Difference between revisions of "Master Projects"

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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.  
 
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.  
  
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[MORE PROJECTS TO COME!]
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=== Theory:  Unbiased global analysis of heavy quark fragmentation functions ===
  
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[[Last years MSc Projects|Last year's MSc Projects]]
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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.
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"Further information [[http://pcteserver.mi.infn.it/~nnpdf/VU/2018-MasterProject-DFFs.pdf here]]
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''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''
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=== Theory:  The quark and gluon internal structure of heavy nuclei in the LHC era  ===
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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).
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"Further information [[http://pcteserver.mi.infn.it/~nnpdf/VU/2018-MasterProject-nPDFs.pdf here]]
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''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''
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=== Theory:  Combined QCD analysis of parton distribution and fragmentation functions ===
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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.
  
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"Further information [[http://pcteserver.mi.infn.it/~nnpdf/VU/2018-MasterProject-FFpPDFs.pdf here]]
  
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=== Extreme Astronomy – Preparing for CTA, the Next-Generation Gamma-Ray Observatory ===
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''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''
  
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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.
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=== The Modulation Experiment: Data Analysis ===
  
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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.
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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.
  
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''Contact: [mailto:d.berge@nikhef.nl David Berge], [mailto:maurice.stephan@uva.nl Maurice Stephan]''
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''Contact: [mailto:z37@nikhef.nl Auke Colijn]''
  
 
=== The XENON Dark Matter Experiment: Data Analysis ===
 
=== The XENON Dark Matter Experiment: Data Analysis ===
  
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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.  
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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.  
  
 
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''
 
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''
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''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''
 
''Contact: [mailto:decowski@nikhef.nl Patrick Decowski]''
  
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=== Astroparticle Physics at the LHC ===
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=== LHCb: A Scintillator Fibers Tracker ===
  
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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.
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The LHCb collaboration is upgrading the present tracking system
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constructing a new tracker based on scintillating fibers combined
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with silicon photo-multipliers (SiPM): the SciFi Tracker!
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Nikhef plays a key role in the project, as we will build the
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SciFi fibers modules, the cold-box enclosure housing the SiPMs,
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and a large part of the on-detector electronics. In all these
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areas, interesting test hardware and software has to be realized,
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and several research topics for a Master project are available,
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taking the student in contact with state-of-the-art particle detectors,
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in a large team of physicists and engineers. Possible collaborations
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with the Nikhef R&D group can also be envisaged.
  
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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/).
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''Contact: [mailto:antonio@nikhef.nl Antonio Pellegrino]''
  
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''Contact: [mailto:d.berge@nikhef.nl David Berge], [mailto:david.salek@cern.ch David Salek]''
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=== LHCb: Discovery of the Decay Lb --> p Ds+ ===
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This project aims to measure the branching fraction of the decay Lb->p Ds+ (bud -> uud + ds).  
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The decay Lb->p Ds+ is quite rare, because it occurs through the transition of a b-quark to a u-quark.  
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It has not been measured yet (although some LHCb colleagues claim to have seen it).
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This decay is interesting, because
  
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=== ATLAS : Beyond Standard Model with multiple leptons ===
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1) It is sensitive to the b->u coupling (CKM-element Vub), which determination is heavily debated.
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2) It can quantify non-factorisable QCD effects in b-baryon decays.
  
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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.).
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The decay is closely related to B0->pi-Ds+, which proceeds through a similar Feynman diagram.
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Also, the final state of B0->pi-Ds+ is almost identical to Lb->p Ds+.
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The aim is to determine the relative branching fraction of Lb->pDs+ with respect to B0->D+pi- decays,  
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in close collaboration with the PhD (who will study BR(B0->pi-Ds+)/BR(B0->D+pi-) ).
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This project will result in a journal publication on behalf of the LHCb collaboration, written by you.
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For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used.  
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This is a project that is closely related to previous analyses in the group.
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Weekly video meetings with CERN coordinate the efforts with in the LHCb collaboration.
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Relevant information:
  
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''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina]''
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[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]].
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[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]].
  
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=== ATLAS : Search for supersymmetric dark matter-like particles ===
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''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''
  
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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++.
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=== LHCb:  Measurement of B0 -> pi Ds- , the b -> u quark transition ===
  
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''Contact: [mailto:h26@nikhef.nl Paul de Jong]''
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This project aims to measure the branching fraction of the decay B0->pi Ds+.
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This decay is closely related to Lb->p Ds+ (see above), and close collaboration between the two master projects is foreseen.
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This research was started by a previous master student.
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The new measurement will finish the work, and include the new data from 2015 and 2016.
  
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===  ATLAS inner tracker upgrade ===
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See Mick Mulders [http://www.nikhef.nl/pub/experiments/bfys/lhcb/Theses/master/2015_MickMulder.pdf master thesis] for more information.
  
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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.
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''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''
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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.
 
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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.
 
  
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''Contact: [mailto:Peter.Vankov@cern.NOSPAMch Peter Vankov]''
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=== LHCb: A search for heavy neutrinos in the decay of W bosons at LHCb ===
  
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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.
  
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=== ATLAS : Model testing for Beyond the Standard Model Higgs  ===
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''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen and Elena Dall'Occo]''
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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.
 
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''Contact: [mailto:verkerke@nikhef.nl Wouter Verkerke],  [mailto:lbrenner@nikhef.nl Lydia Brenner]''
 
  
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=== Theory & ATLAS: How to violate lepton flavour? ===
 
  
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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.
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=== LHCb: Searches for new pentaquarks ===
  
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''Contact: [mailto:devries.jordy@gmail.com Jordy de Vries], [mailto:olya@nikhef.nl Olya Igonkina], [mailto:Robert.Fleischer@nikhef.nl Robert Fleischer]''
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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.  
  
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=== KM3NeT : Reconstruction of first neutrinos in KM3NeT ===
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See [https://arxiv.org/abs/1406.0755 arXiv:1406.0755] for more information.
  
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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.
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''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg]''
  
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''Contact: [mailto:rbruijn@nikhef.nl Ronald Bruijn]''
 
  
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=== Neutrino mass hierarchy with KM3NeT/ORCA ===
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=== ATLAS : Double Higgs searches with multiple leptons ===
  
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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.
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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).
  
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''Contact: [mailto:aart.heijboer@nikhef.nl Aart Heijboer]''
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''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and Marcus Morgenstern and Pepijn Bakker]''
  
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=== All-flavor-neutrino analysis of ANTARES data ===
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=== ATLAS : A search for lepton flavor violation with tau decays ===
  
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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.
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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
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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.
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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).
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Programming skills are essential, mainly C++ and root will be used.
 
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Also other options for analyses of the ANTARES data are available.
 
  
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''Contact: [mailto:dosamt@nikhef.nl Dorothea Samtleben]''
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''Contact: [mailto:O.Igonkina@nikhef.nl Olya Igonkina and Matteo Bedognetti]''
  
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=== ALICE: Particle Polarization in Strong Magnetic Fields ===
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=== ALICE : Particle polarisation in strong magnetic fields ===
 
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.  
 
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.  
  
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''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''
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''Contact: [mailto:Paul.Kuijer@nikhef.nl Paul Kuijer and Panos Christakoglou]''
  
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=== ALICE: Forward Particle Production from the Color Glass Condensate ===
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=== ALICE : Blast-Wave Model in heavy-ion collisions ===
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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)
 
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Blast-Wave Model in Heavy-Ion collisions
 
 
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.  
 
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.  
  
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''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''
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''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''
  
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=== ALICE: Energy Loss of Energetic Quarks and Gluons in the Quark-Gluon Plasma ===
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=== ALICE : Higher Harmonic Flow ===
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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.  
+
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.  
  
−
''Contact: [mailto:marco.van.leeuwen@nikhef.nl M. van Leeuwen]''
+
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''
  
−
=== ALICE: Chiral Magnetic Effect and the Strong CP Problem ===  
+
=== ALICE : Chiral Magnetic Effect and the Strong CP Problem ===
 
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.  
 
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.  
  
−
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''
+
''Contact: [mailto:Panos.Christakoglou@nikhef.nl Panos Christakoglou and Paul Kuijer]''
  
−
=== ALICE: Quantum Coherence in Particle Production with Intensity Interferometry ===
+
=== DR&D : Medical X-ray Imaging ===
−
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.
+
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:
−
 
 
−
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann]''
 
−
 
 
−
=== ALICE: Higher Harmonic Flow ===
 
−
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.
 
−
 
 
−
''Contact: [mailto:Panos.Christakoglou@nikhef.nl P. Christakoglou], [mailto:Paul.Kuijer@nikhef.nl P. Kuijer]''
 
−
 
 
−
=== ALICE: A New Detector for Very High-Energy Photons: FoCal ===
 
−
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.
 
−
 
 
−
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann] [mailto:marco.van.leeuwen@nikhef.nl M. van Leeuwen]''
 
−
 
 
−
=== ALICE: Thermal Photon Emission: Quark-Gluon Plasma or Hadron Gas? ===
 
−
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.
 
−
 
 
−
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann]''
 
−
 
 
−
=== A New Detector for Proton Therapy and Proton Computed Tomography ===
 
−
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.
 
−
 
 
−
''Contact: [mailto:T.Peitzmann@uu.nl T. Peitzmann]''
 
−
 
 
−
=== Medical X-ray Imaging ===
 
−
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:  
 
 
* Medipix3RX characterization in all its operation modes and gains.  
 
* Medipix3RX characterization in all its operation modes and gains.  
 
* Spectral CT and scarce sampling 3D reconstruction  
 
* Spectral CT and scarce sampling 3D reconstruction  
 
* 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.
 
* 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.
  
−
''Contact: [mailto:johnid@nikhef.nl John Idarraga],[mailto:nielsvb@nihef.nl Niels van Bakel]''
+
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman],[mailto:martinfr@nihef.nl Martin Fransen]''
  
−
=== Compton camera ===
+
=== DR&D : Compton camera ===
−
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.
+
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.
  
 
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman]''
 
''Contact: [mailto:koffeman@nikhef.nl Els Koffeman]''
  
−
=== The Modulation experiment ===
+
=== KM3NeT : Reconstruction of first neutrino interactions in KM3NeT ===
−
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.
 
  
−
''Contact: [mailto:colijn@nikhef.nl Auke Colijn]''
+
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.
  
−
===  Acoustic detection of ultra-high energy cosmic-ray neutrinos ===
+
Programming skills are essential, mostly root and C++ will be used.
−
The study of the cosmic neutrinos of energies above 10^17 eV, so-called ultra-high
 
−
energy neutrinos, provides a unique view on the universe and may provide insight in
 
−
the origin of the most violent sources, such as gamma ray bursts, supernovae or even
 
−
dark matter. The energy deposition of cosmic neutrinos in water induces 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 that is 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.
 
  
−
Students have the possibility to participate to this project is the following ways:
+
'' Contact: [mailto:bruijn@nikhef.nl Ronald Bruijn]''
−
(i) Modeling of cosmic rays induced acoustic signal in a neutrino telescope.
 
−
Keywords: Cosmic rays, Monte Carlo, signal processing, telescope optimization.
 
−
(ii) Testing and optimization of fiber optical hydrophone for a large scale neutrino
 
−
telescope. Keywords: Experimental, physics, system design.
 
  
−
The work will be (partly) executed in Delft.  
+
=== ANTARES: Analysis of IceCube neutrino sources. ===
  
−
''Contact: [mailto:ernst-jan.buis@tno.NOSPAMnl Ernst-Jan Buis]''
+
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.
 +
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.
  
−
=== LHCb: A Scintillator Fibers Tracker ===
+
Programming skills are essential, mainly C++ and root will be used.
 +
 
 +
'' Contact: [mailto:dosamt@nikhef.nl Dorothea Samtleben]''
  
−
The LHCb collaboration is upgrading the present tracking system
 
−
constructing a new tracker based on scintillating fibers combined
 
−
with silicon photo-multipliers (SiPM): the SciFi Tracker!
 
−
Nikhef plays a key role in the project, as we will build the
 
−
SciFi fibers modules, the cold-box enclosure housing the SiPMs,
 
−
and a large part of the on-detector electronics. In all these
 
−
areas, interesting test hardware and software has to be realized,
 
−
and several research topics for a Master project are available,
 
−
taking the student in contact with state-of-the-art particle detectors,
 
−
in a large team of physicists and engineers. Possible collaborations
 
−
with the Nikhef R&D group can also be envisaged.
 
  
−
''Contact: [mailto:antonio@nikhef.nl Antonio Pellegrino]''
+
=== ATLAS: Implementation of Morphing techniques for ATLAS top physics analysis. ===
  
−
=== LHCb: Discovery of the Decay Lb --> p Ds+ ===
+
Perhaps the most promising gateway to physics beyond the Standard Model is the top quark, the heaviest elementary particle. Particularly
−
This project aims to measure the branching fraction of the decay Lb->p Ds+ (bud -> uud + ds).  
+
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
−
The decay Lb->p Ds+ is quite rare, because it occurs through the transition of a b-quark to a u-quark.  
+
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.  
−
It has not been measured yet (although some LHCb colleagues claim to have seen it).
 
−
This decay is interesting, because
 
  
−
1) It is sensitive to the b->u coupling (CKM-element Vub), which determination is heavily debated.
+
Affinity with software is essential, mainly C++ and root will be used.  
−
2) It can quantify non-factorisable QCD effects in b-baryon decays.
 
  
−
The decay is closely related to B0->pi-Ds+, which proceeds through a similar Feynman diagram.
+
'' Contact: [mailto:h73@nikhef.nl Marcel Vreeswijk]''
−
Also, the final state of B0->pi-Ds+ is almost identical to Lb->p Ds+.
 
−
The aim is to determine the relative branching fraction of Lb->pDs+ with respect to B0->D+pi- decays,
 
−
in close collaboration with the PhD (who will study BR(B0->pi-Ds+)/BR(B0->D+pi-) ).
 
−
This project will result in a journal publication on behalf of the LHCb collaboration, written by you.
 
−
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.
 
−
Relevant information:
 
  
−
[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]].
+
=== Theory – Probing electroweak symmetry breaking with Higgs pair production at the LHC and beyond ===
−
[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]].
 
  
−
''Contact: [mailto:h71@nikhef.nl Niels Tuning and Lennaert Bel and Mick Mulder]''
+
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.
  
−
=== LHCb: A search for heavy neutrinos in the decay of W bosons at LHCb ===
+
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].
  
−
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.
+
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''
  
−
''Contact: [mailto:wouterh@nikhef.nl Wouter Hulsbergen and Elena Dall'Occo]''
+
=== Theory – Constraining the proton structure with Run II LHC data ===
  
 +
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.
  
−
=== LHCb: A search for Majorana neutrinos in the decay of Bc mesons at LHCb ===
+
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].
  
−
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.
+
''Contact: [mailto:j.rojo@vu.nl Juan Rojo]''
  
−
arXiv:1401.5361 [hep-ex]. arXiv:1201.5600 [hep-ex]. arXiv:11602.09112 [hep-ph]
 
  
−
''Contact: [mailto:patrick.koppenburg@cern.ch Patrick Koppenburg and Flavio Archilli]''
+
[[Last years MSc Projects|Last year's MSc Projects]]

Revision as of 10:13, 11 February 2018

Master Thesis Research Projects

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.

Theory: Unbiased global analysis of heavy quark fragmentation functions

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.

"Further information [here]

Contact: Juan Rojo

Theory: The quark and gluon internal structure of heavy nuclei in the LHC era

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).

"Further information [here]

Contact: Juan Rojo

Theory: Combined QCD analysis of parton distribution and fragmentation functions

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.

"Further information [here]

Contact: Juan Rojo

The Modulation Experiment: Data Analysis

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.

Contact: Auke Colijn

The XENON Dark Matter Experiment: Data Analysis

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.

Contact: Patrick Decowski

XAMS Dark Matter R&D Setup

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.

Contact: Patrick Decowski

LHCb: A Scintillator Fibers Tracker

The LHCb collaboration is upgrading the present tracking system constructing a new tracker based on scintillating fibers combined with silicon photo-multipliers (SiPM): the SciFi Tracker! Nikhef plays a key role in the project, as we will build the SciFi fibers modules, the cold-box enclosure housing the SiPMs, and a large part of the on-detector electronics. In all these areas, interesting test hardware and software has to be realized, and several research topics for a Master project are available, taking the student in contact with state-of-the-art particle detectors, in a large team of physicists and engineers. Possible collaborations with the Nikhef R&D group can also be envisaged.

Contact: Antonio Pellegrino

LHCb: Discovery of the Decay Lb --> p Ds+

This project aims to measure the branching fraction of the decay Lb->p Ds+ (bud -> uud + ds). The decay Lb->p Ds+ is quite rare, because it occurs through the transition of a b-quark to a u-quark. It has not been measured yet (although some LHCb colleagues claim to have seen it). This decay is interesting, because

1) It is sensitive to the b->u coupling (CKM-element Vub), which determination is heavily debated. 2) It can quantify non-factorisable QCD effects in b-baryon decays.

The decay is closely related to B0->pi-Ds+, which proceeds through a similar Feynman diagram. Also, the final state of B0->pi-Ds+ is almost identical to Lb->p Ds+. The aim is to determine the relative branching fraction of Lb->pDs+ with respect to B0->D+pi- decays, in close collaboration with the PhD (who will study BR(B0->pi-Ds+)/BR(B0->D+pi-) ). This project will result in a journal publication on behalf of the LHCb collaboration, written by you. 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. Relevant information:

[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]]. [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]].

Contact: Niels Tuning and Lennaert Bel and Mick Mulder

LHCb: Measurement of B0 -> pi Ds- , the b -> u quark transition

This project aims to measure the branching fraction of the decay B0->pi Ds+. This decay is closely related to Lb->p Ds+ (see above), and close collaboration between the two master projects is foreseen. This research was started by a previous master student. The new measurement will finish the work, and include the new data from 2015 and 2016.

See Mick Mulders master thesis for more information.

Contact: Niels Tuning and Lennaert Bel and Mick Mulder

LHCb: A search for heavy neutrinos in the decay of W bosons at LHCb

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.

Contact: Wouter Hulsbergen and Elena Dall'Occo


LHCb: Searches for new pentaquarks

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.

See arXiv:1406.0755 for more information.

Contact: Patrick Koppenburg


ATLAS : Double Higgs searches with multiple leptons

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).

Contact: Olya Igonkina and Marcus Morgenstern and Pepijn Bakker

ATLAS : A search for lepton flavor violation with tau decays

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 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).

Contact: Olya Igonkina and Matteo Bedognetti

ALICE : Particle polarisation in strong magnetic fields

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.

Contact: Paul Kuijer and Panos Christakoglou

ALICE : Blast-Wave Model in heavy-ion collisions

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.

Contact: Panos Christakoglou and Paul Kuijer

ALICE : Higher Harmonic Flow

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.

Contact: Panos Christakoglou and Paul Kuijer

ALICE : Chiral Magnetic Effect and the Strong CP Problem

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.

Contact: Panos Christakoglou and Paul Kuijer

DR&D : Medical X-ray Imaging

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:

  • Medipix3RX characterization in all its operation modes and gains.
  • Spectral CT and scarce sampling 3D reconstruction
  • 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.

Contact: Els Koffeman,Martin Fransen

DR&D : Compton camera

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.

Contact: Els Koffeman

KM3NeT : Reconstruction of first neutrino interactions in KM3NeT

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.

Programming skills are essential, mostly root and C++ will be used.

Contact: Ronald Bruijn

ANTARES: Analysis of IceCube neutrino sources.

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. 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.

Programming skills are essential, mainly C++ and root will be used.

Contact: Dorothea Samtleben


ATLAS: Implementation of Morphing techniques for ATLAS top physics analysis.

Perhaps the most promising gateway to physics beyond the Standard Model is the top quark, the heaviest elementary particle. Particularly 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 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.

Affinity with software is essential, mainly C++ and root will be used.

Contact: Marcel Vreeswijk

Theory – Probing electroweak symmetry breaking with Higgs pair production at the LHC and beyond

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.

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: [1].

Contact: Juan Rojo

Theory – Constraining the proton structure with Run II LHC data

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.

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: [2].

Contact: Juan Rojo


Last year's MSc Projects

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