladder. While multiple similar observations are expected to improve the precision of the measurement, a statistical method of cross correlation with galaxy catalogues of gravitational-wave distance estimates is expected to work even without identified electromagnetic transients, and for binary black hole mergers in particular. The project would primarily be a study of various systematic effects in this analysis and correcting for them. The work will involve use of computational techniques to analyze LIGO-Virgo data. Some prior experience of programmimg is expected.<br />
<br />
''Contact: [mailto:archis@nikhef.nl Archisman Ghosh] and [mailto:vdbroeck@nikhef.nl Chris Van Den Broeck]''<br />
<br />
=== Detector R&D: Spectral X-ray imaging - Looking at colours the eyes can't see ===<br />
<br />
When a conventional X-ray image is made to analyse the composition of a sample, or to perform a medical examination on a patient, one acquires an image that only shows intensities. One obtains a ‘black and white’ image. Most of the information carried by the photon energy is lost. Lacking spectral information can result in an ambiguity between material composition and amount of material in the sample. If the X-ray intensity as a function of the energy can be measured (i.e. a ‘colour’ X-ray image) more information can be obtained from a sample. This translates to less required dose and/or to a better understanding of the sample that is being investigated. For example, two fields that can benefit from spectral X-ray imaging are mammography and real time CT.<br />
<br />
X-ray detectors based on Medipix/Timepix pixel chips have spectral resolving capabilities and can be used to make polychromatic X-ray images. Medipix and Timepix chips have branched from pixel chips developed for detectors for high energy physics collider experiments.<br />
<br />
Activities in the field of (spectral) CT scans are performed in a collaboration between two institutes (Nikhef and CWI) and two companies (ASI and XRE).<br />
<br />
Some activities that students can work on: <br />
<br />
- Medical X-ray imaging (CT and ‘flat’ X-ray images): Detection of iodine contrast agent. Detection of calcifications (hint for a tumour).<br />
<br />
- Material research: Using spectral information to identify materials and recognise compounds.<br />
<br />
- Determine how much existing applications can benefit from spectral X-ray imaging and look for potential new applications. <br />
<br />
- Characterise, calibrate, optimise X-ray imaging detector systems. <br />
<br />
''Contact: [mailto:martinfr@nikhef.nl Martin Fransen]''<br />
<br />
=== Detector R&D: Compton camera ===<br />
<br />
In the Nikhef R&D group we develop instrumentation for particle physics but we also investigate how particle physics detectors can be used for different purposes. A successful development is the Medipix chip that can be used in X-ray imaging. For use in large scale medical applications compton scattering limits however the energy resolving possibilities. You will investigate whether it is in principle possible to design a X-ray application that detects the compton scattered electron and the absorbed photon. Your ideas can be tested in practice in the lab where a X-ray scan can be performed.<br />
<br />
''Contact: [mailto:martinfr@nikhef.nl Martin Fransen]''<br />
<br />
=== Detector R&D: Holographic projector ===<br />
<br />
A difficulty in generating holograms (based on the interference of light) is the required dense pixel pitch. One would need a pixel pitch of less than 200 nanometer. With larger pixels artefacts occur due to spatial under sampling. A pixel pitch of 200 nanometer is difficult, if not, impossible, to achieve, especially for larger areas. Another challenge is the massive amount of computing power that would be required to control such a dense pixel matrix. <br />
<br />
A new holographic projection method has been developed that reduces under sampling artefacts for projectors with a ‘low’ pixel density. It is using 'pixels' at random but known positions, resulting in an array of (coherent) light points that lacks (or has strongly surpressed) spatial periodicity. As a result a holographic projector can be built with a significantly lower pixel density and correspondingly less required computing power. This could bring holography in reach for many applications like display, lithography, 3D printing, metrology, etc..<br />
<br />
Of course, nothing comes for free: With less pixels, holograms become noisier and the contrast will be reduced. The big question: How do we determine the requirements (in terms of pixel density, pixel positioning, etc..) for the holographic projector based on requirements for the holograms?<br />
Requirements for a hologram can be expressed in terms of: Noise, contrast, resolution, suppression of under sampling artefacts, etc.. <br />
<br />
For this project we are building a proof of concept holographic emitter. This set-up will be used to verify simulation results (and also to project some cool holograms of course). <br />
<br />
Students can do hands on lab-work (building and testing the proto type projector) and/or work on setting up simulation methods and models. Simulations in this field can be highly parallelized and are preferably written for parallel computing and/or GPU computing.<br />
<br />
<br />
''Contact: [mailto:martinfr@nikhef.nl Martin Fransen]<br />
<br />
=== Detector R&D: Laser Interferometer Space Antenna (LISA) ===<br />
<br />
The space-based gravitational wave antenna LISA is without doubt one of the most challenging space missions ever proposed. ESA plans to launch around 2030 three spacecrafts that are separated by a few million kilometers to measure tiny variations in the distances between test-masses located in each spacecraft to detect the gravitational waves from sources such as supermassive black holes. The triangular constellation of the LISA mission is dynamic requiring a constant fine tuning related to the pointing of the laser links between the spacecrafts and a simultaneous refocusing of the telescope. The noise sources related to the laser links are expected to provide a dominant contribution to the LISA performance.<br />
<br />
An update and extension of the LISA science simulation software is needed to assess the hardware development for LISA at Nikhef, TNO and SRON. A position is therefore available for a master student to study the impact of instrumental noise on the performance of LISA. Realistic simulations based on hardware (noise) characterization measurements that were done at TNO will be carried out and compared to the expected tantalizing gravitational wave sources.<br />
<br />
Key words: LISA, space, gravitational waves, simulations, signal processing<br />
<br />
''Contact: [mailto:nielsvb@nikhef.nl Niels van Bakel],[mailto:ernst-jan.buis@tno.nl Ernst-Jan Buis]''<br />
<br />
=== KM3NeT : Reconstruction of first neutrino interactions in KM3NeT ===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first two strings with sensitive photodetectors have been deployed 2015&2016. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In order to identify neutrinos an accurate reconstruction and optimal understanding of the backgrounds are crucial. In this project we will use the available data to identify and reconstruct the first neutrino interactions in the KM3NeT detector and with this pave the path towards neutrino astronomy.<br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
<br />
'' Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn]''<br />
<br />
=== ANTARES: Analysis of IceCube neutrino sources. ===<br />
<br />
The only evidence for high energetic neutrinos from cosmic sources so far comes from detections with the IceCube detector. Most of the detected events were reconstructed with a large uncertainty on their direction, which has prevented an association to astrophysical sources. Only for the high energetic muon neutrino candidates a high resolution in the direction has been achieved, but also for those no significant correlation to astrophysical sources has to date been detected.<br />
The ANTARES neutrino telescope has since 2007 continuously taken neutrino data with high angular resolution, which can be exploited to further scrutinize the locations of these neutrino sources. In this project we will address the neutrino sources in a stacked analysis to further probe the origin of the neutrinos with enhanced sensitivity.<br />
<br />
Programming skills are essential, mainly C++ and root will be used. <br />
<br />
'' Contact: [mailto:dosamt@nikhef.nl Dorothea Samtleben]''<br />
<br />
=== VU LaserLaB: Measuring the electric dipole moment (EDM) of the electron ===<br />
<br />
In collaboration with Nikhef and the Van Swinderen Institute for Particle Physics and Gravity at the University of Groningen, we have recently started an exciting project to measure the electric dipole moment (EDM) of the electron in cold beams of barium-fluoride molecules. The eEDM, which is predicted by the Standard Model of particle physics to be extremely small, is a powerful probe to explore physics beyond this Standard Model. All extensions to the Standard Model, most prominently supersymmetry, naturally predict an electron EDM that is just below the current experimental limits. We aim to improve on the best current measurement by at least an order of magnitude. To do so we will perform a precision measurement on a slow beam of laser-cooled BaF molecules. With this low-energy precision experiment, we test physics at energies comparable to those of LHC! <br />
<br />
At LaserLaB VU, we are responsible for building and testing a cryogenic source of BaF molecules. The main parts of this source are currently being constructed in the workshop. We are looking for enthusiastic master students to help setup the laser system that will be used to detect BaF. Furthermore, projects are available to perform simulations of trajectory simulations to design a lens system that guides the BaF molecules from the exit of the cryogenic source to the experiment.<br />
<br />
'' Contact: [mailto:H.L.Bethlem@vu.nl Rick Bethlem]''<br />
<br />
<br />
=== VU LaserLab: Physics beyond the Standard model from molecules ===<br />
<br />
Our team, with a number of staff members (Ubachs, Eikema, Salumbides, Bethlem, Koelemeij) focuses on precision measurements in the hydrogen molecule, and its isotopomers. The work aims at testing the QED calculations of energy levels in H2, D2, T2, HD, etc. with the most precise measurements, where all kind of experimental laser techniques play a role (cw and pulsed lasers, atomic clocks, frequency combs, molecular beams). Also a target of studies is the connection to the "Proton size puzzle", which may be solved through studies in the hydrogen molecular isotopes.<br />
<br />
In the past half year we have produced a number of important results that are described in<br />
the following papers:<br />
* Frequency comb (Ramsey type) electronic excitations in the H2 molecule:<br />
see: Deep-ultraviolet frequency metrology of H2 for tests of molecular quantum theory<br />
http://www.nat.vu.nl/~wimu/Publications/Altmann-PRL-2018.pdf<br />
* ''Precision measurement of an infrared transition in the HD molecule''<br />
see: Sub-Doppler frequency metrology in HD for tests of fundamental physics: https://arxiv.org/abs/1712.08438<br />
* ''The first precision study in molecular tritium T2''<br />
see: Relativistic and QED effects in the fundamental vibration of T2: http://arxiv.org/abs/1803.03161<br />
* ''Dissociation energy of the hydrogen molecule at 10^-9 accuracy'' paper submitted to Phys. Rev. Lett.<br />
* ''Probing QED and fundamental constants through laser spectroscopy of vibrational transitions in HD+'' <br />
This is also a study of the hydrogen molecular ion HD+, where important results were obtained not so long ago, and where we have a strong activity: http://www.nat.vu.nl/~wimu/Publications/ncomms10385.pdf<br />
<br />
These five results mark the various directions we are pursuing, and in all directions we aim at obtaining improvements. Specific projects with students can be defined; those are mostly experimental, although there might be some theoretical tasks, like:<br />
* Performing calculations of hyperfine structures<br />
<br />
As for the theory there might also be an international connection for specifically bright theory students: we collaborate closely with prof. Krzystof Pachucki; we might find an opportunity<br />
for a student to perform (the best !) QED calculations in molecules, when working in Warsaw and partly in Amsterdam. Prof Frederic Merkt from the ETH Zurich, an expert in the field, will come to work with us on "hydrogen"<br />
during August - Dec 2018 while on sabbatical.<br />
<br />
'' Contact: [mailto:w.m.g.ubachs@vu.nl Wim Ubachs] [mailto:k.s.e.eikema@vu.nl Kjeld Eikema] [mailto:h.l.bethlem@vu.nl Rick Bethlem]''<br />
<br />
<br />
<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=360Master Projects2019-03-11T09:25:17Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
== Projects with September 2019 start ==<br />
<br />
=== Theory: The Effective Field Theory Pathway to New Physics at the LHC ===<br />
<br />
A very promising framework to parametrise in a robust and model-independent way deviations from the Standard Model (SM) induced by new heavy particles is the Standard Model Effective Field Theory (SMEFT). In this formalism, Beyond the SM effects are encapsulated in higher-dimensional operators constructed from SM fields respecting their symmetry properties. In this project, we aim to carry out a global analysis of the SMEFT from high-precision LHC data, including Higgs boson production, flavour observables, and low-energy measurements. This analysis will be carried out in the context of the recently developed SMEFiT approach [1] based on Machine Learning techniques to efficiently explore the complex theory parameter space. The ultimate goal is either to uncover glimpses of new particles or interactions at the LHC, or to derive the most stringent model-independent bounds to date on general theories of New Physics.<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]"<br />
<br />
[1] https://arxiv.org/abs/1901.05965<br />
<br />
=== Theory: Pinning down the initial state of heavy-ion collisions with Machine Learning ===<br />
<br />
It has been known for more than three decades that the parton distribution functions (PDFs) of nucleons bound within heavy nuclei are modified with respect to their free-nucleon counterparts. Despite active experimental and theoretical investigations, the underlying mechanisms that drive these in-medium modifications of nucleon substructure have yet to be fully understood. The determination of nuclear PDFs is a topic of high relevance in order both to improve our fundamental understanding of the strong interactions in the nuclear environment, as well as and for the interpretation of heavy ion collisions at RHIC and the LHC, in particular for the characterization of the Quark-Gluon Plasma. The goal of this project is to exploit Machine Learning and Artificial Intelligence tools [1,2] (neural networks trained by stochastic gradient descent) to pin down the initial state of heavy ion collisions by using recent measurements from proton-lead collisions at the LHC. Emphasis will be put on the poorly-known nuclear modifications of the gluon PDFs, which are still mostly ''terra incognita'' and highly relevant for phenomenological applications. In addition to theory calculations, the project will also involve code development using modern AI/ML tools such as TensorFlow and Keras.<br />
<br />
[1] https://arxiv.org/abs/1811.05858<br />
[2] https://arxiv.org/abs/1410.8849<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]"<br />
<br />
<br />
=== Dark Matter: XENON1T Data Analysis ===<br />
The XENON collaboration has used the XENON1T detector to achieve the world’s most sensitive direct detection dark matter results and is currently building the XENONnT successor experiment. The detectors operate at the Gran Sasso underground laboratory and consist of so-called dual-phase xenon time-projection chambers filled with ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the data from the XENON1T detector. The work will consist of understanding the detector signals and applying machine learning tools such as deep neutral networks to improve the reconstruction performance in our Python-based analysis tool, following the approach described in arXiv:1804.09641. The final goal is to improve the energy and position reconstruction uncertainties for the dark matter search. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter: XAMS R&D Setup ===<br />
The Amsterdam Dark Matter group operates an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 4kg of ultra-pure liquid xenon. We plan to use this detector for the development of new detection techniques (such as utilizing new photosensors) and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENON experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data him/herself. You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Dark Matter: DARWIN Sensitivity Studies ===<br />
DARWIN is the "ultimate" direct detection dark matter experiment, with the goal to reach the so-called "neutrino floor", when neutrinos become a hard-to-reduce background. The large and exquisitely clean xenon mass will allow DARWIN to also be sensitive to other physics signals such as solar neutrinos, double-beta decay from Xe-136, axions and axion-like particles etc. While the experiment will only start in 2025, we are in the midst of optimizing the experiment, which is driven by simulations. We have an opening for a student to work on the GEANT4 Monte Carlo simulations for DARWIN, as part of a simulation team together with the University of Freiburg and Zurich. We are also working on a "fast simulation" that could be included in this framework. It is your opportunity to steer the optimization of a large and unique experiment. This project requires good programming skills (Python and C++) and data analysis/physics interpretation skills. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski] and [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== The Modulation Experiment: Data Analysis ===<br />
There exist a few measurements that suggest an annual modulation in the activity of radioactive sources. With a few groups from the XENON collaboration we have developed four sets of table-top experiments to investigate this effect on a few well known radioactive sources. The experiments are under construction in Purdue University (USA), a mountain top in Switzerland, a beach in Rio de Janeiro and the last one at Nikhef in Amsterdam. We urgently need a master student to (1) analyze the first big data set, and (2) contribute to the first physics paper from the experiment. We are looking for all-round physicists with interest in both lab-work and data-analysis. The student(s) will directly collaborate with the other groups in this small collaboration (around 10 people), and the goal is to have the first physics publication ready by the end of the project. During the 2018-2019 season there are positions for two MSc students.<br />
<br />
''Contact: [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== ATLAS : Excited lepton searches with multiple leptons ===<br />
<br />
The Standard Model of particle physics (SM) is extremely successful, but would it hold against check with data containing multiple leptons? Although very rare process, the production of leptons is calculated in SM with high precision. On detector side the leptons (electrons and muons) are easy to reconstruct and such a sample contains very little "non-lepton" background. This analysis has an ambitious goal to find beyond Standard Model processes like Excited leptons using events with 4 leptons. With this project, the student would gain close familiarity with modern experimental techniques (statistical analysis, SM predictions, search for rare signals), with Monte Carlo generators and the standard HEP analysis tools (ROOT, C++, python).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and Marcus Morgenstern and Pepijn Bakker]''<br />
<br />
=== ATLAS : A search for lepton non-universality in Bc meson decays ===<br />
<br />
Recently, LHCb experiment has reported a number of intriguing deviations from SM in leptonic decays of B mesons. With this project we would like to probe if ATLAS also observes the same kind of deviation, e.g. in Bc->Jpsi+tau+nu channel w.r.t BC->Jpsi+mu+nu. Success of project will be essential to understand if we finally observe beyond SM process or if LHCb has some detector bias. The student would gain close familiarity with modern experimental techniques (statistical analysis, SM predictions, search for rare signals), background suppression techniques and the standard HEP analysis tools (ROOT, C++, python).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and JJ Teoh]''<br />
<br />
<br />
== Projects with September 2018 start ==<br />
<br />
<br />
<br />
=== Theory: Stress-testing the Standard Model at the high-energy frontier ===<br />
<br />
A suitable framework to parametrise in a model-independent way deviations from the SM induced by new heavy particles is the Standard Model Effective Field Theory (SMEFT). In this formalism, bSM effects are encapsulated in higher-dimensional operators constructed from SM fields respecting their symmetry properties. Here we aim to perform a global analysis of the SMEFT from high-precision LHC data. This will be achieved by extending the NNPDF fitting framework to constrain the SMEFT coefficients, with the ultimate aim of identifying possible bSM signals.<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory: The quark and gluon internal structure of heavy nuclei in the LHC era ===<br />
<br />
A precise knowledge of the parton distribution functions (PDFs) of the proton is essential in order to make predictions for the Standard Model and beyond at hadron colliders. The presence of nuclear medium and collective phenomena which involve several nucleons modifies the parton distribution functions of nuclei (nPDFs) compared to those of a free nucleon. These modifications have been investigated by different groups using global analyses of high energy nuclear reaction world data. It is important to determine the nPDFs not only for establishing perturbative QCD factorisation in nuclei but also for applications to heavy-ion physics and neutrino physics. In this project the student will join an ongoing effort towards the determination of a data-driven model of nPDFs, and will learn how to construct tailored Artificial Neural Networks (ANNs). <br />
<br />
"Further information [[http://pcteserver.mi.infn.it/~nnpdf/VU/2018-MasterProject-nPDFs.pdf here]]<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory: Combined QCD analysis of parton distribution and fragmentation functions ===<br />
<br />
The formation of hadrons from quarks and gluons, or collectively partons, is a fundamental QCD process that has yet to be fully understood. Since parton-to-hadron fragmentation occurs over long-distance scales, such information can only be extracted from experimental observables that identify mesons and baryons in the final state. Recent progress has been made to determine these fragmentation functions (FFs) from charged pion and kaon production in single inclusive e+e−-annihilation (SIA) and additionally pp-collisions and semi-inclusive deep inelastic scattering (SIDIS). However, charged hadron production in unpolarized pp and inelastic lepton-proton scattering also require information about the momentum distributions of the quarks and gluons in the proton, which is encoded in non-perturbative parton distribution functions (PDFs). In this project, a simultaneous treatment of both PDFs and FFs in a global QCD analysis of single inclusive hadron production processes will be made to determine the individual parton-to-hadron FFs. Furthermore, a robust statistical methodology with an artificial neural network learning algorithm will be used to obtain a precise estimation of the FF uncertainties. This work will emphasis in particular the impact of pp-collision and SIDIS data on the gluon and separated quark/anti-quark FFs, respectively.<br />
<br />
"Further information [[http://pcteserver.mi.infn.it/~nnpdf/VU/2018-MasterProject-FFpPDFs.pdf here]]<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
<br />
=== ALICE: Charm is in the Quark Gluon Plasma ===<br />
The goal of heavy-ion physics is to study the Quark Gluon Plasma (QGP), a hot and dense medium where quarks and gluons move freely over large distances, larger than the typical size of a hadron. Hydrodynamic simulations expect that the QGP will expand under its own pressure, and cool while expanding. These simulations are particularly successful in describing some of the key observables measured experimentally, such as particle spectra and various orders of flow harmonics. Charm quarks are produced very early during the evolution of a heavy-ion collision and can thus serve as an idea probe of the properties of the QGP. The goal of the project is to study higher order flow harmonics (e.g. triangular flow - v3) that are more sensitive to the transport properties of the QGP for charm-mesons, such as D0, D*, Ds. This will be the first ever measurement of this kind. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== ALICE: Probing the time evolution of particle production in the Quark-Gluon Plasma ===<br />
Particle production is governed by conservation laws, such as local charge conservation. The latter ensures that each charged particle is balanced by an oppositely-charged partner, created at the same location in space and time. The charge-dependent angular correlations, traditionally studied with the balance function, have emerged as a powerful tool to probe the properties of the Quark-Gluon Plasma (QGP) created in high energy collisions. The goal of this project is to take full advantage of the unique, among all LHC experiments, capabilities of the ALICE detector that is able to identify particles to extend the studies to different particle species (e.g. pions, kaons, protons…). These studies are highly anticipated by both the experimental and theoretical communities.<br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== ALICE: CP violating effects in QCD: looking for the chiral magnetic effect with ALICE at the LHC ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, which is called Chiral Magnetic Effect (CME). The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, but background effects have not yet been properly disentangled. In this project you will develop and test new observables of the CME, trying to understand and discriminate the background sources that affects such a measurement. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou]''<br />
<br />
=== LHCb: Searching for dark matter in exotic six-quark particles ===<br />
3/4 of the mass in the Universe is of unknown type. Many hypotheses about this dark matter have been proposed, but none confirmed. Recently it has been proposed that it could be made of particles made of the six quarks uuddss. Such a particle could be produced in decays of heavy baryons. It is proposed to use Xi_b baryons produced at LHCb to search for such a state. The latter would appear as missing 4-momentum in a kinematically constrained decay. The project consists in optimising a selection and applying it to LHCb data. See [https://arxiv.org/abs/1708.08951 arXiv:1708.08951]<br />
<br />
''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
<br />
<br />
=== LHCb: Measurement of BR(B0 → Ds+ Ds-) ===<br />
<br />
This project aims to discover the branching fraction of the decay B0->Ds- Ds+. The decay B0->Ds- Ds+ is quite rare, because it occurs through the exchange of a W-boson between the b and the d-quark of the B0-meson. This decay proceeds via Cabibbo-suppressed W-exchange and has not yet been observed; theoretical calculations predict a branching fraction at the order of 10^-5 with a best experimental upper limit of 3.6x10^-5.<br />
A measurement of the decay rate of B0 -> Ds+Ds- relative to that of B0 -> D+D- can provide an estimate of the W-exchange contribution to the latter decay, a crucial piece of information for extracting the CKM angle gamma from B0 -> D(*)D(*).<br />
The aim is to determine the relative branching fraction of B0->Ds+Ds- with respect to B0->Ds+D- decays (which has the best known branching ratio at present, (7.2 +- 0.8)x10^-3), in close collaboration with the PhD. The aim is that this project results in a journal publication on behalf of the LHCb collaboration. For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. This is a project that is closely related to previous analyses in the group. Weekly video meetings with CERN coordinate the efforts with in the LHCb collaboration.<br />
Relevant information: <br />
[1] M.Jung and S.Schacht, "Standard Model Predictions and New Physics Sensitivity in B -> DD Decays" https://arxiv.org/pdf/1410.8396.pdf<br />
[2] L.Bel, K.de Bruyn, R. Fleischer, M.Mulder, N.Tuning, "Anatomy of B -> DD Decays" https://arxiv.org/pdf/1505.01361.pdf<br />
[3] A.Zupanc et al [Belle Collaboration] "Improved measurement of B0 -> DsD+ and search for B0 -> Ds+Ds at Belle" https://arxiv.org/pdf/hep-ex/0703040.pdf<br />
[4] B.Aubert et al. [Babar Collaboration] "Search for the W-exchange decays B0 -> DD+" https://arxiv.org/pdf/hep-ex/0510051.pdf<br />
[5] R.Aaij et al. [LHCb Collaboration], "First observations of B0s -> D+D, Ds+D and D0D0 decays" https://arxiv.org/pdf/1302.5854.pdf<br />
<br />
''Contact: [mailto:niels.tuning@nikhef.nl Niels Tuning], [mailto:m.veronesi@nikhef.nl Michele Veronesi (PhD)], [mailto:s.esen@nikhef.nl Sevda Esen (postdoc)]''<br />
<br />
=== LHCb: Measurement of relative ratio of B+ → D0D+ and B+ → D0Ds decays ===<br />
<br />
This decay is closely related to B0->Ds- Ds+ (see above), and close collaboration between the two master projects is foreseen. The decay mode B+->D0D+ is expected to be dominated by tree diagrams with some additional contributions from penguin diagrams. Assuming SU(3) symmetry, measurement of its branching fraction relative to Cabibbo-favored B+->D0D will enable better understanding of penguin contributions to the CP violating mixing phase.<br />
Relevant information: <br />
[1] L.Bel, K.de Bruyn, R. Fleischer, M.Mulder, N.Tuning, "Anatomy of B -> DD Decays" https://arxiv.org/pdf/1505.01361.pdf<br />
[2] R.Aaij et al. [LHCb Collaboration], "First observations of B0s -> D+D, Ds+D and D0D0 decays" https://arxiv.org/pdf/1302.5854.pdf<br />
[3] PDG: http://pdglive.lbl.gov/BranchingRatio.action?desig=261&parCode=S041<br />
<br />
''Contact: [mailto:niels.tuning@nikhef.nl Niels Tuning], [mailto:m.veronesi@nikhef.nl Michele Veronesi (PhD)], [mailto:s.esen@nikhef.nl Sevda Esen (postdoc)]''<br />
<br />
=== Virgo: Searching for gravitational waves from compact binary coalescence ===<br />
<br />
Matched-filter searches for gravitational-wave signals from binary neutron stars, binary black holes and neutron-star-black-hole systems have been successful but many simplifications have been made. There are a number of avenues to explore for research, including expanding the parameter space to include precessing binaries or intermediate-mass black hole binaries, implementing multivariate statistics with analytic and machine learning techniques, and developing deeper searches by coordinating with gamma-ray triggers. These projects will include development work (python, C) and will be implemented in the upcoming Virgo/LIGO science runs, potentially leading to new discoveries and physics.<br />
<br />
''Contact: [mailto:caudills@nikhef.nl Sarah Caudill]''<br />
<br />
=== Virgo: Simulations of Binary Neutron Star Mergers and applications for multimessenger astronomy ===<br />
<br />
With the detection of the binary neutron star merger in August 2017 (GW170817) a new era of multi-messenger astronomy started. GW170817 proved that neutron star mergers are ideal laboratories to constrain the equation of state of cold supranuclear matter, to study the central engines of short GRBs, and to understand the origin and production of heavy elements.<br />
The fundamental tool to understand the last stages of the binary dynamics are numerical relativity simulations. In this project the student will be introduced to the basics of numerical relativity simulations of binary neutron star simulations and will be able to perform simulations on its own. Based on these simulations and the first experience it will be possible to focus on one of the following aspects: <br />
<br />
- the estimation of the ejected material released from the merger and the development of models for the electromagnetic signals<br />
<br />
- further improvement of gravitational waveform models including numerical relativity information<br />
<br />
- further improvement of the construction of the initial conditions of binary neutron star simulations<br />
<br />
- code improvements of the evolution code incorporating additional microphysical aspects as magnetic fields, tabulated equation of states, or neutrino leakage schemes.<br />
<br />
- studying the merger properties of neutron stars with exotic objects as boson or axion stars. <br />
<br />
''Contact: [mailto:diettim@nikhef.nl Tim Dietrich]''<br />
<br />
=== Virgo: Measuring cosmological parameters from gravitational-wave observations of compact binaries ===<br />
<br />
Gravitational wave observation of the binary neutron star merger GW170817 with its coincident optical counterpart led to a first "standard siren" measurement of the Hubble parameter independent of the cosmological distance ladder. While multiple similar observations are expected to improve the precision of the measurement, a statistical method of cross correlation with galaxy catalogues of gravitational-wave distance estimates is expected to work even without identified electromagnetic transients, and for binary black hole mergers in particular. The project would primarily be a study of various systematic effects in this analysis and correcting for them. The work will involve use of computational techniques to analyze LIGO-Virgo data. Some prior experience of programmimg is expected.<br />
<br />
''Contact: [mailto:archis@nikhef.nl Archisman Ghosh] and [mailto:vdbroeck@nikhef.nl Chris Van Den Broeck]''<br />
<br />
=== Detector R&D: Spectral X-ray imaging - Looking at colours the eyes can't see ===<br />
<br />
When a conventional X-ray image is made to analyse the composition of a sample, or to perform a medical examination on a patient, one acquires an image that only shows intensities. One obtains a ‘black and white’ image. Most of the information carried by the photon energy is lost. Lacking spectral information can result in an ambiguity between material composition and amount of material in the sample. If the X-ray intensity as a function of the energy can be measured (i.e. a ‘colour’ X-ray image) more information can be obtained from a sample. This translates to less required dose and/or to a better understanding of the sample that is being investigated. For example, two fields that can benefit from spectral X-ray imaging are mammography and real time CT.<br />
<br />
X-ray detectors based on Medipix/Timepix pixel chips have spectral resolving capabilities and can be used to make polychromatic X-ray images. Medipix and Timepix chips have branched from pixel chips developed for detectors for high energy physics collider experiments.<br />
<br />
Activities in the field of (spectral) CT scans are performed in a collaboration between two institutes (Nikhef and CWI) and two companies (ASI and XRE).<br />
<br />
Some activities that students can work on: <br />
<br />
- Medical X-ray imaging (CT and ‘flat’ X-ray images): Detection of iodine contrast agent. Detection of calcifications (hint for a tumour).<br />
<br />
- Material research: Using spectral information to identify materials and recognise compounds.<br />
<br />
- Determine how much existing applications can benefit from spectral X-ray imaging and look for potential new applications. <br />
<br />
- Characterise, calibrate, optimise X-ray imaging detector systems. <br />
<br />
''Contact: [mailto:martinfr@nikhef.nl Martin Fransen]''<br />
<br />
=== Detector R&D: Compton camera ===<br />
<br />
In the Nikhef R&D group we develop instrumentation for particle physics but we also investigate how particle physics detectors can be used for different purposes. A successful development is the Medipix chip that can be used in X-ray imaging. For use in large scale medical applications compton scattering limits however the energy resolving possibilities. You will investigate whether it is in principle possible to design a X-ray application that detects the compton scattered electron and the absorbed photon. Your ideas can be tested in practice in the lab where a X-ray scan can be performed.<br />
<br />
''Contact: [mailto:martinfr@nikhef.nl Martin Fransen]''<br />
<br />
=== Detector R&D: Holographic projector ===<br />
<br />
A difficulty in generating holograms (based on the interference of light) is the required dense pixel pitch. One would need a pixel pitch of less than 200 nanometer. With larger pixels artefacts occur due to spatial under sampling. A pixel pitch of 200 nanometer is difficult, if not, impossible, to achieve, especially for larger areas. Another challenge is the massive amount of computing power that would be required to control such a dense pixel matrix. <br />
<br />
A new holographic projection method has been developed that reduces under sampling artefacts for projectors with a ‘low’ pixel density. It is using 'pixels' at random but known positions, resulting in an array of (coherent) light points that lacks (or has strongly surpressed) spatial periodicity. As a result a holographic projector can be built with a significantly lower pixel density and correspondingly less required computing power. This could bring holography in reach for many applications like display, lithography, 3D printing, metrology, etc..<br />
<br />
Of course, nothing comes for free: With less pixels, holograms become noisier and the contrast will be reduced. The big question: How do we determine the requirements (in terms of pixel density, pixel positioning, etc..) for the holographic projector based on requirements for the holograms?<br />
Requirements for a hologram can be expressed in terms of: Noise, contrast, resolution, suppression of under sampling artefacts, etc.. <br />
<br />
For this project we are building a proof of concept holographic emitter. This set-up will be used to verify simulation results (and also to project some cool holograms of course). <br />
<br />
Students can do hands on lab-work (building and testing the proto type projector) and/or work on setting up simulation methods and models. Simulations in this field can be highly parallelized and are preferably written for parallel computing and/or GPU computing.<br />
<br />
<br />
''Contact: [mailto:martinfr@nikhef.nl Martin Fransen]<br />
<br />
=== Detector R&D: Laser Interferometer Space Antenna (LISA) ===<br />
<br />
The space-based gravitational wave antenna LISA is without doubt one of the most challenging space missions ever proposed. ESA plans to launch around 2030 three spacecrafts that are separated by a few million kilometers to measure tiny variations in the distances between test-masses located in each spacecraft to detect the gravitational waves from sources such as supermassive black holes. The triangular constellation of the LISA mission is dynamic requiring a constant fine tuning related to the pointing of the laser links between the spacecrafts and a simultaneous refocusing of the telescope. The noise sources related to the laser links are expected to provide a dominant contribution to the LISA performance.<br />
<br />
An update and extension of the LISA science simulation software is needed to assess the hardware development for LISA at Nikhef, TNO and SRON. A position is therefore available for a master student to study the impact of instrumental noise on the performance of LISA. Realistic simulations based on hardware (noise) characterization measurements that were done at TNO will be carried out and compared to the expected tantalizing gravitational wave sources.<br />
<br />
Key words: LISA, space, gravitational waves, simulations, signal processing<br />
<br />
''Contact: [mailto:nielsvb@nikhef.nl Niels van Bakel],[mailto:ernst-jan.buis@tno.nl Ernst-Jan Buis]''<br />
<br />
=== KM3NeT : Reconstruction of first neutrino interactions in KM3NeT ===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first two strings with sensitive photodetectors have been deployed 2015&2016. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In order to identify neutrinos an accurate reconstruction and optimal understanding of the backgrounds are crucial. In this project we will use the available data to identify and reconstruct the first neutrino interactions in the KM3NeT detector and with this pave the path towards neutrino astronomy.<br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
<br />
'' Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn]''<br />
<br />
=== ANTARES: Analysis of IceCube neutrino sources. ===<br />
<br />
The only evidence for high energetic neutrinos from cosmic sources so far comes from detections with the IceCube detector. Most of the detected events were reconstructed with a large uncertainty on their direction, which has prevented an association to astrophysical sources. Only for the high energetic muon neutrino candidates a high resolution in the direction has been achieved, but also for those no significant correlation to astrophysical sources has to date been detected.<br />
The ANTARES neutrino telescope has since 2007 continuously taken neutrino data with high angular resolution, which can be exploited to further scrutinize the locations of these neutrino sources. In this project we will address the neutrino sources in a stacked analysis to further probe the origin of the neutrinos with enhanced sensitivity.<br />
<br />
Programming skills are essential, mainly C++ and root will be used. <br />
<br />
'' Contact: [mailto:dosamt@nikhef.nl Dorothea Samtleben]''<br />
<br />
=== VU LaserLaB: Measuring the electric dipole moment (EDM) of the electron ===<br />
<br />
In collaboration with Nikhef and the Van Swinderen Institute for Particle Physics and Gravity at the University of Groningen, we have recently started an exciting project to measure the electric dipole moment (EDM) of the electron in cold beams of barium-fluoride molecules. The eEDM, which is predicted by the Standard Model of particle physics to be extremely small, is a powerful probe to explore physics beyond this Standard Model. All extensions to the Standard Model, most prominently supersymmetry, naturally predict an electron EDM that is just below the current experimental limits. We aim to improve on the best current measurement by at least an order of magnitude. To do so we will perform a precision measurement on a slow beam of laser-cooled BaF molecules. With this low-energy precision experiment, we test physics at energies comparable to those of LHC! <br />
<br />
At LaserLaB VU, we are responsible for building and testing a cryogenic source of BaF molecules. The main parts of this source are currently being constructed in the workshop. We are looking for enthusiastic master students to help setup the laser system that will be used to detect BaF. Furthermore, projects are available to perform simulations of trajectory simulations to design a lens system that guides the BaF molecules from the exit of the cryogenic source to the experiment.<br />
<br />
'' Contact: [mailto:H.L.Bethlem@vu.nl Rick Bethlem]''<br />
<br />
<br />
=== VU LaserLab: Physics beyond the Standard model from molecules ===<br />
<br />
Our team, with a number of staff members (Ubachs, Eikema, Salumbides, Bethlem, Koelemeij) focuses on precision measurements in the hydrogen molecule, and its isotopomers. The work aims at testing the QED calculations of energy levels in H2, D2, T2, HD, etc. with the most precise measurements, where all kind of experimental laser techniques play a role (cw and pulsed lasers, atomic clocks, frequency combs, molecular beams). Also a target of studies is the connection to the "Proton size puzzle", which may be solved through studies in the hydrogen molecular isotopes.<br />
<br />
In the past half year we have produced a number of important results that are described in<br />
the following papers:<br />
* Frequency comb (Ramsey type) electronic excitations in the H2 molecule:<br />
see: Deep-ultraviolet frequency metrology of H2 for tests of molecular quantum theory<br />
http://www.nat.vu.nl/~wimu/Publications/Altmann-PRL-2018.pdf<br />
* ''Precision measurement of an infrared transition in the HD molecule''<br />
see: Sub-Doppler frequency metrology in HD for tests of fundamental physics: https://arxiv.org/abs/1712.08438<br />
* ''The first precision study in molecular tritium T2''<br />
see: Relativistic and QED effects in the fundamental vibration of T2: http://arxiv.org/abs/1803.03161<br />
* ''Dissociation energy of the hydrogen molecule at 10^-9 accuracy'' paper submitted to Phys. Rev. Lett.<br />
* ''Probing QED and fundamental constants through laser spectroscopy of vibrational transitions in HD+'' <br />
This is also a study of the hydrogen molecular ion HD+, where important results were obtained not so long ago, and where we have a strong activity: http://www.nat.vu.nl/~wimu/Publications/ncomms10385.pdf<br />
<br />
These five results mark the various directions we are pursuing, and in all directions we aim at obtaining improvements. Specific projects with students can be defined; those are mostly experimental, although there might be some theoretical tasks, like:<br />
* Performing calculations of hyperfine structures<br />
<br />
As for the theory there might also be an international connection for specifically bright theory students: we collaborate closely with prof. Krzystof Pachucki; we might find an opportunity<br />
for a student to perform (the best !) QED calculations in molecules, when working in Warsaw and partly in Amsterdam. Prof Frederic Merkt from the ETH Zurich, an expert in the field, will come to work with us on "hydrogen"<br />
during August - Dec 2018 while on sabbatical.<br />
<br />
'' Contact: [mailto:w.m.g.ubachs@vu.nl Wim Ubachs] [mailto:k.s.e.eikema@vu.nl Kjeld Eikema] [mailto:h.l.bethlem@vu.nl Rick Bethlem]''<br />
<br />
<br />
<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=285Master Projects2018-04-09T05:38:58Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
<br />
== New Projects [start in September 2018] ==<br />
<br />
<br />
=== The XENON Dark Matter Experiment: Data Analysis ===<br />
<br />
The XENON collaboration is operating the XENON1T detector, the world’s most sensitive direct detection dark matter experiment. The Nikhef group is playing an important role in this experiment. The detector operates at the Gran Sasso underground laboratory and consists of a so-called dual-phase xenon time-projection chamber filled with 3200kg of ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the data from this detector. The work will consist of understanding the signals that come out of the detector and applying machine learning tools to improve the reconstruction performance in our Python-based analysis tool. The final goal is to improve the signal-to-background for the dark matter search. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== The Modulation Experiment: Data Analysis ===<br />
<br />
There exist a few measurements that suggest an annual modulation in the activity of radioactive sources. With a few groups from the XENON collaboration we have developed four sets of table-top experiments to investigate this effect on a few well known radioactive sources. The experiments are under construction in Purdue University (USA), a mountain top in Switzerland, a beach in Rio de Janeiro and the last one at Nikhef in Amsterdam. We urgently need a master student to (1) analyze the first big data set, and (2) contribute to the first physics paper from the experiment. We are looking for all-round physicists with interest in both lab-work and data-analysis. The student(s) will directly collaborate with the other groups in this small collaboration (around 10 people), and the goal is to have the first physics publication ready by the end of the project. During the 2018-2019 season there are positions for two MSc students.<br />
<br />
''Contact: [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Theory: Stress-testing the Standard Model at the high-energy frontier ===<br />
<br />
A suitable framework to parametrise in a model-independent way deviations from the SM induced by new heavy particles is the Standard Model Effective Field Theory (SMEFT). In this formalism, bSM effects are encapsulated in higher-dimensional operators constructed from SM fields respecting their symmetry properties. Here we aim to perform a global analysis of the SMEFT from high-precision LHC data. This will be achieved by extending the NNPDF fitting framework to constrain the SMEFT coefficients, with the ultimate aim of identifying possible bSM signals.<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory: The quark and gluon internal structure of heavy nuclei in the LHC era ===<br />
<br />
A precise knowledge of the parton distribution functions (PDFs) of the proton is essential in order to make predictions for the Standard Model and beyond at hadron colliders. The presence of nuclear medium and collective phenomena which involve several nucleons modifies the parton distribution functions of nuclei (nPDFs) compared to those of a free nucleon. These modifications have been investigated by different groups using global analyses of high energy nuclear reaction world data. It is important to determine the nPDFs not only for establishing perturbative QCD factorisation in nuclei but also for applications to heavy-ion physics and neutrino physics. In this project the student will join an ongoing effort towards the determination of a data-driven model of nPDFs, and will learn how to construct tailored Artificial Neural Networks (ANNs). <br />
<br />
"Further information [[http://pcteserver.mi.infn.it/~nnpdf/VU/2018-MasterProject-nPDFs.pdf here]]<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory: Combined QCD analysis of parton distribution and fragmentation functions ===<br />
<br />
The formation of hadrons from quarks and gluons, or collectively partons, is a fundamental QCD process that has yet to be fully understood. Since parton-to-hadron fragmentation occurs over long-distance scales, such information can only be extracted from experimental observables that identify mesons and baryons in the final state. Recent progress has been made to determine these fragmentation functions (FFs) from charged pion and kaon production in single inclusive e+e−-annihilation (SIA) and additionally pp-collisions and semi-inclusive deep inelastic scattering (SIDIS). However, charged hadron production in unpolarized pp and inelastic lepton-proton scattering also require information about the momentum distributions of the quarks and gluons in the proton, which is encoded in non-perturbative parton distribution functions (PDFs). In this project, a simultaneous treatment of both PDFs and FFs in a global QCD analysis of single inclusive hadron production processes will be made to determine the individual parton-to-hadron FFs. Furthermore, a robust statistical methodology with an artificial neural network learning algorithm will be used to obtain a precise estimation of the FF uncertainties. This work will emphasis in particular the impact of pp-collision and SIDIS data on the gluon and separated quark/anti-quark FFs, respectively.<br />
<br />
"Further information [[http://pcteserver.mi.infn.it/~nnpdf/VU/2018-MasterProject-FFpPDFs.pdf here]]<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
<br />
=== ATLAS : Double Higgs searches with multiple leptons ===<br />
<br />
The Standard Model of particle physics (SM) is extremely successful, but would it hold against check with data containing multiple leptons? Although very rare process, the production of leptons is calculated in SM with high precision. On detector side the leptons (electrons and muons) are easy to reconstruct and such a sample contains very little "non-lepton" background. This analysis has an ambitious goal to reconstruct events with two Higgs bosons using events with 4 leptons. With this project, the student would gain close familiarity with modern experimental techniques (statistical analysis, SM predictions, search for rare signals), with Monte Carlo generators and the standard HEP analysis tools (ROOT, C++, python).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and Marcus Morgenstern and Pepijn Bakker]''<br />
<br />
=== ATLAS : A search for lepton flavor violation with tau decays ===<br />
<br />
Quarks mix, neutrinos mix, charged leptons do not mix. Why? Is that really how the nature works, or is it just a limitation in our detection techniques. ATLAS has recorded now a huge sample of data. Even such difficult final states as tau->3mu become accessible. However, the decays of charm and beauty mesons could spoil the picture with decays that resembles the signal. The goal of the project is to understand what<br />
background decays are present and to find a way to suppress them. Success of project will allow much higher sensitivity to beyond Standard Model physics of tau->3mu. The student would gain close familiarity with modern experimental techniques (statistical analysis, SM predictions, search for rare signals), background suppression techniques and the standard HEP analysis tools (ROOT, C++, python).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and Edwin Chow]''<br />
<br />
<br />
=== ATLAS : A search for lepton non-universality in Bc meson decays ===<br />
<br />
Recently, LHCb experiment has reported a number of intriguing deviations from SM in leptonic decays of B mesons. With this project we would like to probe if ATLAS also observes the same kind of deviation, e.g. in Bc->Jpsi+tau+nu channel w.r.t BC->Jpsi+mu+nu. Success of project will be essential to understand if we finally observe beyond SM process or if LHCb has some detector bias. The student would gain close familiarity with modern experimental techniques (statistical analysis, SM predictions, search for rare signals), background suppression techniques and the standard HEP analysis tools (ROOT, C++, python).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and Edwin Chow]''<br />
<br />
<br />
=== LHCb: Searching for dark matter in exotic six-quark particles ===<br />
3/4 of the mass in the Universe is of unknown type. Many hypotheses about this dark matter have been proposed, but none confirmed. Recently it has been proposed that it could be made of particles made of the six quarks uuddss. Such a particle could be produced in decays of heavy baryons. It is proposed to use Xi_b baryons produced at LHCb to search for such a state. The latter would appear as missing 4-momentum in a kinematically constrained decay. The project consists in optimising a selection and applying it to LHCb data. See [https://arxiv.org/abs/1708.08951 arXiv:1708.08951]<br />
<br />
''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
<br />
=== Virgo: Searching for gravitational waves from compact binary coalescence ===<br />
<br />
Matched-filter searches for gravitational-wave signals from binary neutron stars, binary black holes and neutron-star-black-hole systems have been successful but many simplifications have been made. There are a number of avenues to explore for research, including expanding the parameter space to include precessing binaries or intermediate-mass black hole binaries, implementing multivariate statistics with analytic and machine learning techniques, and developing deeper searches by coordinating with gamma-ray triggers. These projects will include development work (python, C) and will be implemented in the upcoming Virgo/LIGO science runs, potentially leading to new discoveries and physics.<br />
<br />
''Contact: [mailto:caudills@nikhef.nl Sarah Caudill]''<br />
<br />
----<br />
<br />
== OLD Projects [from last year] ==<br />
<br />
<br />
<br />
=== The Modulation Experiment: Data Analysis ===<br />
<br />
There exist a few measurements that suggest an annual modulation in the activity of radioactive sources. With a few groups from the XENON collaboration we have developed four sets of table-top experiments to investigate this effect on a few well known radioactive sources. The experiments are under construction in Purdue University (USA), a mountain top in Switzerland, a beach in Rio de Janeiro and the last one at Nikhef in Amsterdam. We urgently need a master student to (1) analyze the first big data set, and (2) contribute to the first physics paper from the experiment. We are looking for an all-round physicist with interest in both lab-work and data-analysis. The student will directly collaborate with the other groups in this small collaboration (around 10 people), and the goal is to have the first physics publication ready by the end of the project.<br />
<br />
''Contact: [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== The XENON Dark Matter Experiment: Data Analysis ===<br />
<br />
The XENON collaboration has started operating the XENON1T detector, the world’s most sensitive direct detection dark matter experiment. The Nikhef group is playing an important role in this experiment. The detector operates at the Gran Sasso underground laboratory and consists of a so-called dual-phase xenon time-projection chamber filled with 3200kg of ultra-pure xenon. Our group has an opening for a motivated MSc student to do data-analysis on this new detector. The work will consist of understanding the signals that come out of the detector and in particular focus on the so-called double scatter events. We are interested in developing methods in order to interpret the response of the detector better and are developing sophisticated statistical tools to do this. This work will include looking at data and developing new algorithms in our Python-based analysis tool. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== XAMS Dark Matter R&D Setup ===<br />
<br />
The Amsterdam Dark Matter group has built an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 4kg of ultra-pure liquid xenon. We plan to use this detector for the development of new detection techniques (such as utilizing new photosensors) and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENON experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data him/herself. You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== LHCb: A Scintillator Fibers Tracker ===<br />
<br />
The LHCb collaboration is upgrading the present tracking system<br />
constructing a new tracker based on scintillating fibers combined<br />
with silicon photo-multipliers (SiPM): the SciFi Tracker!<br />
Nikhef plays a key role in the project, as we will build the<br />
SciFi fibers modules, the cold-box enclosure housing the SiPMs,<br />
and a large part of the on-detector electronics. In all these<br />
areas, interesting test hardware and software has to be realized,<br />
and several research topics for a Master project are available,<br />
taking the student in contact with state-of-the-art particle detectors,<br />
in a large team of physicists and engineers. Possible collaborations<br />
with the Nikhef R&D group can also be envisaged.<br />
<br />
''Contact: [mailto:antonio@nikhef.nl Antonio Pellegrino]''<br />
<br />
=== LHCb: Discovery of the Decay Lb --> p Ds+ ===<br />
This project aims to measure the branching fraction of the decay Lb->p Ds+ (bud -> uud + ds). <br />
The decay Lb->p Ds+ is quite rare, because it occurs through the transition of a b-quark to a u-quark. <br />
It has not been measured yet (although some LHCb colleagues claim to have seen it).<br />
This decay is interesting, because <br />
<br />
1) It is sensitive to the b->u coupling (CKM-element Vub), which determination is heavily debated.<br />
2) It can quantify non-factorisable QCD effects in b-baryon decays.<br />
<br />
The decay is closely related to B0->pi-Ds+, which proceeds through a similar Feynman diagram. <br />
Also, the final state of B0->pi-Ds+ is almost identical to Lb->p Ds+. <br />
The aim is to determine the relative branching fraction of Lb->pDs+ with respect to B0->D+pi- decays, <br />
in close collaboration with the PhD (who will study BR(B0->pi-Ds+)/BR(B0->D+pi-) ).<br />
This project will result in a journal publication on behalf of the LHCb collaboration, written by you. <br />
For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. <br />
This is a project that is closely related to previous analyses in the group. <br />
Weekly video meetings with CERN coordinate the efforts with in the LHCb collaboration.<br />
Relevant information:<br />
<br />
[1] R.Aaij et al. [LHCb Collaboration], ``Determination of the branching fractions of B0s->DsK and B0->DsK, JHEP 05 (2015) 019 [arXiv:1412.7654 [hep-ex]].<br />
[2] R. Fleischer, N. Serra and N. Tuning, ``Tests of Factorization and SU(3) Relations in B Decays into Heavy-Light Final States, Phys. Rev. D 83, 014017 (2011) [arXiv:1012.2784 [hep-ph]].<br />
<br />
''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''<br />
<br />
=== LHCb: Measurement of B0 -> pi Ds- , the b -> u quark transition ===<br />
<br />
This project aims to measure the branching fraction of the decay B0->pi Ds+.<br />
This decay is closely related to Lb->p Ds+ (see above), and close collaboration between the two master projects is foreseen.<br />
This research was started by a previous master student. <br />
The new measurement will finish the work, and include the new data from 2015 and 2016.<br />
<br />
See Mick Mulders [http://www.nikhef.nl/pub/experiments/bfys/lhcb/Theses/master/2015_MickMulder.pdf master thesis] for more information.<br />
<br />
''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''<br />
<br />
=== LHCb: A search for heavy neutrinos in the decay of W bosons at LHCb ===<br />
<br />
Neutrinos are arguably the most mysterious of all known fundamental fermions as they are both much lighter than all others and only weakly interacting. It is thought that the tiny mass of neutrinos can be explained by their mixing with so-far unknown, much heavier, neutrino-like particles. In this research proposal we look for these new neutrinos in the decay of the SM W-boson using data with the LHCb experiment at CERN. The W boson is assumed to decay to a heavy neutrino and a muon. The heavy neutrino subsequently decays to a muon and a pair of quarks. Both like-sign and opposite-sign muon pairs will be studied. The result of the analysis will either be a limit on the production of the new neutrinos or the discovery of something entirely new.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen and Elena Dall'Occo]''<br />
<br />
<br />
=== ALICE : Particle polarisation in strong magnetic fields ===<br />
When two atomic nuclei, moving in opposite directions, collide off- center then the Quark Gluon Plasma (QGP) created in the overlap zone is expected to rotate. The nucleons not participating in the collision represent electric currents generating an intense magnetic field. The magnetic field could be as large as 10^{18} gauss, orders of magnitude larger than the strongest magnetic fields found in astronomical objects. Proving the existence of the rotation and/or the magnetic field could be done by checking if particles with spin are aligned with the rotation axis or if charged particles have different production rates relative to the direction of the magnetic field. In particular, the longitudinal and transverse polarisation of the Lambda^0 baryon will be studied. This project requires some affinity with computer programming. <br />
<br />
''Contact: [mailto:Paul.Kuijer@nikhef.nl Paul Kuijer and Panos Christakoglou]''<br />
<br />
=== ALICE : Blast-Wave Model in heavy-ion collisions ===<br />
The goal of heavy-ion physics is to study the Quark Gluon Plasma (QGP), a hot and dense medium where quarks and gluons move freely over large distances, larger than the typical size of a hadron. Hydrodynamic simulations expect that the QGP will expand under its own pressure, and cool while expanding. These simulations are particularly successful in describing some of the key observables measured experimentally, such as particle spectra and elliptic flow. A reasonable reproduction of the same observables is also achieved with models that use parameterisations that resemble the hydrodynamical evolution of the system assuming a given freeze-out scenario, usually referred to as blast-wave models. The goal of this project is to work on different blast wave parametrisations, test their dependence on the input parameters and extend their applicability by including more observables studied in heavy-ion collisions in the global fit. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== ALICE : Higher Harmonic Flow ===<br />
When two ions collide, if the impact parameter is not zero, the overlap region is not isotropic. This spatial anisotropy of the overlap region is transformed into an anisotropy in momentum space through interactions between partons and at a later stage between the produced particles. It was recently realized that the overlap region of the colliding nuclei exhibits an irregular shape. These irregularities originate from the initial density profile of nucleons participating in the collision which is not smooth and is different from one event to the other. The resulting higher order flow harmonics (e.g. v3, v4, and v5, usually referred to as triangular, quadrangular, and pentangular flow, respectively) and in particular their transverse momentum dependence are argued to be more sensitive probes than elliptic flow not only of the initial geometry and its fluctuations but also of shear viscosity over entropy density (η/s). The goal of this project is to study v3, v4, and v5 for identified particles in collisions of heavy-ions at the LHC. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== ALICE : Chiral Magnetic Effect and the Strong CP Problem ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, which is called Chiral Magnetic Effect (CME). The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, but background effects have not yet been properly disentangled. In this project you will develop and test new observables of the CME, trying to understand and discriminate the background sources that affects such a measurement. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== DR&D : Medical X-ray Imaging ===<br />
With the upcoming of true multi-threshold X-Ray detectors the possibilities for Spectral Imaging with low dose, including spectral CT, is now a reality around the corner. The Medipix3RX chip, from the Medipix Collaboration (CERN) features up to 8 programmable thresholds which can select energy bins without a threshold scan. A number of projects could be derived from the R&D activities with the Medipix3RX within the Nikhef R&D group on X-ray imaging for medical applications:<br />
* Medipix3RX characterization in all its operation modes and gains. <br />
* Spectral CT and scarce sampling 3D reconstruction <br />
* Charge sharing: the charge-sum capabilities of the chip can be exploited to further understand the problem of charge sharing in pixelized detectors. A combination of the characterization of the charge-summing mode plus the use of both planar, and 3D sensors, at the light of MC simulation, could reveal valuable information about charge sharing.<br />
<br />
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman],[mailto:martinfr@nihef.nl Martin Fransen]''<br />
<br />
=== DR&D : Compton camera ===<br />
In the Nikhef R&D group we develop instrumentation for particle physics but we also investigate how particle physics detectors can be used for different purposes. A succesfull development is the Medipix chip that can be used in X-ray imaging. For use in large scale medical applications compton scattering limits however the energy resolving possibilities. You will investigate whether it is in principle possible to design a X-ray application that detects the compton scattered electron and the absorbed photon. Your ideas can be tested in practice in the lab where a X-ray scan can be performed.<br />
<br />
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman]''<br />
<br />
=== KM3NeT : Reconstruction of first neutrino interactions in KM3NeT ===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first two strings with sensitive photodetectors have been deployed 2015&2016, in total 30 to be deployed til end of next year. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In order to identify neutrinos an accurate reconstruction and optimal understanding of the backgrounds are crucial. In this project we will use the available data to identify and reconstruct the first neutrino interactions in the KM3NeT detector and with this pave the path towards neutrino astronomy.<br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
<br />
'' Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn]''<br />
<br />
=== ANTARES: Analysis of IceCube neutrino sources. ===<br />
<br />
The only evidence for high energetic neutrinos from cosmic sources so far comes from detections with the IceCube detector. Most of the detected events were reconstructed with a large uncertainty on their direction, which has prevented an association to astrophysical sources. Only for the high energetic muon neutrino candidates a high resolution in the direction has been achieved, but also for those no significant correlation to astrophysical sources has to date been detected.<br />
The ANTARES neutrino telescope has since 2007 continuously taken neutrino data with high angular resolution, which can be exploited to further scrutinize the locations of these neutrino sources. In this project we will address the neutrino sources in a stacked analysis to further probe the origin of the neutrinos with enhanced sensitivity.<br />
<br />
Programming skills are essential, mainly C++ and root will be used. <br />
<br />
'' Contact: [mailto:dosamt@nikhef.nl Dorothea Samtleben]''<br />
<br />
<br />
=== ATLAS: Implementation of Morphing techniques for ATLAS top physics analysis. ===<br />
<br />
Perhaps the most promising gateway to physics beyond the Standard Model is the top quark, the heaviest elementary particle. Particularly<br />
interesting is how the different top quark spin states influence the angular distribution of electrons and other decays products, which can be measured very accurately. New interactions would alter this coupling, leading to decay patterns that are different from those predicted by<br />
the Standard Model. At Nikhef we are implementing NLO predictions of the so called dimension-6 operators to describe several measurable distributions. To confront these distributions with data, a continues parametrization is required. For this purpose, we want to introduce a novel technique in top quark analysis which is based on Morphing. The project consist of an implementation of Morphing to parametrize the top's angular distributions and to demonstrate that the paramdeters can be extracted in a fitting procedure using (pseudo)data. <br />
<br />
Affinity with software is essential, mainly C++ and root will be used. <br />
<br />
'' Contact: [mailto:h73@nikhef.nl Marcel Vreeswijk]''<br />
<br />
=== Theory – Probing electroweak symmetry breaking with Higgs pair production at the LHC and beyond ===<br />
<br />
The measurement of Higgs pair production will be a cornerstone of the LHC program in the coming years. Double Higgs production provides a crucial window upon the mechanism of electroweak symmetry breaking, and has a unique sensitivity to a number of currently unknown Higgs couplings, like the Higgs self-coupling λ and the coupling between a pair of Higgs bosons and two vector bosons. In this project, the student will explore the feasibility of the measurement of Higgs pair production in the 4b final state both at the LHC and at future 100 TeV collider. A number of production modes will be considered, including gluon-fusion, vector-boson-fusion, as well as Higgs pair production in association with a top-quark pair. A key ingredient of the project will be the exploitation of multivariate techniques such as Artificial Neural Networks and other multivariate discriminants to enhance the ratio of di-Higgs signal over backgrounds. <br />
<br />
The project involves to estimate the precision that can be achieved in the extraction of the Higgs self-coupling for a number of assumptions about the performance of the LHC detectors, and in particular to quantify the information that can be extracted from the Run II dataset with L = 300 1/fb . A similar approach will be applied to the determination of other unknown properties of the Higgs sector, such as the coupling between two Higgs bosons and two weak vector bosons, as well as the Wilson coefficients of higher-dimensional operators in the Standard Model Effective Field Theory (SM-EFT). Additional information on this project can be found here: [http://pcteserver.mi.infn.it/~nnpdf/VU/2017-MasterProject-HH.pdf].<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory – Constraining the proton structure with Run II LHC data ===<br />
<br />
The non-perturbative dynamics that determine the energy distribution of quarks and gluons inside protons, the so-called parton distribution functions (PDFs), cannot be computed from first principles from Quantum Chromodynamics (QCD), and need to be determined from experimental data. PDFs are an essential ingredient for the scientific program at the Large Hadron Collider (LHC), from Higgs characterisation to searches for New Physics beyond the Standard Model. One recent breakthrough in PDF analysis has been the exploitation of the constraints from LHC data. From direct photons to top quark pair production cross-sections and charmed meson differential distributions, LHC measurements are now a central ingredient of PDF fits, providing important information on poorly-known PDFs such as the large and small-x gluon or the large-x antiquarks. With the upcoming availability of data from the Run II of the LHC, at a center-of-mass energy of 13 TeV, these constraints are expected to become even more stringent.<br />
<br />
In this project, the implications of PDF-sensitive measurements at the LHC 13 TeV will be quantified. Processes that will be considered include jet and dijet production at the multi-TeV scale, single-top quark production, and weak boson production in association with heavy quarks, among several others. These studies will be performed using the NNPDF fitting framework, based on artificial neural networks and genetic algorithms. The phenomenological implications of the improved PDF modelling for Higgs and new physics searches at the LHC will also be explored. Additional information on this project can be found here: [http://pcteserver.mi.infn.it/~nnpdf/talks/MSc_projects/2017-MasterProject-PDFs.pdf].<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=276Master Projects2018-03-16T07:22:52Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
<br />
== New Projects [start in September 2018] ==<br />
<br />
<br />
=== The XENON Dark Matter Experiment: Data Analysis ===<br />
<br />
The XENON collaboration is operating the XENON1T detector, the world’s most sensitive direct detection dark matter experiment. The Nikhef group is playing an important role in this experiment. The detector operates at the Gran Sasso underground laboratory and consists of a so-called dual-phase xenon time-projection chamber filled with 3200kg of ultra-pure xenon. Our group has an opening for a motivated MSc student to do analysis with the data from this detector. The work will consist of understanding the signals that come out of the detector and applying machine learning tools to improve the reconstruction performance in our Python-based analysis tool. The final goal is to improve the signal-to-background for the dark matter search. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== The Modulation Experiment: Data Analysis ===<br />
<br />
There exist a few measurements that suggest an annual modulation in the activity of radioactive sources. With a few groups from the XENON collaboration we have developed four sets of table-top experiments to investigate this effect on a few well known radioactive sources. The experiments are under construction in Purdue University (USA), a mountain top in Switzerland, a beach in Rio de Janeiro and the last one at Nikhef in Amsterdam. We urgently need a master student to (1) analyze the first big data set, and (2) contribute to the first physics paper from the experiment. We are looking for an all-round physicist with interest in both lab-work and data-analysis. The student will directly collaborate with the other groups in this small collaboration (around 10 people), and the goal is to have the first physics publication ready by the end of the project.<br />
<br />
''Contact: [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== Theory: Unbiased global analysis of heavy quark fragmentation functions ===<br />
<br />
The hadronisation of quarks and gluons into D mesons is of particular relevance in the era of the Large Hadron Collider (LHC). For example, production cross sections are used to constrain the gluon parton distribution function (PDF) at small momentum fractions, they play a vital role in cosmic-ray and neutrino astrophysics, and they provide the background to study modifications of heavy flavour yields in heavy-ion collisions. In perturbative Quantum Chromodynamics (QCD), the hadronisation of partons into hadrons is encoded in nonperturbative fragmentation functions (FFs). In the case of charmed hadrons, like the mesons, the heavy quark mass introduces an additional large scale – apart from some other hard scale that characterises the process – whose effects are perturbatively computable. This project is about a determination of the FFs of D mesons from a QCD analysis of data. Measurements of cross sections in a broad range of single-inclusive hadron production will be considered, namely in electron-positron annihilation, and in hadron-hadron collisions (including in-jet fragmentation). The analysis will be carried through the well-established NNPDF framework. Its main pillars are Monte Carlo sampling for the representation of data uncertainties, and neural networks for the parametrisation of PDFs. The project will allow for the acquisition of a broad set of data analysis computational techniques, widely used in high-energy physics and beyond.<br />
<br />
"Further information [[http://pcteserver.mi.infn.it/~nnpdf/VU/2018-MasterProject-DFFs.pdf here]]<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory: The quark and gluon internal structure of heavy nuclei in the LHC era ===<br />
<br />
A precise knowledge of the parton distribution functions (PDFs) of the proton is essential in order to make predictions for the Standard Model and beyond at hadron colliders. The presence of nuclear medium and collective phenomena which involve several nucleons modifies the parton distribution functions of nuclei (nPDFs) compared to those of a free nucleon. These modifications have been investigated by different groups using global analyses of high energy nuclear reaction world data. It is important to determine the nPDFs not only for establishing perturbative QCD factorisation in nuclei but also for applications to heavy-ion physics and neutrino physics. In this project the student will join an ongoing effort towards the determination of a data-driven model of nPDFs, and will learn how to construct tailored Artificial Neural Networks (ANNs). <br />
<br />
"Further information [[http://pcteserver.mi.infn.it/~nnpdf/VU/2018-MasterProject-nPDFs.pdf here]]<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory: Combined QCD analysis of parton distribution and fragmentation functions ===<br />
<br />
The formation of hadrons from quarks and gluons, or collectively partons, is a fundamental QCD process that has yet to be fully understood. Since parton-to-hadron fragmentation occurs over long-distance scales, such information can only be extracted from experimental observables that identify mesons and baryons in the final state. Recent progress has been made to determine these fragmentation functions (FFs) from charged pion and kaon production in single inclusive e+e−-annihilation (SIA) and additionally pp-collisions and semi-inclusive deep inelastic scattering (SIDIS). However, charged hadron production in unpolarized pp and inelastic lepton-proton scattering also require information about the momentum distributions of the quarks and gluons in the proton, which is encoded in non-perturbative parton distribution functions (PDFs). In this project, a simultaneous treatment of both PDFs and FFs in a global QCD analysis of single inclusive hadron production processes will be made to determine the individual parton-to-hadron FFs. Furthermore, a robust statistical methodology with an artificial neural network learning algorithm will be used to obtain a precise estimation of the FF uncertainties. This work will emphasis in particular the impact of pp-collision and SIDIS data on the gluon and separated quark/anti-quark FFs, respectively.<br />
<br />
"Further information [[http://pcteserver.mi.infn.it/~nnpdf/VU/2018-MasterProject-FFpPDFs.pdf here]]<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
----<br />
<br />
== OLD Projects [from last year] ==<br />
<br />
<br />
<br />
=== The Modulation Experiment: Data Analysis ===<br />
<br />
There exist a few measurements that suggest an annual modulation in the activity of radioactive sources. With a few groups from the XENON collaboration we have developed four sets of table-top experiments to investigate this effect on a few well known radioactive sources. The experiments are under construction in Purdue University (USA), a mountain top in Switzerland, a beach in Rio de Janeiro and the last one at Nikhef in Amsterdam. We urgently need a master student to (1) analyze the first big data set, and (2) contribute to the first physics paper from the experiment. We are looking for an all-round physicist with interest in both lab-work and data-analysis. The student will directly collaborate with the other groups in this small collaboration (around 10 people), and the goal is to have the first physics publication ready by the end of the project.<br />
<br />
''Contact: [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== The XENON Dark Matter Experiment: Data Analysis ===<br />
<br />
The XENON collaboration has started operating the XENON1T detector, the world’s most sensitive direct detection dark matter experiment. The Nikhef group is playing an important role in this experiment. The detector operates at the Gran Sasso underground laboratory and consists of a so-called dual-phase xenon time-projection chamber filled with 3200kg of ultra-pure xenon. Our group has an opening for a motivated MSc student to do data-analysis on this new detector. The work will consist of understanding the signals that come out of the detector and in particular focus on the so-called double scatter events. We are interested in developing methods in order to interpret the response of the detector better and are developing sophisticated statistical tools to do this. This work will include looking at data and developing new algorithms in our Python-based analysis tool. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== XAMS Dark Matter R&D Setup ===<br />
<br />
The Amsterdam Dark Matter group has built an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 4kg of ultra-pure liquid xenon. We plan to use this detector for the development of new detection techniques (such as utilizing new photosensors) and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENON experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data him/herself. You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== LHCb: A Scintillator Fibers Tracker ===<br />
<br />
The LHCb collaboration is upgrading the present tracking system<br />
constructing a new tracker based on scintillating fibers combined<br />
with silicon photo-multipliers (SiPM): the SciFi Tracker!<br />
Nikhef plays a key role in the project, as we will build the<br />
SciFi fibers modules, the cold-box enclosure housing the SiPMs,<br />
and a large part of the on-detector electronics. In all these<br />
areas, interesting test hardware and software has to be realized,<br />
and several research topics for a Master project are available,<br />
taking the student in contact with state-of-the-art particle detectors,<br />
in a large team of physicists and engineers. Possible collaborations<br />
with the Nikhef R&D group can also be envisaged.<br />
<br />
''Contact: [mailto:antonio@nikhef.nl Antonio Pellegrino]''<br />
<br />
=== LHCb: Discovery of the Decay Lb --> p Ds+ ===<br />
This project aims to measure the branching fraction of the decay Lb->p Ds+ (bud -> uud + ds). <br />
The decay Lb->p Ds+ is quite rare, because it occurs through the transition of a b-quark to a u-quark. <br />
It has not been measured yet (although some LHCb colleagues claim to have seen it).<br />
This decay is interesting, because <br />
<br />
1) It is sensitive to the b->u coupling (CKM-element Vub), which determination is heavily debated.<br />
2) It can quantify non-factorisable QCD effects in b-baryon decays.<br />
<br />
The decay is closely related to B0->pi-Ds+, which proceeds through a similar Feynman diagram. <br />
Also, the final state of B0->pi-Ds+ is almost identical to Lb->p Ds+. <br />
The aim is to determine the relative branching fraction of Lb->pDs+ with respect to B0->D+pi- decays, <br />
in close collaboration with the PhD (who will study BR(B0->pi-Ds+)/BR(B0->D+pi-) ).<br />
This project will result in a journal publication on behalf of the LHCb collaboration, written by you. <br />
For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. <br />
This is a project that is closely related to previous analyses in the group. <br />
Weekly video meetings with CERN coordinate the efforts with in the LHCb collaboration.<br />
Relevant information:<br />
<br />
[1] R.Aaij et al. [LHCb Collaboration], ``Determination of the branching fractions of B0s->DsK and B0->DsK, JHEP 05 (2015) 019 [arXiv:1412.7654 [hep-ex]].<br />
[2] R. Fleischer, N. Serra and N. Tuning, ``Tests of Factorization and SU(3) Relations in B Decays into Heavy-Light Final States, Phys. Rev. D 83, 014017 (2011) [arXiv:1012.2784 [hep-ph]].<br />
<br />
''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''<br />
<br />
=== LHCb: Measurement of B0 -> pi Ds- , the b -> u quark transition ===<br />
<br />
This project aims to measure the branching fraction of the decay B0->pi Ds+.<br />
This decay is closely related to Lb->p Ds+ (see above), and close collaboration between the two master projects is foreseen.<br />
This research was started by a previous master student. <br />
The new measurement will finish the work, and include the new data from 2015 and 2016.<br />
<br />
See Mick Mulders [http://www.nikhef.nl/pub/experiments/bfys/lhcb/Theses/master/2015_MickMulder.pdf master thesis] for more information.<br />
<br />
''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''<br />
<br />
=== LHCb: A search for heavy neutrinos in the decay of W bosons at LHCb ===<br />
<br />
Neutrinos are arguably the most mysterious of all known fundamental fermions as they are both much lighter than all others and only weakly interacting. It is thought that the tiny mass of neutrinos can be explained by their mixing with so-far unknown, much heavier, neutrino-like particles. In this research proposal we look for these new neutrinos in the decay of the SM W-boson using data with the LHCb experiment at CERN. The W boson is assumed to decay to a heavy neutrino and a muon. The heavy neutrino subsequently decays to a muon and a pair of quarks. Both like-sign and opposite-sign muon pairs will be studied. The result of the analysis will either be a limit on the production of the new neutrinos or the discovery of something entirely new.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen and Elena Dall'Occo]''<br />
<br />
<br />
=== LHCb: Searches for new pentaquarks ===<br />
<br />
In 2015 LHCb surprisingly discovered states containing five quarks, called Pc+ pentaquarks. Such particles question our understanding of confinement, the principle that forces quarks to remain in a single hadron. Which hadrons are allowed and which are not? The pentaquarks were found in the decay of the Lambda_b baryon to a Pc+ and a kaon, and Pc+ to a J/psi and a proton. This project aims at studying other similar but yet unobserved decays which could reveal the presence of the know Pc+, or yet unknown pentaquarks. The student will optimise a selection for finding such a decay in LHCb data using machine learning techniques. <br />
<br />
See [https://arxiv.org/abs/1406.0755 arXiv:1406.0755] for more information.<br />
<br />
''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
<br />
<br />
=== ATLAS : Double Higgs searches with multiple leptons ===<br />
<br />
The Standard Model of particle physics (SM) is extremely successful, but would it hold against check with data containing multiple leptons? Although very rare process, the production of leptons is calculated in SM with high precision. On detector side the leptons (electrons and muons) are easy to reconstruct and such a sample contains very little "non-lepton" background. This analysis has an ambitious goal to reconstruct events with two Higgs bosons using events with 4 leptons. With this project, the student would gain close familiarity with modern experimental techniques (statistical analysis, SM predictions, search for rare signals), with Monte Carlo generators and the standard HEP analysis tools (ROOT, C++, python).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and Marcus Morgenstern and Pepijn Bakker]''<br />
<br />
=== ATLAS : A search for lepton flavor violation with tau decays ===<br />
<br />
Quarks mix, neutrinos mix, charged leptons do not mix. Why? Is that really how the nature works, or is it just a limitation in our detection techniques. ATLAS has recorded now a huge sample of data. Even such difficult final states as tau->3mu become accessible. However, the decays of charm and beauty mesons could spoil the picture with decays that resembles the signal. The goal of the project is to understand what<br />
background decays are present and to find a way to suppress them. Success of project will allow much higher sensitivity to beyond Standard Model physics of tau->3mu. The student would gain close familiarity with modern experimental techniques (statistical analysis, SM predictions, search for rare signals), background suppression techniques and the standard HEP analysis tools (ROOT, C++, python).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and Matteo Bedognetti]''<br />
<br />
=== ALICE : Particle polarisation in strong magnetic fields ===<br />
When two atomic nuclei, moving in opposite directions, collide off- center then the Quark Gluon Plasma (QGP) created in the overlap zone is expected to rotate. The nucleons not participating in the collision represent electric currents generating an intense magnetic field. The magnetic field could be as large as 10^{18} gauss, orders of magnitude larger than the strongest magnetic fields found in astronomical objects. Proving the existence of the rotation and/or the magnetic field could be done by checking if particles with spin are aligned with the rotation axis or if charged particles have different production rates relative to the direction of the magnetic field. In particular, the longitudinal and transverse polarisation of the Lambda^0 baryon will be studied. This project requires some affinity with computer programming. <br />
<br />
''Contact: [mailto:Paul.Kuijer@nikhef.nl Paul Kuijer and Panos Christakoglou]''<br />
<br />
=== ALICE : Blast-Wave Model in heavy-ion collisions ===<br />
The goal of heavy-ion physics is to study the Quark Gluon Plasma (QGP), a hot and dense medium where quarks and gluons move freely over large distances, larger than the typical size of a hadron. Hydrodynamic simulations expect that the QGP will expand under its own pressure, and cool while expanding. These simulations are particularly successful in describing some of the key observables measured experimentally, such as particle spectra and elliptic flow. A reasonable reproduction of the same observables is also achieved with models that use parameterisations that resemble the hydrodynamical evolution of the system assuming a given freeze-out scenario, usually referred to as blast-wave models. The goal of this project is to work on different blast wave parametrisations, test their dependence on the input parameters and extend their applicability by including more observables studied in heavy-ion collisions in the global fit. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== ALICE : Higher Harmonic Flow ===<br />
When two ions collide, if the impact parameter is not zero, the overlap region is not isotropic. This spatial anisotropy of the overlap region is transformed into an anisotropy in momentum space through interactions between partons and at a later stage between the produced particles. It was recently realized that the overlap region of the colliding nuclei exhibits an irregular shape. These irregularities originate from the initial density profile of nucleons participating in the collision which is not smooth and is different from one event to the other. The resulting higher order flow harmonics (e.g. v3, v4, and v5, usually referred to as triangular, quadrangular, and pentangular flow, respectively) and in particular their transverse momentum dependence are argued to be more sensitive probes than elliptic flow not only of the initial geometry and its fluctuations but also of shear viscosity over entropy density (η/s). The goal of this project is to study v3, v4, and v5 for identified particles in collisions of heavy-ions at the LHC. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== ALICE : Chiral Magnetic Effect and the Strong CP Problem ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, which is called Chiral Magnetic Effect (CME). The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, but background effects have not yet been properly disentangled. In this project you will develop and test new observables of the CME, trying to understand and discriminate the background sources that affects such a measurement. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== DR&D : Medical X-ray Imaging ===<br />
With the upcoming of true multi-threshold X-Ray detectors the possibilities for Spectral Imaging with low dose, including spectral CT, is now a reality around the corner. The Medipix3RX chip, from the Medipix Collaboration (CERN) features up to 8 programmable thresholds which can select energy bins without a threshold scan. A number of projects could be derived from the R&D activities with the Medipix3RX within the Nikhef R&D group on X-ray imaging for medical applications:<br />
* Medipix3RX characterization in all its operation modes and gains. <br />
* Spectral CT and scarce sampling 3D reconstruction <br />
* Charge sharing: the charge-sum capabilities of the chip can be exploited to further understand the problem of charge sharing in pixelized detectors. A combination of the characterization of the charge-summing mode plus the use of both planar, and 3D sensors, at the light of MC simulation, could reveal valuable information about charge sharing.<br />
<br />
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman],[mailto:martinfr@nihef.nl Martin Fransen]''<br />
<br />
=== DR&D : Compton camera ===<br />
In the Nikhef R&D group we develop instrumentation for particle physics but we also investigate how particle physics detectors can be used for different purposes. A succesfull development is the Medipix chip that can be used in X-ray imaging. For use in large scale medical applications compton scattering limits however the energy resolving possibilities. You will investigate whether it is in principle possible to design a X-ray application that detects the compton scattered electron and the absorbed photon. Your ideas can be tested in practice in the lab where a X-ray scan can be performed.<br />
<br />
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman]''<br />
<br />
=== KM3NeT : Reconstruction of first neutrino interactions in KM3NeT ===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first two strings with sensitive photodetectors have been deployed 2015&2016, in total 30 to be deployed til end of next year. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In order to identify neutrinos an accurate reconstruction and optimal understanding of the backgrounds are crucial. In this project we will use the available data to identify and reconstruct the first neutrino interactions in the KM3NeT detector and with this pave the path towards neutrino astronomy.<br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
<br />
'' Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn]''<br />
<br />
=== ANTARES: Analysis of IceCube neutrino sources. ===<br />
<br />
The only evidence for high energetic neutrinos from cosmic sources so far comes from detections with the IceCube detector. Most of the detected events were reconstructed with a large uncertainty on their direction, which has prevented an association to astrophysical sources. Only for the high energetic muon neutrino candidates a high resolution in the direction has been achieved, but also for those no significant correlation to astrophysical sources has to date been detected.<br />
The ANTARES neutrino telescope has since 2007 continuously taken neutrino data with high angular resolution, which can be exploited to further scrutinize the locations of these neutrino sources. In this project we will address the neutrino sources in a stacked analysis to further probe the origin of the neutrinos with enhanced sensitivity.<br />
<br />
Programming skills are essential, mainly C++ and root will be used. <br />
<br />
'' Contact: [mailto:dosamt@nikhef.nl Dorothea Samtleben]''<br />
<br />
<br />
=== ATLAS: Implementation of Morphing techniques for ATLAS top physics analysis. ===<br />
<br />
Perhaps the most promising gateway to physics beyond the Standard Model is the top quark, the heaviest elementary particle. Particularly<br />
interesting is how the different top quark spin states influence the angular distribution of electrons and other decays products, which can be measured very accurately. New interactions would alter this coupling, leading to decay patterns that are different from those predicted by<br />
the Standard Model. At Nikhef we are implementing NLO predictions of the so called dimension-6 operators to describe several measurable distributions. To confront these distributions with data, a continues parametrization is required. For this purpose, we want to introduce a novel technique in top quark analysis which is based on Morphing. The project consist of an implementation of Morphing to parametrize the top's angular distributions and to demonstrate that the paramdeters can be extracted in a fitting procedure using (pseudo)data. <br />
<br />
Affinity with software is essential, mainly C++ and root will be used. <br />
<br />
'' Contact: [mailto:h73@nikhef.nl Marcel Vreeswijk]''<br />
<br />
=== Theory – Probing electroweak symmetry breaking with Higgs pair production at the LHC and beyond ===<br />
<br />
The measurement of Higgs pair production will be a cornerstone of the LHC program in the coming years. Double Higgs production provides a crucial window upon the mechanism of electroweak symmetry breaking, and has a unique sensitivity to a number of currently unknown Higgs couplings, like the Higgs self-coupling λ and the coupling between a pair of Higgs bosons and two vector bosons. In this project, the student will explore the feasibility of the measurement of Higgs pair production in the 4b final state both at the LHC and at future 100 TeV collider. A number of production modes will be considered, including gluon-fusion, vector-boson-fusion, as well as Higgs pair production in association with a top-quark pair. A key ingredient of the project will be the exploitation of multivariate techniques such as Artificial Neural Networks and other multivariate discriminants to enhance the ratio of di-Higgs signal over backgrounds. <br />
<br />
The project involves to estimate the precision that can be achieved in the extraction of the Higgs self-coupling for a number of assumptions about the performance of the LHC detectors, and in particular to quantify the information that can be extracted from the Run II dataset with L = 300 1/fb . A similar approach will be applied to the determination of other unknown properties of the Higgs sector, such as the coupling between two Higgs bosons and two weak vector bosons, as well as the Wilson coefficients of higher-dimensional operators in the Standard Model Effective Field Theory (SM-EFT). Additional information on this project can be found here: [http://pcteserver.mi.infn.it/~nnpdf/VU/2017-MasterProject-HH.pdf].<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory – Constraining the proton structure with Run II LHC data ===<br />
<br />
The non-perturbative dynamics that determine the energy distribution of quarks and gluons inside protons, the so-called parton distribution functions (PDFs), cannot be computed from first principles from Quantum Chromodynamics (QCD), and need to be determined from experimental data. PDFs are an essential ingredient for the scientific program at the Large Hadron Collider (LHC), from Higgs characterisation to searches for New Physics beyond the Standard Model. One recent breakthrough in PDF analysis has been the exploitation of the constraints from LHC data. From direct photons to top quark pair production cross-sections and charmed meson differential distributions, LHC measurements are now a central ingredient of PDF fits, providing important information on poorly-known PDFs such as the large and small-x gluon or the large-x antiquarks. With the upcoming availability of data from the Run II of the LHC, at a center-of-mass energy of 13 TeV, these constraints are expected to become even more stringent.<br />
<br />
In this project, the implications of PDF-sensitive measurements at the LHC 13 TeV will be quantified. Processes that will be considered include jet and dijet production at the multi-TeV scale, single-top quark production, and weak boson production in association with heavy quarks, among several others. These studies will be performed using the NNPDF fitting framework, based on artificial neural networks and genetic algorithms. The phenomenological implications of the improved PDF modelling for Higgs and new physics searches at the LHC will also be explored. Additional information on this project can be found here: [http://pcteserver.mi.infn.it/~nnpdf/talks/MSc_projects/2017-MasterProject-PDFs.pdf].<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=268Master Projects2018-02-11T08:13:19Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
=== Theory: Unbiased global analysis of heavy quark fragmentation functions ===<br />
<br />
The hadronisation of quarks and gluons into D mesons is of particular relevance in the era of the Large Hadron Collider (LHC). For example, production cross sections are used to constrain the gluon parton distribution function (PDF) at small momentum fractions, they play a vital role in cosmic-ray and neutrino astrophysics, and they provide the background to study modifications of heavy flavour yields in heavy-ion collisions. In perturbative Quantum Chromodynamics (QCD), the hadronisation of partons into hadrons is encoded in nonperturbative fragmentation functions (FFs). In the case of charmed hadrons, like the mesons, the heavy quark mass introduces an additional large scale – apart from some other hard scale that characterises the process – whose effects are perturbatively computable. This project is about a determination of the FFs of D mesons from a QCD analysis of data. Measurements of cross sections in a broad range of single-inclusive hadron production will be considered, namely in electron-positron annihilation, and in hadron-hadron collisions (including in-jet fragmentation). The analysis will be carried through the well-established NNPDF framework. Its main pillars are Monte Carlo sampling for the representation of data uncertainties, and neural networks for the parametrisation of PDFs. The project will allow for the acquisition of a broad set of data analysis computational techniques, widely used in high-energy physics and beyond.<br />
<br />
"Further information [[http://pcteserver.mi.infn.it/~nnpdf/VU/2018-MasterProject-DFFs.pdf here]]<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory: The quark and gluon internal structure of heavy nuclei in the LHC era ===<br />
<br />
A precise knowledge of the parton distribution functions (PDFs) of the proton is essential in order to make predictions for the Standard Model and beyond at hadron colliders. The presence of nuclear medium and collective phenomena which involve several nucleons modifies the parton distribution functions of nuclei (nPDFs) compared to those of a free nucleon. These modifications have been investigated by different groups using global analyses of high energy nuclear reaction world data. It is important to determine the nPDFs not only for establishing perturbative QCD factorisation in nuclei but also for applications to heavy-ion physics and neutrino physics. In this project the student will join an ongoing effort towards the determination of a data-driven model of nPDFs, and will learn how to construct tailored Artificial Neural Networks (ANNs). <br />
<br />
"Further information [[http://pcteserver.mi.infn.it/~nnpdf/VU/2018-MasterProject-nPDFs.pdf here]]<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory: Combined QCD analysis of parton distribution and fragmentation functions ===<br />
<br />
The formation of hadrons from quarks and gluons, or collectively partons, is a fundamental QCD process that has yet to be fully understood. Since parton-to-hadron fragmentation occurs over long-distance scales, such information can only be extracted from experimental observables that identify mesons and baryons in the final state. Recent progress has been made to determine these fragmentation functions (FFs) from charged pion and kaon production in single inclusive e+e−-annihilation (SIA) and additionally pp-collisions and semi-inclusive deep inelastic scattering (SIDIS). However, charged hadron production in unpolarized pp and inelastic lepton-proton scattering also require information about the momentum distributions of the quarks and gluons in the proton, which is encoded in non-perturbative parton distribution functions (PDFs). In this project, a simultaneous treatment of both PDFs and FFs in a global QCD analysis of single inclusive hadron production processes will be made to determine the individual parton-to-hadron FFs. Furthermore, a robust statistical methodology with an artificial neural network learning algorithm will be used to obtain a precise estimation of the FF uncertainties. This work will emphasis in particular the impact of pp-collision and SIDIS data on the gluon and separated quark/anti-quark FFs, respectively.<br />
<br />
"Further information [[http://pcteserver.mi.infn.it/~nnpdf/VU/2018-MasterProject-FFpPDFs.pdf here]]<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== The Modulation Experiment: Data Analysis ===<br />
<br />
There exist a few measurements that suggest an annual modulation in the activity of radioactive sources. With a few groups from the XENON collaboration we have developed four sets of table-top experiments to investigate this effect on a few well known radioactive sources. The experiments are under construction in Purdue University (USA), a mountain top in Switzerland, a beach in Rio de Janeiro and the last one at Nikhef in Amsterdam. We urgently need a master student to (1) analyze the first big data set, and (2) contribute to the first physics paper from the experiment. We are looking for an all-round physicist with interest in both lab-work and data-analysis. The student will directly collaborate with the other groups in this small collaboration (around 10 people), and the goal is to have the first physics publication ready by the end of the project.<br />
<br />
''Contact: [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== The XENON Dark Matter Experiment: Data Analysis ===<br />
<br />
The XENON collaboration has started operating the XENON1T detector, the world’s most sensitive direct detection dark matter experiment. The Nikhef group is playing an important role in this experiment. The detector operates at the Gran Sasso underground laboratory and consists of a so-called dual-phase xenon time-projection chamber filled with 3200kg of ultra-pure xenon. Our group has an opening for a motivated MSc student to do data-analysis on this new detector. The work will consist of understanding the signals that come out of the detector and in particular focus on the so-called double scatter events. We are interested in developing methods in order to interpret the response of the detector better and are developing sophisticated statistical tools to do this. This work will include looking at data and developing new algorithms in our Python-based analysis tool. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== XAMS Dark Matter R&D Setup ===<br />
<br />
The Amsterdam Dark Matter group has built an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 4kg of ultra-pure liquid xenon. We plan to use this detector for the development of new detection techniques (such as utilizing new photosensors) and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENON experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data him/herself. You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== LHCb: A Scintillator Fibers Tracker ===<br />
<br />
The LHCb collaboration is upgrading the present tracking system<br />
constructing a new tracker based on scintillating fibers combined<br />
with silicon photo-multipliers (SiPM): the SciFi Tracker!<br />
Nikhef plays a key role in the project, as we will build the<br />
SciFi fibers modules, the cold-box enclosure housing the SiPMs,<br />
and a large part of the on-detector electronics. In all these<br />
areas, interesting test hardware and software has to be realized,<br />
and several research topics for a Master project are available,<br />
taking the student in contact with state-of-the-art particle detectors,<br />
in a large team of physicists and engineers. Possible collaborations<br />
with the Nikhef R&D group can also be envisaged.<br />
<br />
''Contact: [mailto:antonio@nikhef.nl Antonio Pellegrino]''<br />
<br />
=== LHCb: Discovery of the Decay Lb --> p Ds+ ===<br />
This project aims to measure the branching fraction of the decay Lb->p Ds+ (bud -> uud + ds). <br />
The decay Lb->p Ds+ is quite rare, because it occurs through the transition of a b-quark to a u-quark. <br />
It has not been measured yet (although some LHCb colleagues claim to have seen it).<br />
This decay is interesting, because <br />
<br />
1) It is sensitive to the b->u coupling (CKM-element Vub), which determination is heavily debated.<br />
2) It can quantify non-factorisable QCD effects in b-baryon decays.<br />
<br />
The decay is closely related to B0->pi-Ds+, which proceeds through a similar Feynman diagram. <br />
Also, the final state of B0->pi-Ds+ is almost identical to Lb->p Ds+. <br />
The aim is to determine the relative branching fraction of Lb->pDs+ with respect to B0->D+pi- decays, <br />
in close collaboration with the PhD (who will study BR(B0->pi-Ds+)/BR(B0->D+pi-) ).<br />
This project will result in a journal publication on behalf of the LHCb collaboration, written by you. <br />
For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. <br />
This is a project that is closely related to previous analyses in the group. <br />
Weekly video meetings with CERN coordinate the efforts with in the LHCb collaboration.<br />
Relevant information:<br />
<br />
[1] R.Aaij et al. [LHCb Collaboration], ``Determination of the branching fractions of B0s->DsK and B0->DsK, JHEP 05 (2015) 019 [arXiv:1412.7654 [hep-ex]].<br />
[2] R. Fleischer, N. Serra and N. Tuning, ``Tests of Factorization and SU(3) Relations in B Decays into Heavy-Light Final States, Phys. Rev. D 83, 014017 (2011) [arXiv:1012.2784 [hep-ph]].<br />
<br />
''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''<br />
<br />
=== LHCb: Measurement of B0 -> pi Ds- , the b -> u quark transition ===<br />
<br />
This project aims to measure the branching fraction of the decay B0->pi Ds+.<br />
This decay is closely related to Lb->p Ds+ (see above), and close collaboration between the two master projects is foreseen.<br />
This research was started by a previous master student. <br />
The new measurement will finish the work, and include the new data from 2015 and 2016.<br />
<br />
See Mick Mulders [http://www.nikhef.nl/pub/experiments/bfys/lhcb/Theses/master/2015_MickMulder.pdf master thesis] for more information.<br />
<br />
''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''<br />
<br />
=== LHCb: A search for heavy neutrinos in the decay of W bosons at LHCb ===<br />
<br />
Neutrinos are arguably the most mysterious of all known fundamental fermions as they are both much lighter than all others and only weakly interacting. It is thought that the tiny mass of neutrinos can be explained by their mixing with so-far unknown, much heavier, neutrino-like particles. In this research proposal we look for these new neutrinos in the decay of the SM W-boson using data with the LHCb experiment at CERN. The W boson is assumed to decay to a heavy neutrino and a muon. The heavy neutrino subsequently decays to a muon and a pair of quarks. Both like-sign and opposite-sign muon pairs will be studied. The result of the analysis will either be a limit on the production of the new neutrinos or the discovery of something entirely new.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen and Elena Dall'Occo]''<br />
<br />
<br />
=== LHCb: Searches for new pentaquarks ===<br />
<br />
In 2015 LHCb surprisingly discovered states containing five quarks, called Pc+ pentaquarks. Such particles question our understanding of confinement, the principle that forces quarks to remain in a single hadron. Which hadrons are allowed and which are not? The pentaquarks were found in the decay of the Lambda_b baryon to a Pc+ and a kaon, and Pc+ to a J/psi and a proton. This project aims at studying other similar but yet unobserved decays which could reveal the presence of the know Pc+, or yet unknown pentaquarks. The student will optimise a selection for finding such a decay in LHCb data using machine learning techniques. <br />
<br />
See [https://arxiv.org/abs/1406.0755 arXiv:1406.0755] for more information.<br />
<br />
''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
<br />
<br />
=== ATLAS : Double Higgs searches with multiple leptons ===<br />
<br />
The Standard Model of particle physics (SM) is extremely successful, but would it hold against check with data containing multiple leptons? Although very rare process, the production of leptons is calculated in SM with high precision. On detector side the leptons (electrons and muons) are easy to reconstruct and such a sample contains very little "non-lepton" background. This analysis has an ambitious goal to reconstruct events with two Higgs bosons using events with 4 leptons. With this project, the student would gain close familiarity with modern experimental techniques (statistical analysis, SM predictions, search for rare signals), with Monte Carlo generators and the standard HEP analysis tools (ROOT, C++, python).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and Marcus Morgenstern and Pepijn Bakker]''<br />
<br />
=== ATLAS : A search for lepton flavor violation with tau decays ===<br />
<br />
Quarks mix, neutrinos mix, charged leptons do not mix. Why? Is that really how the nature works, or is it just a limitation in our detection techniques. ATLAS has recorded now a huge sample of data. Even such difficult final states as tau->3mu become accessible. However, the decays of charm and beauty mesons could spoil the picture with decays that resembles the signal. The goal of the project is to understand what<br />
background decays are present and to find a way to suppress them. Success of project will allow much higher sensitivity to beyond Standard Model physics of tau->3mu. The student would gain close familiarity with modern experimental techniques (statistical analysis, SM predictions, search for rare signals), background suppression techniques and the standard HEP analysis tools (ROOT, C++, python).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and Matteo Bedognetti]''<br />
<br />
=== ALICE : Particle polarisation in strong magnetic fields ===<br />
When two atomic nuclei, moving in opposite directions, collide off- center then the Quark Gluon Plasma (QGP) created in the overlap zone is expected to rotate. The nucleons not participating in the collision represent electric currents generating an intense magnetic field. The magnetic field could be as large as 10^{18} gauss, orders of magnitude larger than the strongest magnetic fields found in astronomical objects. Proving the existence of the rotation and/or the magnetic field could be done by checking if particles with spin are aligned with the rotation axis or if charged particles have different production rates relative to the direction of the magnetic field. In particular, the longitudinal and transverse polarisation of the Lambda^0 baryon will be studied. This project requires some affinity with computer programming. <br />
<br />
''Contact: [mailto:Paul.Kuijer@nikhef.nl Paul Kuijer and Panos Christakoglou]''<br />
<br />
=== ALICE : Blast-Wave Model in heavy-ion collisions ===<br />
The goal of heavy-ion physics is to study the Quark Gluon Plasma (QGP), a hot and dense medium where quarks and gluons move freely over large distances, larger than the typical size of a hadron. Hydrodynamic simulations expect that the QGP will expand under its own pressure, and cool while expanding. These simulations are particularly successful in describing some of the key observables measured experimentally, such as particle spectra and elliptic flow. A reasonable reproduction of the same observables is also achieved with models that use parameterisations that resemble the hydrodynamical evolution of the system assuming a given freeze-out scenario, usually referred to as blast-wave models. The goal of this project is to work on different blast wave parametrisations, test their dependence on the input parameters and extend their applicability by including more observables studied in heavy-ion collisions in the global fit. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== ALICE : Higher Harmonic Flow ===<br />
When two ions collide, if the impact parameter is not zero, the overlap region is not isotropic. This spatial anisotropy of the overlap region is transformed into an anisotropy in momentum space through interactions between partons and at a later stage between the produced particles. It was recently realized that the overlap region of the colliding nuclei exhibits an irregular shape. These irregularities originate from the initial density profile of nucleons participating in the collision which is not smooth and is different from one event to the other. The resulting higher order flow harmonics (e.g. v3, v4, and v5, usually referred to as triangular, quadrangular, and pentangular flow, respectively) and in particular their transverse momentum dependence are argued to be more sensitive probes than elliptic flow not only of the initial geometry and its fluctuations but also of shear viscosity over entropy density (η/s). The goal of this project is to study v3, v4, and v5 for identified particles in collisions of heavy-ions at the LHC. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== ALICE : Chiral Magnetic Effect and the Strong CP Problem ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, which is called Chiral Magnetic Effect (CME). The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, but background effects have not yet been properly disentangled. In this project you will develop and test new observables of the CME, trying to understand and discriminate the background sources that affects such a measurement. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== DR&D : Medical X-ray Imaging ===<br />
With the upcoming of true multi-threshold X-Ray detectors the possibilities for Spectral Imaging with low dose, including spectral CT, is now a reality around the corner. The Medipix3RX chip, from the Medipix Collaboration (CERN) features up to 8 programmable thresholds which can select energy bins without a threshold scan. A number of projects could be derived from the R&D activities with the Medipix3RX within the Nikhef R&D group on X-ray imaging for medical applications:<br />
* Medipix3RX characterization in all its operation modes and gains. <br />
* Spectral CT and scarce sampling 3D reconstruction <br />
* Charge sharing: the charge-sum capabilities of the chip can be exploited to further understand the problem of charge sharing in pixelized detectors. A combination of the characterization of the charge-summing mode plus the use of both planar, and 3D sensors, at the light of MC simulation, could reveal valuable information about charge sharing.<br />
<br />
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman],[mailto:martinfr@nihef.nl Martin Fransen]''<br />
<br />
=== DR&D : Compton camera ===<br />
In the Nikhef R&D group we develop instrumentation for particle physics but we also investigate how particle physics detectors can be used for different purposes. A succesfull development is the Medipix chip that can be used in X-ray imaging. For use in large scale medical applications compton scattering limits however the energy resolving possibilities. You will investigate whether it is in principle possible to design a X-ray application that detects the compton scattered electron and the absorbed photon. Your ideas can be tested in practice in the lab where a X-ray scan can be performed.<br />
<br />
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman]''<br />
<br />
=== KM3NeT : Reconstruction of first neutrino interactions in KM3NeT ===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first two strings with sensitive photodetectors have been deployed 2015&2016, in total 30 to be deployed til end of next year. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In order to identify neutrinos an accurate reconstruction and optimal understanding of the backgrounds are crucial. In this project we will use the available data to identify and reconstruct the first neutrino interactions in the KM3NeT detector and with this pave the path towards neutrino astronomy.<br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
<br />
'' Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn]''<br />
<br />
=== ANTARES: Analysis of IceCube neutrino sources. ===<br />
<br />
The only evidence for high energetic neutrinos from cosmic sources so far comes from detections with the IceCube detector. Most of the detected events were reconstructed with a large uncertainty on their direction, which has prevented an association to astrophysical sources. Only for the high energetic muon neutrino candidates a high resolution in the direction has been achieved, but also for those no significant correlation to astrophysical sources has to date been detected.<br />
The ANTARES neutrino telescope has since 2007 continuously taken neutrino data with high angular resolution, which can be exploited to further scrutinize the locations of these neutrino sources. In this project we will address the neutrino sources in a stacked analysis to further probe the origin of the neutrinos with enhanced sensitivity.<br />
<br />
Programming skills are essential, mainly C++ and root will be used. <br />
<br />
'' Contact: [mailto:dosamt@nikhef.nl Dorothea Samtleben]''<br />
<br />
<br />
=== ATLAS: Implementation of Morphing techniques for ATLAS top physics analysis. ===<br />
<br />
Perhaps the most promising gateway to physics beyond the Standard Model is the top quark, the heaviest elementary particle. Particularly<br />
interesting is how the different top quark spin states influence the angular distribution of electrons and other decays products, which can be measured very accurately. New interactions would alter this coupling, leading to decay patterns that are different from those predicted by<br />
the Standard Model. At Nikhef we are implementing NLO predictions of the so called dimension-6 operators to describe several measurable distributions. To confront these distributions with data, a continues parametrization is required. For this purpose, we want to introduce a novel technique in top quark analysis which is based on Morphing. The project consist of an implementation of Morphing to parametrize the top's angular distributions and to demonstrate that the paramdeters can be extracted in a fitting procedure using (pseudo)data. <br />
<br />
Affinity with software is essential, mainly C++ and root will be used. <br />
<br />
'' Contact: [mailto:h73@nikhef.nl Marcel Vreeswijk]''<br />
<br />
=== Theory – Probing electroweak symmetry breaking with Higgs pair production at the LHC and beyond ===<br />
<br />
The measurement of Higgs pair production will be a cornerstone of the LHC program in the coming years. Double Higgs production provides a crucial window upon the mechanism of electroweak symmetry breaking, and has a unique sensitivity to a number of currently unknown Higgs couplings, like the Higgs self-coupling λ and the coupling between a pair of Higgs bosons and two vector bosons. In this project, the student will explore the feasibility of the measurement of Higgs pair production in the 4b final state both at the LHC and at future 100 TeV collider. A number of production modes will be considered, including gluon-fusion, vector-boson-fusion, as well as Higgs pair production in association with a top-quark pair. A key ingredient of the project will be the exploitation of multivariate techniques such as Artificial Neural Networks and other multivariate discriminants to enhance the ratio of di-Higgs signal over backgrounds. <br />
<br />
The project involves to estimate the precision that can be achieved in the extraction of the Higgs self-coupling for a number of assumptions about the performance of the LHC detectors, and in particular to quantify the information that can be extracted from the Run II dataset with L = 300 1/fb . A similar approach will be applied to the determination of other unknown properties of the Higgs sector, such as the coupling between two Higgs bosons and two weak vector bosons, as well as the Wilson coefficients of higher-dimensional operators in the Standard Model Effective Field Theory (SM-EFT). Additional information on this project can be found here: [http://pcteserver.mi.infn.it/~nnpdf/VU/2017-MasterProject-HH.pdf].<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory – Constraining the proton structure with Run II LHC data ===<br />
<br />
The non-perturbative dynamics that determine the energy distribution of quarks and gluons inside protons, the so-called parton distribution functions (PDFs), cannot be computed from first principles from Quantum Chromodynamics (QCD), and need to be determined from experimental data. PDFs are an essential ingredient for the scientific program at the Large Hadron Collider (LHC), from Higgs characterisation to searches for New Physics beyond the Standard Model. One recent breakthrough in PDF analysis has been the exploitation of the constraints from LHC data. From direct photons to top quark pair production cross-sections and charmed meson differential distributions, LHC measurements are now a central ingredient of PDF fits, providing important information on poorly-known PDFs such as the large and small-x gluon or the large-x antiquarks. With the upcoming availability of data from the Run II of the LHC, at a center-of-mass energy of 13 TeV, these constraints are expected to become even more stringent.<br />
<br />
In this project, the implications of PDF-sensitive measurements at the LHC 13 TeV will be quantified. Processes that will be considered include jet and dijet production at the multi-TeV scale, single-top quark production, and weak boson production in association with heavy quarks, among several others. These studies will be performed using the NNPDF fitting framework, based on artificial neural networks and genetic algorithms. The phenomenological implications of the improved PDF modelling for Higgs and new physics searches at the LHC will also be explored. Additional information on this project can be found here: [http://pcteserver.mi.infn.it/~nnpdf/talks/MSc_projects/2017-MasterProject-PDFs.pdf].<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=267Master Projects2018-02-11T07:41:32Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
=== Theory: Unbiased global analysis of heavy quark fragmentation functions ===<br />
<br />
The hadronisation of quarks and gluons into D mesons is of particular relevance in the era of the Large Hadron Collider (LHC). For example, production cross sections are used to constrain the gluon parton distribution function (PDF) at small momentum fractions, they play a vital role in cosmic-ray and neutrino astrophysics, and they provide the background to study modifications of heavy flavour yields in heavy-ion collisions. In perturbative Quantum Chromodynamics (QCD), the hadronisation of partons into hadrons is encoded in nonperturbative fragmentation functions (FFs). In the case of charmed hadrons, like the mesons, the heavy quark mass introduces an additional large scale – apart from some other hard scale that characterises the process – whose effects are perturbatively computable. This project is about a determination of the FFs of D mesons from a QCD analysis of data. Measurements of cross sections in a broad range of single-inclusive hadron production will be considered, namely in electron-positron annihilation, and in hadron-hadron collisions (including in-jet fragmentation). The analysis will be carried through the well-established NNPDF framework. Its main pillars are Monte Carlo sampling for the representation of data uncertainties, and neural networks for the parametrisation of PDFs. The project will allow for the acquisition of a broad set of data analysis computational techniques, widely used in high-energy physics and beyond.<br />
<br />
"Further information [[http://pcteserver.mi.infn.it/~nnpdf/VU/2018-MasterProject-DFFs.pdf here]]<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory: Combined QCD analysis of parton distribution and fragmentation functions ===<br />
<br />
The formation of hadrons from quarks and gluons, or collectively partons, is a fundamental QCD process that has yet to be fully understood. Since parton-to-hadron fragmentation occurs over long-distance scales, such information can only be extracted from expe imental observables that identify mesons and baryons in the final state. Recent progress has been made to determine these fragmentation functions (FFs) from charged pion and kaon production in single inclusive e+e−-annihilation (SIA) and additionally pp-collisions and semi-inclusive deep inelastic scattering (SIDIS). However, charged hadron production in unpolarized pp and inelastic lepton-proton scattering also require information about the momentum distributions of the quarks and gluons in the proton, which is encoded in non-perturbative parton distribution functions (PDFs). In this project, a simultaneous treatment of both PDFs and FFs in a global QCD analysis of single inclusive hadron production processes will be made to determine the individual parton-to-hadron FFs. Furthermore, a robust statistical methodology with an artificial neural network learning algorithm will be used to obtain a precise estimation of the FF uncertainties. This work will emphasis in particular the impact of pp-collision and SIDIS data on the gluon and separated quark/anti-quark FFs, respectively.<br />
<br />
"Further information [[http://pcteserver.mi.infn.it/~nnpdf/VU/2018-MasterProject-FFpPDFs.pdf here]]<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
<br />
=== The Modulation Experiment: Data Analysis ===<br />
<br />
<br />
There exist a few measurements that suggest an annual modulation in the activity of radioactive sources. With a few groups from the XENON collaboration we have developed four sets of table-top experiments to investigate this effect on a few well known radioactive sources. The experiments are under construction in Purdue University (USA), a mountain top in Switzerland, a beach in Rio de Janeiro and the last one at Nikhef in Amsterdam. We urgently need a master student to (1) analyze the first big data set, and (2) contribute to the first physics paper from the experiment. We are looking for an all-round physicist with interest in both lab-work and data-analysis. The student will directly collaborate with the other groups in this small collaboration (around 10 people), and the goal is to have the first physics publication ready by the end of the project.<br />
<br />
''Contact: [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== The XENON Dark Matter Experiment: Data Analysis ===<br />
<br />
The XENON collaboration has started operating the XENON1T detector, the world’s most sensitive direct detection dark matter experiment. The Nikhef group is playing an important role in this experiment. The detector operates at the Gran Sasso underground laboratory and consists of a so-called dual-phase xenon time-projection chamber filled with 3200kg of ultra-pure xenon. Our group has an opening for a motivated MSc student to do data-analysis on this new detector. The work will consist of understanding the signals that come out of the detector and in particular focus on the so-called double scatter events. We are interested in developing methods in order to interpret the response of the detector better and are developing sophisticated statistical tools to do this. This work will include looking at data and developing new algorithms in our Python-based analysis tool. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== XAMS Dark Matter R&D Setup ===<br />
<br />
The Amsterdam Dark Matter group has built an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 4kg of ultra-pure liquid xenon. We plan to use this detector for the development of new detection techniques (such as utilizing new photosensors) and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENON experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data him/herself. You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== LHCb: A Scintillator Fibers Tracker ===<br />
<br />
The LHCb collaboration is upgrading the present tracking system<br />
constructing a new tracker based on scintillating fibers combined<br />
with silicon photo-multipliers (SiPM): the SciFi Tracker!<br />
Nikhef plays a key role in the project, as we will build the<br />
SciFi fibers modules, the cold-box enclosure housing the SiPMs,<br />
and a large part of the on-detector electronics. In all these<br />
areas, interesting test hardware and software has to be realized,<br />
and several research topics for a Master project are available,<br />
taking the student in contact with state-of-the-art particle detectors,<br />
in a large team of physicists and engineers. Possible collaborations<br />
with the Nikhef R&D group can also be envisaged.<br />
<br />
''Contact: [mailto:antonio@nikhef.nl Antonio Pellegrino]''<br />
<br />
=== LHCb: Discovery of the Decay Lb --> p Ds+ ===<br />
This project aims to measure the branching fraction of the decay Lb->p Ds+ (bud -> uud + ds). <br />
The decay Lb->p Ds+ is quite rare, because it occurs through the transition of a b-quark to a u-quark. <br />
It has not been measured yet (although some LHCb colleagues claim to have seen it).<br />
This decay is interesting, because <br />
<br />
1) It is sensitive to the b->u coupling (CKM-element Vub), which determination is heavily debated.<br />
2) It can quantify non-factorisable QCD effects in b-baryon decays.<br />
<br />
The decay is closely related to B0->pi-Ds+, which proceeds through a similar Feynman diagram. <br />
Also, the final state of B0->pi-Ds+ is almost identical to Lb->p Ds+. <br />
The aim is to determine the relative branching fraction of Lb->pDs+ with respect to B0->D+pi- decays, <br />
in close collaboration with the PhD (who will study BR(B0->pi-Ds+)/BR(B0->D+pi-) ).<br />
This project will result in a journal publication on behalf of the LHCb collaboration, written by you. <br />
For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. <br />
This is a project that is closely related to previous analyses in the group. <br />
Weekly video meetings with CERN coordinate the efforts with in the LHCb collaboration.<br />
Relevant information:<br />
<br />
[1] R.Aaij et al. [LHCb Collaboration], ``Determination of the branching fractions of B0s->DsK and B0->DsK, JHEP 05 (2015) 019 [arXiv:1412.7654 [hep-ex]].<br />
[2] R. Fleischer, N. Serra and N. Tuning, ``Tests of Factorization and SU(3) Relations in B Decays into Heavy-Light Final States, Phys. Rev. D 83, 014017 (2011) [arXiv:1012.2784 [hep-ph]].<br />
<br />
''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''<br />
<br />
=== LHCb: Measurement of B0 -> pi Ds- , the b -> u quark transition ===<br />
<br />
This project aims to measure the branching fraction of the decay B0->pi Ds+.<br />
This decay is closely related to Lb->p Ds+ (see above), and close collaboration between the two master projects is foreseen.<br />
This research was started by a previous master student. <br />
The new measurement will finish the work, and include the new data from 2015 and 2016.<br />
<br />
See Mick Mulders [http://www.nikhef.nl/pub/experiments/bfys/lhcb/Theses/master/2015_MickMulder.pdf master thesis] for more information.<br />
<br />
''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''<br />
<br />
=== LHCb: A search for heavy neutrinos in the decay of W bosons at LHCb ===<br />
<br />
Neutrinos are arguably the most mysterious of all known fundamental fermions as they are both much lighter than all others and only weakly interacting. It is thought that the tiny mass of neutrinos can be explained by their mixing with so-far unknown, much heavier, neutrino-like particles. In this research proposal we look for these new neutrinos in the decay of the SM W-boson using data with the LHCb experiment at CERN. The W boson is assumed to decay to a heavy neutrino and a muon. The heavy neutrino subsequently decays to a muon and a pair of quarks. Both like-sign and opposite-sign muon pairs will be studied. The result of the analysis will either be a limit on the production of the new neutrinos or the discovery of something entirely new.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen and Elena Dall'Occo]''<br />
<br />
<br />
=== LHCb: Searches for new pentaquarks ===<br />
<br />
In 2015 LHCb surprisingly discovered states containing five quarks, called Pc+ pentaquarks. Such particles question our understanding of confinement, the principle that forces quarks to remain in a single hadron. Which hadrons are allowed and which are not? The pentaquarks were found in the decay of the Lambda_b baryon to a Pc+ and a kaon, and Pc+ to a J/psi and a proton. This project aims at studying other similar but yet unobserved decays which could reveal the presence of the know Pc+, or yet unknown pentaquarks. The student will optimise a selection for finding such a decay in LHCb data using machine learning techniques. <br />
<br />
See [https://arxiv.org/abs/1406.0755 arXiv:1406.0755] for more information.<br />
<br />
''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
<br />
<br />
=== ATLAS : Double Higgs searches with multiple leptons ===<br />
<br />
The Standard Model of particle physics (SM) is extremely successful, but would it hold against check with data containing multiple leptons? Although very rare process, the production of leptons is calculated in SM with high precision. On detector side the leptons (electrons and muons) are easy to reconstruct and such a sample contains very little "non-lepton" background. This analysis has an ambitious goal to reconstruct events with two Higgs bosons using events with 4 leptons. With this project, the student would gain close familiarity with modern experimental techniques (statistical analysis, SM predictions, search for rare signals), with Monte Carlo generators and the standard HEP analysis tools (ROOT, C++, python).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and Marcus Morgenstern and Pepijn Bakker]''<br />
<br />
=== ATLAS : A search for lepton flavor violation with tau decays ===<br />
<br />
Quarks mix, neutrinos mix, charged leptons do not mix. Why? Is that really how the nature works, or is it just a limitation in our detection techniques. ATLAS has recorded now a huge sample of data. Even such difficult final states as tau->3mu become accessible. However, the decays of charm and beauty mesons could spoil the picture with decays that resembles the signal. The goal of the project is to understand what<br />
background decays are present and to find a way to suppress them. Success of project will allow much higher sensitivity to beyond Standard Model physics of tau->3mu. The student would gain close familiarity with modern experimental techniques (statistical analysis, SM predictions, search for rare signals), background suppression techniques and the standard HEP analysis tools (ROOT, C++, python).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and Matteo Bedognetti]''<br />
<br />
=== ALICE : Particle polarisation in strong magnetic fields ===<br />
When two atomic nuclei, moving in opposite directions, collide off- center then the Quark Gluon Plasma (QGP) created in the overlap zone is expected to rotate. The nucleons not participating in the collision represent electric currents generating an intense magnetic field. The magnetic field could be as large as 10^{18} gauss, orders of magnitude larger than the strongest magnetic fields found in astronomical objects. Proving the existence of the rotation and/or the magnetic field could be done by checking if particles with spin are aligned with the rotation axis or if charged particles have different production rates relative to the direction of the magnetic field. In particular, the longitudinal and transverse polarisation of the Lambda^0 baryon will be studied. This project requires some affinity with computer programming. <br />
<br />
''Contact: [mailto:Paul.Kuijer@nikhef.nl Paul Kuijer and Panos Christakoglou]''<br />
<br />
=== ALICE : Blast-Wave Model in heavy-ion collisions ===<br />
The goal of heavy-ion physics is to study the Quark Gluon Plasma (QGP), a hot and dense medium where quarks and gluons move freely over large distances, larger than the typical size of a hadron. Hydrodynamic simulations expect that the QGP will expand under its own pressure, and cool while expanding. These simulations are particularly successful in describing some of the key observables measured experimentally, such as particle spectra and elliptic flow. A reasonable reproduction of the same observables is also achieved with models that use parameterisations that resemble the hydrodynamical evolution of the system assuming a given freeze-out scenario, usually referred to as blast-wave models. The goal of this project is to work on different blast wave parametrisations, test their dependence on the input parameters and extend their applicability by including more observables studied in heavy-ion collisions in the global fit. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== ALICE : Higher Harmonic Flow ===<br />
When two ions collide, if the impact parameter is not zero, the overlap region is not isotropic. This spatial anisotropy of the overlap region is transformed into an anisotropy in momentum space through interactions between partons and at a later stage between the produced particles. It was recently realized that the overlap region of the colliding nuclei exhibits an irregular shape. These irregularities originate from the initial density profile of nucleons participating in the collision which is not smooth and is different from one event to the other. The resulting higher order flow harmonics (e.g. v3, v4, and v5, usually referred to as triangular, quadrangular, and pentangular flow, respectively) and in particular their transverse momentum dependence are argued to be more sensitive probes than elliptic flow not only of the initial geometry and its fluctuations but also of shear viscosity over entropy density (η/s). The goal of this project is to study v3, v4, and v5 for identified particles in collisions of heavy-ions at the LHC. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== ALICE : Chiral Magnetic Effect and the Strong CP Problem ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, which is called Chiral Magnetic Effect (CME). The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, but background effects have not yet been properly disentangled. In this project you will develop and test new observables of the CME, trying to understand and discriminate the background sources that affects such a measurement. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== DR&D : Medical X-ray Imaging ===<br />
With the upcoming of true multi-threshold X-Ray detectors the possibilities for Spectral Imaging with low dose, including spectral CT, is now a reality around the corner. The Medipix3RX chip, from the Medipix Collaboration (CERN) features up to 8 programmable thresholds which can select energy bins without a threshold scan. A number of projects could be derived from the R&D activities with the Medipix3RX within the Nikhef R&D group on X-ray imaging for medical applications:<br />
* Medipix3RX characterization in all its operation modes and gains. <br />
* Spectral CT and scarce sampling 3D reconstruction <br />
* Charge sharing: the charge-sum capabilities of the chip can be exploited to further understand the problem of charge sharing in pixelized detectors. A combination of the characterization of the charge-summing mode plus the use of both planar, and 3D sensors, at the light of MC simulation, could reveal valuable information about charge sharing.<br />
<br />
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman],[mailto:martinfr@nihef.nl Martin Fransen]''<br />
<br />
=== DR&D : Compton camera ===<br />
In the Nikhef R&D group we develop instrumentation for particle physics but we also investigate how particle physics detectors can be used for different purposes. A succesfull development is the Medipix chip that can be used in X-ray imaging. For use in large scale medical applications compton scattering limits however the energy resolving possibilities. You will investigate whether it is in principle possible to design a X-ray application that detects the compton scattered electron and the absorbed photon. Your ideas can be tested in practice in the lab where a X-ray scan can be performed.<br />
<br />
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman]''<br />
<br />
=== KM3NeT : Reconstruction of first neutrino interactions in KM3NeT ===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first two strings with sensitive photodetectors have been deployed 2015&2016, in total 30 to be deployed til end of next year. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In order to identify neutrinos an accurate reconstruction and optimal understanding of the backgrounds are crucial. In this project we will use the available data to identify and reconstruct the first neutrino interactions in the KM3NeT detector and with this pave the path towards neutrino astronomy.<br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
<br />
'' Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn]''<br />
<br />
=== ANTARES: Analysis of IceCube neutrino sources. ===<br />
<br />
The only evidence for high energetic neutrinos from cosmic sources so far comes from detections with the IceCube detector. Most of the detected events were reconstructed with a large uncertainty on their direction, which has prevented an association to astrophysical sources. Only for the high energetic muon neutrino candidates a high resolution in the direction has been achieved, but also for those no significant correlation to astrophysical sources has to date been detected.<br />
The ANTARES neutrino telescope has since 2007 continuously taken neutrino data with high angular resolution, which can be exploited to further scrutinize the locations of these neutrino sources. In this project we will address the neutrino sources in a stacked analysis to further probe the origin of the neutrinos with enhanced sensitivity.<br />
<br />
Programming skills are essential, mainly C++ and root will be used. <br />
<br />
'' Contact: [mailto:dosamt@nikhef.nl Dorothea Samtleben]''<br />
<br />
<br />
=== ATLAS: Implementation of Morphing techniques for ATLAS top physics analysis. ===<br />
<br />
Perhaps the most promising gateway to physics beyond the Standard Model is the top quark, the heaviest elementary particle. Particularly<br />
interesting is how the different top quark spin states influence the angular distribution of electrons and other decays products, which can be measured very accurately. New interactions would alter this coupling, leading to decay patterns that are different from those predicted by<br />
the Standard Model. At Nikhef we are implementing NLO predictions of the so called dimension-6 operators to describe several measurable distributions. To confront these distributions with data, a continues parametrization is required. For this purpose, we want to introduce a novel technique in top quark analysis which is based on Morphing. The project consist of an implementation of Morphing to parametrize the top's angular distributions and to demonstrate that the paramdeters can be extracted in a fitting procedure using (pseudo)data. <br />
<br />
Affinity with software is essential, mainly C++ and root will be used. <br />
<br />
'' Contact: [mailto:h73@nikhef.nl Marcel Vreeswijk]''<br />
<br />
=== Theory – Probing electroweak symmetry breaking with Higgs pair production at the LHC and beyond ===<br />
<br />
The measurement of Higgs pair production will be a cornerstone of the LHC program in the coming years. Double Higgs production provides a crucial window upon the mechanism of electroweak symmetry breaking, and has a unique sensitivity to a number of currently unknown Higgs couplings, like the Higgs self-coupling λ and the coupling between a pair of Higgs bosons and two vector bosons. In this project, the student will explore the feasibility of the measurement of Higgs pair production in the 4b final state both at the LHC and at future 100 TeV collider. A number of production modes will be considered, including gluon-fusion, vector-boson-fusion, as well as Higgs pair production in association with a top-quark pair. A key ingredient of the project will be the exploitation of multivariate techniques such as Artificial Neural Networks and other multivariate discriminants to enhance the ratio of di-Higgs signal over backgrounds. <br />
<br />
The project involves to estimate the precision that can be achieved in the extraction of the Higgs self-coupling for a number of assumptions about the performance of the LHC detectors, and in particular to quantify the information that can be extracted from the Run II dataset with L = 300 1/fb . A similar approach will be applied to the determination of other unknown properties of the Higgs sector, such as the coupling between two Higgs bosons and two weak vector bosons, as well as the Wilson coefficients of higher-dimensional operators in the Standard Model Effective Field Theory (SM-EFT). Additional information on this project can be found here: [http://pcteserver.mi.infn.it/~nnpdf/VU/2017-MasterProject-HH.pdf].<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory – Constraining the proton structure with Run II LHC data ===<br />
<br />
The non-perturbative dynamics that determine the energy distribution of quarks and gluons inside protons, the so-called parton distribution functions (PDFs), cannot be computed from first principles from Quantum Chromodynamics (QCD), and need to be determined from experimental data. PDFs are an essential ingredient for the scientific program at the Large Hadron Collider (LHC), from Higgs characterisation to searches for New Physics beyond the Standard Model. One recent breakthrough in PDF analysis has been the exploitation of the constraints from LHC data. From direct photons to top quark pair production cross-sections and charmed meson differential distributions, LHC measurements are now a central ingredient of PDF fits, providing important information on poorly-known PDFs such as the large and small-x gluon or the large-x antiquarks. With the upcoming availability of data from the Run II of the LHC, at a center-of-mass energy of 13 TeV, these constraints are expected to become even more stringent.<br />
<br />
In this project, the implications of PDF-sensitive measurements at the LHC 13 TeV will be quantified. Processes that will be considered include jet and dijet production at the multi-TeV scale, single-top quark production, and weak boson production in association with heavy quarks, among several others. These studies will be performed using the NNPDF fitting framework, based on artificial neural networks and genetic algorithms. The phenomenological implications of the improved PDF modelling for Higgs and new physics searches at the LHC will also be explored. Additional information on this project can be found here: [http://pcteserver.mi.infn.it/~nnpdf/talks/MSc_projects/2017-MasterProject-PDFs.pdf].<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=230Master Projects2018-02-08T07:48:51Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
=== Theory: Combined QCD analysis of parton distribution and fragmentation functions ===<br />
<br />
The formation of hadrons from quarks and gluons, or collectively partons, is a fundamental QCD process that has yet to be fully understood. Since parton-to-hadron fragmentation occurs over long-distance scales, such information can only be extracted from expe imental observables that identify mesons and baryons in the final state. Recent progress has been made to determine these fragmentation functions (FFs) from charged pion and kaon production in single inclusive e+e−-annihilation (SIA) and additionally pp-collisions and semi-inclusive deep inelastic scattering (SIDIS). However, charged hadron production in unpolarized pp and inelastic lepton-proton scattering also require information about the momentum distributions of the quarks and gluons in the proton, which is encoded in non-perturbative parton distribution functions (PDFs). In this project, a simultaneous treatment of both PDFs and FFs in a global QCD analysis of single inclusive hadron production processes will be made to determine the individual parton-to-hadron FFs. Furthermore, a robust statistical methodology with an artificial neural network learning algorithm will be used to obtain a precise estimation of the FF uncertainties. This work will emphasis in particular the impact of pp-collision and SIDIS data on the gluon and separated quark/anti-quark FFs, respectively.<br />
<br />
"Further information [[http://pcteserver.mi.infn.it/~nnpdf/VU/2018-MasterProject-FFpPDFs.pdf here]]<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
<br />
=== The Modulation Experiment: Data Analysis ===<br />
<br />
<br />
There exist a few measurements that suggest an annual modulation in the activity of radioactive sources. With a few groups from the XENON collaboration we have developed four sets of table-top experiments to investigate this effect on a few well known radioactive sources. The experiments are under construction in Purdue University (USA), a mountain top in Switzerland, a beach in Rio de Janeiro and the last one at Nikhef in Amsterdam. We urgently need a master student to (1) analyze the first big data set, and (2) contribute to the first physics paper from the experiment. We are looking for an all-round physicist with interest in both lab-work and data-analysis. The student will directly collaborate with the other groups in this small collaboration (around 10 people), and the goal is to have the first physics publication ready by the end of the project.<br />
<br />
''Contact: [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== The XENON Dark Matter Experiment: Data Analysis ===<br />
<br />
The XENON collaboration has started operating the XENON1T detector, the world’s most sensitive direct detection dark matter experiment. The Nikhef group is playing an important role in this experiment. The detector operates at the Gran Sasso underground laboratory and consists of a so-called dual-phase xenon time-projection chamber filled with 3200kg of ultra-pure xenon. Our group has an opening for a motivated MSc student to do data-analysis on this new detector. The work will consist of understanding the signals that come out of the detector and in particular focus on the so-called double scatter events. We are interested in developing methods in order to interpret the response of the detector better and are developing sophisticated statistical tools to do this. This work will include looking at data and developing new algorithms in our Python-based analysis tool. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== XAMS Dark Matter R&D Setup ===<br />
<br />
The Amsterdam Dark Matter group has built an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 4kg of ultra-pure liquid xenon. We plan to use this detector for the development of new detection techniques (such as utilizing new photosensors) and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENON experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data him/herself. You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== LHCb: A Scintillator Fibers Tracker ===<br />
<br />
The LHCb collaboration is upgrading the present tracking system<br />
constructing a new tracker based on scintillating fibers combined<br />
with silicon photo-multipliers (SiPM): the SciFi Tracker!<br />
Nikhef plays a key role in the project, as we will build the<br />
SciFi fibers modules, the cold-box enclosure housing the SiPMs,<br />
and a large part of the on-detector electronics. In all these<br />
areas, interesting test hardware and software has to be realized,<br />
and several research topics for a Master project are available,<br />
taking the student in contact with state-of-the-art particle detectors,<br />
in a large team of physicists and engineers. Possible collaborations<br />
with the Nikhef R&D group can also be envisaged.<br />
<br />
''Contact: [mailto:antonio@nikhef.nl Antonio Pellegrino]''<br />
<br />
=== LHCb: Discovery of the Decay Lb --> p Ds+ ===<br />
This project aims to measure the branching fraction of the decay Lb->p Ds+ (bud -> uud + ds). <br />
The decay Lb->p Ds+ is quite rare, because it occurs through the transition of a b-quark to a u-quark. <br />
It has not been measured yet (although some LHCb colleagues claim to have seen it).<br />
This decay is interesting, because <br />
<br />
1) It is sensitive to the b->u coupling (CKM-element Vub), which determination is heavily debated.<br />
2) It can quantify non-factorisable QCD effects in b-baryon decays.<br />
<br />
The decay is closely related to B0->pi-Ds+, which proceeds through a similar Feynman diagram. <br />
Also, the final state of B0->pi-Ds+ is almost identical to Lb->p Ds+. <br />
The aim is to determine the relative branching fraction of Lb->pDs+ with respect to B0->D+pi- decays, <br />
in close collaboration with the PhD (who will study BR(B0->pi-Ds+)/BR(B0->D+pi-) ).<br />
This project will result in a journal publication on behalf of the LHCb collaboration, written by you. <br />
For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. <br />
This is a project that is closely related to previous analyses in the group. <br />
Weekly video meetings with CERN coordinate the efforts with in the LHCb collaboration.<br />
Relevant information:<br />
<br />
[1] R.Aaij et al. [LHCb Collaboration], ``Determination of the branching fractions of B0s->DsK and B0->DsK, JHEP 05 (2015) 019 [arXiv:1412.7654 [hep-ex]].<br />
[2] R. Fleischer, N. Serra and N. Tuning, ``Tests of Factorization and SU(3) Relations in B Decays into Heavy-Light Final States, Phys. Rev. D 83, 014017 (2011) [arXiv:1012.2784 [hep-ph]].<br />
<br />
''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''<br />
<br />
=== LHCb: Measurement of B0 -> pi Ds- , the b -> u quark transition ===<br />
<br />
This project aims to measure the branching fraction of the decay B0->pi Ds+.<br />
This decay is closely related to Lb->p Ds+ (see above), and close collaboration between the two master projects is foreseen.<br />
This research was started by a previous master student. <br />
The new measurement will finish the work, and include the new data from 2015 and 2016.<br />
<br />
See Mick Mulders [http://www.nikhef.nl/pub/experiments/bfys/lhcb/Theses/master/2015_MickMulder.pdf master thesis] for more information.<br />
<br />
''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''<br />
<br />
=== LHCb: A search for heavy neutrinos in the decay of W bosons at LHCb ===<br />
<br />
Neutrinos are arguably the most mysterious of all known fundamental fermions as they are both much lighter than all others and only weakly interacting. It is thought that the tiny mass of neutrinos can be explained by their mixing with so-far unknown, much heavier, neutrino-like particles. In this research proposal we look for these new neutrinos in the decay of the SM W-boson using data with the LHCb experiment at CERN. The W boson is assumed to decay to a heavy neutrino and a muon. The heavy neutrino subsequently decays to a muon and a pair of quarks. Both like-sign and opposite-sign muon pairs will be studied. The result of the analysis will either be a limit on the production of the new neutrinos or the discovery of something entirely new.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen and Elena Dall'Occo]''<br />
<br />
<br />
=== LHCb: Searches for new pentaquarks ===<br />
<br />
In 2015 LHCb surprisingly discovered states containing five quarks, called Pc+ pentaquarks. Such particles question our understanding of confinement, the principle that forces quarks to remain in a single hadron. Which hadrons are allowed and which are not? The pentaquarks were found in the decay of the Lambda_b baryon to a Pc+ and a kaon, and Pc+ to a J/psi and a proton. This project aims at studying other similar but yet unobserved decays which could reveal the presence of the know Pc+, or yet unknown pentaquarks. The student will optimise a selection for finding such a decay in LHCb data using machine learning techniques. <br />
<br />
See [https://arxiv.org/abs/1406.0755 arXiv:1406.0755] for more information.<br />
<br />
''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
<br />
<br />
=== ATLAS : Double Higgs searches with multiple leptons ===<br />
<br />
The Standard Model of particle physics (SM) is extremely successful, but would it hold against check with data containing multiple leptons? Although very rare process, the production of leptons is calculated in SM with high precision. On detector side the leptons (electrons and muons) are easy to reconstruct and such a sample contains very little "non-lepton" background. This analysis has an ambitious goal to reconstruct events with two Higgs bosons using events with 4 leptons. With this project, the student would gain close familiarity with modern experimental techniques (statistical analysis, SM predictions, search for rare signals), with Monte Carlo generators and the standard HEP analysis tools (ROOT, C++, python).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and Marcus Morgenstern and Pepijn Bakker]''<br />
<br />
=== ATLAS : A search for lepton flavor violation with tau decays ===<br />
<br />
Quarks mix, neutrinos mix, charged leptons do not mix. Why? Is that really how the nature works, or is it just a limitation in our detection techniques. ATLAS has recorded now a huge sample of data. Even such difficult final states as tau->3mu become accessible. However, the decays of charm and beauty mesons could spoil the picture with decays that resembles the signal. The goal of the project is to understand what<br />
background decays are present and to find a way to suppress them. Success of project will allow much higher sensitivity to beyond Standard Model physics of tau->3mu. The student would gain close familiarity with modern experimental techniques (statistical analysis, SM predictions, search for rare signals), background suppression techniques and the standard HEP analysis tools (ROOT, C++, python).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and Matteo Bedognetti]''<br />
<br />
=== ALICE : Particle polarisation in strong magnetic fields ===<br />
When two atomic nuclei, moving in opposite directions, collide off- center then the Quark Gluon Plasma (QGP) created in the overlap zone is expected to rotate. The nucleons not participating in the collision represent electric currents generating an intense magnetic field. The magnetic field could be as large as 10^{18} gauss, orders of magnitude larger than the strongest magnetic fields found in astronomical objects. Proving the existence of the rotation and/or the magnetic field could be done by checking if particles with spin are aligned with the rotation axis or if charged particles have different production rates relative to the direction of the magnetic field. In particular, the longitudinal and transverse polarisation of the Lambda^0 baryon will be studied. This project requires some affinity with computer programming. <br />
<br />
''Contact: [mailto:Paul.Kuijer@nikhef.nl Paul Kuijer and Panos Christakoglou]''<br />
<br />
=== ALICE : Blast-Wave Model in heavy-ion collisions ===<br />
The goal of heavy-ion physics is to study the Quark Gluon Plasma (QGP), a hot and dense medium where quarks and gluons move freely over large distances, larger than the typical size of a hadron. Hydrodynamic simulations expect that the QGP will expand under its own pressure, and cool while expanding. These simulations are particularly successful in describing some of the key observables measured experimentally, such as particle spectra and elliptic flow. A reasonable reproduction of the same observables is also achieved with models that use parameterisations that resemble the hydrodynamical evolution of the system assuming a given freeze-out scenario, usually referred to as blast-wave models. The goal of this project is to work on different blast wave parametrisations, test their dependence on the input parameters and extend their applicability by including more observables studied in heavy-ion collisions in the global fit. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== ALICE : Higher Harmonic Flow ===<br />
When two ions collide, if the impact parameter is not zero, the overlap region is not isotropic. This spatial anisotropy of the overlap region is transformed into an anisotropy in momentum space through interactions between partons and at a later stage between the produced particles. It was recently realized that the overlap region of the colliding nuclei exhibits an irregular shape. These irregularities originate from the initial density profile of nucleons participating in the collision which is not smooth and is different from one event to the other. The resulting higher order flow harmonics (e.g. v3, v4, and v5, usually referred to as triangular, quadrangular, and pentangular flow, respectively) and in particular their transverse momentum dependence are argued to be more sensitive probes than elliptic flow not only of the initial geometry and its fluctuations but also of shear viscosity over entropy density (η/s). The goal of this project is to study v3, v4, and v5 for identified particles in collisions of heavy-ions at the LHC. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== ALICE : Chiral Magnetic Effect and the Strong CP Problem ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, which is called Chiral Magnetic Effect (CME). The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, but background effects have not yet been properly disentangled. In this project you will develop and test new observables of the CME, trying to understand and discriminate the background sources that affects such a measurement. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== DR&D : Medical X-ray Imaging ===<br />
With the upcoming of true multi-threshold X-Ray detectors the possibilities for Spectral Imaging with low dose, including spectral CT, is now a reality around the corner. The Medipix3RX chip, from the Medipix Collaboration (CERN) features up to 8 programmable thresholds which can select energy bins without a threshold scan. A number of projects could be derived from the R&D activities with the Medipix3RX within the Nikhef R&D group on X-ray imaging for medical applications:<br />
* Medipix3RX characterization in all its operation modes and gains. <br />
* Spectral CT and scarce sampling 3D reconstruction <br />
* Charge sharing: the charge-sum capabilities of the chip can be exploited to further understand the problem of charge sharing in pixelized detectors. A combination of the characterization of the charge-summing mode plus the use of both planar, and 3D sensors, at the light of MC simulation, could reveal valuable information about charge sharing.<br />
<br />
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman],[mailto:martinfr@nihef.nl Martin Fransen]''<br />
<br />
=== DR&D : Compton camera ===<br />
In the Nikhef R&D group we develop instrumentation for particle physics but we also investigate how particle physics detectors can be used for different purposes. A succesfull development is the Medipix chip that can be used in X-ray imaging. For use in large scale medical applications compton scattering limits however the energy resolving possibilities. You will investigate whether it is in principle possible to design a X-ray application that detects the compton scattered electron and the absorbed photon. Your ideas can be tested in practice in the lab where a X-ray scan can be performed.<br />
<br />
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman]''<br />
<br />
=== KM3NeT : Reconstruction of first neutrino interactions in KM3NeT ===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first two strings with sensitive photodetectors have been deployed 2015&2016, in total 30 to be deployed til end of next year. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In order to identify neutrinos an accurate reconstruction and optimal understanding of the backgrounds are crucial. In this project we will use the available data to identify and reconstruct the first neutrino interactions in the KM3NeT detector and with this pave the path towards neutrino astronomy.<br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
<br />
'' Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn]''<br />
<br />
=== ANTARES: Analysis of IceCube neutrino sources. ===<br />
<br />
The only evidence for high energetic neutrinos from cosmic sources so far comes from detections with the IceCube detector. Most of the detected events were reconstructed with a large uncertainty on their direction, which has prevented an association to astrophysical sources. Only for the high energetic muon neutrino candidates a high resolution in the direction has been achieved, but also for those no significant correlation to astrophysical sources has to date been detected.<br />
The ANTARES neutrino telescope has since 2007 continuously taken neutrino data with high angular resolution, which can be exploited to further scrutinize the locations of these neutrino sources. In this project we will address the neutrino sources in a stacked analysis to further probe the origin of the neutrinos with enhanced sensitivity.<br />
<br />
Programming skills are essential, mainly C++ and root will be used. <br />
<br />
'' Contact: [mailto:dosamt@nikhef.nl Dorothea Samtleben]''<br />
<br />
<br />
=== ATLAS: Implementation of Morphing techniques for ATLAS top physics analysis. ===<br />
<br />
Perhaps the most promising gateway to physics beyond the Standard Model is the top quark, the heaviest elementary particle. Particularly<br />
interesting is how the different top quark spin states influence the angular distribution of electrons and other decays products, which can be measured very accurately. New interactions would alter this coupling, leading to decay patterns that are different from those predicted by<br />
the Standard Model. At Nikhef we are implementing NLO predictions of the so called dimension-6 operators to describe several measurable distributions. To confront these distributions with data, a continues parametrization is required. For this purpose, we want to introduce a novel technique in top quark analysis which is based on Morphing. The project consist of an implementation of Morphing to parametrize the top's angular distributions and to demonstrate that the paramdeters can be extracted in a fitting procedure using (pseudo)data. <br />
<br />
Affinity with software is essential, mainly C++ and root will be used. <br />
<br />
'' Contact: [mailto:h73@nikhef.nl Marcel Vreeswijk]''<br />
<br />
=== Theory – Probing electroweak symmetry breaking with Higgs pair production at the LHC and beyond ===<br />
<br />
The measurement of Higgs pair production will be a cornerstone of the LHC program in the coming years. Double Higgs production provides a crucial window upon the mechanism of electroweak symmetry breaking, and has a unique sensitivity to a number of currently unknown Higgs couplings, like the Higgs self-coupling λ and the coupling between a pair of Higgs bosons and two vector bosons. In this project, the student will explore the feasibility of the measurement of Higgs pair production in the 4b final state both at the LHC and at future 100 TeV collider. A number of production modes will be considered, including gluon-fusion, vector-boson-fusion, as well as Higgs pair production in association with a top-quark pair. A key ingredient of the project will be the exploitation of multivariate techniques such as Artificial Neural Networks and other multivariate discriminants to enhance the ratio of di-Higgs signal over backgrounds. <br />
<br />
The project involves to estimate the precision that can be achieved in the extraction of the Higgs self-coupling for a number of assumptions about the performance of the LHC detectors, and in particular to quantify the information that can be extracted from the Run II dataset with L = 300 1/fb . A similar approach will be applied to the determination of other unknown properties of the Higgs sector, such as the coupling between two Higgs bosons and two weak vector bosons, as well as the Wilson coefficients of higher-dimensional operators in the Standard Model Effective Field Theory (SM-EFT). Additional information on this project can be found here: [http://pcteserver.mi.infn.it/~nnpdf/VU/2017-MasterProject-HH.pdf].<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory – Constraining the proton structure with Run II LHC data ===<br />
<br />
The non-perturbative dynamics that determine the energy distribution of quarks and gluons inside protons, the so-called parton distribution functions (PDFs), cannot be computed from first principles from Quantum Chromodynamics (QCD), and need to be determined from experimental data. PDFs are an essential ingredient for the scientific program at the Large Hadron Collider (LHC), from Higgs characterisation to searches for New Physics beyond the Standard Model. One recent breakthrough in PDF analysis has been the exploitation of the constraints from LHC data. From direct photons to top quark pair production cross-sections and charmed meson differential distributions, LHC measurements are now a central ingredient of PDF fits, providing important information on poorly-known PDFs such as the large and small-x gluon or the large-x antiquarks. With the upcoming availability of data from the Run II of the LHC, at a center-of-mass energy of 13 TeV, these constraints are expected to become even more stringent.<br />
<br />
In this project, the implications of PDF-sensitive measurements at the LHC 13 TeV will be quantified. Processes that will be considered include jet and dijet production at the multi-TeV scale, single-top quark production, and weak boson production in association with heavy quarks, among several others. These studies will be performed using the NNPDF fitting framework, based on artificial neural networks and genetic algorithms. The phenomenological implications of the improved PDF modelling for Higgs and new physics searches at the LHC will also be explored. Additional information on this project can be found here: [http://pcteserver.mi.infn.it/~nnpdf/talks/MSc_projects/2017-MasterProject-PDFs.pdf].<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=229Master Projects2018-02-08T07:48:37Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
=== Theory: Combined QCD analysis of parton distribution and fragmentation functions ===<br />
<br />
The formation of hadrons from quarks and gluons, or collectively partons, is a fundamental QCD process that has yet to be fully understood. Since parton-to-hadron fragmentation occurs over long-distance scales, such information can only be extracted from expe imental observables that identify mesons and baryons in the final state. Recent progress has been made to determine these fragmentation functions (FFs) from charged pion and kaon production in single inclusive e+e−-annihilation (SIA) and additionally pp-collisions and semi-inclusive deep inelastic scattering (SIDIS). However, charged hadron production in unpolarized pp and inelastic lepton-proton scattering also require information about the momentum distributions of the quarks and gluons in the proton, which is encoded in non-perturbative parton distribution functions (PDFs). In this project, a simultaneous treatment of both PDFs and FFs in a global QCD analysis of single inclusive hadron production processes will be made to determine the individual parton-to-hadron FFs. Furthermore, a robust statistical methodology with an artificial neural network learning algorithm will be used to obtain a precise estimation of the FF uncertainties. This work will emphasis in particular the impact of pp-collision and SIDIS data on the gluon and separated quark/anti-quark FFs, respectively.<br />
<br />
"Further information [[http://pcteserver.mi.infn.it/~nnpdf/VU/2018-MasterProject-FFpPDFs.pdf | here]]<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
<br />
=== The Modulation Experiment: Data Analysis ===<br />
<br />
<br />
There exist a few measurements that suggest an annual modulation in the activity of radioactive sources. With a few groups from the XENON collaboration we have developed four sets of table-top experiments to investigate this effect on a few well known radioactive sources. The experiments are under construction in Purdue University (USA), a mountain top in Switzerland, a beach in Rio de Janeiro and the last one at Nikhef in Amsterdam. We urgently need a master student to (1) analyze the first big data set, and (2) contribute to the first physics paper from the experiment. We are looking for an all-round physicist with interest in both lab-work and data-analysis. The student will directly collaborate with the other groups in this small collaboration (around 10 people), and the goal is to have the first physics publication ready by the end of the project.<br />
<br />
''Contact: [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== The XENON Dark Matter Experiment: Data Analysis ===<br />
<br />
The XENON collaboration has started operating the XENON1T detector, the world’s most sensitive direct detection dark matter experiment. The Nikhef group is playing an important role in this experiment. The detector operates at the Gran Sasso underground laboratory and consists of a so-called dual-phase xenon time-projection chamber filled with 3200kg of ultra-pure xenon. Our group has an opening for a motivated MSc student to do data-analysis on this new detector. The work will consist of understanding the signals that come out of the detector and in particular focus on the so-called double scatter events. We are interested in developing methods in order to interpret the response of the detector better and are developing sophisticated statistical tools to do this. This work will include looking at data and developing new algorithms in our Python-based analysis tool. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== XAMS Dark Matter R&D Setup ===<br />
<br />
The Amsterdam Dark Matter group has built an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 4kg of ultra-pure liquid xenon. We plan to use this detector for the development of new detection techniques (such as utilizing new photosensors) and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENON experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data him/herself. You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== LHCb: A Scintillator Fibers Tracker ===<br />
<br />
The LHCb collaboration is upgrading the present tracking system<br />
constructing a new tracker based on scintillating fibers combined<br />
with silicon photo-multipliers (SiPM): the SciFi Tracker!<br />
Nikhef plays a key role in the project, as we will build the<br />
SciFi fibers modules, the cold-box enclosure housing the SiPMs,<br />
and a large part of the on-detector electronics. In all these<br />
areas, interesting test hardware and software has to be realized,<br />
and several research topics for a Master project are available,<br />
taking the student in contact with state-of-the-art particle detectors,<br />
in a large team of physicists and engineers. Possible collaborations<br />
with the Nikhef R&D group can also be envisaged.<br />
<br />
''Contact: [mailto:antonio@nikhef.nl Antonio Pellegrino]''<br />
<br />
=== LHCb: Discovery of the Decay Lb --> p Ds+ ===<br />
This project aims to measure the branching fraction of the decay Lb->p Ds+ (bud -> uud + ds). <br />
The decay Lb->p Ds+ is quite rare, because it occurs through the transition of a b-quark to a u-quark. <br />
It has not been measured yet (although some LHCb colleagues claim to have seen it).<br />
This decay is interesting, because <br />
<br />
1) It is sensitive to the b->u coupling (CKM-element Vub), which determination is heavily debated.<br />
2) It can quantify non-factorisable QCD effects in b-baryon decays.<br />
<br />
The decay is closely related to B0->pi-Ds+, which proceeds through a similar Feynman diagram. <br />
Also, the final state of B0->pi-Ds+ is almost identical to Lb->p Ds+. <br />
The aim is to determine the relative branching fraction of Lb->pDs+ with respect to B0->D+pi- decays, <br />
in close collaboration with the PhD (who will study BR(B0->pi-Ds+)/BR(B0->D+pi-) ).<br />
This project will result in a journal publication on behalf of the LHCb collaboration, written by you. <br />
For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. <br />
This is a project that is closely related to previous analyses in the group. <br />
Weekly video meetings with CERN coordinate the efforts with in the LHCb collaboration.<br />
Relevant information:<br />
<br />
[1] R.Aaij et al. [LHCb Collaboration], ``Determination of the branching fractions of B0s->DsK and B0->DsK, JHEP 05 (2015) 019 [arXiv:1412.7654 [hep-ex]].<br />
[2] R. Fleischer, N. Serra and N. Tuning, ``Tests of Factorization and SU(3) Relations in B Decays into Heavy-Light Final States, Phys. Rev. D 83, 014017 (2011) [arXiv:1012.2784 [hep-ph]].<br />
<br />
''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''<br />
<br />
=== LHCb: Measurement of B0 -> pi Ds- , the b -> u quark transition ===<br />
<br />
This project aims to measure the branching fraction of the decay B0->pi Ds+.<br />
This decay is closely related to Lb->p Ds+ (see above), and close collaboration between the two master projects is foreseen.<br />
This research was started by a previous master student. <br />
The new measurement will finish the work, and include the new data from 2015 and 2016.<br />
<br />
See Mick Mulders [http://www.nikhef.nl/pub/experiments/bfys/lhcb/Theses/master/2015_MickMulder.pdf master thesis] for more information.<br />
<br />
''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''<br />
<br />
=== LHCb: A search for heavy neutrinos in the decay of W bosons at LHCb ===<br />
<br />
Neutrinos are arguably the most mysterious of all known fundamental fermions as they are both much lighter than all others and only weakly interacting. It is thought that the tiny mass of neutrinos can be explained by their mixing with so-far unknown, much heavier, neutrino-like particles. In this research proposal we look for these new neutrinos in the decay of the SM W-boson using data with the LHCb experiment at CERN. The W boson is assumed to decay to a heavy neutrino and a muon. The heavy neutrino subsequently decays to a muon and a pair of quarks. Both like-sign and opposite-sign muon pairs will be studied. The result of the analysis will either be a limit on the production of the new neutrinos or the discovery of something entirely new.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen and Elena Dall'Occo]''<br />
<br />
<br />
=== LHCb: Searches for new pentaquarks ===<br />
<br />
In 2015 LHCb surprisingly discovered states containing five quarks, called Pc+ pentaquarks. Such particles question our understanding of confinement, the principle that forces quarks to remain in a single hadron. Which hadrons are allowed and which are not? The pentaquarks were found in the decay of the Lambda_b baryon to a Pc+ and a kaon, and Pc+ to a J/psi and a proton. This project aims at studying other similar but yet unobserved decays which could reveal the presence of the know Pc+, or yet unknown pentaquarks. The student will optimise a selection for finding such a decay in LHCb data using machine learning techniques. <br />
<br />
See [https://arxiv.org/abs/1406.0755 arXiv:1406.0755] for more information.<br />
<br />
''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
<br />
<br />
=== ATLAS : Double Higgs searches with multiple leptons ===<br />
<br />
The Standard Model of particle physics (SM) is extremely successful, but would it hold against check with data containing multiple leptons? Although very rare process, the production of leptons is calculated in SM with high precision. On detector side the leptons (electrons and muons) are easy to reconstruct and such a sample contains very little "non-lepton" background. This analysis has an ambitious goal to reconstruct events with two Higgs bosons using events with 4 leptons. With this project, the student would gain close familiarity with modern experimental techniques (statistical analysis, SM predictions, search for rare signals), with Monte Carlo generators and the standard HEP analysis tools (ROOT, C++, python).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and Marcus Morgenstern and Pepijn Bakker]''<br />
<br />
=== ATLAS : A search for lepton flavor violation with tau decays ===<br />
<br />
Quarks mix, neutrinos mix, charged leptons do not mix. Why? Is that really how the nature works, or is it just a limitation in our detection techniques. ATLAS has recorded now a huge sample of data. Even such difficult final states as tau->3mu become accessible. However, the decays of charm and beauty mesons could spoil the picture with decays that resembles the signal. The goal of the project is to understand what<br />
background decays are present and to find a way to suppress them. Success of project will allow much higher sensitivity to beyond Standard Model physics of tau->3mu. The student would gain close familiarity with modern experimental techniques (statistical analysis, SM predictions, search for rare signals), background suppression techniques and the standard HEP analysis tools (ROOT, C++, python).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and Matteo Bedognetti]''<br />
<br />
=== ALICE : Particle polarisation in strong magnetic fields ===<br />
When two atomic nuclei, moving in opposite directions, collide off- center then the Quark Gluon Plasma (QGP) created in the overlap zone is expected to rotate. The nucleons not participating in the collision represent electric currents generating an intense magnetic field. The magnetic field could be as large as 10^{18} gauss, orders of magnitude larger than the strongest magnetic fields found in astronomical objects. Proving the existence of the rotation and/or the magnetic field could be done by checking if particles with spin are aligned with the rotation axis or if charged particles have different production rates relative to the direction of the magnetic field. In particular, the longitudinal and transverse polarisation of the Lambda^0 baryon will be studied. This project requires some affinity with computer programming. <br />
<br />
''Contact: [mailto:Paul.Kuijer@nikhef.nl Paul Kuijer and Panos Christakoglou]''<br />
<br />
=== ALICE : Blast-Wave Model in heavy-ion collisions ===<br />
The goal of heavy-ion physics is to study the Quark Gluon Plasma (QGP), a hot and dense medium where quarks and gluons move freely over large distances, larger than the typical size of a hadron. Hydrodynamic simulations expect that the QGP will expand under its own pressure, and cool while expanding. These simulations are particularly successful in describing some of the key observables measured experimentally, such as particle spectra and elliptic flow. A reasonable reproduction of the same observables is also achieved with models that use parameterisations that resemble the hydrodynamical evolution of the system assuming a given freeze-out scenario, usually referred to as blast-wave models. The goal of this project is to work on different blast wave parametrisations, test their dependence on the input parameters and extend their applicability by including more observables studied in heavy-ion collisions in the global fit. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== ALICE : Higher Harmonic Flow ===<br />
When two ions collide, if the impact parameter is not zero, the overlap region is not isotropic. This spatial anisotropy of the overlap region is transformed into an anisotropy in momentum space through interactions between partons and at a later stage between the produced particles. It was recently realized that the overlap region of the colliding nuclei exhibits an irregular shape. These irregularities originate from the initial density profile of nucleons participating in the collision which is not smooth and is different from one event to the other. The resulting higher order flow harmonics (e.g. v3, v4, and v5, usually referred to as triangular, quadrangular, and pentangular flow, respectively) and in particular their transverse momentum dependence are argued to be more sensitive probes than elliptic flow not only of the initial geometry and its fluctuations but also of shear viscosity over entropy density (η/s). The goal of this project is to study v3, v4, and v5 for identified particles in collisions of heavy-ions at the LHC. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== ALICE : Chiral Magnetic Effect and the Strong CP Problem ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, which is called Chiral Magnetic Effect (CME). The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, but background effects have not yet been properly disentangled. In this project you will develop and test new observables of the CME, trying to understand and discriminate the background sources that affects such a measurement. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== DR&D : Medical X-ray Imaging ===<br />
With the upcoming of true multi-threshold X-Ray detectors the possibilities for Spectral Imaging with low dose, including spectral CT, is now a reality around the corner. The Medipix3RX chip, from the Medipix Collaboration (CERN) features up to 8 programmable thresholds which can select energy bins without a threshold scan. A number of projects could be derived from the R&D activities with the Medipix3RX within the Nikhef R&D group on X-ray imaging for medical applications:<br />
* Medipix3RX characterization in all its operation modes and gains. <br />
* Spectral CT and scarce sampling 3D reconstruction <br />
* Charge sharing: the charge-sum capabilities of the chip can be exploited to further understand the problem of charge sharing in pixelized detectors. A combination of the characterization of the charge-summing mode plus the use of both planar, and 3D sensors, at the light of MC simulation, could reveal valuable information about charge sharing.<br />
<br />
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman],[mailto:martinfr@nihef.nl Martin Fransen]''<br />
<br />
=== DR&D : Compton camera ===<br />
In the Nikhef R&D group we develop instrumentation for particle physics but we also investigate how particle physics detectors can be used for different purposes. A succesfull development is the Medipix chip that can be used in X-ray imaging. For use in large scale medical applications compton scattering limits however the energy resolving possibilities. You will investigate whether it is in principle possible to design a X-ray application that detects the compton scattered electron and the absorbed photon. Your ideas can be tested in practice in the lab where a X-ray scan can be performed.<br />
<br />
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman]''<br />
<br />
=== KM3NeT : Reconstruction of first neutrino interactions in KM3NeT ===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first two strings with sensitive photodetectors have been deployed 2015&2016, in total 30 to be deployed til end of next year. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In order to identify neutrinos an accurate reconstruction and optimal understanding of the backgrounds are crucial. In this project we will use the available data to identify and reconstruct the first neutrino interactions in the KM3NeT detector and with this pave the path towards neutrino astronomy.<br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
<br />
'' Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn]''<br />
<br />
=== ANTARES: Analysis of IceCube neutrino sources. ===<br />
<br />
The only evidence for high energetic neutrinos from cosmic sources so far comes from detections with the IceCube detector. Most of the detected events were reconstructed with a large uncertainty on their direction, which has prevented an association to astrophysical sources. Only for the high energetic muon neutrino candidates a high resolution in the direction has been achieved, but also for those no significant correlation to astrophysical sources has to date been detected.<br />
The ANTARES neutrino telescope has since 2007 continuously taken neutrino data with high angular resolution, which can be exploited to further scrutinize the locations of these neutrino sources. In this project we will address the neutrino sources in a stacked analysis to further probe the origin of the neutrinos with enhanced sensitivity.<br />
<br />
Programming skills are essential, mainly C++ and root will be used. <br />
<br />
'' Contact: [mailto:dosamt@nikhef.nl Dorothea Samtleben]''<br />
<br />
<br />
=== ATLAS: Implementation of Morphing techniques for ATLAS top physics analysis. ===<br />
<br />
Perhaps the most promising gateway to physics beyond the Standard Model is the top quark, the heaviest elementary particle. Particularly<br />
interesting is how the different top quark spin states influence the angular distribution of electrons and other decays products, which can be measured very accurately. New interactions would alter this coupling, leading to decay patterns that are different from those predicted by<br />
the Standard Model. At Nikhef we are implementing NLO predictions of the so called dimension-6 operators to describe several measurable distributions. To confront these distributions with data, a continues parametrization is required. For this purpose, we want to introduce a novel technique in top quark analysis which is based on Morphing. The project consist of an implementation of Morphing to parametrize the top's angular distributions and to demonstrate that the paramdeters can be extracted in a fitting procedure using (pseudo)data. <br />
<br />
Affinity with software is essential, mainly C++ and root will be used. <br />
<br />
'' Contact: [mailto:h73@nikhef.nl Marcel Vreeswijk]''<br />
<br />
=== Theory – Probing electroweak symmetry breaking with Higgs pair production at the LHC and beyond ===<br />
<br />
The measurement of Higgs pair production will be a cornerstone of the LHC program in the coming years. Double Higgs production provides a crucial window upon the mechanism of electroweak symmetry breaking, and has a unique sensitivity to a number of currently unknown Higgs couplings, like the Higgs self-coupling λ and the coupling between a pair of Higgs bosons and two vector bosons. In this project, the student will explore the feasibility of the measurement of Higgs pair production in the 4b final state both at the LHC and at future 100 TeV collider. A number of production modes will be considered, including gluon-fusion, vector-boson-fusion, as well as Higgs pair production in association with a top-quark pair. A key ingredient of the project will be the exploitation of multivariate techniques such as Artificial Neural Networks and other multivariate discriminants to enhance the ratio of di-Higgs signal over backgrounds. <br />
<br />
The project involves to estimate the precision that can be achieved in the extraction of the Higgs self-coupling for a number of assumptions about the performance of the LHC detectors, and in particular to quantify the information that can be extracted from the Run II dataset with L = 300 1/fb . A similar approach will be applied to the determination of other unknown properties of the Higgs sector, such as the coupling between two Higgs bosons and two weak vector bosons, as well as the Wilson coefficients of higher-dimensional operators in the Standard Model Effective Field Theory (SM-EFT). Additional information on this project can be found here: [http://pcteserver.mi.infn.it/~nnpdf/VU/2017-MasterProject-HH.pdf].<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory – Constraining the proton structure with Run II LHC data ===<br />
<br />
The non-perturbative dynamics that determine the energy distribution of quarks and gluons inside protons, the so-called parton distribution functions (PDFs), cannot be computed from first principles from Quantum Chromodynamics (QCD), and need to be determined from experimental data. PDFs are an essential ingredient for the scientific program at the Large Hadron Collider (LHC), from Higgs characterisation to searches for New Physics beyond the Standard Model. One recent breakthrough in PDF analysis has been the exploitation of the constraints from LHC data. From direct photons to top quark pair production cross-sections and charmed meson differential distributions, LHC measurements are now a central ingredient of PDF fits, providing important information on poorly-known PDFs such as the large and small-x gluon or the large-x antiquarks. With the upcoming availability of data from the Run II of the LHC, at a center-of-mass energy of 13 TeV, these constraints are expected to become even more stringent.<br />
<br />
In this project, the implications of PDF-sensitive measurements at the LHC 13 TeV will be quantified. Processes that will be considered include jet and dijet production at the multi-TeV scale, single-top quark production, and weak boson production in association with heavy quarks, among several others. These studies will be performed using the NNPDF fitting framework, based on artificial neural networks and genetic algorithms. The phenomenological implications of the improved PDF modelling for Higgs and new physics searches at the LHC will also be explored. Additional information on this project can be found here: [http://pcteserver.mi.infn.it/~nnpdf/talks/MSc_projects/2017-MasterProject-PDFs.pdf].<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=228Master Projects2018-02-08T07:47:42Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
=== Theory: Combined QCD analysis of parton distribution and fragmentation functions ===<br />
<br />
The formation of hadrons from quarks and gluons, or collectively partons, is a fundamental QCD process that has yet to be fully understood. Since parton-to-hadron fragmentation occurs over long-distance scales, such information can only be extracted from expe imental observables that identify mesons and baryons in the final state. Recent progress has been made to determine these fragmentation functions (FFs) from charged pion and kaon production in single inclusive e+e−-annihilation (SIA) and additionally pp-collisions and semi-inclusive deep inelastic scattering (SIDIS). However, charged hadron production in unpolarized pp and inelastic lepton-proton scattering also require information about the momentum distributions of the quarks and gluons in the proton, which is encoded in non-perturbative parton distribution functions (PDFs). In this project, a simultaneous treatment of both PDFs and FFs in a global QCD analysis of single inclusive hadron production processes will be made to determine the individual parton-to-hadron FFs. Furthermore, a robust statistical methodology with an artificial neural network learning algorithm will be used to obtain a precise estimation of the FF uncertainties. This work will emphasis in particular the impact of pp-collision and SIDIS data on the gluon and separated quark/anti-quark FFs, respectively.<br />
<br />
"Further information [href:http://pcteserver.mi.infn.it/~nnpdf/VU/2018-MasterProject-FFpPDFs.pdf here]<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
<br />
=== The Modulation Experiment: Data Analysis ===<br />
<br />
<br />
There exist a few measurements that suggest an annual modulation in the activity of radioactive sources. With a few groups from the XENON collaboration we have developed four sets of table-top experiments to investigate this effect on a few well known radioactive sources. The experiments are under construction in Purdue University (USA), a mountain top in Switzerland, a beach in Rio de Janeiro and the last one at Nikhef in Amsterdam. We urgently need a master student to (1) analyze the first big data set, and (2) contribute to the first physics paper from the experiment. We are looking for an all-round physicist with interest in both lab-work and data-analysis. The student will directly collaborate with the other groups in this small collaboration (around 10 people), and the goal is to have the first physics publication ready by the end of the project.<br />
<br />
''Contact: [mailto:z37@nikhef.nl Auke Colijn]''<br />
<br />
=== The XENON Dark Matter Experiment: Data Analysis ===<br />
<br />
The XENON collaboration has started operating the XENON1T detector, the world’s most sensitive direct detection dark matter experiment. The Nikhef group is playing an important role in this experiment. The detector operates at the Gran Sasso underground laboratory and consists of a so-called dual-phase xenon time-projection chamber filled with 3200kg of ultra-pure xenon. Our group has an opening for a motivated MSc student to do data-analysis on this new detector. The work will consist of understanding the signals that come out of the detector and in particular focus on the so-called double scatter events. We are interested in developing methods in order to interpret the response of the detector better and are developing sophisticated statistical tools to do this. This work will include looking at data and developing new algorithms in our Python-based analysis tool. There will also be opportunity to do data-taking shifts at the Gran Sasso underground laboratory in Italy. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== XAMS Dark Matter R&D Setup ===<br />
<br />
The Amsterdam Dark Matter group has built an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 4kg of ultra-pure liquid xenon. We plan to use this detector for the development of new detection techniques (such as utilizing new photosensors) and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENON experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data him/herself. You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== LHCb: A Scintillator Fibers Tracker ===<br />
<br />
The LHCb collaboration is upgrading the present tracking system<br />
constructing a new tracker based on scintillating fibers combined<br />
with silicon photo-multipliers (SiPM): the SciFi Tracker!<br />
Nikhef plays a key role in the project, as we will build the<br />
SciFi fibers modules, the cold-box enclosure housing the SiPMs,<br />
and a large part of the on-detector electronics. In all these<br />
areas, interesting test hardware and software has to be realized,<br />
and several research topics for a Master project are available,<br />
taking the student in contact with state-of-the-art particle detectors,<br />
in a large team of physicists and engineers. Possible collaborations<br />
with the Nikhef R&D group can also be envisaged.<br />
<br />
''Contact: [mailto:antonio@nikhef.nl Antonio Pellegrino]''<br />
<br />
=== LHCb: Discovery of the Decay Lb --> p Ds+ ===<br />
This project aims to measure the branching fraction of the decay Lb->p Ds+ (bud -> uud + ds). <br />
The decay Lb->p Ds+ is quite rare, because it occurs through the transition of a b-quark to a u-quark. <br />
It has not been measured yet (although some LHCb colleagues claim to have seen it).<br />
This decay is interesting, because <br />
<br />
1) It is sensitive to the b->u coupling (CKM-element Vub), which determination is heavily debated.<br />
2) It can quantify non-factorisable QCD effects in b-baryon decays.<br />
<br />
The decay is closely related to B0->pi-Ds+, which proceeds through a similar Feynman diagram. <br />
Also, the final state of B0->pi-Ds+ is almost identical to Lb->p Ds+. <br />
The aim is to determine the relative branching fraction of Lb->pDs+ with respect to B0->D+pi- decays, <br />
in close collaboration with the PhD (who will study BR(B0->pi-Ds+)/BR(B0->D+pi-) ).<br />
This project will result in a journal publication on behalf of the LHCb collaboration, written by you. <br />
For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. <br />
This is a project that is closely related to previous analyses in the group. <br />
Weekly video meetings with CERN coordinate the efforts with in the LHCb collaboration.<br />
Relevant information:<br />
<br />
[1] R.Aaij et al. [LHCb Collaboration], ``Determination of the branching fractions of B0s->DsK and B0->DsK, JHEP 05 (2015) 019 [arXiv:1412.7654 [hep-ex]].<br />
[2] R. Fleischer, N. Serra and N. Tuning, ``Tests of Factorization and SU(3) Relations in B Decays into Heavy-Light Final States, Phys. Rev. D 83, 014017 (2011) [arXiv:1012.2784 [hep-ph]].<br />
<br />
''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''<br />
<br />
=== LHCb: Measurement of B0 -> pi Ds- , the b -> u quark transition ===<br />
<br />
This project aims to measure the branching fraction of the decay B0->pi Ds+.<br />
This decay is closely related to Lb->p Ds+ (see above), and close collaboration between the two master projects is foreseen.<br />
This research was started by a previous master student. <br />
The new measurement will finish the work, and include the new data from 2015 and 2016.<br />
<br />
See Mick Mulders [http://www.nikhef.nl/pub/experiments/bfys/lhcb/Theses/master/2015_MickMulder.pdf master thesis] for more information.<br />
<br />
''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''<br />
<br />
=== LHCb: A search for heavy neutrinos in the decay of W bosons at LHCb ===<br />
<br />
Neutrinos are arguably the most mysterious of all known fundamental fermions as they are both much lighter than all others and only weakly interacting. It is thought that the tiny mass of neutrinos can be explained by their mixing with so-far unknown, much heavier, neutrino-like particles. In this research proposal we look for these new neutrinos in the decay of the SM W-boson using data with the LHCb experiment at CERN. The W boson is assumed to decay to a heavy neutrino and a muon. The heavy neutrino subsequently decays to a muon and a pair of quarks. Both like-sign and opposite-sign muon pairs will be studied. The result of the analysis will either be a limit on the production of the new neutrinos or the discovery of something entirely new.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen and Elena Dall'Occo]''<br />
<br />
<br />
=== LHCb: Searches for new pentaquarks ===<br />
<br />
In 2015 LHCb surprisingly discovered states containing five quarks, called Pc+ pentaquarks. Such particles question our understanding of confinement, the principle that forces quarks to remain in a single hadron. Which hadrons are allowed and which are not? The pentaquarks were found in the decay of the Lambda_b baryon to a Pc+ and a kaon, and Pc+ to a J/psi and a proton. This project aims at studying other similar but yet unobserved decays which could reveal the presence of the know Pc+, or yet unknown pentaquarks. The student will optimise a selection for finding such a decay in LHCb data using machine learning techniques. <br />
<br />
See [https://arxiv.org/abs/1406.0755 arXiv:1406.0755] for more information.<br />
<br />
''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''<br />
<br />
<br />
=== ATLAS : Double Higgs searches with multiple leptons ===<br />
<br />
The Standard Model of particle physics (SM) is extremely successful, but would it hold against check with data containing multiple leptons? Although very rare process, the production of leptons is calculated in SM with high precision. On detector side the leptons (electrons and muons) are easy to reconstruct and such a sample contains very little "non-lepton" background. This analysis has an ambitious goal to reconstruct events with two Higgs bosons using events with 4 leptons. With this project, the student would gain close familiarity with modern experimental techniques (statistical analysis, SM predictions, search for rare signals), with Monte Carlo generators and the standard HEP analysis tools (ROOT, C++, python).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and Marcus Morgenstern and Pepijn Bakker]''<br />
<br />
=== ATLAS : A search for lepton flavor violation with tau decays ===<br />
<br />
Quarks mix, neutrinos mix, charged leptons do not mix. Why? Is that really how the nature works, or is it just a limitation in our detection techniques. ATLAS has recorded now a huge sample of data. Even such difficult final states as tau->3mu become accessible. However, the decays of charm and beauty mesons could spoil the picture with decays that resembles the signal. The goal of the project is to understand what<br />
background decays are present and to find a way to suppress them. Success of project will allow much higher sensitivity to beyond Standard Model physics of tau->3mu. The student would gain close familiarity with modern experimental techniques (statistical analysis, SM predictions, search for rare signals), background suppression techniques and the standard HEP analysis tools (ROOT, C++, python).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and Matteo Bedognetti]''<br />
<br />
=== ALICE : Particle polarisation in strong magnetic fields ===<br />
When two atomic nuclei, moving in opposite directions, collide off- center then the Quark Gluon Plasma (QGP) created in the overlap zone is expected to rotate. The nucleons not participating in the collision represent electric currents generating an intense magnetic field. The magnetic field could be as large as 10^{18} gauss, orders of magnitude larger than the strongest magnetic fields found in astronomical objects. Proving the existence of the rotation and/or the magnetic field could be done by checking if particles with spin are aligned with the rotation axis or if charged particles have different production rates relative to the direction of the magnetic field. In particular, the longitudinal and transverse polarisation of the Lambda^0 baryon will be studied. This project requires some affinity with computer programming. <br />
<br />
''Contact: [mailto:Paul.Kuijer@nikhef.nl Paul Kuijer and Panos Christakoglou]''<br />
<br />
=== ALICE : Blast-Wave Model in heavy-ion collisions ===<br />
The goal of heavy-ion physics is to study the Quark Gluon Plasma (QGP), a hot and dense medium where quarks and gluons move freely over large distances, larger than the typical size of a hadron. Hydrodynamic simulations expect that the QGP will expand under its own pressure, and cool while expanding. These simulations are particularly successful in describing some of the key observables measured experimentally, such as particle spectra and elliptic flow. A reasonable reproduction of the same observables is also achieved with models that use parameterisations that resemble the hydrodynamical evolution of the system assuming a given freeze-out scenario, usually referred to as blast-wave models. The goal of this project is to work on different blast wave parametrisations, test their dependence on the input parameters and extend their applicability by including more observables studied in heavy-ion collisions in the global fit. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== ALICE : Higher Harmonic Flow ===<br />
When two ions collide, if the impact parameter is not zero, the overlap region is not isotropic. This spatial anisotropy of the overlap region is transformed into an anisotropy in momentum space through interactions between partons and at a later stage between the produced particles. It was recently realized that the overlap region of the colliding nuclei exhibits an irregular shape. These irregularities originate from the initial density profile of nucleons participating in the collision which is not smooth and is different from one event to the other. The resulting higher order flow harmonics (e.g. v3, v4, and v5, usually referred to as triangular, quadrangular, and pentangular flow, respectively) and in particular their transverse momentum dependence are argued to be more sensitive probes than elliptic flow not only of the initial geometry and its fluctuations but also of shear viscosity over entropy density (η/s). The goal of this project is to study v3, v4, and v5 for identified particles in collisions of heavy-ions at the LHC. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== ALICE : Chiral Magnetic Effect and the Strong CP Problem ===<br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, which is called Chiral Magnetic Effect (CME). The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, but background effects have not yet been properly disentangled. In this project you will develop and test new observables of the CME, trying to understand and discriminate the background sources that affects such a measurement. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''<br />
<br />
=== DR&D : Medical X-ray Imaging ===<br />
With the upcoming of true multi-threshold X-Ray detectors the possibilities for Spectral Imaging with low dose, including spectral CT, is now a reality around the corner. The Medipix3RX chip, from the Medipix Collaboration (CERN) features up to 8 programmable thresholds which can select energy bins without a threshold scan. A number of projects could be derived from the R&D activities with the Medipix3RX within the Nikhef R&D group on X-ray imaging for medical applications:<br />
* Medipix3RX characterization in all its operation modes and gains. <br />
* Spectral CT and scarce sampling 3D reconstruction <br />
* Charge sharing: the charge-sum capabilities of the chip can be exploited to further understand the problem of charge sharing in pixelized detectors. A combination of the characterization of the charge-summing mode plus the use of both planar, and 3D sensors, at the light of MC simulation, could reveal valuable information about charge sharing.<br />
<br />
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman],[mailto:martinfr@nihef.nl Martin Fransen]''<br />
<br />
=== DR&D : Compton camera ===<br />
In the Nikhef R&D group we develop instrumentation for particle physics but we also investigate how particle physics detectors can be used for different purposes. A succesfull development is the Medipix chip that can be used in X-ray imaging. For use in large scale medical applications compton scattering limits however the energy resolving possibilities. You will investigate whether it is in principle possible to design a X-ray application that detects the compton scattered electron and the absorbed photon. Your ideas can be tested in practice in the lab where a X-ray scan can be performed.<br />
<br />
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman]''<br />
<br />
=== KM3NeT : Reconstruction of first neutrino interactions in KM3NeT ===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first two strings with sensitive photodetectors have been deployed 2015&2016, in total 30 to be deployed til end of next year. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. In order to identify neutrinos an accurate reconstruction and optimal understanding of the backgrounds are crucial. In this project we will use the available data to identify and reconstruct the first neutrino interactions in the KM3NeT detector and with this pave the path towards neutrino astronomy.<br />
<br />
Programming skills are essential, mostly root and C++ will be used.<br />
<br />
'' Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn]''<br />
<br />
=== ANTARES: Analysis of IceCube neutrino sources. ===<br />
<br />
The only evidence for high energetic neutrinos from cosmic sources so far comes from detections with the IceCube detector. Most of the detected events were reconstructed with a large uncertainty on their direction, which has prevented an association to astrophysical sources. Only for the high energetic muon neutrino candidates a high resolution in the direction has been achieved, but also for those no significant correlation to astrophysical sources has to date been detected.<br />
The ANTARES neutrino telescope has since 2007 continuously taken neutrino data with high angular resolution, which can be exploited to further scrutinize the locations of these neutrino sources. In this project we will address the neutrino sources in a stacked analysis to further probe the origin of the neutrinos with enhanced sensitivity.<br />
<br />
Programming skills are essential, mainly C++ and root will be used. <br />
<br />
'' Contact: [mailto:dosamt@nikhef.nl Dorothea Samtleben]''<br />
<br />
<br />
=== ATLAS: Implementation of Morphing techniques for ATLAS top physics analysis. ===<br />
<br />
Perhaps the most promising gateway to physics beyond the Standard Model is the top quark, the heaviest elementary particle. Particularly<br />
interesting is how the different top quark spin states influence the angular distribution of electrons and other decays products, which can be measured very accurately. New interactions would alter this coupling, leading to decay patterns that are different from those predicted by<br />
the Standard Model. At Nikhef we are implementing NLO predictions of the so called dimension-6 operators to describe several measurable distributions. To confront these distributions with data, a continues parametrization is required. For this purpose, we want to introduce a novel technique in top quark analysis which is based on Morphing. The project consist of an implementation of Morphing to parametrize the top's angular distributions and to demonstrate that the paramdeters can be extracted in a fitting procedure using (pseudo)data. <br />
<br />
Affinity with software is essential, mainly C++ and root will be used. <br />
<br />
'' Contact: [mailto:h73@nikhef.nl Marcel Vreeswijk]''<br />
<br />
=== Theory – Probing electroweak symmetry breaking with Higgs pair production at the LHC and beyond ===<br />
<br />
The measurement of Higgs pair production will be a cornerstone of the LHC program in the coming years. Double Higgs production provides a crucial window upon the mechanism of electroweak symmetry breaking, and has a unique sensitivity to a number of currently unknown Higgs couplings, like the Higgs self-coupling λ and the coupling between a pair of Higgs bosons and two vector bosons. In this project, the student will explore the feasibility of the measurement of Higgs pair production in the 4b final state both at the LHC and at future 100 TeV collider. A number of production modes will be considered, including gluon-fusion, vector-boson-fusion, as well as Higgs pair production in association with a top-quark pair. A key ingredient of the project will be the exploitation of multivariate techniques such as Artificial Neural Networks and other multivariate discriminants to enhance the ratio of di-Higgs signal over backgrounds. <br />
<br />
The project involves to estimate the precision that can be achieved in the extraction of the Higgs self-coupling for a number of assumptions about the performance of the LHC detectors, and in particular to quantify the information that can be extracted from the Run II dataset with L = 300 1/fb . A similar approach will be applied to the determination of other unknown properties of the Higgs sector, such as the coupling between two Higgs bosons and two weak vector bosons, as well as the Wilson coefficients of higher-dimensional operators in the Standard Model Effective Field Theory (SM-EFT). Additional information on this project can be found here: [http://pcteserver.mi.infn.it/~nnpdf/VU/2017-MasterProject-HH.pdf].<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory – Constraining the proton structure with Run II LHC data ===<br />
<br />
The non-perturbative dynamics that determine the energy distribution of quarks and gluons inside protons, the so-called parton distribution functions (PDFs), cannot be computed from first principles from Quantum Chromodynamics (QCD), and need to be determined from experimental data. PDFs are an essential ingredient for the scientific program at the Large Hadron Collider (LHC), from Higgs characterisation to searches for New Physics beyond the Standard Model. One recent breakthrough in PDF analysis has been the exploitation of the constraints from LHC data. From direct photons to top quark pair production cross-sections and charmed meson differential distributions, LHC measurements are now a central ingredient of PDF fits, providing important information on poorly-known PDFs such as the large and small-x gluon or the large-x antiquarks. With the upcoming availability of data from the Run II of the LHC, at a center-of-mass energy of 13 TeV, these constraints are expected to become even more stringent.<br />
<br />
In this project, the implications of PDF-sensitive measurements at the LHC 13 TeV will be quantified. Processes that will be considered include jet and dijet production at the multi-TeV scale, single-top quark production, and weak boson production in association with heavy quarks, among several others. These studies will be performed using the NNPDF fitting framework, based on artificial neural networks and genetic algorithms. The phenomenological implications of the improved PDF modelling for Higgs and new physics searches at the LHC will also be explored. Additional information on this project can be found here: [http://pcteserver.mi.infn.it/~nnpdf/talks/MSc_projects/2017-MasterProject-PDFs.pdf].<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=134Master Projects2017-01-30T12:58:50Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
[MORE PROJECTS TO COME!]<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]<br />
<br />
=== Theory – Probing electroweak symmetry breaking with Higgs pair production at the LHC and beyond ===<br />
<br />
The measurement of Higgs pair production will be a cornerstone of the LHC program in the coming years. Double Higgs production provides a crucial window upon the mechanism of electroweak symmetry breaking, and has a unique sensitivity to a number of currently unknown Higgs couplings, like the Higgs self-coupling λ and the coupling between a pair of Higgs bosons and two vector bosons. In this project, the student will explore the feasibility of the measurement of Higgs pair production in the 4b final state both at the LHC and at future 100 TeV collider. A number of production modes will be considered, including gluon-fusion, vector-boson-fusion, as well as Higgs pair production in association with a top-quark pair. A key ingredient of the project will be the exploitation of multivariate techniques such as Artificial Neural Networks and other multivariate discriminants to enhance the ratio of di-Higgs signal over backgrounds. <br />
<br />
The project involves to estimate the precision that can be achieved in the extraction of the Higgs self-coupling for a number of assumptions about the performance of the LHC detectors, and in particular to quantify the information that can be extracted from the Run II dataset with L = 300 1/fb . A similar approach will be applied to the determination of other unknown properties of the Higgs sector, such as the coupling between two Higgs bosons and two weak vector bosons, as well as the Wilson coefficients of higher-dimensional operators in the Standard Model Effective Field Theory (SM-EFT). Additional information on this project can be found here: [http://pcteserver.mi.infn.it/~nnpdf/VU/2017-MasterProject-HH.pdf].<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Theory – Constraining the proton structure with Run II LHC data ===<br />
<br />
The non-perturbative dynamics that determine the energy distribution of quarks and gluons inside protons, the so-called parton distribution functions (PDFs), cannot be computed from first principles from Quantum Chromodynamics (QCD), and need to be determined from experimental data. PDFs are an essential ingredient for the scientific program at the Large Hadron Collider (LHC), from Higgs characterisation to searches for New Physics beyond the Standard Model. One recent breakthrough in PDF analysis has been the exploitation of the constraints from LHC data. From direct photons to top quark pair production cross-sections and charmed meson differential distributions, LHC measurements are now a central ingredient of PDF fits, providing important information on poorly-known PDFs such as the large and small-x gluon or the large-x antiquarks. With the upcoming availability of data from the Run II of the LHC, at a center-of-mass energy of 13 TeV, these constraints are expected to become even more stringent.<br />
<br />
In this project, the implications of PDF-sensitive measurements at the LHC 13 TeV will be quantified. Processes that will be considered include jet and dijet production at the multi-TeV scale, single-top quark production, and weak boson production in association with heavy quarks, among several others. These studies will be performed using the NNPDF fitting framework, based on artificial neural networks and genetic algorithms. The phenomenological implications of the improved PDF modelling for Higgs and new physics searches at the LHC will also be explored. Additional information on this project can be found here: [http://pcteserver.mi.infn.it/~nnpdf/talks/MSc_projects/2017-MasterProject-PDFs.pdf].<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Extreme Astronomy – Preparing for CTA, the Next-Generation Gamma-Ray Observatory ===<br />
<br />
The Cherenkov Telescope Array (CTA) is a planned facility for measuring gamma rays from space covering more than four orders of magnitude in energy, up to energies exceeding 100 TeV. CTA employs the imaging atmospheric Cherenkov technique to measure properties of cosmic gamma rays. This technique is based on measuring Cherenkov light emitted during the development of a gamma-ray air shower. CTA will be built at two experimental sites, one in the Northern, one in the Southern hemisphere, and will consist of up to 100 telescopes. It represents a major leap forward in sensitivity and precision for gamma-ray astronomy, and will allow us to explore very-high-energy processes of the extreme Universe at an unprecedented level.<br />
<br />
Several master projects are available in the CTA group of UvA and the students will participate in photonic and electronic R&D studies contributing to the starting phase of CTA. These studies will either focus on laboratory-based measurements or simulations of novel kinds of single-photon detectors, referred to as silicon photomultipliers (SiPMs). By means of these simulations the performance of SiPMs used for arrays of Cherenkov telescopes will be assessed and their optimal operational parameters will be evaluated. Within one of the laboratory-based projects different types of SiPMs will be characterised and a measuring system to calibrate the photosensors will be designed and operated. In a different project various imaging and non-imaging light sources will be used to study the trigger performance of a CTA prototype camera.<br />
<br />
''Contact: [mailto:d.berge@nikhef.nl David Berge], [mailto:maurice.stephan@uva.nl Maurice Stephan]''<br />
<br />
=== The XENON Dark Matter Experiment: Data Analysis ===<br />
<br />
The XENON collaboration is currently commissioning the XENON1T detector, soon to be the world’s most sensitive direct detection dark matter experiment, with the Nikhef group playing an important role in this work. The detector operates at the Gran Sasso underground laboratory and consists of a so-called dual-phase xenon time-projection chamber filled with 3500kg of ultra-pure xenon. Our group has an opening for a motivated MSc student to do data-analysis on this new detector. The work will consist of understanding the signals that come out of the detector and in particular focus on the so-called double scatter events. We are interested in developing methods in order to interpret the response of the detector better and are developing sophisticated statistical tools to do this. This work will include looking at data and developing new algorithms in our Python-based analysis tool. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== XAMS Dark Matter R&D Setup ===<br />
<br />
The Amsterdam Dark Matter group has built an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 4kg of ultra-pure liquid xenon. We plan to use this detector for the development of new detection techniques (such as utilizing new photosensors) and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENON experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data him/herself. You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== ATLAS : Astroparticle Physics at the LHC ===<br />
<br />
Understanding particle acceleration up to very high energies in the Universe requires Earth-bound experimental techniques that exploit the Earth’s atmosphere as detection medium. Only the shear size of the atmosphere provides a sufficiently large sensitive area to measure the very rare highest energy particles from the cosmos as they impinge on the Earth. The idea of the atmospheric measurement is simple: a cosmic particle hitting the atmosphere is being absorbed by developing into an air shower, a spray of secondary particles that originates in the collision of the primary cosmic particle with air molecules, and successive interactions of those secondary particles in the atmosphere. Such air showers can be traced and therefore measured on Earth, providing information about the energy, type, and direction of the primary cosmic particle, by different means. Important examples of such atmospheric detection techniques include the measurement of muons with particle counters at the Earth’s surface and the measurement of Cherenkov or Fluorescence light emitted during the air shower development. The connection between measured quantities like particle numbers or light intensity and original quantities like particle energy or type is in all cases inferred using simulations of particle collisions and cascades in the atmosphere.<br />
<br />
The goal of this master project is to exploit data of proton collisions measured with ATLAS, an experiment at the Large Hadron Collider (LHC), the highest energy human particle collider currently operating at CERN in Geneva (Switzerland), to test and improve simulations of particle collisions in the atmosphere up to the highest known energies (a few times 1020 eV). The student will work on ATLAS data analysis and Monte Carlo simulations of particle collisions, both for simulating proton colliding in ATLAS and cosmic-ray protons colliding with air molecules in the atmosphere. The ultimate goal is to improve Monte Carlo model predictions used for experiments like the upcoming CTA (http://www.cta-observatory.org/) and Auger (http://www.auger.org/).<br />
<br />
''Contact: [mailto:d.berge@nikhef.nl David Berge], [mailto:david.salek@cern.ch David Salek]''<br />
<br />
=== ATLAS : Beyond Standard Model with multiple leptons ===<br />
<br />
The Standard Model of particle physics (SM) is extremely successful, but would it hold against of check of with data containing multiple leptons? Although very rare process, the production of leptons is calculated in SM with high precision. On detector side the leptons (electrons and muons) are easy to reconstruct and such a sample contains very little "non-lepton" background. This analysis has a very ambitious goal to test many final states at once, without over-tuning for a specific model. The second step would then be to test obtained results against models of composite structure of leptons or presence of heavy right handed neutrinos favored in seesaw theories. With this project, the student would gain close familiarity with modern experimental techniques (statistical analysis, SM background estimates, etc.), with Monte Carlo generators and the standard HEP analysis tools (ROOT, C++, etc.).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina]''<br />
<br />
=== ATLAS : Search for supersymmetric dark matter-like particles ===<br />
<br />
Supersymmetry is a theory of physics beyond the Standard Model of particle physics that makes a link between fermions and bosons. Apart from many other attractive features, supersymmetry also predicts a particle that may be a candidate for dark matter. Such particles, and their related particles, may be produced at the LHC. Searching for them, however, is challenging. The production cross-sections are small, and the final states are difficult to measure, for example because the final state particles may have little energy, and are ignored by the ATLAS trigger and reconstruction software. In this project we will investigate the measurement of such particles, with the aim to improve the current ATLAS search strategy. You will then apply the improved analysis to the ATLAS data (to be) collected in 2016. In the project you will learn modern experimental analysis techniques, as well as programming in ROOT and C++.<br />
<br />
''Contact: [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
=== ATLAS inner tracker upgrade ===<br />
<br />
Research description: One of the key sub-systems of the ATLAS experiment at the Large Hadron Collider (LHC) is the Inner Detector (ID), designed to provide excellent charged particles momentum and vertex resolution measurements.<br />
At Phase-2 of the LHC run the operating luminosity of the collider will be increased significantly. This will imply an upgrade of all ATLAS subsystems. In particular, the ID will be fully replaced with a tracker completely made of Silicon, having higher granularity and radiation hardness. The R&D process for the new ATLAS ID is now ongoing. Different geometrical layouts are simulated and their performance is studied under different operating conditions in search for the optimal detector architecture. Also, the performance of the new Si-sensors/modules is under investigation with dedicated laboratory tests.<br />
The focus of the project could be on the simulation of the High-Luminosity LHC version of the ATLAS Inner Detector. The student will learn how a high-energy physics experiment is designed and optimized. Alternatively, if possible at that moment, the student could work on a project at the Nikhef Silicon laboratory at the test-bench for new ATLAS Si-strip detectors and participate in the quality assurance procedure for the new ATLAS Si detectors. <br />
<br />
''Contact: [mailto:Peter.Vankov@cern.NOSPAMch Peter Vankov]''<br />
<br />
<br />
=== ATLAS : Model testing for Beyond the Standard Model Higgs ===<br />
Recently there's been a lot of excitement about hints for new Beyond the Standard Model (BSM) physics. When the search for the Higgs was ongoing we had a model to test possible bumps against, now we are looking for any new particle and there are many models available. Testing the newest results from the LHC is challenging because of low statistics and model uncertainties. In this project we will investigate different BSM Higgs models that could possible explain the newest results of the LHC. For this we will use the data collected in 2015 and the data that will be collected in 2016. In the end we will set limits on the tested models (or discover a new particle). During the project you will learn modern experimental analysis techniques as well as programming.<br />
<br />
''Contact: [mailto:verkerke@nikhef.nl Wouter Verkerke], [mailto:lbrenner@nikhef.nl Lydia Brenner]''<br />
<br />
=== Theory & ATLAS: How to violate lepton flavour? ===<br />
<br />
One of the big outstanding questions in particle physics is what has caused the matter-antimatter asymmetry in the Universe. One of the possible solutions is related to processes that violate lepton flavour. Such phenomena could be observable in the ATLAS experiment at the Large Hadron Collider. In fact, recent data show a hint for the violation of lepton flavour in the decay of the Higgs boson into a mu and tau lepton. However, additional experimental and theoretical investigations are necessary to further probe this very interesting phenomenon. The goal of this project is to identify complementary lepton flavour violating processes and to study correlations between them and other flavour probes. The work will involve theoretical calculations and a classification of the most useful observables for the ATLAS experiment.<br />
<br />
''Contact: [mailto:devries.jordy@gmail.com Jordy de Vries], [mailto:olya@nikhef.nl Olya Igonkina], [mailto:Robert.Fleischer@nikhef.nl Robert Fleischer]''<br />
<br />
=== KM3NeT : Reconstruction of first neutrinos in KM3NeT ===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first string with sensitive photodetectors has been deployed end of 2015, in total 30 will be deployed til end of 2017. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. The performance and calibration of the detector will be evaluated also in comparison with simulations. Procedures to identify and also optimally reconstruct the directions of the muons and neutrinos will be developed to verify the performance and potential of the detector and to pave the path towards the neutrino astronomy. Programming skills are essential, mostly root and C++ will be used.<br />
<br />
''Contact: [mailto:rbruijn@nikhef.nl Ronald Bruijn]''<br />
<br />
=== Neutrino mass hierarchy with KM3NeT/ORCA ===<br />
<br />
Neutrinos exist in three flavors and are known to oscillate between flavors whereby the detected flavor depends on the (partly) known oscillation parameters, the mass differences, their energy and travel length. The neutrino telescope KM3NeT is planning for a dedicated set of detection units in order to pursue an oscillation measurement of an unprecedented precision using neutrinos from atmospheric interactions and with this enabling the measurement of the so far still unknown neutrino mass hierarchy. The measurement of this subtle effect requires unprecedented precision in the reconstruction and identification of the flavor, energy and direction. Various projects are available in the reconstruction and evaluation of the mass hierarchy using dedicated simulations. Programming skills are essential, mainly C++ and root will be used.<br />
<br />
''Contact: [mailto:aart.heijboer@nikhef.nl Aart Heijboer]''<br />
<br />
=== All-flavor-neutrino analysis of ANTARES data ===<br />
<br />
The ANTARES neutrino telescope has been taking data continuously since 2007. Most analyses of the data have been performed using the signature of a muon neutrino interaction whereby a long track can be reconstructed in the detector.<br />
Recent developments allowed for the first time also the reconstruction of a cascade signature in the detector at high angular resolution so that also electron and tau neutrino interactions can be detected (here these two are not distinguishable from each other). A search for neutrinos from cosmic sources on the first 6 years of data has by now been accomplished using this new reconstruction. In this project this search will be continued and exploited also on 2 more years of data for a dedicated optimized analysis of the Galactic Center to probe the possible neutrino emission from this highly interesting region.<br />
Programming skills are essential, mainly C++ and root will be used.<br />
Also other options for analyses of the ANTARES data are available.<br />
<br />
''Contact: [mailto:dosamt@nikhef.nl Dorothea Samtleben]''<br />
<br />
=== ALICE: Particle Polarization in Strong Magnetic Fields ===<br />
When two atomic nuclei, moving in opposite directions, collide off- center then the Quark Gluon Plasma (QGP) created in the overlap zone is expected to rotate. The nucleons not participating in the collision represent electric currents generating an intense magnetic field. The magnetic field could be as large as 10^{18} gauss, orders of magnitude larger than the strongest magnetic fields found in astronomical objects. Proving the existence of the rotation and/or the magnetic field could be done by checking if particles with spin are aligned with the rotation axis or if charged particles have different production rates relative to the direction of the magnetic field. In particular, the longitudinal and transverse polarisation of the Lambda^0 baryon will be studied. This project requires some affinity with computer programming. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''<br />
<br />
=== ALICE: Forward Particle Production from the Color Glass Condensate === <br />
It has been proposed that a new state of matter (the color-glass condensate, or CGC) may provide a universal description of hadronic collisions (e.g. proton-proton collisions) at very high energy. The CGC may be seen as the classical field limit of Quantum Chromodynamics, and a framework for calculating observables from this state has been developed. Several measurements are consistent with the assumption of a CGC, but no experimental proof exists so far. In this project we intend to perform a systematic study of the sensitivity to the CGC of different possible measurements at the LHC. The work will be performed in close collaboration with an external world expert in this field. It is advantageous to have a good background in theoretical physics. (contact: T. Peitzmann, M. van Leeuwen)<br />
Blast-Wave Model in Heavy-Ion collisions<br />
The goal of heavy-ion physics is to study the Quark Gluon Plasma (QGP), a hot and dense medium where quarks and gluons move freely over large distances, larger than the typical size of a hadron. Hydrodynamic simulations expect that the QGP will expand under its own pressure, and cool while expanding. These simulations are particularly successful in describing some of the key observables measured experimentally, such as particle spectra and elliptic flow. A reasonable reproduction of the same observables is also achieved with models that use parameterisations that resemble the hydrodynamical evolution of the system assuming a given freeze-out scenario, usually referred to as blast-wave models. The goal of this project is to work on different blast wave parametrisations, test their dependence on the input parameters and extend their applicability by including more observables studied in heavy-ion collisions in the global fit. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''<br />
<br />
=== ALICE: Energy Loss of Energetic Quarks and Gluons in the Quark-Gluon Plasma ===<br />
One of the ways to study the quark-gluon plasma that is formed in high-energy nuclear collisions, is using high-energy partons (quarks or gluons) that are produced early in the collision and interact with the quark-gluon plasma as they propagate through it. There are several current open questions related to this topic, which can be explored in a Master's project. For example, we would like to use a new Monte Carlo generator model (JEWEL) of the collision to see whether we can measure the shape of the collision region using measurements of hadron pairs. In the project you will collaborate with one the PhD students in our group to use the model to generate predictions of measurements and compare those to data analysis results. Depending on your interests, the project can focus more on the modeling aspects or on the analysis of experimental data from the ALICE detector at the LHC. <br />
<br />
''Contact: [mailto:marco.van.leeuwen@nikhef.nl M. van Leeuwen]''<br />
<br />
=== ALICE: Chiral Magnetic Effect and the Strong CP Problem === <br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, which is called Chiral Magnetic Effect (CME). The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, but background effects have not yet been properly disentangled. In this project you will develop and test new observables of the CME, trying to understand and discriminate the background sources that affects such a measurement. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''<br />
<br />
=== ALICE: Quantum Coherence in Particle Production with Intensity Interferometry ===<br />
Intensity interferometry – also known as HBT-effect or Bose-Einstein-correlations – is a method to study the space-time structure of the particle-emitting source in high-energy physics. The main interest so far has been on the width of correlation functions in momentum space, which reflects the space-time information. The strength of the correlation also carries information, but this has been ignored by many people. The correlation strength is in particular influenced by the degree of coherence of particle production. Recently new studies have been performed to extract this degree of coherence, however, many other effects might distort such a measurement, in particular the production of pions via resonance decay. In this project we will study the role of resonance decays for a measurement of coherence in intensity interferometry and try to establish possible correction methods for any distortions they may cause. We will perform theoretical model calculations with Monte-Carlo simulation methods.<br />
<br />
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann]''<br />
<br />
=== ALICE: Higher Harmonic Flow ===<br />
When two ions collide, if the impact parameter is not zero, the overlap region is not isotropic. This spatial anisotropy of the overlap region is transformed into an anisotropy in momentum space through interactions between partons and at a later stage between the produced particles. It was recently realized that the overlap region of the colliding nuclei exhibits an irregular shape. These irregularities originate from the initial density profile of nucleons participating in the collision which is not smooth and is different from one event to the other. The resulting higher order flow harmonics (e.g. v3, v4, and v5, usually referred to as triangular, quadrangular, and pentangular flow, respectively) and in particular their transverse momentum dependence are argued to be more sensitive probes than elliptic flow not only of the initial geometry and its fluctuations but also of shear viscosity over entropy density (η/s). The goal of this project is to study v3, v4, and v5 for identified particles in collisions of heavy-ions at the LHC. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''<br />
<br />
=== ALICE: A New Detector for Very High-Energy Photons: FoCal === <br />
High-energy photons are important messenger particles in particle physics. In particular direct photons (i.e. directly produced from elementary scattering processes) are interesting, but it is a difficult task to discriminate them from the photons originating from particle decays. Existing detector have limited capabilities for such a discrimination, in particular at the highest energies. Our institute has pioneered a detector based on a new concept, a digital pixel calorimeter with Si-sensors of unprecedented granularity. First proof-of-principle measurements have already been performed. In this project we will study the performance of a particular detector design for measurements of direct photons at the LHC and optimize the design parameters for such a measurement. Performance studies for other measurements – e.g. jets, J/ψ, or ϒ particles – may be carried out in addition. <br />
<br />
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann] [mailto:marco.van.leeuwen@nikhef.nl M. van Leeuwen]''<br />
<br />
=== ALICE: Thermal Photon Emission: Quark-Gluon Plasma or Hadron Gas? ===<br />
Recently, measurements of thermal photon emission in high-energy nuclear collisions have been performed at RHIC and at LHC. It is generally believed that a quark-gluon plasma equation of state is the natural description of the hot initial phase of these collisions, and so far only theoretical model calculations including such a phase have been compared to those measurements. In this project we will revisit hadron gas models and try to reproduce the thermal photon yield together with other observables. In this work we will use and possibly modify Monte Carlo implementations of relativistic hydrodynamics, tune it to existing data of hadron production and then estimate the photon production from the same model. The model implementation will be based on previous work of external theoretical colleagues and will be carried out in collaboration with them.<br />
<br />
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann]''<br />
<br />
=== A New Detector for Proton Therapy and Proton Computed Tomography ===<br />
Conventional imaging of humans in medical treatment relies mostly on electromagnetic radiation (CT, MRT) or positrons (PET). A recently proposed new imaging strategy, in particular in the context of proton therapy for cancer treatment, is to use proton beams. Current detectors for the scattered protons have severe limitations, in particular for their precision and measurement times. New development of intelligent Si-sensors in particle physics offer possibilities to develop much more efficient detectors for such proton CT measurements. We will perform R&D on the use of new silicon pixel detectors developed in the context of the ALICE experiment at CERN for such medical applications. Studies will include Monte-Carlo simulations of a possible detector setup and measurements with the first samples of the appropriate silicon sensors, which will become available in early 2016. The project will be carried out in the context of a scientific collaboration with Bergen University, Norway. <br />
<br />
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann]''<br />
<br />
=== Medical X-ray Imaging ===<br />
With the upcoming of true multi-threshold X-Ray detectors the possibilities for Spectral Imaging with low dose, including spectral CT, is now a reality around the corner. The Medipix3RX chip, from the Medipix Collaboration (CERN) features up to 8 programmable thresholds which can select energy bins without a threshold scan. A number of projects could be derived from the R&D activities with the Medipix3RX within the Nikhef R&D group on X-ray imaging for medical applications: <br />
* Medipix3RX characterization in all its operation modes and gains. <br />
* Spectral CT and scarce sampling 3D reconstruction <br />
* Charge sharing: the charge-sum capabilities of the chip can be exploited to further understand the problem of charge sharing in pixelized detectors. A combination of the characterization of the charge-summing mode plus the use of both planar, and 3D sensors, at the light of MC simulation, could reveal valuable information about charge sharing.<br />
<br />
''Contact: [mailto:johnid@nikhef.nl John Idarraga],[mailto:nielsvb@nihef.nl Niels van Bakel]''<br />
<br />
=== Compton camera ===<br />
In the Nikhef R&D group we develop instrumentation for particle physics but we also investigate how particle physics detectors can be used for different purposes. A succesfull development is the Medipix chip that can be used in Xray imaging. For use in large scale medical applications compton scattering limits however the energy resolving possibilities. You will investigate whether it is in principle possible to design a Xray application that detects the compton scattered elctron and the absorbed photon. Your ideas can be tested in practice in the lab where a Xray scan can be performed.<br />
<br />
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman]''<br />
<br />
=== The Modulation experiment ===<br />
There exist a few measurements that suggest an annual modulation in the activity of radioactive sources. With a few groups from the XENON collaboration we have developed four sets of table-top experiments to investigate this effect on a few well known radioactive sources. The experiments are under construction in Purdue University (USA), a mountain top in Switzerland, a beach in Rio de Janeiro and the last one at Nikhef in Amsterdam. We urgently need a master student to (1) do the final commissioning of the experiment, (2) collect the 1st big data set, and (3) analyse the first data. We are looking for an all-round physicist with interest in both lab-work and data-analysis. The student will directly collaborate with the other groups in this small collaboration (around 10 people), and the goal is to have the first publication ready by the end of the project.<br />
<br />
''Contact: [mailto:colijn@nikhef.nl Auke Colijn]''<br />
<br />
=== Acoustic detection of ultra-high energy cosmic-ray neutrinos ===<br />
The study of the cosmic neutrinos of energies above 10^17 eV, so-called ultra-high<br />
energy neutrinos, provides a unique view on the universe and may provide insight in<br />
the origin of the most violent sources, such as gamma ray bursts, supernovae or even<br />
dark matter. The energy deposition of cosmic neutrinos in water induces a thermo-acoustic<br />
signal, which can be detected using sensitive hydrophones. The expected neutrino<br />
flux is however extremely low and the signal that neutrinos induce is small. TNO<br />
is presently developing sensitive hydrophone technology that is based on fiber optics.<br />
Optical fibers form a natural way to create a distributed sensing system. Using this<br />
technology a large scale neutrino telescope can be built in the deep sea. TNO is aiming<br />
for a prototype hydrophone which will form the building block of a future telescope.<br />
<br />
Students have the possibility to participate to this project is the following ways:<br />
(i) Modeling of cosmic rays induced acoustic signal in a neutrino telescope.<br />
Keywords: Cosmic rays, Monte Carlo, signal processing, telescope optimization.<br />
(ii) Testing and optimization of fiber optical hydrophone for a large scale neutrino<br />
telescope. Keywords: Experimental, physics, system design.<br />
<br />
The work will be (partly) executed in Delft. <br />
<br />
''Contact: [mailto:ernst-jan.buis@tno.NOSPAMnl Ernst-Jan Buis]''<br />
<br />
=== LHCb: A Scintillator Fibers Tracker ===<br />
<br />
The LHCb collaboration is upgrading the present tracking system<br />
constructing a new tracker based on scintillating fibers combined<br />
with silicon photo-multipliers (SiPM): the SciFi Tracker!<br />
Nikhef plays a key role in the project, as we will build the<br />
SciFi fibers modules, the cold-box enclosure housing the SiPMs,<br />
and a large part of the on-detector electronics. In all these<br />
areas, interesting test hardware and software has to be realized,<br />
and several research topics for a Master project are available,<br />
taking the student in contact with state-of-the-art particle detectors,<br />
in a large team of physicists and engineers. Possible collaborations<br />
with the Nikhef R&D group can also be envisaged.<br />
<br />
''Contact: [mailto:antonio@nikhef.nl Antonio Pellegrino]''<br />
<br />
=== LHCb: Discovery of the Decay Lb --> p Ds+ ===<br />
This project aims to measure the branching fraction of the decay Lb->p Ds+ (bud -> uud + ds). <br />
The decay Lb->p Ds+ is quite rare, because it occurs through the transition of a b-quark to a u-quark. <br />
It has not been measured yet (although some LHCb colleagues claim to have seen it).<br />
This decay is interesting, because <br />
<br />
1) It is sensitive to the b->u coupling (CKM-element Vub), which determination is heavily debated.<br />
2) It can quantify non-factorisable QCD effects in b-baryon decays.<br />
<br />
The decay is closely related to B0->pi-Ds+, which proceeds through a similar Feynman diagram. <br />
Also, the final state of B0->pi-Ds+ is almost identical to Lb->p Ds+. <br />
The aim is to determine the relative branching fraction of Lb->pDs+ with respect to B0->D+pi- decays, <br />
in close collaboration with the PhD (who will study BR(B0->pi-Ds+)/BR(B0->D+pi-) ).<br />
This project will result in a journal publication on behalf of the LHCb collaboration, written by you. <br />
For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. <br />
This is a project that is closely related to previous analyses in the group. <br />
Weekly video meetings with CERN coordinate the efforts with in the LHCb collaboration.<br />
Relevant information:<br />
<br />
[1] R.Aaij et al. [LHCb Collaboration], ``Determination of the branching fractions of B0s->DsK and B0->DsK, JHEP 05 (2015) 019 [arXiv:1412.7654 [hep-ex]].<br />
[2] R. Fleischer, N. Serra and N. Tuning, ``Tests of Factorization and SU(3) Relations in B Decays into Heavy-Light Final States, Phys. Rev. D 83, 014017 (2011) [arXiv:1012.2784 [hep-ph]].<br />
<br />
''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''<br />
<br />
=== LHCb: A search for heavy neutrinos in the decay of W bosons at LHCb ===<br />
<br />
Neutrinos are arguably the most mysterious of all known fundamental fermions as they are both much lighter than all others and only weakly interacting. It is thought that the tiny mass of neutrinos can be explained by their mixing with so-far unknown, much heavier, neutrino-like particles. In this research proposal we look for these new neutrinos in the decay of the SM W-boson using data with the LHCb experiment at CERN. The W boson is assumed to decay to a heavy neutrino and a muon. The heavy neutrino subsequently decays to a muon and a pair of quarks. Both like-sign and opposite-sign muon pairs will be studied. The result of the analysis will either be a limit on the production of the new neutrinos or the discovery of something entirely new.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen and Elena Dall'Occo]''<br />
<br />
<br />
=== LHCb: A search for Majorana neutrinos in the decay of Bc mesons at LHCb ===<br />
<br />
Neutrinos can either be their own anti-particles, in which case they are called "Majorana" particles, or Dirac fermions. It is thought that the tiny mass of neutrinos can be explained by their mixing with so-far unknown, much heavier, neutrino-like particles. LHCb has looked for off-shell Majorana neutrinos in the decays B+->pi-mu+mu+ and B+->D(*)-mu+mu+. Both decays suffer from suppression from Cabibbo-Kobayashi-Maskawa matrix elements, or from low reconstruction efficiencies. Although its production rate is much lower, the Bc meson provides a potentially more promising decay channel: Bc->J/psimu+mu+pi-. The Master student will design and optimise a selection, study potential backgrounds and perform a search in view of setting a stringent limit, or an observation of new physics.<br />
<br />
arXiv:1401.5361 [hep-ex]. arXiv:1201.5600 [hep-ex]. arXiv:11602.09112 [hep-ph]<br />
<br />
''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg and Flavio Archilli]''</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=115Master Projects2016-10-18T08:34:54Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
[MORE PROJECTS TO COME!]<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]<br />
<br />
=== Theory – Constraining the proton structure with Run II LHC data ===<br />
<br />
The non-perturbative dynamics that determine the energy distribution of quarks and gluons inside protons, the so-called parton distribution functions (PDFs), cannot be computed from first principles from Quantum Chromodynamics (QCD), and need to be determined from experimental data. PDFs are an essential ingredient for the scientific program at the Large Hadron Collider (LHC), from Higgs characterisation to searches for New Physics beyond the Standard Model. One recent breakthrough in PDF analysis has been the exploitation of the constraints from LHC data. From direct photons to top quark pair production cross-sections and charmed meson differential distributions, LHC measurements are now a central ingredient of PDF fits, providing important information on poorly-known PDFs such as the large and small-x gluon or the large-x antiquarks. With the upcoming availability of data from the Run II of the LHC, at a center-of-mass energy of 13 TeV, these constraints are expected to become even more stringent.<br />
<br />
In this project, the implications of PDF-sensitive measurements at the LHC 13 TeV will be quantified. Processes that will be considered include jet and dijet production at the multi-TeV scale, single-top quark production, and weak boson production in association with heavy quarks, among several others. These studies will be performed using the NNPDF fitting framework, based on artificial neural networks and genetic algorithms. The phenomenological implications of the improved PDF modelling for Higgs and new physics searches at the LHC will also be explored. Additional information on this project can be found here: [http://pcteserver.mi.infn.it/~nnpdf/talks/MSc_projects/2017-MasterProject-PDFs.pdf].<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Extreme Astronomy – Preparing for CTA, the Next-Generation Gamma-Ray Observatory ===<br />
<br />
The Cherenkov Telescope Array (CTA) is a planned facility for measuring gamma rays from space covering more than four orders of magnitude in energy, up to energies exceeding 100 TeV. CTA employs the imaging atmospheric Cherenkov technique to measure properties of cosmic gamma rays. This technique is based on measuring Cherenkov light emitted during the development of a gamma-ray air shower. CTA will be built at two experimental sites, one in the Northern, one in the Southern hemisphere, and will consist of up to 100 telescopes. It represents a major leap forward in sensitivity and precision for gamma-ray astronomy, and will allow us to explore very-high-energy processes of the extreme Universe at an unprecedented level.<br />
<br />
Several master projects are available in the CTA group of UvA and the students will participate in photonic and electronic R&D studies contributing to the starting phase of CTA. These studies will either focus on laboratory-based measurements or simulations of novel kinds of single-photon detectors, referred to as silicon photomultipliers (SiPMs). By means of these simulations the performance of SiPMs used for arrays of Cherenkov telescopes will be assessed and their optimal operational parameters will be evaluated. Within one of the laboratory-based projects different types of SiPMs will be characterised and a measuring system to calibrate the photosensors will be designed and operated. In a different project various imaging and non-imaging light sources will be used to study the trigger performance of a CTA prototype camera.<br />
<br />
''Contact: [mailto:d.berge@nikhef.nl David Berge], [mailto:maurice.stephan@uva.nl Maurice Stephan]''<br />
<br />
=== The XENON Dark Matter Experiment: Data Analysis ===<br />
<br />
The XENON collaboration is currently commissioning the XENON1T detector, soon to be the world’s most sensitive direct detection dark matter experiment, with the Nikhef group playing an important role in this work. The detector operates at the Gran Sasso underground laboratory and consists of a so-called dual-phase xenon time-projection chamber filled with 3500kg of ultra-pure xenon. Our group has an opening for a motivated MSc student to do data-analysis on this new detector. The work will consist of understanding the signals that come out of the detector and in particular focus on the so-called double scatter events. We are interested in developing methods in order to interpret the response of the detector better and are developing sophisticated statistical tools to do this. This work will include looking at data and developing new algorithms in our Python-based analysis tool. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== XAMS Dark Matter R&D Setup ===<br />
<br />
The Amsterdam Dark Matter group has built an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 4kg of ultra-pure liquid xenon. We plan to use this detector for the development of new detection techniques (such as utilizing new photosensors) and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENON experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data him/herself. You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== ATLAS : Astroparticle Physics at the LHC ===<br />
<br />
Understanding particle acceleration up to very high energies in the Universe requires Earth-bound experimental techniques that exploit the Earth’s atmosphere as detection medium. Only the shear size of the atmosphere provides a sufficiently large sensitive area to measure the very rare highest energy particles from the cosmos as they impinge on the Earth. The idea of the atmospheric measurement is simple: a cosmic particle hitting the atmosphere is being absorbed by developing into an air shower, a spray of secondary particles that originates in the collision of the primary cosmic particle with air molecules, and successive interactions of those secondary particles in the atmosphere. Such air showers can be traced and therefore measured on Earth, providing information about the energy, type, and direction of the primary cosmic particle, by different means. Important examples of such atmospheric detection techniques include the measurement of muons with particle counters at the Earth’s surface and the measurement of Cherenkov or Fluorescence light emitted during the air shower development. The connection between measured quantities like particle numbers or light intensity and original quantities like particle energy or type is in all cases inferred using simulations of particle collisions and cascades in the atmosphere.<br />
<br />
The goal of this master project is to exploit data of proton collisions measured with ATLAS, an experiment at the Large Hadron Collider (LHC), the highest energy human particle collider currently operating at CERN in Geneva (Switzerland), to test and improve simulations of particle collisions in the atmosphere up to the highest known energies (a few times 1020 eV). The student will work on ATLAS data analysis and Monte Carlo simulations of particle collisions, both for simulating proton colliding in ATLAS and cosmic-ray protons colliding with air molecules in the atmosphere. The ultimate goal is to improve Monte Carlo model predictions used for experiments like the upcoming CTA (http://www.cta-observatory.org/) and Auger (http://www.auger.org/).<br />
<br />
''Contact: [mailto:d.berge@nikhef.nl David Berge], [mailto:david.salek@cern.ch David Salek]''<br />
<br />
=== ATLAS : Beyond Standard Model with multiple leptons ===<br />
<br />
The Standard Model of particle physics (SM) is extremely successful, but would it hold against of check of with data containing multiple leptons? Although very rare process, the production of leptons is calculated in SM with high precision. On detector side the leptons (electrons and muons) are easy to reconstruct and such a sample contains very little "non-lepton" background. This analysis has a very ambitious goal to test many final states at once, without over-tuning for a specific model. The second step would then be to test obtained results against models of composite structure of leptons or presence of heavy right handed neutrinos favored in seesaw theories. With this project, the student would gain close familiarity with modern experimental techniques (statistical analysis, SM background estimates, etc.), with Monte Carlo generators and the standard HEP analysis tools (ROOT, C++, etc.).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina]''<br />
<br />
=== ATLAS : Search for supersymmetric dark matter-like particles ===<br />
<br />
Supersymmetry is a theory of physics beyond the Standard Model of particle physics that makes a link between fermions and bosons. Apart from many other attractive features, supersymmetry also predicts a particle that may be a candidate for dark matter. Such particles, and their related particles, may be produced at the LHC. Searching for them, however, is challenging. The production cross-sections are small, and the final states are difficult to measure, for example because the final state particles may have little energy, and are ignored by the ATLAS trigger and reconstruction software. In this project we will investigate the measurement of such particles, with the aim to improve the current ATLAS search strategy. You will then apply the improved analysis to the ATLAS data (to be) collected in 2016. In the project you will learn modern experimental analysis techniques, as well as programming in ROOT and C++.<br />
<br />
''Contact: [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
=== ATLAS inner tracker upgrade ===<br />
<br />
Research description: One of the key sub-systems of the ATLAS experiment at the Large Hadron Collider (LHC) is the Inner Detector (ID), designed to provide excellent charged particles momentum and vertex resolution measurements.<br />
At Phase-2 of the LHC run the operating luminosity of the collider will be increased significantly. This will imply an upgrade of all ATLAS subsystems. In particular, the ID will be fully replaced with a tracker completely made of Silicon, having higher granularity and radiation hardness. The R&D process for the new ATLAS ID is now ongoing. Different geometrical layouts are simulated and their performance is studied under different operating conditions in search for the optimal detector architecture. Also, the performance of the new Si-sensors/modules is under investigation with dedicated laboratory tests.<br />
The focus of the project could be on the simulation of the High-Luminosity LHC version of the ATLAS Inner Detector. The student will learn how a high-energy physics experiment is designed and optimized. Alternatively, if possible at that moment, the student could work on a project at the Nikhef Silicon laboratory at the test-bench for new ATLAS Si-strip detectors and participate in the quality assurance procedure for the new ATLAS Si detectors. <br />
<br />
''Contact: [mailto:Peter.Vankov@cern.NOSPAMch Peter Vankov]''<br />
<br />
<br />
=== ATLAS : Model testing for Beyond the Standard Model Higgs ===<br />
Recently there's been a lot of excitement about hints for new Beyond the Standard Model (BSM) physics. When the search for the Higgs was ongoing we had a model to test possible bumps against, now we are looking for any new particle and there are many models available. Testing the newest results from the LHC is challenging because of low statistics and model uncertainties. In this project we will investigate different BSM Higgs models that could possible explain the newest results of the LHC. For this we will use the data collected in 2015 and the data that will be collected in 2016. In the end we will set limits on the tested models (or discover a new particle). During the project you will learn modern experimental analysis techniques as well as programming.<br />
<br />
''Contact: [mailto:verkerke@nikhef.nl Wouter Verkerke], [mailto:lbrenner@nikhef.nl Lydia Brenner]''<br />
<br />
=== Theory & ATLAS: How to violate lepton flavour? ===<br />
<br />
One of the big outstanding questions in particle physics is what has caused the matter-antimatter asymmetry in the Universe. One of the possible solutions is related to processes that violate lepton flavour. Such phenomena could be observable in the ATLAS experiment at the Large Hadron Collider. In fact, recent data show a hint for the violation of lepton flavour in the decay of the Higgs boson into a mu and tau lepton. However, additional experimental and theoretical investigations are necessary to further probe this very interesting phenomenon. The goal of this project is to identify complementary lepton flavour violating processes and to study correlations between them and other flavour probes. The work will involve theoretical calculations and a classification of the most useful observables for the ATLAS experiment.<br />
<br />
''Contact: [mailto:devries.jordy@gmail.com Jordy de Vries], [mailto:olya@nikhef.nl Olya Igonkina], [mailto:Robert.Fleischer@nikhef.nl Robert Fleischer]''<br />
<br />
=== KM3NeT : Reconstruction of first neutrinos in KM3NeT ===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first string with sensitive photodetectors has been deployed end of 2015, in total 30 will be deployed til end of 2017. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. The performance and calibration of the detector will be evaluated also in comparison with simulations. Procedures to identify and also optimally reconstruct the directions of the muons and neutrinos will be developed to verify the performance and potential of the detector and to pave the path towards the neutrino astronomy. Programming skills are essential, mostly root and C++ will be used.<br />
<br />
''Contact: [mailto:rbruijn@nikhef.nl Ronald Bruijn]''<br />
<br />
=== Neutrino mass hierarchy with KM3NeT/ORCA ===<br />
<br />
Neutrinos exist in three flavors and are known to oscillate between flavors whereby the detected flavor depends on the (partly) known oscillation parameters, the mass differences, their energy and travel length. The neutrino telescope KM3NeT is planning for a dedicated set of detection units in order to pursue an oscillation measurement of an unprecedented precision using neutrinos from atmospheric interactions and with this enabling the measurement of the so far still unknown neutrino mass hierarchy. The measurement of this subtle effect requires unprecedented precision in the reconstruction and identification of the flavor, energy and direction. Various projects are available in the reconstruction and evaluation of the mass hierarchy using dedicated simulations. Programming skills are essential, mainly C++ and root will be used.<br />
<br />
''Contact: [mailto:aart.heijboer@nikhef.nl Aart Heijboer]''<br />
<br />
=== All-flavor-neutrino analysis of ANTARES data ===<br />
<br />
The ANTARES neutrino telescope has been taking data continuously since 2007. Most analyses of the data have been performed using the signature of a muon neutrino interaction whereby a long track can be reconstructed in the detector.<br />
Recent developments allowed for the first time also the reconstruction of a cascade signature in the detector at high angular resolution so that also electron and tau neutrino interactions can be detected (here these two are not distinguishable from each other). A search for neutrinos from cosmic sources on the first 6 years of data has by now been accomplished using this new reconstruction. In this project this search will be continued and exploited also on 2 more years of data for a dedicated optimized analysis of the Galactic Center to probe the possible neutrino emission from this highly interesting region.<br />
Programming skills are essential, mainly C++ and root will be used.<br />
Also other options for analyses of the ANTARES data are available.<br />
<br />
''Contact: [mailto:dosamt@nikhef.nl Dorothea Samtleben]''<br />
<br />
=== ALICE: Particle Polarization in Strong Magnetic Fields ===<br />
When two atomic nuclei, moving in opposite directions, collide off- center then the Quark Gluon Plasma (QGP) created in the overlap zone is expected to rotate. The nucleons not participating in the collision represent electric currents generating an intense magnetic field. The magnetic field could be as large as 10^{18} gauss, orders of magnitude larger than the strongest magnetic fields found in astronomical objects. Proving the existence of the rotation and/or the magnetic field could be done by checking if particles with spin are aligned with the rotation axis or if charged particles have different production rates relative to the direction of the magnetic field. In particular, the longitudinal and transverse polarisation of the Lambda^0 baryon will be studied. This project requires some affinity with computer programming. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''<br />
<br />
=== ALICE: Forward Particle Production from the Color Glass Condensate === <br />
It has been proposed that a new state of matter (the color-glass condensate, or CGC) may provide a universal description of hadronic collisions (e.g. proton-proton collisions) at very high energy. The CGC may be seen as the classical field limit of Quantum Chromodynamics, and a framework for calculating observables from this state has been developed. Several measurements are consistent with the assumption of a CGC, but no experimental proof exists so far. In this project we intend to perform a systematic study of the sensitivity to the CGC of different possible measurements at the LHC. The work will be performed in close collaboration with an external world expert in this field. It is advantageous to have a good background in theoretical physics. (contact: T. Peitzmann, M. van Leeuwen)<br />
Blast-Wave Model in Heavy-Ion collisions<br />
The goal of heavy-ion physics is to study the Quark Gluon Plasma (QGP), a hot and dense medium where quarks and gluons move freely over large distances, larger than the typical size of a hadron. Hydrodynamic simulations expect that the QGP will expand under its own pressure, and cool while expanding. These simulations are particularly successful in describing some of the key observables measured experimentally, such as particle spectra and elliptic flow. A reasonable reproduction of the same observables is also achieved with models that use parameterisations that resemble the hydrodynamical evolution of the system assuming a given freeze-out scenario, usually referred to as blast-wave models. The goal of this project is to work on different blast wave parametrisations, test their dependence on the input parameters and extend their applicability by including more observables studied in heavy-ion collisions in the global fit. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''<br />
<br />
=== ALICE: Energy Loss of Energetic Quarks and Gluons in the Quark-Gluon Plasma ===<br />
One of the ways to study the quark-gluon plasma that is formed in high-energy nuclear collisions, is using high-energy partons (quarks or gluons) that are produced early in the collision and interact with the quark-gluon plasma as they propagate through it. There are several current open questions related to this topic, which can be explored in a Master's project. For example, we would like to use a new Monte Carlo generator model (JEWEL) of the collision to see whether we can measure the shape of the collision region using measurements of hadron pairs. In the project you will collaborate with one the PhD students in our group to use the model to generate predictions of measurements and compare those to data analysis results. Depending on your interests, the project can focus more on the modeling aspects or on the analysis of experimental data from the ALICE detector at the LHC. <br />
<br />
''Contact: [mailto:marco.van.leeuwen@nikhef.nl M. van Leeuwen]''<br />
<br />
=== ALICE: Chiral Magnetic Effect and the Strong CP Problem === <br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, which is called Chiral Magnetic Effect (CME). The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, but background effects have not yet been properly disentangled. In this project you will develop and test new observables of the CME, trying to understand and discriminate the background sources that affects such a measurement. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''<br />
<br />
=== ALICE: Quantum Coherence in Particle Production with Intensity Interferometry ===<br />
Intensity interferometry – also known as HBT-effect or Bose-Einstein-correlations – is a method to study the space-time structure of the particle-emitting source in high-energy physics. The main interest so far has been on the width of correlation functions in momentum space, which reflects the space-time information. The strength of the correlation also carries information, but this has been ignored by many people. The correlation strength is in particular influenced by the degree of coherence of particle production. Recently new studies have been performed to extract this degree of coherence, however, many other effects might distort such a measurement, in particular the production of pions via resonance decay. In this project we will study the role of resonance decays for a measurement of coherence in intensity interferometry and try to establish possible correction methods for any distortions they may cause. We will perform theoretical model calculations with Monte-Carlo simulation methods.<br />
<br />
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann]''<br />
<br />
=== ALICE: Higher Harmonic Flow ===<br />
When two ions collide, if the impact parameter is not zero, the overlap region is not isotropic. This spatial anisotropy of the overlap region is transformed into an anisotropy in momentum space through interactions between partons and at a later stage between the produced particles. It was recently realized that the overlap region of the colliding nuclei exhibits an irregular shape. These irregularities originate from the initial density profile of nucleons participating in the collision which is not smooth and is different from one event to the other. The resulting higher order flow harmonics (e.g. v3, v4, and v5, usually referred to as triangular, quadrangular, and pentangular flow, respectively) and in particular their transverse momentum dependence are argued to be more sensitive probes than elliptic flow not only of the initial geometry and its fluctuations but also of shear viscosity over entropy density (η/s). The goal of this project is to study v3, v4, and v5 for identified particles in collisions of heavy-ions at the LHC. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''<br />
<br />
=== ALICE: A New Detector for Very High-Energy Photons: FoCal === <br />
High-energy photons are important messenger particles in particle physics. In particular direct photons (i.e. directly produced from elementary scattering processes) are interesting, but it is a difficult task to discriminate them from the photons originating from particle decays. Existing detector have limited capabilities for such a discrimination, in particular at the highest energies. Our institute has pioneered a detector based on a new concept, a digital pixel calorimeter with Si-sensors of unprecedented granularity. First proof-of-principle measurements have already been performed. In this project we will study the performance of a particular detector design for measurements of direct photons at the LHC and optimize the design parameters for such a measurement. Performance studies for other measurements – e.g. jets, J/ψ, or ϒ particles – may be carried out in addition. <br />
<br />
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann] [mailto:marco.van.leeuwen@nikhef.nl M. van Leeuwen]''<br />
<br />
=== ALICE: Thermal Photon Emission: Quark-Gluon Plasma or Hadron Gas? ===<br />
Recently, measurements of thermal photon emission in high-energy nuclear collisions have been performed at RHIC and at LHC. It is generally believed that a quark-gluon plasma equation of state is the natural description of the hot initial phase of these collisions, and so far only theoretical model calculations including such a phase have been compared to those measurements. In this project we will revisit hadron gas models and try to reproduce the thermal photon yield together with other observables. In this work we will use and possibly modify Monte Carlo implementations of relativistic hydrodynamics, tune it to existing data of hadron production and then estimate the photon production from the same model. The model implementation will be based on previous work of external theoretical colleagues and will be carried out in collaboration with them.<br />
<br />
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann]''<br />
<br />
=== A New Detector for Proton Therapy and Proton Computed Tomography ===<br />
Conventional imaging of humans in medical treatment relies mostly on electromagnetic radiation (CT, MRT) or positrons (PET). A recently proposed new imaging strategy, in particular in the context of proton therapy for cancer treatment, is to use proton beams. Current detectors for the scattered protons have severe limitations, in particular for their precision and measurement times. New development of intelligent Si-sensors in particle physics offer possibilities to develop much more efficient detectors for such proton CT measurements. We will perform R&D on the use of new silicon pixel detectors developed in the context of the ALICE experiment at CERN for such medical applications. Studies will include Monte-Carlo simulations of a possible detector setup and measurements with the first samples of the appropriate silicon sensors, which will become available in early 2016. The project will be carried out in the context of a scientific collaboration with Bergen University, Norway. <br />
<br />
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann]''<br />
<br />
=== Medical X-ray Imaging ===<br />
With the upcoming of true multi-threshold X-Ray detectors the possibilities for Spectral Imaging with low dose, including spectral CT, is now a reality around the corner. The Medipix3RX chip, from the Medipix Collaboration (CERN) features up to 8 programmable thresholds which can select energy bins without a threshold scan. A number of projects could be derived from the R&D activities with the Medipix3RX within the Nikhef R&D group on X-ray imaging for medical applications: <br />
* Medipix3RX characterization in all its operation modes and gains. <br />
* Spectral CT and scarce sampling 3D reconstruction <br />
* Charge sharing: the charge-sum capabilities of the chip can be exploited to further understand the problem of charge sharing in pixelized detectors. A combination of the characterization of the charge-summing mode plus the use of both planar, and 3D sensors, at the light of MC simulation, could reveal valuable information about charge sharing.<br />
<br />
''Contact: [mailto:johnid@nikhef.nl John Idarraga],[mailto:nielsvb@nihef.nl Niels van Bakel]''<br />
<br />
=== Compton camera ===<br />
In the Nikhef R&D group we develop instrumentation for particle physics but we also investigate how particle physics detectors can be used for different purposes. A succesfull development is the Medipix chip that can be used in Xray imaging. For use in large scale medical applications compton scattering limits however the energy resolving possibilities. You will investigate whether it is in principle possible to design a Xray application that detects the compton scattered elctron and the absorbed photon. Your ideas can be tested in practice in the lab where a Xray scan can be performed.<br />
<br />
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman]''<br />
<br />
=== The Modulation experiment ===<br />
There exist a few measurements that suggest an annual modulation in the activity of radioactive sources. With a few groups from the XENON collaboration we have developed four sets of table-top experiments to investigate this effect on a few well known radioactive sources. The experiments are under construction in Purdue University (USA), a mountain top in Switzerland, a beach in Rio de Janeiro and the last one at Nikhef in Amsterdam. We urgently need a master student to (1) do the final commissioning of the experiment, (2) collect the 1st big data set, and (3) analyse the first data. We are looking for an all-round physicist with interest in both lab-work and data-analysis. The student will directly collaborate with the other groups in this small collaboration (around 10 people), and the goal is to have the first publication ready by the end of the project.<br />
<br />
''Contact: [mailto:colijn@nikhef.nl Auke Colijn]''<br />
<br />
=== Acoustic detection of ultra-high energy cosmic-ray neutrinos ===<br />
The study of the cosmic neutrinos of energies above 10^17 eV, so-called ultra-high<br />
energy neutrinos, provides a unique view on the universe and may provide insight in<br />
the origin of the most violent sources, such as gamma ray bursts, supernovae or even<br />
dark matter. The energy deposition of cosmic neutrinos in water induces a thermo-acoustic<br />
signal, which can be detected using sensitive hydrophones. The expected neutrino<br />
flux is however extremely low and the signal that neutrinos induce is small. TNO<br />
is presently developing sensitive hydrophone technology that is based on fiber optics.<br />
Optical fibers form a natural way to create a distributed sensing system. Using this<br />
technology a large scale neutrino telescope can be built in the deep sea. TNO is aiming<br />
for a prototype hydrophone which will form the building block of a future telescope.<br />
<br />
Students have the possibility to participate to this project is the following ways:<br />
(i) Modeling of cosmic rays induced acoustic signal in a neutrino telescope.<br />
Keywords: Cosmic rays, Monte Carlo, signal processing, telescope optimization.<br />
(ii) Testing and optimization of fiber optical hydrophone for a large scale neutrino<br />
telescope. Keywords: Experimental, physics, system design.<br />
<br />
The work will be (partly) executed in Delft. <br />
<br />
''Contact: [mailto:ernst-jan.buis@tno.NOSPAMnl Ernst-Jan Buis]''<br />
<br />
=== LHCb: A Scintillator Fibers Tracker ===<br />
<br />
The LHCb collaboration is upgrading the present tracking system<br />
constructing a new tracker based on scintillating fibers combined<br />
with silicon photo-multipliers (SiPM): the SciFi Tracker!<br />
Nikhef plays a key role in the project, as we will build the<br />
SciFi fibers modules, the cold-box enclosure housing the SiPMs,<br />
and a large part of the on-detector electronics. In all these<br />
areas, interesting test hardware and software has to be realized,<br />
and several research topics for a Master project are available,<br />
taking the student in contact with state-of-the-art particle detectors,<br />
in a large team of physicists and engineers. Possible collaborations<br />
with the Nikhef R&D group can also be envisaged.<br />
<br />
''Contact: [mailto:antonio@nikhef.nl Antonio Pellegrino]''<br />
<br />
=== LHCb: Discovery of the Decay Lb --> p Ds+ ===<br />
This project aims to measure the branching fraction of the decay Lb->p Ds+ (bud -> uud + ds). <br />
The decay Lb->p Ds+ is quite rare, because it occurs through the transition of a b-quark to a u-quark. <br />
It has not been measured yet (although some LHCb colleagues claim to have seen it).<br />
This decay is interesting, because <br />
<br />
1) It is sensitive to the b->u coupling (CKM-element Vub), which determination is heavily debated.<br />
2) It can quantify non-factorisable QCD effects in b-baryon decays.<br />
<br />
The decay is closely related to B0->pi-Ds+, which proceeds through a similar Feynman diagram. <br />
Also, the final state of B0->pi-Ds+ is almost identical to Lb->p Ds+. <br />
The aim is to determine the relative branching fraction of Lb->pDs+ with respect to B0->D+pi- decays, <br />
in close collaboration with the PhD (who will study BR(B0->pi-Ds+)/BR(B0->D+pi-) ).<br />
This project will result in a journal publication on behalf of the LHCb collaboration, written by you. <br />
For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. <br />
This is a project that is closely related to previous analyses in the group. <br />
Weekly video meetings with CERN coordinate the efforts with in the LHCb collaboration.<br />
Relevant information:<br />
<br />
[1] R.Aaij et al. [LHCb Collaboration], ``Determination of the branching fractions of B0s->DsK and B0->DsK, JHEP 05 (2015) 019 [arXiv:1412.7654 [hep-ex]].<br />
[2] R. Fleischer, N. Serra and N. Tuning, ``Tests of Factorization and SU(3) Relations in B Decays into Heavy-Light Final States, Phys. Rev. D 83, 014017 (2011) [arXiv:1012.2784 [hep-ph]].<br />
<br />
''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''<br />
<br />
=== LHCb: A search for heavy neutrinos in the decay of W bosons at LHCb ===<br />
<br />
Neutrinos are arguably the most mysterious of all known fundamental fermions as they are both much lighter than all others and only weakly interacting. It is thought that the tiny mass of neutrinos can be explained by their mixing with so-far unknown, much heavier, neutrino-like particles. In this research proposal we look for these new neutrinos in the decay of the SM W-boson using data with the LHCb experiment at CERN. The W boson is assumed to decay to a heavy neutrino and a muon. The heavy neutrino subsequently decays to a muon and a pair of quarks. Both like-sign and opposite-sign muon pairs will be studied. The result of the analysis will either be a limit on the production of the new neutrinos or the discovery of something entirely new.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen and Elena Dall'Occo]''<br />
<br />
<br />
=== LHCb: A search for Majorana neutrinos in the decay of Bc mesons at LHCb ===<br />
<br />
Neutrinos can either be their own anti-particles, in which case they are called "Majorana" particles, or Dirac fermions. It is thought that the tiny mass of neutrinos can be explained by their mixing with so-far unknown, much heavier, neutrino-like particles. LHCb has looked for off-shell Majorana neutrinos in the decays B+->pi-mu+mu+ and B+->D(*)-mu+mu+. Both decays suffer from suppression from Cabibbo-Kobayashi-Maskawa matrix elements, or from low reconstruction efficiencies. Although its production rate is much lower, the Bc meson provides a potentially more promising decay channel: Bc->J/psimu+mu+pi-. The Master student will design and optimise a selection, study potential backgrounds and perform a search in view of setting a stringent limit, or an observation of new physics.<br />
<br />
arXiv:1401.5361 [hep-ex]. arXiv:1201.5600 [hep-ex]. arXiv:11602.09112 [hep-ph]<br />
<br />
''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg and Flavio Archilli]''</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=114Master Projects2016-10-18T08:34:37Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
[MORE PROJECTS TO COME!]<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]<br />
<br />
=== Theory – Constraining the proton structure with Run II LHC data ===<br />
<br />
The non-perturbative dynamics that determine the energy distribution of quarks and gluons inside protons, the so-called parton distribution functions (PDFs), cannot be computed from first principles from Quantum Chromodynamics (QCD), and need to be determined from experimental data. PDFs are an essential ingredient for the scientific program at the Large Hadron Collider (LHC), from Higgs characterisation to searches for New Physics beyond the Standard Model. One recent breakthrough in PDF analysis has been the exploitation of the constraints from LHC data. From direct photons to top quark pair production cross-sections and charmed meson differential distributions, LHC measurements are now a central ingredient of PDF fits, providing important information on poorly-known PDFs such as the large and small-x gluon or the large-x antiquarks. With the upcoming availability of data from the Run II of the LHC, at a center-of-mass energy of 13 TeV, these constraints are expected to become even more stringent.<br />
<br />
In this project, the implications of PDF-sensitive measurements at the LHC 13 TeV will be quantified. Processes that will be considered include jet and dijet production at the multi-TeV scale, single-top quark production, and weak boson production in association with heavy quarks, among several others. These studies will be performed using the NNPDF fitting framework, based on artificial neural networks and genetic algorithms. The phenomenological implications of the improved PDF modelling for Higgs and new physics searches at the LHC will also be explored. Additional information on this project can be found [http://pcteserver.mi.infn.it/~nnpdf/talks/MSc_projects/2017-MasterProject-PDFs.pdf].<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Extreme Astronomy – Preparing for CTA, the Next-Generation Gamma-Ray Observatory ===<br />
<br />
The Cherenkov Telescope Array (CTA) is a planned facility for measuring gamma rays from space covering more than four orders of magnitude in energy, up to energies exceeding 100 TeV. CTA employs the imaging atmospheric Cherenkov technique to measure properties of cosmic gamma rays. This technique is based on measuring Cherenkov light emitted during the development of a gamma-ray air shower. CTA will be built at two experimental sites, one in the Northern, one in the Southern hemisphere, and will consist of up to 100 telescopes. It represents a major leap forward in sensitivity and precision for gamma-ray astronomy, and will allow us to explore very-high-energy processes of the extreme Universe at an unprecedented level.<br />
<br />
Several master projects are available in the CTA group of UvA and the students will participate in photonic and electronic R&D studies contributing to the starting phase of CTA. These studies will either focus on laboratory-based measurements or simulations of novel kinds of single-photon detectors, referred to as silicon photomultipliers (SiPMs). By means of these simulations the performance of SiPMs used for arrays of Cherenkov telescopes will be assessed and their optimal operational parameters will be evaluated. Within one of the laboratory-based projects different types of SiPMs will be characterised and a measuring system to calibrate the photosensors will be designed and operated. In a different project various imaging and non-imaging light sources will be used to study the trigger performance of a CTA prototype camera.<br />
<br />
''Contact: [mailto:d.berge@nikhef.nl David Berge], [mailto:maurice.stephan@uva.nl Maurice Stephan]''<br />
<br />
=== The XENON Dark Matter Experiment: Data Analysis ===<br />
<br />
The XENON collaboration is currently commissioning the XENON1T detector, soon to be the world’s most sensitive direct detection dark matter experiment, with the Nikhef group playing an important role in this work. The detector operates at the Gran Sasso underground laboratory and consists of a so-called dual-phase xenon time-projection chamber filled with 3500kg of ultra-pure xenon. Our group has an opening for a motivated MSc student to do data-analysis on this new detector. The work will consist of understanding the signals that come out of the detector and in particular focus on the so-called double scatter events. We are interested in developing methods in order to interpret the response of the detector better and are developing sophisticated statistical tools to do this. This work will include looking at data and developing new algorithms in our Python-based analysis tool. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== XAMS Dark Matter R&D Setup ===<br />
<br />
The Amsterdam Dark Matter group has built an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 4kg of ultra-pure liquid xenon. We plan to use this detector for the development of new detection techniques (such as utilizing new photosensors) and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENON experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data him/herself. You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== ATLAS : Astroparticle Physics at the LHC ===<br />
<br />
Understanding particle acceleration up to very high energies in the Universe requires Earth-bound experimental techniques that exploit the Earth’s atmosphere as detection medium. Only the shear size of the atmosphere provides a sufficiently large sensitive area to measure the very rare highest energy particles from the cosmos as they impinge on the Earth. The idea of the atmospheric measurement is simple: a cosmic particle hitting the atmosphere is being absorbed by developing into an air shower, a spray of secondary particles that originates in the collision of the primary cosmic particle with air molecules, and successive interactions of those secondary particles in the atmosphere. Such air showers can be traced and therefore measured on Earth, providing information about the energy, type, and direction of the primary cosmic particle, by different means. Important examples of such atmospheric detection techniques include the measurement of muons with particle counters at the Earth’s surface and the measurement of Cherenkov or Fluorescence light emitted during the air shower development. The connection between measured quantities like particle numbers or light intensity and original quantities like particle energy or type is in all cases inferred using simulations of particle collisions and cascades in the atmosphere.<br />
<br />
The goal of this master project is to exploit data of proton collisions measured with ATLAS, an experiment at the Large Hadron Collider (LHC), the highest energy human particle collider currently operating at CERN in Geneva (Switzerland), to test and improve simulations of particle collisions in the atmosphere up to the highest known energies (a few times 1020 eV). The student will work on ATLAS data analysis and Monte Carlo simulations of particle collisions, both for simulating proton colliding in ATLAS and cosmic-ray protons colliding with air molecules in the atmosphere. The ultimate goal is to improve Monte Carlo model predictions used for experiments like the upcoming CTA (http://www.cta-observatory.org/) and Auger (http://www.auger.org/).<br />
<br />
''Contact: [mailto:d.berge@nikhef.nl David Berge], [mailto:david.salek@cern.ch David Salek]''<br />
<br />
=== ATLAS : Beyond Standard Model with multiple leptons ===<br />
<br />
The Standard Model of particle physics (SM) is extremely successful, but would it hold against of check of with data containing multiple leptons? Although very rare process, the production of leptons is calculated in SM with high precision. On detector side the leptons (electrons and muons) are easy to reconstruct and such a sample contains very little "non-lepton" background. This analysis has a very ambitious goal to test many final states at once, without over-tuning for a specific model. The second step would then be to test obtained results against models of composite structure of leptons or presence of heavy right handed neutrinos favored in seesaw theories. With this project, the student would gain close familiarity with modern experimental techniques (statistical analysis, SM background estimates, etc.), with Monte Carlo generators and the standard HEP analysis tools (ROOT, C++, etc.).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina]''<br />
<br />
=== ATLAS : Search for supersymmetric dark matter-like particles ===<br />
<br />
Supersymmetry is a theory of physics beyond the Standard Model of particle physics that makes a link between fermions and bosons. Apart from many other attractive features, supersymmetry also predicts a particle that may be a candidate for dark matter. Such particles, and their related particles, may be produced at the LHC. Searching for them, however, is challenging. The production cross-sections are small, and the final states are difficult to measure, for example because the final state particles may have little energy, and are ignored by the ATLAS trigger and reconstruction software. In this project we will investigate the measurement of such particles, with the aim to improve the current ATLAS search strategy. You will then apply the improved analysis to the ATLAS data (to be) collected in 2016. In the project you will learn modern experimental analysis techniques, as well as programming in ROOT and C++.<br />
<br />
''Contact: [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
=== ATLAS inner tracker upgrade ===<br />
<br />
Research description: One of the key sub-systems of the ATLAS experiment at the Large Hadron Collider (LHC) is the Inner Detector (ID), designed to provide excellent charged particles momentum and vertex resolution measurements.<br />
At Phase-2 of the LHC run the operating luminosity of the collider will be increased significantly. This will imply an upgrade of all ATLAS subsystems. In particular, the ID will be fully replaced with a tracker completely made of Silicon, having higher granularity and radiation hardness. The R&D process for the new ATLAS ID is now ongoing. Different geometrical layouts are simulated and their performance is studied under different operating conditions in search for the optimal detector architecture. Also, the performance of the new Si-sensors/modules is under investigation with dedicated laboratory tests.<br />
The focus of the project could be on the simulation of the High-Luminosity LHC version of the ATLAS Inner Detector. The student will learn how a high-energy physics experiment is designed and optimized. Alternatively, if possible at that moment, the student could work on a project at the Nikhef Silicon laboratory at the test-bench for new ATLAS Si-strip detectors and participate in the quality assurance procedure for the new ATLAS Si detectors. <br />
<br />
''Contact: [mailto:Peter.Vankov@cern.NOSPAMch Peter Vankov]''<br />
<br />
<br />
=== ATLAS : Model testing for Beyond the Standard Model Higgs ===<br />
Recently there's been a lot of excitement about hints for new Beyond the Standard Model (BSM) physics. When the search for the Higgs was ongoing we had a model to test possible bumps against, now we are looking for any new particle and there are many models available. Testing the newest results from the LHC is challenging because of low statistics and model uncertainties. In this project we will investigate different BSM Higgs models that could possible explain the newest results of the LHC. For this we will use the data collected in 2015 and the data that will be collected in 2016. In the end we will set limits on the tested models (or discover a new particle). During the project you will learn modern experimental analysis techniques as well as programming.<br />
<br />
''Contact: [mailto:verkerke@nikhef.nl Wouter Verkerke], [mailto:lbrenner@nikhef.nl Lydia Brenner]''<br />
<br />
=== Theory & ATLAS: How to violate lepton flavour? ===<br />
<br />
One of the big outstanding questions in particle physics is what has caused the matter-antimatter asymmetry in the Universe. One of the possible solutions is related to processes that violate lepton flavour. Such phenomena could be observable in the ATLAS experiment at the Large Hadron Collider. In fact, recent data show a hint for the violation of lepton flavour in the decay of the Higgs boson into a mu and tau lepton. However, additional experimental and theoretical investigations are necessary to further probe this very interesting phenomenon. The goal of this project is to identify complementary lepton flavour violating processes and to study correlations between them and other flavour probes. The work will involve theoretical calculations and a classification of the most useful observables for the ATLAS experiment.<br />
<br />
''Contact: [mailto:devries.jordy@gmail.com Jordy de Vries], [mailto:olya@nikhef.nl Olya Igonkina], [mailto:Robert.Fleischer@nikhef.nl Robert Fleischer]''<br />
<br />
=== KM3NeT : Reconstruction of first neutrinos in KM3NeT ===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first string with sensitive photodetectors has been deployed end of 2015, in total 30 will be deployed til end of 2017. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. The performance and calibration of the detector will be evaluated also in comparison with simulations. Procedures to identify and also optimally reconstruct the directions of the muons and neutrinos will be developed to verify the performance and potential of the detector and to pave the path towards the neutrino astronomy. Programming skills are essential, mostly root and C++ will be used.<br />
<br />
''Contact: [mailto:rbruijn@nikhef.nl Ronald Bruijn]''<br />
<br />
=== Neutrino mass hierarchy with KM3NeT/ORCA ===<br />
<br />
Neutrinos exist in three flavors and are known to oscillate between flavors whereby the detected flavor depends on the (partly) known oscillation parameters, the mass differences, their energy and travel length. The neutrino telescope KM3NeT is planning for a dedicated set of detection units in order to pursue an oscillation measurement of an unprecedented precision using neutrinos from atmospheric interactions and with this enabling the measurement of the so far still unknown neutrino mass hierarchy. The measurement of this subtle effect requires unprecedented precision in the reconstruction and identification of the flavor, energy and direction. Various projects are available in the reconstruction and evaluation of the mass hierarchy using dedicated simulations. Programming skills are essential, mainly C++ and root will be used.<br />
<br />
''Contact: [mailto:aart.heijboer@nikhef.nl Aart Heijboer]''<br />
<br />
=== All-flavor-neutrino analysis of ANTARES data ===<br />
<br />
The ANTARES neutrino telescope has been taking data continuously since 2007. Most analyses of the data have been performed using the signature of a muon neutrino interaction whereby a long track can be reconstructed in the detector.<br />
Recent developments allowed for the first time also the reconstruction of a cascade signature in the detector at high angular resolution so that also electron and tau neutrino interactions can be detected (here these two are not distinguishable from each other). A search for neutrinos from cosmic sources on the first 6 years of data has by now been accomplished using this new reconstruction. In this project this search will be continued and exploited also on 2 more years of data for a dedicated optimized analysis of the Galactic Center to probe the possible neutrino emission from this highly interesting region.<br />
Programming skills are essential, mainly C++ and root will be used.<br />
Also other options for analyses of the ANTARES data are available.<br />
<br />
''Contact: [mailto:dosamt@nikhef.nl Dorothea Samtleben]''<br />
<br />
=== ALICE: Particle Polarization in Strong Magnetic Fields ===<br />
When two atomic nuclei, moving in opposite directions, collide off- center then the Quark Gluon Plasma (QGP) created in the overlap zone is expected to rotate. The nucleons not participating in the collision represent electric currents generating an intense magnetic field. The magnetic field could be as large as 10^{18} gauss, orders of magnitude larger than the strongest magnetic fields found in astronomical objects. Proving the existence of the rotation and/or the magnetic field could be done by checking if particles with spin are aligned with the rotation axis or if charged particles have different production rates relative to the direction of the magnetic field. In particular, the longitudinal and transverse polarisation of the Lambda^0 baryon will be studied. This project requires some affinity with computer programming. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''<br />
<br />
=== ALICE: Forward Particle Production from the Color Glass Condensate === <br />
It has been proposed that a new state of matter (the color-glass condensate, or CGC) may provide a universal description of hadronic collisions (e.g. proton-proton collisions) at very high energy. The CGC may be seen as the classical field limit of Quantum Chromodynamics, and a framework for calculating observables from this state has been developed. Several measurements are consistent with the assumption of a CGC, but no experimental proof exists so far. In this project we intend to perform a systematic study of the sensitivity to the CGC of different possible measurements at the LHC. The work will be performed in close collaboration with an external world expert in this field. It is advantageous to have a good background in theoretical physics. (contact: T. Peitzmann, M. van Leeuwen)<br />
Blast-Wave Model in Heavy-Ion collisions<br />
The goal of heavy-ion physics is to study the Quark Gluon Plasma (QGP), a hot and dense medium where quarks and gluons move freely over large distances, larger than the typical size of a hadron. Hydrodynamic simulations expect that the QGP will expand under its own pressure, and cool while expanding. These simulations are particularly successful in describing some of the key observables measured experimentally, such as particle spectra and elliptic flow. A reasonable reproduction of the same observables is also achieved with models that use parameterisations that resemble the hydrodynamical evolution of the system assuming a given freeze-out scenario, usually referred to as blast-wave models. The goal of this project is to work on different blast wave parametrisations, test their dependence on the input parameters and extend their applicability by including more observables studied in heavy-ion collisions in the global fit. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''<br />
<br />
=== ALICE: Energy Loss of Energetic Quarks and Gluons in the Quark-Gluon Plasma ===<br />
One of the ways to study the quark-gluon plasma that is formed in high-energy nuclear collisions, is using high-energy partons (quarks or gluons) that are produced early in the collision and interact with the quark-gluon plasma as they propagate through it. There are several current open questions related to this topic, which can be explored in a Master's project. For example, we would like to use a new Monte Carlo generator model (JEWEL) of the collision to see whether we can measure the shape of the collision region using measurements of hadron pairs. In the project you will collaborate with one the PhD students in our group to use the model to generate predictions of measurements and compare those to data analysis results. Depending on your interests, the project can focus more on the modeling aspects or on the analysis of experimental data from the ALICE detector at the LHC. <br />
<br />
''Contact: [mailto:marco.van.leeuwen@nikhef.nl M. van Leeuwen]''<br />
<br />
=== ALICE: Chiral Magnetic Effect and the Strong CP Problem === <br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, which is called Chiral Magnetic Effect (CME). The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, but background effects have not yet been properly disentangled. In this project you will develop and test new observables of the CME, trying to understand and discriminate the background sources that affects such a measurement. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''<br />
<br />
=== ALICE: Quantum Coherence in Particle Production with Intensity Interferometry ===<br />
Intensity interferometry – also known as HBT-effect or Bose-Einstein-correlations – is a method to study the space-time structure of the particle-emitting source in high-energy physics. The main interest so far has been on the width of correlation functions in momentum space, which reflects the space-time information. The strength of the correlation also carries information, but this has been ignored by many people. The correlation strength is in particular influenced by the degree of coherence of particle production. Recently new studies have been performed to extract this degree of coherence, however, many other effects might distort such a measurement, in particular the production of pions via resonance decay. In this project we will study the role of resonance decays for a measurement of coherence in intensity interferometry and try to establish possible correction methods for any distortions they may cause. We will perform theoretical model calculations with Monte-Carlo simulation methods.<br />
<br />
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann]''<br />
<br />
=== ALICE: Higher Harmonic Flow ===<br />
When two ions collide, if the impact parameter is not zero, the overlap region is not isotropic. This spatial anisotropy of the overlap region is transformed into an anisotropy in momentum space through interactions between partons and at a later stage between the produced particles. It was recently realized that the overlap region of the colliding nuclei exhibits an irregular shape. These irregularities originate from the initial density profile of nucleons participating in the collision which is not smooth and is different from one event to the other. The resulting higher order flow harmonics (e.g. v3, v4, and v5, usually referred to as triangular, quadrangular, and pentangular flow, respectively) and in particular their transverse momentum dependence are argued to be more sensitive probes than elliptic flow not only of the initial geometry and its fluctuations but also of shear viscosity over entropy density (η/s). The goal of this project is to study v3, v4, and v5 for identified particles in collisions of heavy-ions at the LHC. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''<br />
<br />
=== ALICE: A New Detector for Very High-Energy Photons: FoCal === <br />
High-energy photons are important messenger particles in particle physics. In particular direct photons (i.e. directly produced from elementary scattering processes) are interesting, but it is a difficult task to discriminate them from the photons originating from particle decays. Existing detector have limited capabilities for such a discrimination, in particular at the highest energies. Our institute has pioneered a detector based on a new concept, a digital pixel calorimeter with Si-sensors of unprecedented granularity. First proof-of-principle measurements have already been performed. In this project we will study the performance of a particular detector design for measurements of direct photons at the LHC and optimize the design parameters for such a measurement. Performance studies for other measurements – e.g. jets, J/ψ, or ϒ particles – may be carried out in addition. <br />
<br />
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann] [mailto:marco.van.leeuwen@nikhef.nl M. van Leeuwen]''<br />
<br />
=== ALICE: Thermal Photon Emission: Quark-Gluon Plasma or Hadron Gas? ===<br />
Recently, measurements of thermal photon emission in high-energy nuclear collisions have been performed at RHIC and at LHC. It is generally believed that a quark-gluon plasma equation of state is the natural description of the hot initial phase of these collisions, and so far only theoretical model calculations including such a phase have been compared to those measurements. In this project we will revisit hadron gas models and try to reproduce the thermal photon yield together with other observables. In this work we will use and possibly modify Monte Carlo implementations of relativistic hydrodynamics, tune it to existing data of hadron production and then estimate the photon production from the same model. The model implementation will be based on previous work of external theoretical colleagues and will be carried out in collaboration with them.<br />
<br />
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann]''<br />
<br />
=== A New Detector for Proton Therapy and Proton Computed Tomography ===<br />
Conventional imaging of humans in medical treatment relies mostly on electromagnetic radiation (CT, MRT) or positrons (PET). A recently proposed new imaging strategy, in particular in the context of proton therapy for cancer treatment, is to use proton beams. Current detectors for the scattered protons have severe limitations, in particular for their precision and measurement times. New development of intelligent Si-sensors in particle physics offer possibilities to develop much more efficient detectors for such proton CT measurements. We will perform R&D on the use of new silicon pixel detectors developed in the context of the ALICE experiment at CERN for such medical applications. Studies will include Monte-Carlo simulations of a possible detector setup and measurements with the first samples of the appropriate silicon sensors, which will become available in early 2016. The project will be carried out in the context of a scientific collaboration with Bergen University, Norway. <br />
<br />
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann]''<br />
<br />
=== Medical X-ray Imaging ===<br />
With the upcoming of true multi-threshold X-Ray detectors the possibilities for Spectral Imaging with low dose, including spectral CT, is now a reality around the corner. The Medipix3RX chip, from the Medipix Collaboration (CERN) features up to 8 programmable thresholds which can select energy bins without a threshold scan. A number of projects could be derived from the R&D activities with the Medipix3RX within the Nikhef R&D group on X-ray imaging for medical applications: <br />
* Medipix3RX characterization in all its operation modes and gains. <br />
* Spectral CT and scarce sampling 3D reconstruction <br />
* Charge sharing: the charge-sum capabilities of the chip can be exploited to further understand the problem of charge sharing in pixelized detectors. A combination of the characterization of the charge-summing mode plus the use of both planar, and 3D sensors, at the light of MC simulation, could reveal valuable information about charge sharing.<br />
<br />
''Contact: [mailto:johnid@nikhef.nl John Idarraga],[mailto:nielsvb@nihef.nl Niels van Bakel]''<br />
<br />
=== Compton camera ===<br />
In the Nikhef R&D group we develop instrumentation for particle physics but we also investigate how particle physics detectors can be used for different purposes. A succesfull development is the Medipix chip that can be used in Xray imaging. For use in large scale medical applications compton scattering limits however the energy resolving possibilities. You will investigate whether it is in principle possible to design a Xray application that detects the compton scattered elctron and the absorbed photon. Your ideas can be tested in practice in the lab where a Xray scan can be performed.<br />
<br />
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman]''<br />
<br />
=== The Modulation experiment ===<br />
There exist a few measurements that suggest an annual modulation in the activity of radioactive sources. With a few groups from the XENON collaboration we have developed four sets of table-top experiments to investigate this effect on a few well known radioactive sources. The experiments are under construction in Purdue University (USA), a mountain top in Switzerland, a beach in Rio de Janeiro and the last one at Nikhef in Amsterdam. We urgently need a master student to (1) do the final commissioning of the experiment, (2) collect the 1st big data set, and (3) analyse the first data. We are looking for an all-round physicist with interest in both lab-work and data-analysis. The student will directly collaborate with the other groups in this small collaboration (around 10 people), and the goal is to have the first publication ready by the end of the project.<br />
<br />
''Contact: [mailto:colijn@nikhef.nl Auke Colijn]''<br />
<br />
=== Acoustic detection of ultra-high energy cosmic-ray neutrinos ===<br />
The study of the cosmic neutrinos of energies above 10^17 eV, so-called ultra-high<br />
energy neutrinos, provides a unique view on the universe and may provide insight in<br />
the origin of the most violent sources, such as gamma ray bursts, supernovae or even<br />
dark matter. The energy deposition of cosmic neutrinos in water induces a thermo-acoustic<br />
signal, which can be detected using sensitive hydrophones. The expected neutrino<br />
flux is however extremely low and the signal that neutrinos induce is small. TNO<br />
is presently developing sensitive hydrophone technology that is based on fiber optics.<br />
Optical fibers form a natural way to create a distributed sensing system. Using this<br />
technology a large scale neutrino telescope can be built in the deep sea. TNO is aiming<br />
for a prototype hydrophone which will form the building block of a future telescope.<br />
<br />
Students have the possibility to participate to this project is the following ways:<br />
(i) Modeling of cosmic rays induced acoustic signal in a neutrino telescope.<br />
Keywords: Cosmic rays, Monte Carlo, signal processing, telescope optimization.<br />
(ii) Testing and optimization of fiber optical hydrophone for a large scale neutrino<br />
telescope. Keywords: Experimental, physics, system design.<br />
<br />
The work will be (partly) executed in Delft. <br />
<br />
''Contact: [mailto:ernst-jan.buis@tno.NOSPAMnl Ernst-Jan Buis]''<br />
<br />
=== LHCb: A Scintillator Fibers Tracker ===<br />
<br />
The LHCb collaboration is upgrading the present tracking system<br />
constructing a new tracker based on scintillating fibers combined<br />
with silicon photo-multipliers (SiPM): the SciFi Tracker!<br />
Nikhef plays a key role in the project, as we will build the<br />
SciFi fibers modules, the cold-box enclosure housing the SiPMs,<br />
and a large part of the on-detector electronics. In all these<br />
areas, interesting test hardware and software has to be realized,<br />
and several research topics for a Master project are available,<br />
taking the student in contact with state-of-the-art particle detectors,<br />
in a large team of physicists and engineers. Possible collaborations<br />
with the Nikhef R&D group can also be envisaged.<br />
<br />
''Contact: [mailto:antonio@nikhef.nl Antonio Pellegrino]''<br />
<br />
=== LHCb: Discovery of the Decay Lb --> p Ds+ ===<br />
This project aims to measure the branching fraction of the decay Lb->p Ds+ (bud -> uud + ds). <br />
The decay Lb->p Ds+ is quite rare, because it occurs through the transition of a b-quark to a u-quark. <br />
It has not been measured yet (although some LHCb colleagues claim to have seen it).<br />
This decay is interesting, because <br />
<br />
1) It is sensitive to the b->u coupling (CKM-element Vub), which determination is heavily debated.<br />
2) It can quantify non-factorisable QCD effects in b-baryon decays.<br />
<br />
The decay is closely related to B0->pi-Ds+, which proceeds through a similar Feynman diagram. <br />
Also, the final state of B0->pi-Ds+ is almost identical to Lb->p Ds+. <br />
The aim is to determine the relative branching fraction of Lb->pDs+ with respect to B0->D+pi- decays, <br />
in close collaboration with the PhD (who will study BR(B0->pi-Ds+)/BR(B0->D+pi-) ).<br />
This project will result in a journal publication on behalf of the LHCb collaboration, written by you. <br />
For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. <br />
This is a project that is closely related to previous analyses in the group. <br />
Weekly video meetings with CERN coordinate the efforts with in the LHCb collaboration.<br />
Relevant information:<br />
<br />
[1] R.Aaij et al. [LHCb Collaboration], ``Determination of the branching fractions of B0s->DsK and B0->DsK, JHEP 05 (2015) 019 [arXiv:1412.7654 [hep-ex]].<br />
[2] R. Fleischer, N. Serra and N. Tuning, ``Tests of Factorization and SU(3) Relations in B Decays into Heavy-Light Final States, Phys. Rev. D 83, 014017 (2011) [arXiv:1012.2784 [hep-ph]].<br />
<br />
''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''<br />
<br />
=== LHCb: A search for heavy neutrinos in the decay of W bosons at LHCb ===<br />
<br />
Neutrinos are arguably the most mysterious of all known fundamental fermions as they are both much lighter than all others and only weakly interacting. It is thought that the tiny mass of neutrinos can be explained by their mixing with so-far unknown, much heavier, neutrino-like particles. In this research proposal we look for these new neutrinos in the decay of the SM W-boson using data with the LHCb experiment at CERN. The W boson is assumed to decay to a heavy neutrino and a muon. The heavy neutrino subsequently decays to a muon and a pair of quarks. Both like-sign and opposite-sign muon pairs will be studied. The result of the analysis will either be a limit on the production of the new neutrinos or the discovery of something entirely new.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen and Elena Dall'Occo]''<br />
<br />
<br />
=== LHCb: A search for Majorana neutrinos in the decay of Bc mesons at LHCb ===<br />
<br />
Neutrinos can either be their own anti-particles, in which case they are called "Majorana" particles, or Dirac fermions. It is thought that the tiny mass of neutrinos can be explained by their mixing with so-far unknown, much heavier, neutrino-like particles. LHCb has looked for off-shell Majorana neutrinos in the decays B+->pi-mu+mu+ and B+->D(*)-mu+mu+. Both decays suffer from suppression from Cabibbo-Kobayashi-Maskawa matrix elements, or from low reconstruction efficiencies. Although its production rate is much lower, the Bc meson provides a potentially more promising decay channel: Bc->J/psimu+mu+pi-. The Master student will design and optimise a selection, study potential backgrounds and perform a search in view of setting a stringent limit, or an observation of new physics.<br />
<br />
arXiv:1401.5361 [hep-ex]. arXiv:1201.5600 [hep-ex]. arXiv:11602.09112 [hep-ph]<br />
<br />
''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg and Flavio Archilli]''</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=113Master Projects2016-10-18T08:34:20Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
[MORE PROJECTS TO COME!]<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]<br />
<br />
=== Theory – Constraining the proton structure with Run II LHC data ===<br />
<br />
The non-perturbative dynamics that determine the energy distribution of quarks and gluons inside protons, the so-called parton distribution functions (PDFs), cannot be computed from first principles from Quantum Chromodynamics (QCD), and need to be determined from experimental data. PDFs are an essential ingredient for the scientific program at the Large Hadron Collider (LHC), from Higgs characterisation to searches for New Physics beyond the Standard Model. One recent breakthrough in PDF analysis has been the exploitation of the constraints from LHC data. From direct photons to top quark pair production cross-sections and charmed meson differential distributions, LHC measurements are now a central ingredient of PDF fits, providing important information on poorly-known PDFs such as the large and small-x gluon or the large-x antiquarks. With the upcoming availability of data from the Run II of the LHC, at a center-of-mass energy of 13 TeV, these constraints are expected to become even more stringent.<br />
<br />
In this project, the implications of PDF-sensitive measurements at the LHC 13 TeV will be quantified. Processes that will be considered include jet and dijet production at the multi-TeV scale, single-top quark production, and weak boson production in association with heavy quarks, among several others. These studies will be performed using the NNPDF fitting framework, based on artificial neural networks and genetic algorithms. The phenomenological implications of the improved PDF modelling for Higgs and new physics searches at the LHC will also be explored. Additional information on this project can be found [here|http://pcteserver.mi.infn.it/~nnpdf/talks/MSc_projects/2017-MasterProject-PDFs.pdf].<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Extreme Astronomy – Preparing for CTA, the Next-Generation Gamma-Ray Observatory ===<br />
<br />
The Cherenkov Telescope Array (CTA) is a planned facility for measuring gamma rays from space covering more than four orders of magnitude in energy, up to energies exceeding 100 TeV. CTA employs the imaging atmospheric Cherenkov technique to measure properties of cosmic gamma rays. This technique is based on measuring Cherenkov light emitted during the development of a gamma-ray air shower. CTA will be built at two experimental sites, one in the Northern, one in the Southern hemisphere, and will consist of up to 100 telescopes. It represents a major leap forward in sensitivity and precision for gamma-ray astronomy, and will allow us to explore very-high-energy processes of the extreme Universe at an unprecedented level.<br />
<br />
Several master projects are available in the CTA group of UvA and the students will participate in photonic and electronic R&D studies contributing to the starting phase of CTA. These studies will either focus on laboratory-based measurements or simulations of novel kinds of single-photon detectors, referred to as silicon photomultipliers (SiPMs). By means of these simulations the performance of SiPMs used for arrays of Cherenkov telescopes will be assessed and their optimal operational parameters will be evaluated. Within one of the laboratory-based projects different types of SiPMs will be characterised and a measuring system to calibrate the photosensors will be designed and operated. In a different project various imaging and non-imaging light sources will be used to study the trigger performance of a CTA prototype camera.<br />
<br />
''Contact: [mailto:d.berge@nikhef.nl David Berge], [mailto:maurice.stephan@uva.nl Maurice Stephan]''<br />
<br />
=== The XENON Dark Matter Experiment: Data Analysis ===<br />
<br />
The XENON collaboration is currently commissioning the XENON1T detector, soon to be the world’s most sensitive direct detection dark matter experiment, with the Nikhef group playing an important role in this work. The detector operates at the Gran Sasso underground laboratory and consists of a so-called dual-phase xenon time-projection chamber filled with 3500kg of ultra-pure xenon. Our group has an opening for a motivated MSc student to do data-analysis on this new detector. The work will consist of understanding the signals that come out of the detector and in particular focus on the so-called double scatter events. We are interested in developing methods in order to interpret the response of the detector better and are developing sophisticated statistical tools to do this. This work will include looking at data and developing new algorithms in our Python-based analysis tool. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== XAMS Dark Matter R&D Setup ===<br />
<br />
The Amsterdam Dark Matter group has built an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 4kg of ultra-pure liquid xenon. We plan to use this detector for the development of new detection techniques (such as utilizing new photosensors) and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENON experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data him/herself. You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== ATLAS : Astroparticle Physics at the LHC ===<br />
<br />
Understanding particle acceleration up to very high energies in the Universe requires Earth-bound experimental techniques that exploit the Earth’s atmosphere as detection medium. Only the shear size of the atmosphere provides a sufficiently large sensitive area to measure the very rare highest energy particles from the cosmos as they impinge on the Earth. The idea of the atmospheric measurement is simple: a cosmic particle hitting the atmosphere is being absorbed by developing into an air shower, a spray of secondary particles that originates in the collision of the primary cosmic particle with air molecules, and successive interactions of those secondary particles in the atmosphere. Such air showers can be traced and therefore measured on Earth, providing information about the energy, type, and direction of the primary cosmic particle, by different means. Important examples of such atmospheric detection techniques include the measurement of muons with particle counters at the Earth’s surface and the measurement of Cherenkov or Fluorescence light emitted during the air shower development. The connection between measured quantities like particle numbers or light intensity and original quantities like particle energy or type is in all cases inferred using simulations of particle collisions and cascades in the atmosphere.<br />
<br />
The goal of this master project is to exploit data of proton collisions measured with ATLAS, an experiment at the Large Hadron Collider (LHC), the highest energy human particle collider currently operating at CERN in Geneva (Switzerland), to test and improve simulations of particle collisions in the atmosphere up to the highest known energies (a few times 1020 eV). The student will work on ATLAS data analysis and Monte Carlo simulations of particle collisions, both for simulating proton colliding in ATLAS and cosmic-ray protons colliding with air molecules in the atmosphere. The ultimate goal is to improve Monte Carlo model predictions used for experiments like the upcoming CTA (http://www.cta-observatory.org/) and Auger (http://www.auger.org/).<br />
<br />
''Contact: [mailto:d.berge@nikhef.nl David Berge], [mailto:david.salek@cern.ch David Salek]''<br />
<br />
=== ATLAS : Beyond Standard Model with multiple leptons ===<br />
<br />
The Standard Model of particle physics (SM) is extremely successful, but would it hold against of check of with data containing multiple leptons? Although very rare process, the production of leptons is calculated in SM with high precision. On detector side the leptons (electrons and muons) are easy to reconstruct and such a sample contains very little "non-lepton" background. This analysis has a very ambitious goal to test many final states at once, without over-tuning for a specific model. The second step would then be to test obtained results against models of composite structure of leptons or presence of heavy right handed neutrinos favored in seesaw theories. With this project, the student would gain close familiarity with modern experimental techniques (statistical analysis, SM background estimates, etc.), with Monte Carlo generators and the standard HEP analysis tools (ROOT, C++, etc.).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina]''<br />
<br />
=== ATLAS : Search for supersymmetric dark matter-like particles ===<br />
<br />
Supersymmetry is a theory of physics beyond the Standard Model of particle physics that makes a link between fermions and bosons. Apart from many other attractive features, supersymmetry also predicts a particle that may be a candidate for dark matter. Such particles, and their related particles, may be produced at the LHC. Searching for them, however, is challenging. The production cross-sections are small, and the final states are difficult to measure, for example because the final state particles may have little energy, and are ignored by the ATLAS trigger and reconstruction software. In this project we will investigate the measurement of such particles, with the aim to improve the current ATLAS search strategy. You will then apply the improved analysis to the ATLAS data (to be) collected in 2016. In the project you will learn modern experimental analysis techniques, as well as programming in ROOT and C++.<br />
<br />
''Contact: [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
=== ATLAS inner tracker upgrade ===<br />
<br />
Research description: One of the key sub-systems of the ATLAS experiment at the Large Hadron Collider (LHC) is the Inner Detector (ID), designed to provide excellent charged particles momentum and vertex resolution measurements.<br />
At Phase-2 of the LHC run the operating luminosity of the collider will be increased significantly. This will imply an upgrade of all ATLAS subsystems. In particular, the ID will be fully replaced with a tracker completely made of Silicon, having higher granularity and radiation hardness. The R&D process for the new ATLAS ID is now ongoing. Different geometrical layouts are simulated and their performance is studied under different operating conditions in search for the optimal detector architecture. Also, the performance of the new Si-sensors/modules is under investigation with dedicated laboratory tests.<br />
The focus of the project could be on the simulation of the High-Luminosity LHC version of the ATLAS Inner Detector. The student will learn how a high-energy physics experiment is designed and optimized. Alternatively, if possible at that moment, the student could work on a project at the Nikhef Silicon laboratory at the test-bench for new ATLAS Si-strip detectors and participate in the quality assurance procedure for the new ATLAS Si detectors. <br />
<br />
''Contact: [mailto:Peter.Vankov@cern.NOSPAMch Peter Vankov]''<br />
<br />
<br />
=== ATLAS : Model testing for Beyond the Standard Model Higgs ===<br />
Recently there's been a lot of excitement about hints for new Beyond the Standard Model (BSM) physics. When the search for the Higgs was ongoing we had a model to test possible bumps against, now we are looking for any new particle and there are many models available. Testing the newest results from the LHC is challenging because of low statistics and model uncertainties. In this project we will investigate different BSM Higgs models that could possible explain the newest results of the LHC. For this we will use the data collected in 2015 and the data that will be collected in 2016. In the end we will set limits on the tested models (or discover a new particle). During the project you will learn modern experimental analysis techniques as well as programming.<br />
<br />
''Contact: [mailto:verkerke@nikhef.nl Wouter Verkerke], [mailto:lbrenner@nikhef.nl Lydia Brenner]''<br />
<br />
=== Theory & ATLAS: How to violate lepton flavour? ===<br />
<br />
One of the big outstanding questions in particle physics is what has caused the matter-antimatter asymmetry in the Universe. One of the possible solutions is related to processes that violate lepton flavour. Such phenomena could be observable in the ATLAS experiment at the Large Hadron Collider. In fact, recent data show a hint for the violation of lepton flavour in the decay of the Higgs boson into a mu and tau lepton. However, additional experimental and theoretical investigations are necessary to further probe this very interesting phenomenon. The goal of this project is to identify complementary lepton flavour violating processes and to study correlations between them and other flavour probes. The work will involve theoretical calculations and a classification of the most useful observables for the ATLAS experiment.<br />
<br />
''Contact: [mailto:devries.jordy@gmail.com Jordy de Vries], [mailto:olya@nikhef.nl Olya Igonkina], [mailto:Robert.Fleischer@nikhef.nl Robert Fleischer]''<br />
<br />
=== KM3NeT : Reconstruction of first neutrinos in KM3NeT ===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first string with sensitive photodetectors has been deployed end of 2015, in total 30 will be deployed til end of 2017. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. The performance and calibration of the detector will be evaluated also in comparison with simulations. Procedures to identify and also optimally reconstruct the directions of the muons and neutrinos will be developed to verify the performance and potential of the detector and to pave the path towards the neutrino astronomy. Programming skills are essential, mostly root and C++ will be used.<br />
<br />
''Contact: [mailto:rbruijn@nikhef.nl Ronald Bruijn]''<br />
<br />
=== Neutrino mass hierarchy with KM3NeT/ORCA ===<br />
<br />
Neutrinos exist in three flavors and are known to oscillate between flavors whereby the detected flavor depends on the (partly) known oscillation parameters, the mass differences, their energy and travel length. The neutrino telescope KM3NeT is planning for a dedicated set of detection units in order to pursue an oscillation measurement of an unprecedented precision using neutrinos from atmospheric interactions and with this enabling the measurement of the so far still unknown neutrino mass hierarchy. The measurement of this subtle effect requires unprecedented precision in the reconstruction and identification of the flavor, energy and direction. Various projects are available in the reconstruction and evaluation of the mass hierarchy using dedicated simulations. Programming skills are essential, mainly C++ and root will be used.<br />
<br />
''Contact: [mailto:aart.heijboer@nikhef.nl Aart Heijboer]''<br />
<br />
=== All-flavor-neutrino analysis of ANTARES data ===<br />
<br />
The ANTARES neutrino telescope has been taking data continuously since 2007. Most analyses of the data have been performed using the signature of a muon neutrino interaction whereby a long track can be reconstructed in the detector.<br />
Recent developments allowed for the first time also the reconstruction of a cascade signature in the detector at high angular resolution so that also electron and tau neutrino interactions can be detected (here these two are not distinguishable from each other). A search for neutrinos from cosmic sources on the first 6 years of data has by now been accomplished using this new reconstruction. In this project this search will be continued and exploited also on 2 more years of data for a dedicated optimized analysis of the Galactic Center to probe the possible neutrino emission from this highly interesting region.<br />
Programming skills are essential, mainly C++ and root will be used.<br />
Also other options for analyses of the ANTARES data are available.<br />
<br />
''Contact: [mailto:dosamt@nikhef.nl Dorothea Samtleben]''<br />
<br />
=== ALICE: Particle Polarization in Strong Magnetic Fields ===<br />
When two atomic nuclei, moving in opposite directions, collide off- center then the Quark Gluon Plasma (QGP) created in the overlap zone is expected to rotate. The nucleons not participating in the collision represent electric currents generating an intense magnetic field. The magnetic field could be as large as 10^{18} gauss, orders of magnitude larger than the strongest magnetic fields found in astronomical objects. Proving the existence of the rotation and/or the magnetic field could be done by checking if particles with spin are aligned with the rotation axis or if charged particles have different production rates relative to the direction of the magnetic field. In particular, the longitudinal and transverse polarisation of the Lambda^0 baryon will be studied. This project requires some affinity with computer programming. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''<br />
<br />
=== ALICE: Forward Particle Production from the Color Glass Condensate === <br />
It has been proposed that a new state of matter (the color-glass condensate, or CGC) may provide a universal description of hadronic collisions (e.g. proton-proton collisions) at very high energy. The CGC may be seen as the classical field limit of Quantum Chromodynamics, and a framework for calculating observables from this state has been developed. Several measurements are consistent with the assumption of a CGC, but no experimental proof exists so far. In this project we intend to perform a systematic study of the sensitivity to the CGC of different possible measurements at the LHC. The work will be performed in close collaboration with an external world expert in this field. It is advantageous to have a good background in theoretical physics. (contact: T. Peitzmann, M. van Leeuwen)<br />
Blast-Wave Model in Heavy-Ion collisions<br />
The goal of heavy-ion physics is to study the Quark Gluon Plasma (QGP), a hot and dense medium where quarks and gluons move freely over large distances, larger than the typical size of a hadron. Hydrodynamic simulations expect that the QGP will expand under its own pressure, and cool while expanding. These simulations are particularly successful in describing some of the key observables measured experimentally, such as particle spectra and elliptic flow. A reasonable reproduction of the same observables is also achieved with models that use parameterisations that resemble the hydrodynamical evolution of the system assuming a given freeze-out scenario, usually referred to as blast-wave models. The goal of this project is to work on different blast wave parametrisations, test their dependence on the input parameters and extend their applicability by including more observables studied in heavy-ion collisions in the global fit. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''<br />
<br />
=== ALICE: Energy Loss of Energetic Quarks and Gluons in the Quark-Gluon Plasma ===<br />
One of the ways to study the quark-gluon plasma that is formed in high-energy nuclear collisions, is using high-energy partons (quarks or gluons) that are produced early in the collision and interact with the quark-gluon plasma as they propagate through it. There are several current open questions related to this topic, which can be explored in a Master's project. For example, we would like to use a new Monte Carlo generator model (JEWEL) of the collision to see whether we can measure the shape of the collision region using measurements of hadron pairs. In the project you will collaborate with one the PhD students in our group to use the model to generate predictions of measurements and compare those to data analysis results. Depending on your interests, the project can focus more on the modeling aspects or on the analysis of experimental data from the ALICE detector at the LHC. <br />
<br />
''Contact: [mailto:marco.van.leeuwen@nikhef.nl M. van Leeuwen]''<br />
<br />
=== ALICE: Chiral Magnetic Effect and the Strong CP Problem === <br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, which is called Chiral Magnetic Effect (CME). The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, but background effects have not yet been properly disentangled. In this project you will develop and test new observables of the CME, trying to understand and discriminate the background sources that affects such a measurement. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''<br />
<br />
=== ALICE: Quantum Coherence in Particle Production with Intensity Interferometry ===<br />
Intensity interferometry – also known as HBT-effect or Bose-Einstein-correlations – is a method to study the space-time structure of the particle-emitting source in high-energy physics. The main interest so far has been on the width of correlation functions in momentum space, which reflects the space-time information. The strength of the correlation also carries information, but this has been ignored by many people. The correlation strength is in particular influenced by the degree of coherence of particle production. Recently new studies have been performed to extract this degree of coherence, however, many other effects might distort such a measurement, in particular the production of pions via resonance decay. In this project we will study the role of resonance decays for a measurement of coherence in intensity interferometry and try to establish possible correction methods for any distortions they may cause. We will perform theoretical model calculations with Monte-Carlo simulation methods.<br />
<br />
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann]''<br />
<br />
=== ALICE: Higher Harmonic Flow ===<br />
When two ions collide, if the impact parameter is not zero, the overlap region is not isotropic. This spatial anisotropy of the overlap region is transformed into an anisotropy in momentum space through interactions between partons and at a later stage between the produced particles. It was recently realized that the overlap region of the colliding nuclei exhibits an irregular shape. These irregularities originate from the initial density profile of nucleons participating in the collision which is not smooth and is different from one event to the other. The resulting higher order flow harmonics (e.g. v3, v4, and v5, usually referred to as triangular, quadrangular, and pentangular flow, respectively) and in particular their transverse momentum dependence are argued to be more sensitive probes than elliptic flow not only of the initial geometry and its fluctuations but also of shear viscosity over entropy density (η/s). The goal of this project is to study v3, v4, and v5 for identified particles in collisions of heavy-ions at the LHC. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''<br />
<br />
=== ALICE: A New Detector for Very High-Energy Photons: FoCal === <br />
High-energy photons are important messenger particles in particle physics. In particular direct photons (i.e. directly produced from elementary scattering processes) are interesting, but it is a difficult task to discriminate them from the photons originating from particle decays. Existing detector have limited capabilities for such a discrimination, in particular at the highest energies. Our institute has pioneered a detector based on a new concept, a digital pixel calorimeter with Si-sensors of unprecedented granularity. First proof-of-principle measurements have already been performed. In this project we will study the performance of a particular detector design for measurements of direct photons at the LHC and optimize the design parameters for such a measurement. Performance studies for other measurements – e.g. jets, J/ψ, or ϒ particles – may be carried out in addition. <br />
<br />
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann] [mailto:marco.van.leeuwen@nikhef.nl M. van Leeuwen]''<br />
<br />
=== ALICE: Thermal Photon Emission: Quark-Gluon Plasma or Hadron Gas? ===<br />
Recently, measurements of thermal photon emission in high-energy nuclear collisions have been performed at RHIC and at LHC. It is generally believed that a quark-gluon plasma equation of state is the natural description of the hot initial phase of these collisions, and so far only theoretical model calculations including such a phase have been compared to those measurements. In this project we will revisit hadron gas models and try to reproduce the thermal photon yield together with other observables. In this work we will use and possibly modify Monte Carlo implementations of relativistic hydrodynamics, tune it to existing data of hadron production and then estimate the photon production from the same model. The model implementation will be based on previous work of external theoretical colleagues and will be carried out in collaboration with them.<br />
<br />
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann]''<br />
<br />
=== A New Detector for Proton Therapy and Proton Computed Tomography ===<br />
Conventional imaging of humans in medical treatment relies mostly on electromagnetic radiation (CT, MRT) or positrons (PET). A recently proposed new imaging strategy, in particular in the context of proton therapy for cancer treatment, is to use proton beams. Current detectors for the scattered protons have severe limitations, in particular for their precision and measurement times. New development of intelligent Si-sensors in particle physics offer possibilities to develop much more efficient detectors for such proton CT measurements. We will perform R&D on the use of new silicon pixel detectors developed in the context of the ALICE experiment at CERN for such medical applications. Studies will include Monte-Carlo simulations of a possible detector setup and measurements with the first samples of the appropriate silicon sensors, which will become available in early 2016. The project will be carried out in the context of a scientific collaboration with Bergen University, Norway. <br />
<br />
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann]''<br />
<br />
=== Medical X-ray Imaging ===<br />
With the upcoming of true multi-threshold X-Ray detectors the possibilities for Spectral Imaging with low dose, including spectral CT, is now a reality around the corner. The Medipix3RX chip, from the Medipix Collaboration (CERN) features up to 8 programmable thresholds which can select energy bins without a threshold scan. A number of projects could be derived from the R&D activities with the Medipix3RX within the Nikhef R&D group on X-ray imaging for medical applications: <br />
* Medipix3RX characterization in all its operation modes and gains. <br />
* Spectral CT and scarce sampling 3D reconstruction <br />
* Charge sharing: the charge-sum capabilities of the chip can be exploited to further understand the problem of charge sharing in pixelized detectors. A combination of the characterization of the charge-summing mode plus the use of both planar, and 3D sensors, at the light of MC simulation, could reveal valuable information about charge sharing.<br />
<br />
''Contact: [mailto:johnid@nikhef.nl John Idarraga],[mailto:nielsvb@nihef.nl Niels van Bakel]''<br />
<br />
=== Compton camera ===<br />
In the Nikhef R&D group we develop instrumentation for particle physics but we also investigate how particle physics detectors can be used for different purposes. A succesfull development is the Medipix chip that can be used in Xray imaging. For use in large scale medical applications compton scattering limits however the energy resolving possibilities. You will investigate whether it is in principle possible to design a Xray application that detects the compton scattered elctron and the absorbed photon. Your ideas can be tested in practice in the lab where a Xray scan can be performed.<br />
<br />
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman]''<br />
<br />
=== The Modulation experiment ===<br />
There exist a few measurements that suggest an annual modulation in the activity of radioactive sources. With a few groups from the XENON collaboration we have developed four sets of table-top experiments to investigate this effect on a few well known radioactive sources. The experiments are under construction in Purdue University (USA), a mountain top in Switzerland, a beach in Rio de Janeiro and the last one at Nikhef in Amsterdam. We urgently need a master student to (1) do the final commissioning of the experiment, (2) collect the 1st big data set, and (3) analyse the first data. We are looking for an all-round physicist with interest in both lab-work and data-analysis. The student will directly collaborate with the other groups in this small collaboration (around 10 people), and the goal is to have the first publication ready by the end of the project.<br />
<br />
''Contact: [mailto:colijn@nikhef.nl Auke Colijn]''<br />
<br />
=== Acoustic detection of ultra-high energy cosmic-ray neutrinos ===<br />
The study of the cosmic neutrinos of energies above 10^17 eV, so-called ultra-high<br />
energy neutrinos, provides a unique view on the universe and may provide insight in<br />
the origin of the most violent sources, such as gamma ray bursts, supernovae or even<br />
dark matter. The energy deposition of cosmic neutrinos in water induces a thermo-acoustic<br />
signal, which can be detected using sensitive hydrophones. The expected neutrino<br />
flux is however extremely low and the signal that neutrinos induce is small. TNO<br />
is presently developing sensitive hydrophone technology that is based on fiber optics.<br />
Optical fibers form a natural way to create a distributed sensing system. Using this<br />
technology a large scale neutrino telescope can be built in the deep sea. TNO is aiming<br />
for a prototype hydrophone which will form the building block of a future telescope.<br />
<br />
Students have the possibility to participate to this project is the following ways:<br />
(i) Modeling of cosmic rays induced acoustic signal in a neutrino telescope.<br />
Keywords: Cosmic rays, Monte Carlo, signal processing, telescope optimization.<br />
(ii) Testing and optimization of fiber optical hydrophone for a large scale neutrino<br />
telescope. Keywords: Experimental, physics, system design.<br />
<br />
The work will be (partly) executed in Delft. <br />
<br />
''Contact: [mailto:ernst-jan.buis@tno.NOSPAMnl Ernst-Jan Buis]''<br />
<br />
=== LHCb: A Scintillator Fibers Tracker ===<br />
<br />
The LHCb collaboration is upgrading the present tracking system<br />
constructing a new tracker based on scintillating fibers combined<br />
with silicon photo-multipliers (SiPM): the SciFi Tracker!<br />
Nikhef plays a key role in the project, as we will build the<br />
SciFi fibers modules, the cold-box enclosure housing the SiPMs,<br />
and a large part of the on-detector electronics. In all these<br />
areas, interesting test hardware and software has to be realized,<br />
and several research topics for a Master project are available,<br />
taking the student in contact with state-of-the-art particle detectors,<br />
in a large team of physicists and engineers. Possible collaborations<br />
with the Nikhef R&D group can also be envisaged.<br />
<br />
''Contact: [mailto:antonio@nikhef.nl Antonio Pellegrino]''<br />
<br />
=== LHCb: Discovery of the Decay Lb --> p Ds+ ===<br />
This project aims to measure the branching fraction of the decay Lb->p Ds+ (bud -> uud + ds). <br />
The decay Lb->p Ds+ is quite rare, because it occurs through the transition of a b-quark to a u-quark. <br />
It has not been measured yet (although some LHCb colleagues claim to have seen it).<br />
This decay is interesting, because <br />
<br />
1) It is sensitive to the b->u coupling (CKM-element Vub), which determination is heavily debated.<br />
2) It can quantify non-factorisable QCD effects in b-baryon decays.<br />
<br />
The decay is closely related to B0->pi-Ds+, which proceeds through a similar Feynman diagram. <br />
Also, the final state of B0->pi-Ds+ is almost identical to Lb->p Ds+. <br />
The aim is to determine the relative branching fraction of Lb->pDs+ with respect to B0->D+pi- decays, <br />
in close collaboration with the PhD (who will study BR(B0->pi-Ds+)/BR(B0->D+pi-) ).<br />
This project will result in a journal publication on behalf of the LHCb collaboration, written by you. <br />
For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. <br />
This is a project that is closely related to previous analyses in the group. <br />
Weekly video meetings with CERN coordinate the efforts with in the LHCb collaboration.<br />
Relevant information:<br />
<br />
[1] R.Aaij et al. [LHCb Collaboration], ``Determination of the branching fractions of B0s->DsK and B0->DsK, JHEP 05 (2015) 019 [arXiv:1412.7654 [hep-ex]].<br />
[2] R. Fleischer, N. Serra and N. Tuning, ``Tests of Factorization and SU(3) Relations in B Decays into Heavy-Light Final States, Phys. Rev. D 83, 014017 (2011) [arXiv:1012.2784 [hep-ph]].<br />
<br />
''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''<br />
<br />
=== LHCb: A search for heavy neutrinos in the decay of W bosons at LHCb ===<br />
<br />
Neutrinos are arguably the most mysterious of all known fundamental fermions as they are both much lighter than all others and only weakly interacting. It is thought that the tiny mass of neutrinos can be explained by their mixing with so-far unknown, much heavier, neutrino-like particles. In this research proposal we look for these new neutrinos in the decay of the SM W-boson using data with the LHCb experiment at CERN. The W boson is assumed to decay to a heavy neutrino and a muon. The heavy neutrino subsequently decays to a muon and a pair of quarks. Both like-sign and opposite-sign muon pairs will be studied. The result of the analysis will either be a limit on the production of the new neutrinos or the discovery of something entirely new.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen and Elena Dall'Occo]''<br />
<br />
<br />
=== LHCb: A search for Majorana neutrinos in the decay of Bc mesons at LHCb ===<br />
<br />
Neutrinos can either be their own anti-particles, in which case they are called "Majorana" particles, or Dirac fermions. It is thought that the tiny mass of neutrinos can be explained by their mixing with so-far unknown, much heavier, neutrino-like particles. LHCb has looked for off-shell Majorana neutrinos in the decays B+->pi-mu+mu+ and B+->D(*)-mu+mu+. Both decays suffer from suppression from Cabibbo-Kobayashi-Maskawa matrix elements, or from low reconstruction efficiencies. Although its production rate is much lower, the Bc meson provides a potentially more promising decay channel: Bc->J/psimu+mu+pi-. The Master student will design and optimise a selection, study potential backgrounds and perform a search in view of setting a stringent limit, or an observation of new physics.<br />
<br />
arXiv:1401.5361 [hep-ex]. arXiv:1201.5600 [hep-ex]. arXiv:11602.09112 [hep-ph]<br />
<br />
''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg and Flavio Archilli]''</div>Rojo@nikhef.nlhttps://wiki.nikhef.nl/education/index.php?title=Master_Projects&diff=112Master Projects2016-10-18T08:33:42Z<p>Rojo@nikhef.nl: </p>
<hr />
<div>'''Master Thesis Research Projects'''<br />
<br />
The following Master thesis research projects are offered at Nikhef. If you are interested in one of these projects, please contact the coordinator listed with the project. <br />
<br />
[MORE PROJECTS TO COME!]<br />
<br />
[[Last years MSc Projects|Last year's MSc Projects]]<br />
<br />
=== Theory – Constraining the proton structure with Run II LHC data ===<br />
<br />
The non-perturbative dynamics that determine the energy distribution of quarks and gluons inside protons, the so-called parton distribution functions (PDFs), cannot be computed from first principles from Quantum Chromodynamics (QCD), and need to be determined from experimental data. PDFs are an essential ingredient for the scientific program at the Large Hadron Collider (LHC), from Higgs characterisation to searches for New Physics beyond the Standard Model. One recent breakthrough in PDF analysis has been the exploitation of the constraints from LHC data. From direct photons to top quark pair production cross-sections and charmed meson differential distributions, LHC measurements are now a central ingredient of PDF fits, providing important information on poorly-known PDFs such as the large and small-x gluon or the large-x antiquarks. With the upcoming availability of data from the Run II of the LHC, at a center-of-mass energy of 13 TeV, these constraints are expected to become even more stringent.<br />
<br />
In this project, the implications of PDF-sensitive measurements at the LHC 13 TeV will be quantified. Processes that will be considered include jet and dijet production at the multi-TeV scale, single-top quark production, and weak boson production in association with heavy quarks, among several others. These studies will be performed using the NNPDF fitting framework, based on artificial neural networks and genetic algorithms. The phenomenological implications of the improved PDF modelling for Higgs and new physics searches at the LHC will also be explored. Additional information on this project can be found [http://pcteserver.mi.infn.it/~nnpdf/talks/MSc_projects/2017-MasterProject-PDFs.pdf|here].<br />
<br />
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''<br />
<br />
=== Extreme Astronomy – Preparing for CTA, the Next-Generation Gamma-Ray Observatory ===<br />
<br />
The Cherenkov Telescope Array (CTA) is a planned facility for measuring gamma rays from space covering more than four orders of magnitude in energy, up to energies exceeding 100 TeV. CTA employs the imaging atmospheric Cherenkov technique to measure properties of cosmic gamma rays. This technique is based on measuring Cherenkov light emitted during the development of a gamma-ray air shower. CTA will be built at two experimental sites, one in the Northern, one in the Southern hemisphere, and will consist of up to 100 telescopes. It represents a major leap forward in sensitivity and precision for gamma-ray astronomy, and will allow us to explore very-high-energy processes of the extreme Universe at an unprecedented level.<br />
<br />
Several master projects are available in the CTA group of UvA and the students will participate in photonic and electronic R&D studies contributing to the starting phase of CTA. These studies will either focus on laboratory-based measurements or simulations of novel kinds of single-photon detectors, referred to as silicon photomultipliers (SiPMs). By means of these simulations the performance of SiPMs used for arrays of Cherenkov telescopes will be assessed and their optimal operational parameters will be evaluated. Within one of the laboratory-based projects different types of SiPMs will be characterised and a measuring system to calibrate the photosensors will be designed and operated. In a different project various imaging and non-imaging light sources will be used to study the trigger performance of a CTA prototype camera.<br />
<br />
''Contact: [mailto:d.berge@nikhef.nl David Berge], [mailto:maurice.stephan@uva.nl Maurice Stephan]''<br />
<br />
=== The XENON Dark Matter Experiment: Data Analysis ===<br />
<br />
The XENON collaboration is currently commissioning the XENON1T detector, soon to be the world’s most sensitive direct detection dark matter experiment, with the Nikhef group playing an important role in this work. The detector operates at the Gran Sasso underground laboratory and consists of a so-called dual-phase xenon time-projection chamber filled with 3500kg of ultra-pure xenon. Our group has an opening for a motivated MSc student to do data-analysis on this new detector. The work will consist of understanding the signals that come out of the detector and in particular focus on the so-called double scatter events. We are interested in developing methods in order to interpret the response of the detector better and are developing sophisticated statistical tools to do this. This work will include looking at data and developing new algorithms in our Python-based analysis tool. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== XAMS Dark Matter R&D Setup ===<br />
<br />
The Amsterdam Dark Matter group has built an R&D xenon detector at Nikhef. The detector is a dual-phase xenon time-projection chamber and contains about 4kg of ultra-pure liquid xenon. We plan to use this detector for the development of new detection techniques (such as utilizing new photosensors) and to improve the understanding of the response of liquid xenon to various forms of radiation. The results could be directly used in the XENON experiment, the world’s most sensitive direct detection dark matter experiment at the Gran Sasso underground laboratory. We have several interesting projects for this facility. We are looking for someone who is interested in working in a laboratory on high-tech equipment, modifying the detector, taking data and analyzing the data him/herself. You will "own" this experiment. <br />
<br />
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''<br />
<br />
=== ATLAS : Astroparticle Physics at the LHC ===<br />
<br />
Understanding particle acceleration up to very high energies in the Universe requires Earth-bound experimental techniques that exploit the Earth’s atmosphere as detection medium. Only the shear size of the atmosphere provides a sufficiently large sensitive area to measure the very rare highest energy particles from the cosmos as they impinge on the Earth. The idea of the atmospheric measurement is simple: a cosmic particle hitting the atmosphere is being absorbed by developing into an air shower, a spray of secondary particles that originates in the collision of the primary cosmic particle with air molecules, and successive interactions of those secondary particles in the atmosphere. Such air showers can be traced and therefore measured on Earth, providing information about the energy, type, and direction of the primary cosmic particle, by different means. Important examples of such atmospheric detection techniques include the measurement of muons with particle counters at the Earth’s surface and the measurement of Cherenkov or Fluorescence light emitted during the air shower development. The connection between measured quantities like particle numbers or light intensity and original quantities like particle energy or type is in all cases inferred using simulations of particle collisions and cascades in the atmosphere.<br />
<br />
The goal of this master project is to exploit data of proton collisions measured with ATLAS, an experiment at the Large Hadron Collider (LHC), the highest energy human particle collider currently operating at CERN in Geneva (Switzerland), to test and improve simulations of particle collisions in the atmosphere up to the highest known energies (a few times 1020 eV). The student will work on ATLAS data analysis and Monte Carlo simulations of particle collisions, both for simulating proton colliding in ATLAS and cosmic-ray protons colliding with air molecules in the atmosphere. The ultimate goal is to improve Monte Carlo model predictions used for experiments like the upcoming CTA (http://www.cta-observatory.org/) and Auger (http://www.auger.org/).<br />
<br />
''Contact: [mailto:d.berge@nikhef.nl David Berge], [mailto:david.salek@cern.ch David Salek]''<br />
<br />
=== ATLAS : Beyond Standard Model with multiple leptons ===<br />
<br />
The Standard Model of particle physics (SM) is extremely successful, but would it hold against of check of with data containing multiple leptons? Although very rare process, the production of leptons is calculated in SM with high precision. On detector side the leptons (electrons and muons) are easy to reconstruct and such a sample contains very little "non-lepton" background. This analysis has a very ambitious goal to test many final states at once, without over-tuning for a specific model. The second step would then be to test obtained results against models of composite structure of leptons or presence of heavy right handed neutrinos favored in seesaw theories. With this project, the student would gain close familiarity with modern experimental techniques (statistical analysis, SM background estimates, etc.), with Monte Carlo generators and the standard HEP analysis tools (ROOT, C++, etc.).<br />
<br />
''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina]''<br />
<br />
=== ATLAS : Search for supersymmetric dark matter-like particles ===<br />
<br />
Supersymmetry is a theory of physics beyond the Standard Model of particle physics that makes a link between fermions and bosons. Apart from many other attractive features, supersymmetry also predicts a particle that may be a candidate for dark matter. Such particles, and their related particles, may be produced at the LHC. Searching for them, however, is challenging. The production cross-sections are small, and the final states are difficult to measure, for example because the final state particles may have little energy, and are ignored by the ATLAS trigger and reconstruction software. In this project we will investigate the measurement of such particles, with the aim to improve the current ATLAS search strategy. You will then apply the improved analysis to the ATLAS data (to be) collected in 2016. In the project you will learn modern experimental analysis techniques, as well as programming in ROOT and C++.<br />
<br />
''Contact: [mailto:h26@nikhef.nl Paul de Jong]''<br />
<br />
=== ATLAS inner tracker upgrade ===<br />
<br />
Research description: One of the key sub-systems of the ATLAS experiment at the Large Hadron Collider (LHC) is the Inner Detector (ID), designed to provide excellent charged particles momentum and vertex resolution measurements.<br />
At Phase-2 of the LHC run the operating luminosity of the collider will be increased significantly. This will imply an upgrade of all ATLAS subsystems. In particular, the ID will be fully replaced with a tracker completely made of Silicon, having higher granularity and radiation hardness. The R&D process for the new ATLAS ID is now ongoing. Different geometrical layouts are simulated and their performance is studied under different operating conditions in search for the optimal detector architecture. Also, the performance of the new Si-sensors/modules is under investigation with dedicated laboratory tests.<br />
The focus of the project could be on the simulation of the High-Luminosity LHC version of the ATLAS Inner Detector. The student will learn how a high-energy physics experiment is designed and optimized. Alternatively, if possible at that moment, the student could work on a project at the Nikhef Silicon laboratory at the test-bench for new ATLAS Si-strip detectors and participate in the quality assurance procedure for the new ATLAS Si detectors. <br />
<br />
''Contact: [mailto:Peter.Vankov@cern.NOSPAMch Peter Vankov]''<br />
<br />
<br />
=== ATLAS : Model testing for Beyond the Standard Model Higgs ===<br />
Recently there's been a lot of excitement about hints for new Beyond the Standard Model (BSM) physics. When the search for the Higgs was ongoing we had a model to test possible bumps against, now we are looking for any new particle and there are many models available. Testing the newest results from the LHC is challenging because of low statistics and model uncertainties. In this project we will investigate different BSM Higgs models that could possible explain the newest results of the LHC. For this we will use the data collected in 2015 and the data that will be collected in 2016. In the end we will set limits on the tested models (or discover a new particle). During the project you will learn modern experimental analysis techniques as well as programming.<br />
<br />
''Contact: [mailto:verkerke@nikhef.nl Wouter Verkerke], [mailto:lbrenner@nikhef.nl Lydia Brenner]''<br />
<br />
=== Theory & ATLAS: How to violate lepton flavour? ===<br />
<br />
One of the big outstanding questions in particle physics is what has caused the matter-antimatter asymmetry in the Universe. One of the possible solutions is related to processes that violate lepton flavour. Such phenomena could be observable in the ATLAS experiment at the Large Hadron Collider. In fact, recent data show a hint for the violation of lepton flavour in the decay of the Higgs boson into a mu and tau lepton. However, additional experimental and theoretical investigations are necessary to further probe this very interesting phenomenon. The goal of this project is to identify complementary lepton flavour violating processes and to study correlations between them and other flavour probes. The work will involve theoretical calculations and a classification of the most useful observables for the ATLAS experiment.<br />
<br />
''Contact: [mailto:devries.jordy@gmail.com Jordy de Vries], [mailto:olya@nikhef.nl Olya Igonkina], [mailto:Robert.Fleischer@nikhef.nl Robert Fleischer]''<br />
<br />
=== KM3NeT : Reconstruction of first neutrinos in KM3NeT ===<br />
<br />
The neutrino telescope KM3NeT is under construction in the Mediterranean Sea aiming to detect cosmic neutrinos. Its first string with sensitive photodetectors has been deployed end of 2015, in total 30 will be deployed til end of 2017. Already these few strings provide for the option to reconstruct in the detector the abundant muons stemming from interactions of cosmic rays with the atmosphere and to identify neutrino interactions. The performance and calibration of the detector will be evaluated also in comparison with simulations. Procedures to identify and also optimally reconstruct the directions of the muons and neutrinos will be developed to verify the performance and potential of the detector and to pave the path towards the neutrino astronomy. Programming skills are essential, mostly root and C++ will be used.<br />
<br />
''Contact: [mailto:rbruijn@nikhef.nl Ronald Bruijn]''<br />
<br />
=== Neutrino mass hierarchy with KM3NeT/ORCA ===<br />
<br />
Neutrinos exist in three flavors and are known to oscillate between flavors whereby the detected flavor depends on the (partly) known oscillation parameters, the mass differences, their energy and travel length. The neutrino telescope KM3NeT is planning for a dedicated set of detection units in order to pursue an oscillation measurement of an unprecedented precision using neutrinos from atmospheric interactions and with this enabling the measurement of the so far still unknown neutrino mass hierarchy. The measurement of this subtle effect requires unprecedented precision in the reconstruction and identification of the flavor, energy and direction. Various projects are available in the reconstruction and evaluation of the mass hierarchy using dedicated simulations. Programming skills are essential, mainly C++ and root will be used.<br />
<br />
''Contact: [mailto:aart.heijboer@nikhef.nl Aart Heijboer]''<br />
<br />
=== All-flavor-neutrino analysis of ANTARES data ===<br />
<br />
The ANTARES neutrino telescope has been taking data continuously since 2007. Most analyses of the data have been performed using the signature of a muon neutrino interaction whereby a long track can be reconstructed in the detector.<br />
Recent developments allowed for the first time also the reconstruction of a cascade signature in the detector at high angular resolution so that also electron and tau neutrino interactions can be detected (here these two are not distinguishable from each other). A search for neutrinos from cosmic sources on the first 6 years of data has by now been accomplished using this new reconstruction. In this project this search will be continued and exploited also on 2 more years of data for a dedicated optimized analysis of the Galactic Center to probe the possible neutrino emission from this highly interesting region.<br />
Programming skills are essential, mainly C++ and root will be used.<br />
Also other options for analyses of the ANTARES data are available.<br />
<br />
''Contact: [mailto:dosamt@nikhef.nl Dorothea Samtleben]''<br />
<br />
=== ALICE: Particle Polarization in Strong Magnetic Fields ===<br />
When two atomic nuclei, moving in opposite directions, collide off- center then the Quark Gluon Plasma (QGP) created in the overlap zone is expected to rotate. The nucleons not participating in the collision represent electric currents generating an intense magnetic field. The magnetic field could be as large as 10^{18} gauss, orders of magnitude larger than the strongest magnetic fields found in astronomical objects. Proving the existence of the rotation and/or the magnetic field could be done by checking if particles with spin are aligned with the rotation axis or if charged particles have different production rates relative to the direction of the magnetic field. In particular, the longitudinal and transverse polarisation of the Lambda^0 baryon will be studied. This project requires some affinity with computer programming. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''<br />
<br />
=== ALICE: Forward Particle Production from the Color Glass Condensate === <br />
It has been proposed that a new state of matter (the color-glass condensate, or CGC) may provide a universal description of hadronic collisions (e.g. proton-proton collisions) at very high energy. The CGC may be seen as the classical field limit of Quantum Chromodynamics, and a framework for calculating observables from this state has been developed. Several measurements are consistent with the assumption of a CGC, but no experimental proof exists so far. In this project we intend to perform a systematic study of the sensitivity to the CGC of different possible measurements at the LHC. The work will be performed in close collaboration with an external world expert in this field. It is advantageous to have a good background in theoretical physics. (contact: T. Peitzmann, M. van Leeuwen)<br />
Blast-Wave Model in Heavy-Ion collisions<br />
The goal of heavy-ion physics is to study the Quark Gluon Plasma (QGP), a hot and dense medium where quarks and gluons move freely over large distances, larger than the typical size of a hadron. Hydrodynamic simulations expect that the QGP will expand under its own pressure, and cool while expanding. These simulations are particularly successful in describing some of the key observables measured experimentally, such as particle spectra and elliptic flow. A reasonable reproduction of the same observables is also achieved with models that use parameterisations that resemble the hydrodynamical evolution of the system assuming a given freeze-out scenario, usually referred to as blast-wave models. The goal of this project is to work on different blast wave parametrisations, test their dependence on the input parameters and extend their applicability by including more observables studied in heavy-ion collisions in the global fit. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''<br />
<br />
=== ALICE: Energy Loss of Energetic Quarks and Gluons in the Quark-Gluon Plasma ===<br />
One of the ways to study the quark-gluon plasma that is formed in high-energy nuclear collisions, is using high-energy partons (quarks or gluons) that are produced early in the collision and interact with the quark-gluon plasma as they propagate through it. There are several current open questions related to this topic, which can be explored in a Master's project. For example, we would like to use a new Monte Carlo generator model (JEWEL) of the collision to see whether we can measure the shape of the collision region using measurements of hadron pairs. In the project you will collaborate with one the PhD students in our group to use the model to generate predictions of measurements and compare those to data analysis results. Depending on your interests, the project can focus more on the modeling aspects or on the analysis of experimental data from the ALICE detector at the LHC. <br />
<br />
''Contact: [mailto:marco.van.leeuwen@nikhef.nl M. van Leeuwen]''<br />
<br />
=== ALICE: Chiral Magnetic Effect and the Strong CP Problem === <br />
Within the Standard Model, symmetries, such as the combination of charge conjugation (C) and parity (P), known as CP-symmetry, are considered to be key principles of particle physics. The violation of the CP-invariance can be accommodated within the Standard Model in the weak and the strong interactions, however it has only been confirmed experimentally in the former. Theory predicts that in heavy-ion collisions gluonic fields create domains where the parity symmetry is locally violated. This manifests itself in a charge-dependent asymmetry in the production of particles relative to the reaction plane, which is called Chiral Magnetic Effect (CME). The first experimental results from STAR (RHIC) and ALICE (LHC) are consistent with the expectations from the CME, but background effects have not yet been properly disentangled. In this project you will develop and test new observables of the CME, trying to understand and discriminate the background sources that affects such a measurement. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''<br />
<br />
=== ALICE: Quantum Coherence in Particle Production with Intensity Interferometry ===<br />
Intensity interferometry – also known as HBT-effect or Bose-Einstein-correlations – is a method to study the space-time structure of the particle-emitting source in high-energy physics. The main interest so far has been on the width of correlation functions in momentum space, which reflects the space-time information. The strength of the correlation also carries information, but this has been ignored by many people. The correlation strength is in particular influenced by the degree of coherence of particle production. Recently new studies have been performed to extract this degree of coherence, however, many other effects might distort such a measurement, in particular the production of pions via resonance decay. In this project we will study the role of resonance decays for a measurement of coherence in intensity interferometry and try to establish possible correction methods for any distortions they may cause. We will perform theoretical model calculations with Monte-Carlo simulation methods.<br />
<br />
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann]''<br />
<br />
=== ALICE: Higher Harmonic Flow ===<br />
When two ions collide, if the impact parameter is not zero, the overlap region is not isotropic. This spatial anisotropy of the overlap region is transformed into an anisotropy in momentum space through interactions between partons and at a later stage between the produced particles. It was recently realized that the overlap region of the colliding nuclei exhibits an irregular shape. These irregularities originate from the initial density profile of nucleons participating in the collision which is not smooth and is different from one event to the other. The resulting higher order flow harmonics (e.g. v3, v4, and v5, usually referred to as triangular, quadrangular, and pentangular flow, respectively) and in particular their transverse momentum dependence are argued to be more sensitive probes than elliptic flow not only of the initial geometry and its fluctuations but also of shear viscosity over entropy density (η/s). The goal of this project is to study v3, v4, and v5 for identified particles in collisions of heavy-ions at the LHC. <br />
<br />
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''<br />
<br />
=== ALICE: A New Detector for Very High-Energy Photons: FoCal === <br />
High-energy photons are important messenger particles in particle physics. In particular direct photons (i.e. directly produced from elementary scattering processes) are interesting, but it is a difficult task to discriminate them from the photons originating from particle decays. Existing detector have limited capabilities for such a discrimination, in particular at the highest energies. Our institute has pioneered a detector based on a new concept, a digital pixel calorimeter with Si-sensors of unprecedented granularity. First proof-of-principle measurements have already been performed. In this project we will study the performance of a particular detector design for measurements of direct photons at the LHC and optimize the design parameters for such a measurement. Performance studies for other measurements – e.g. jets, J/ψ, or ϒ particles – may be carried out in addition. <br />
<br />
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann] [mailto:marco.van.leeuwen@nikhef.nl M. van Leeuwen]''<br />
<br />
=== ALICE: Thermal Photon Emission: Quark-Gluon Plasma or Hadron Gas? ===<br />
Recently, measurements of thermal photon emission in high-energy nuclear collisions have been performed at RHIC and at LHC. It is generally believed that a quark-gluon plasma equation of state is the natural description of the hot initial phase of these collisions, and so far only theoretical model calculations including such a phase have been compared to those measurements. In this project we will revisit hadron gas models and try to reproduce the thermal photon yield together with other observables. In this work we will use and possibly modify Monte Carlo implementations of relativistic hydrodynamics, tune it to existing data of hadron production and then estimate the photon production from the same model. The model implementation will be based on previous work of external theoretical colleagues and will be carried out in collaboration with them.<br />
<br />
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann]''<br />
<br />
=== A New Detector for Proton Therapy and Proton Computed Tomography ===<br />
Conventional imaging of humans in medical treatment relies mostly on electromagnetic radiation (CT, MRT) or positrons (PET). A recently proposed new imaging strategy, in particular in the context of proton therapy for cancer treatment, is to use proton beams. Current detectors for the scattered protons have severe limitations, in particular for their precision and measurement times. New development of intelligent Si-sensors in particle physics offer possibilities to develop much more efficient detectors for such proton CT measurements. We will perform R&D on the use of new silicon pixel detectors developed in the context of the ALICE experiment at CERN for such medical applications. Studies will include Monte-Carlo simulations of a possible detector setup and measurements with the first samples of the appropriate silicon sensors, which will become available in early 2016. The project will be carried out in the context of a scientific collaboration with Bergen University, Norway. <br />
<br />
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann]''<br />
<br />
=== Medical X-ray Imaging ===<br />
With the upcoming of true multi-threshold X-Ray detectors the possibilities for Spectral Imaging with low dose, including spectral CT, is now a reality around the corner. The Medipix3RX chip, from the Medipix Collaboration (CERN) features up to 8 programmable thresholds which can select energy bins without a threshold scan. A number of projects could be derived from the R&D activities with the Medipix3RX within the Nikhef R&D group on X-ray imaging for medical applications: <br />
* Medipix3RX characterization in all its operation modes and gains. <br />
* Spectral CT and scarce sampling 3D reconstruction <br />
* Charge sharing: the charge-sum capabilities of the chip can be exploited to further understand the problem of charge sharing in pixelized detectors. A combination of the characterization of the charge-summing mode plus the use of both planar, and 3D sensors, at the light of MC simulation, could reveal valuable information about charge sharing.<br />
<br />
''Contact: [mailto:johnid@nikhef.nl John Idarraga],[mailto:nielsvb@nihef.nl Niels van Bakel]''<br />
<br />
=== Compton camera ===<br />
In the Nikhef R&D group we develop instrumentation for particle physics but we also investigate how particle physics detectors can be used for different purposes. A succesfull development is the Medipix chip that can be used in Xray imaging. For use in large scale medical applications compton scattering limits however the energy resolving possibilities. You will investigate whether it is in principle possible to design a Xray application that detects the compton scattered elctron and the absorbed photon. Your ideas can be tested in practice in the lab where a Xray scan can be performed.<br />
<br />
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman]''<br />
<br />
=== The Modulation experiment ===<br />
There exist a few measurements that suggest an annual modulation in the activity of radioactive sources. With a few groups from the XENON collaboration we have developed four sets of table-top experiments to investigate this effect on a few well known radioactive sources. The experiments are under construction in Purdue University (USA), a mountain top in Switzerland, a beach in Rio de Janeiro and the last one at Nikhef in Amsterdam. We urgently need a master student to (1) do the final commissioning of the experiment, (2) collect the 1st big data set, and (3) analyse the first data. We are looking for an all-round physicist with interest in both lab-work and data-analysis. The student will directly collaborate with the other groups in this small collaboration (around 10 people), and the goal is to have the first publication ready by the end of the project.<br />
<br />
''Contact: [mailto:colijn@nikhef.nl Auke Colijn]''<br />
<br />
=== Acoustic detection of ultra-high energy cosmic-ray neutrinos ===<br />
The study of the cosmic neutrinos of energies above 10^17 eV, so-called ultra-high<br />
energy neutrinos, provides a unique view on the universe and may provide insight in<br />
the origin of the most violent sources, such as gamma ray bursts, supernovae or even<br />
dark matter. The energy deposition of cosmic neutrinos in water induces a thermo-acoustic<br />
signal, which can be detected using sensitive hydrophones. The expected neutrino<br />
flux is however extremely low and the signal that neutrinos induce is small. TNO<br />
is presently developing sensitive hydrophone technology that is based on fiber optics.<br />
Optical fibers form a natural way to create a distributed sensing system. Using this<br />
technology a large scale neutrino telescope can be built in the deep sea. TNO is aiming<br />
for a prototype hydrophone which will form the building block of a future telescope.<br />
<br />
Students have the possibility to participate to this project is the following ways:<br />
(i) Modeling of cosmic rays induced acoustic signal in a neutrino telescope.<br />
Keywords: Cosmic rays, Monte Carlo, signal processing, telescope optimization.<br />
(ii) Testing and optimization of fiber optical hydrophone for a large scale neutrino<br />
telescope. Keywords: Experimental, physics, system design.<br />
<br />
The work will be (partly) executed in Delft. <br />
<br />
''Contact: [mailto:ernst-jan.buis@tno.NOSPAMnl Ernst-Jan Buis]''<br />
<br />
=== LHCb: A Scintillator Fibers Tracker ===<br />
<br />
The LHCb collaboration is upgrading the present tracking system<br />
constructing a new tracker based on scintillating fibers combined<br />
with silicon photo-multipliers (SiPM): the SciFi Tracker!<br />
Nikhef plays a key role in the project, as we will build the<br />
SciFi fibers modules, the cold-box enclosure housing the SiPMs,<br />
and a large part of the on-detector electronics. In all these<br />
areas, interesting test hardware and software has to be realized,<br />
and several research topics for a Master project are available,<br />
taking the student in contact with state-of-the-art particle detectors,<br />
in a large team of physicists and engineers. Possible collaborations<br />
with the Nikhef R&D group can also be envisaged.<br />
<br />
''Contact: [mailto:antonio@nikhef.nl Antonio Pellegrino]''<br />
<br />
=== LHCb: Discovery of the Decay Lb --> p Ds+ ===<br />
This project aims to measure the branching fraction of the decay Lb->p Ds+ (bud -> uud + ds). <br />
The decay Lb->p Ds+ is quite rare, because it occurs through the transition of a b-quark to a u-quark. <br />
It has not been measured yet (although some LHCb colleagues claim to have seen it).<br />
This decay is interesting, because <br />
<br />
1) It is sensitive to the b->u coupling (CKM-element Vub), which determination is heavily debated.<br />
2) It can quantify non-factorisable QCD effects in b-baryon decays.<br />
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The decay is closely related to B0->pi-Ds+, which proceeds through a similar Feynman diagram. <br />
Also, the final state of B0->pi-Ds+ is almost identical to Lb->p Ds+. <br />
The aim is to determine the relative branching fraction of Lb->pDs+ with respect to B0->D+pi- decays, <br />
in close collaboration with the PhD (who will study BR(B0->pi-Ds+)/BR(B0->D+pi-) ).<br />
This project will result in a journal publication on behalf of the LHCb collaboration, written by you. <br />
For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. <br />
This is a project that is closely related to previous analyses in the group. <br />
Weekly video meetings with CERN coordinate the efforts with in the LHCb collaboration.<br />
Relevant information:<br />
<br />
[1] R.Aaij et al. [LHCb Collaboration], ``Determination of the branching fractions of B0s->DsK and B0->DsK, JHEP 05 (2015) 019 [arXiv:1412.7654 [hep-ex]].<br />
[2] R. Fleischer, N. Serra and N. Tuning, ``Tests of Factorization and SU(3) Relations in B Decays into Heavy-Light Final States, Phys. Rev. D 83, 014017 (2011) [arXiv:1012.2784 [hep-ph]].<br />
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''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''<br />
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=== LHCb: A search for heavy neutrinos in the decay of W bosons at LHCb ===<br />
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Neutrinos are arguably the most mysterious of all known fundamental fermions as they are both much lighter than all others and only weakly interacting. It is thought that the tiny mass of neutrinos can be explained by their mixing with so-far unknown, much heavier, neutrino-like particles. In this research proposal we look for these new neutrinos in the decay of the SM W-boson using data with the LHCb experiment at CERN. The W boson is assumed to decay to a heavy neutrino and a muon. The heavy neutrino subsequently decays to a muon and a pair of quarks. Both like-sign and opposite-sign muon pairs will be studied. The result of the analysis will either be a limit on the production of the new neutrinos or the discovery of something entirely new.<br />
<br />
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen and Elena Dall'Occo]''<br />
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=== LHCb: A search for Majorana neutrinos in the decay of Bc mesons at LHCb ===<br />
<br />
Neutrinos can either be their own anti-particles, in which case they are called "Majorana" particles, or Dirac fermions. It is thought that the tiny mass of neutrinos can be explained by their mixing with so-far unknown, much heavier, neutrino-like particles. LHCb has looked for off-shell Majorana neutrinos in the decays B+->pi-mu+mu+ and B+->D(*)-mu+mu+. Both decays suffer from suppression from Cabibbo-Kobayashi-Maskawa matrix elements, or from low reconstruction efficiencies. Although its production rate is much lower, the Bc meson provides a potentially more promising decay channel: Bc->J/psimu+mu+pi-. The Master student will design and optimise a selection, study potential backgrounds and perform a search in view of setting a stringent limit, or an observation of new physics.<br />
<br />
arXiv:1401.5361 [hep-ex]. arXiv:1201.5600 [hep-ex]. arXiv:11602.09112 [hep-ph]<br />
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''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg and Flavio Archilli]''</div>Rojo@nikhef.nl