Bachelor Projects

Bachelor Projects 2019

Dark Matter

XAMS

The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso. We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source and liquid scintillatorneutron detector we have acquired for the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study of neutron transport in xenon. Supervisors: A.P. Colijn (colijn_at_nikhef.nl)

Backgrounds in Radioactive Decay Measurements

At Nikhef, the XENON group has a working setup, continuously monitoring the radioactive decay of Cobalt-60, Caesium-137 and Titanium-44. This beautiful setup is however not shielded perfectly; it is still vulnerable to background radioactivity. Our current way of working around this background radiation is to subtract it from our waveforms. You as a BSc student could help us hands-on and with analyses: together, we can disassemble the setup, measure background spectra and implement this in the data analysis. You can use all the data to validate the lifetime of our isotopes!

Supervisors: A.P. Colijn (colijn_at_nikhef.nl)

ATLAS

Project ATLAS-ITk

Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)

Higgs interferentie

In 2012 hebben het ATLAS en het CMS experiment het Higgs deeltje gevonden. Inmiddels zijn we het Higgs boson aan het bestuderen, hoe gedraagt het zich precies, bestaan er meer soorten Higgs bosonen of is er echt maar eentje van? In dit project leer je hoe we een Higgs boson kunnen herkennen in de detector en gaan we kijken naar hoe de signalen veranderen als er meer Higgs bosonen bestaan of misschien wel andere exotische nieuwe deeltjes. Dit doen we door gebruik te maken van quantum interferentie wat plaats vindt tussen het Higgs boson en achtergrondprocessen. Hoe dit precies werkt leer je in het project. Supervisor: Hella Snoek (h.snoek_at_nikhef.nl)

Multilepton general search

With data collected from the Atlas detector a variety of exotics physics possibly existing beyond the standard model are probed. General searches such as the multilepton analysis cover a large area of phase space to maximize the possibility to probe, although not definitively discover, a large variety of possible models. Based on a set of selection criteria and algorithms for particle identification, physicists will arrive at a region where well-modeled Standard Model processes are minimized and, as a direct consequence, the sensitivity to new physics is maximized. The bachelor student is invited to adopt a selection of this phase space of their choosing (alongside the guidance of a PhD supervisor) and produce their own analysis. They will be introduced to many of the cornerstones of data analysis within the ATLAS collaboration and attain a proficiency with many tools that will prove invaluable for those looking to continue in the particle physics. Supervisor: Olga Igonkina (o.igonkina_at_nikhef.nl) en Pepijn Bakker (p.bakker_at_nikhef.nl)

B-Physics - LHCb

Time dependent CP violation

The LHCb experiment studies CP violation withB-meson decays. The project focusses on the measurement of the unitarity angle gamma using decays of the Bs mesons to Ds K. Supervisors: Sevda Esen & Michele Veronesi

Machine learning

Machine learning has proven to be an indispensable tool in the selection of interesting events in high energy physics. Such technologies will become increasingly important as detector upgrades are introduced and data rates increase by orders of magnitude. HEPDrone is a toolkit to enable the creation of a drone classifier from any machine learning classifier, such that different classifiers may be standardised into a single form and executed in parallel. A detailed evaluation of the performance of different drone models in the real production environment of LHCb will give the collaboration a complete idea of not only the advantages of the drone model, but also the limits of drone complexity given the available computing resources. Requirements: Advanced python and Advanced C++ Supervisor: Sean Benson

LHCb simulations of physics beyond the Standard Model

This project is of relatively theoretical and computing nature and performs simulation studies for physics beyond the Standard Model in the context of long lived particles. It is related to test the sensitivity of the LHCb experiment to detect specific signals of physics beyond the Standard Model. supervisor: Carlos Vazquez Sierra

Detector R&D

Fast timing detectoren

Op dit moment maken we veel gebruik van silicon detectoren in onze deeltjes experimenten. Deze zijn gevoelig voor geladen deeltjes en zijn bij uitstek geschikt om de paden vast te leggen die de deeltjes maken die in de botsingen worden gemaakt. Bijvoorbeeld in de Atlas en LHCb experimenten worden tientallen tot honderden deeltjes gemaakt bij elk botsingsgebeurtenis (event) die met 40MHz plaatsvinden. Voor toekomstige deeltjesdetectoren willen we niet alleen het traject vastleggen maar ook met grote precisie een tijdsmeting toevoegen. We hebben hiervoor dus nieuwe detectoren nodig die behalve met een hele hoge snelheid en efficientie de posities van de langsvliegende deeltjes kunnen vastleggen, maar hier ook een zeer nauwkeurige tijdsmeting (in orde van picosecondes) aan kunnen toevoegen. We hebben met verschillende detectoren metingen gedaan, in testbundels op CERN, maar ook in het lab op Nikhef kunnen we metingen doen. In dit project ga je samen met het fast-timing detectoren team op het Nikhef metingen verrichten en de resultaten hiervan bekijken. Contact: Hella Snoek (h.snoek@nikhef.nl)

Muon tomography

In this project we are not looking for where cosmic rays come from. We are looking for what we can use them for instead. The muons in cosmic rays can be used to ‘probe’ massive objects. Muons are short lived particles that carry the same charge as electrons, have a high penetrating power and can be detected relatively easy. It is possible to reconstruct a density distribution within an object by measuring muon scattering and absorption. In this context the objects may be freight containers, buildings, melting furnaces, etc…

Systems that scan objects through the use of muons are often large (objects often need to be enclosed by the system) and complex. The question we want to answer is: Can we develop a smaller, simpler and cheaper system for muon tomography?

A method to detect muons is by using a material that scintillates (emits light) when hit by an ionising particle. When this light emission is prompt after the passage of the muon, timing information of the light can be used to reconstruct the path of the muon. In this experiment we make a muon tracker based on two sheets of scintillating material and photo multiplier tubes (PMTs). Photo multiplier tubes are fast responding and very sensitive light detectors (capable of detecting single photons).

The big question is: How well does this system perform?

Currently a set-up is being build. You have a lot of freedom to choose a focus in this project (theory, simulation, hardware, or a combination of those).

Supervisor: Martin Fransen

Spectral X-ray imaging - Looking at colours the eyes can't see

When a conventional X-ray image is made to analyse the composition of a sample, or to perform a medical examination on a patient, one acquires an image that only shows intensities. One obtains a ‘black and white’ image. Most of the information carried by the photon energy is lost. Lacking spectral information can result in an ambiguity between material composition and amount of material in the sample. If the X-ray intensity as a function of the energy can be measured (i.e. a ‘colour’ X-ray image) more information can be obtained from a sample. This translates to less required dose and/or to a better understanding of the sample that is being investigated. For example, two fields that can benefit from spectral X-ray imaging are mammography and real time CT.

X-ray detectors based on Medipix/Timepix pixel chips have spectral resolving capabilities and can be used to make polychromatic X-ray images. Medipix and Timepix chips have branched from pixel chips developed for detectors for high energy physics collider experiments.

Some themes that students can work on:

- Optimising methods to acquire spectral X-ray images.

- Determining how much existing applications benefit from spectral X-ray imaging and looking for potential new applications.

- Characterising, calibrating, optimising X-ray imaging detector systems.

Supervisor: Martin Fransen

Holographic emitter

A difficulty in generating holograms (based on the interference of light) is the required dense spatial light field sampling. One would need pixels of less than 200 nanometer. With larger pixels artefacts occur due to spatial under sampling. A pixel pitch of 200 nm or less is difficult, if not, impossible, to achieve, especially for larger areas. Another challenge is the massive amount of computing power that is required to control such a dense pixel matrix.

A new holographic projection method has been developed that reduces under sampling artefacts, regardless of spatial sample density. The trick is to create 'pixels' at random but known positions, resulting in an array that lacks any spatial periodicity. As a result a holographic emitter can be built with a significantly lower sample density and less required computing power. This could bring holography in reach for many applications like display, lithography, 3D printing, metrology, etc...

The big question: How does the performance of the holographic emitter depend on sample density and sample positions?

The aspects of a holographic image we are interested in are:

- Noise

- Contrast

- Suppression of under sampling artefacts

- Resolution

For this project we are building a proof of concept holographic emitter. This set-up will be used to verify simulation results (and to make some cool holograms of course).

Supervisor: Martin Fransen

KM3NeT

The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown neutrino mass hierarchy.

The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along 700m long vertical lines, called detection units.

Data analysis of the first deployed KM3NeT detection lines

First detection lines of the KM3NeT neutrino telescope have been deployed in the Mediterranean Sea, and a first data set is available. The lines consist of light-sensitive detectors that record the time of arrival of photons produced by relativistic particles in the deep sea, and their number. In this project we will study the first data to separate various components: photons from potassium decay, bioluminesence, sparks in the photomultipliers, downgoing muons from cosmic rays, and perhaps first neutrinos.

Supervisors: Ronald Bruijn and Paul de Jong

Neutrino oscillation measurements with the KM3NeT neutrino telescope

The ORCA block of the KM3NeT neutrino telescope currently under construction will be able to measure the oscillations of neutrinos produced in interactions of cosmic rays with the earth atmosphere. Fundamental neutrino properties can be deduced from these oscillations measurements, in particular the so-called mass hierarchy of neutrinos. In this project we will simulate the ORCA measurements of neutrino oscillations, and study the dependence of the sensitivity on experimental uncertainties, such as energy resolution and neutrino flavour identification, and theoretical uncertainties, such as the atmospheric neutrino flux and neutrino cross sections. The results will help ORCA to identify the main sources of uncertainty, and therefore to actively try to reduce these and improve the final measurement.

Supervisors: Ronald Bruijn and Paul de Jong

Acoustic detection of neutrino's (eavesdropping on whales)

The study of the cosmic neutrinos of energies above 10¹⁷ eV, the so-called ultra-high energy neutrinos, provides a unique view on the universe and may provide insight in the origin of the most violent sources, such as gamma ray bursts, supernovae or even dark matter. One proposed method of observation is the acoustic detection of neutrinos: The energy deposition of cosmic neutrinos in water induce a thermo-acoustic signal (i.e. sound) that can be detected using sensitive hydrophones. The detection of these extreme neutrinos would have far reaching consequences for astrophysics.

Using a large sensor network consisting of more than 1000 sensitive hydrophones, an acoustics neutrino telescope could be realized in the Mediterranean Sea at a depth of 2 km. While technology development is ongoing, several deep-sea recorders have been deployed off the coast of Greece to characterize the underwater acoustics at large depth in the sea. Understanding of underwater acoustics is crucial for the acoustic detection of neutrinos. An interesting feature of this new underwater experiment is that one of the largest sources of background is the sound of sperm whales and dolphins.

Student project
A position is available for a bachelor student to work on the analysis of the data that has been taken near Pylos, Greece at 800 and 1800 meters depths. Analysing the data will require (developing) signal processing algorithms in Python to extract features from the data, such as sea state noise curves, shipping noise and click sounds from whales. The goal is to get clear view of the (acoustic) environment in the deep sea and to study if, and how, we could distinguish the expected acoustic signals from cosmic neutrinos in the, literally in this case, sea of background.

Note: This project can be carried out at Nikhef or at the TNO laboratories in Delft and the Hague.

For further information, please contact:
Ernst-Jan Buis: ernst-jan.buis@tno.nl
Ivo van Vulpen: ivo.van.vulpen@nikhef.nl

VIRGO

The Advanced LIGO and Advanced Virgo interferometers have recently observed gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.

To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.

In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results.

The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Frank Linde (frank.linde_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)

Bachelor Projects 2017

Extreme Astronomy – Preparing for CTA, the Next-Generation Gamma-Ray Observatory

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.

Two projects for students are available at the CTA group of UvA in the field of optical and photonic R&D contributing to the starting phase of CTA. For the first project the student will conduct measurements to characterise novel kinds of single-photon detectors, referred to as silicon photomultipliers, and evaluate different types of these sensors for their use for CTA. For the second project the student will develop and test an imaging system making use of a liquid crystal display. This flexible light source will be able to mimic images from different light sources of the night sky as seen by cameras of CTA, for instance gamma-ray air showers or stars, and will be used for camera tests and calibration.

Supervisors: David Berge, Maurice Stephan (postdoc)

Dark Matter

Neutrinoless double beta decay sensitivity study in future dark matter detectors

The discovery of neutrino oscillation (Nobel Physics 2015) means that neutrinos have mass. We already know that their masses are tiny, more than one million times smaller than the next-lightest particle in the standard model, the electron. This raises the question if the mass-generation mechanism is the same for neutrinos as it is for the other subatomic particles. In particular, since neutrinos are electrically neutral, they could be their own anti-particles - we call these types of particles Majorana. The only practical way to discover if neutrinos are Majorana is through the search of an extremely rare radioactive decay called neutrinoless double beta decay (0n2b). A few isotopes are candidates for this process, among them Xe-136. The natural abundance of Xe-136 in natural xenon is about 9%, and this gives the opportunity to look for a 0n2b signal in xenon-based dark matter detectors like XENON1T and the future XENONnT and DARWIN detectors.

We are looking for a student interested in doing a sensitivity study for 0n2b in XENONnT and the DARWIN experiments. The first goal will be to understand the physics addressed in neutrinoless double beta decay. Then the student will inventory possible backgrounds for the signal, use a (controversial) claim of a 0n2b signal as a benchmark and finally obtain the sensitivity of these future detectors. The work will involve simulations and analysis, building on an existing framework developed in our group.

Supervisors: M.P. Decowski & A. Tiseni

Shaking Dark Matter detectors

Our XENON1T detector is built in the lab underneath the Gran Sasso mountains in central Italy. The lab is very well suited for low-background experiments due to the 1.5km of rock overburden. However, as you may know, cental Italy has been plagued by earthqaukes over the past decade, with the most recentones occurring in January 2017. We need a BSc student to investigate the details of such earthquakes in our underground lab. What are the magnitdues by which stuff is moving underground? What are the accelerations? What is the potential effect on our experimental setup? What would ahppen if an earthquake happens much closer to our lab? Furthermore we are interested to find out whether Earthquakes can be predicted. Some papers claim that before an earthquake the radon emanating from rock increases. In our lab we measure the radon concentration as a function of time: can you find a correlation between the measurements and recent earthquakes?

If you are interested in finding out more about earthquakes, please contact M.P. Decowski or A.P. Colijn

XAMS - a baby dark matter detector

The Nikhef dark matter group has a small version of the XENON1T detector in the lab. With this detector which is more than a factor 1000 smaller than the newly built XENON1T detector in Gran Sasso we (i) investigate the properties of xenon as a detector, and (ii) aim to improve the methods we use in the XENON1T experiment to detect dark matter. The principles of operation of this smal detector are identical to its big sibling in Gran Sasso.

We are looking for a student interested in dark matter physics, and with a focus on working in the lab (hands-on profile). The student will work with the new AmBe neutron source we have acquired before the start of the project. With such a source we can generate signals in our lab setup that ar identical to the signals we expect from real dark matter interactions in xenon. The goal of this project will be to do the first measurements with the neutron source and analyze the data. Depending on the progress with the hardware we intend to complement the measurements with Monte Carlo study of neutron transport in xenon.

Supervisors: A.P. Colijn & E. Hogenbirk

Radon is bad for Dark Matter

Radon is the dominant background for xenon based dark matter detectors, like the XENON1T experiment. In our lab at Nikhef we are investigating ways to reduce or eliminate the effect of radon on our sensitivity. For our lab setup XAMS we have designed and constructed a radon detector, that can be used in xenon systems at high-pressure. This completely new detector is now waiting for a BSc student to fully chracterize and use it. During this project you will first study the effect that radon contaminations have on dark matter detectors, then you will start working to understand our new radon detector in detail. You will learn howto use a radioactive source to calibrate the detector: this is something which is not easy and has not been done before in our lab. If you manage to succesfully calibrate the detector, we then want to incorporate it into our lab xenon system at Nikhef and maybe at some later stage in the real XENON1T detector!

The profile of the student to work on this project is broad. I expect a good theoretical knowledge in order to quickly get upto speed with understanding dark mater detectors, and in addition I need 'lab-creativity' in order to develop methods for calibrating the new detector. If a good method is developed, it will be used for many years by the Nikhef dark matter group and beyond.

Supervisors: A.P. Colijn & E. Hogenbirk

ATLAS

ATLAS (1): Searching for new physics with the Higgs and W bosons

The strength of the Higgs interactions with electroweak bosons are precisely defined in the Standard Model. Therefore they are sensitive probes of the mechanism of electroweak symmetry breaking and enable searches for new physics beyond the SM. With the data collected by the ATLAS experiment in years 2015-2016 we plan to measure separately the Higgs coupling to longitudinally and transversely polarised W bosons in a process of weak boson fusion. To maximise experimental sensitivity we are developing techniques to separate the signal from background processes. You will take part in investigating possible improvements from reconstructing events in reference frames boosted with respect to the detector. During the project you will learn modern experimental analysis techniques. This project is a part of Vector Boson Scattering Coordination and Action Network (VBSCan) which connects researchers studying this and related topics worldwide.

Supervisors: Pamela Ferrari, Magdalena Slawinska, Bob van Eijk

ATLAS (2): Dark-matter-motivated searches for supersymmetric particles at the LHC

Supersymmetry, a symmetry between fermions and bosons in particle physics, may provide a particle that could be the dark matter in the universe. The observation of an excess of gamma rays originating from the centre of our galaxy could be explained in a model where supersymmetric dark matter particles annihilate each other in the galactic centre, leading to gamma rays.

Given the model parameters, it should also be possible to produce such particles at the LHC, at CERN in Geneva. But it is not so easy to observe them: the signal is small, and the noise (background) is large. In this project, we will use simulations of signal and background to optimize experimental searches for such particles with the ATLAS detector, apply them to the data collected in 2015, and prepare for the new data in 2016 and later.Where possible, we will explore new machine learning techniques.

Supervisors: Paul de Jong, Broos Vermeulen

ATLAS (3): Simulations / Quality tests for the ATLAS High-Luminosity LHC Upgrade

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.

At Phase-2 of the LHC run, in ~2025, 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.

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.

ATLAS (4): Higgs productie in Run-2 van de LHC

In de eerste run van de LHC is onder andere bij het ATLAS experiment het Higgs deeltje gevonden. Nu is de tweede run begonnen en kan het Higgs deeltje worden bevestigd. Door de verhoogde energie ziet de achtergrond er echter heel anders uit, dus is de optimalisatie van het wegsnijden van de achtergronden qua fysica anders. Voor je bachelor project kan met behulp van de ATLAS detector het Higgs deeltje in run twee komen vinden.

Supervisors: Lydia Brenner, Wouter Verkerke

ATLAS (5): De lange staart van het Higgs boson

Na de ontdekking van het Higgs boson in 2012 zijn we druk bezig om te kijken of zijn eigenschappen overeenkomen met de voorspellingen van het Standaard Model. Een van de belangrijkste eigenschappen is de zogenaamde breedte van het Higgs boson. Als het Higgs boson naast de Standaard Model deeltjes ook in exotische nieuwe speeltje uit elkaar kan vallen (bijvoorbeeld donkere materie) dan zal dat ale eerste zichtbaar worden in een afwijking van de breedte tov de verwachting. We gaan in dit project uitzoeken hoe de strategie die nu gebruikt wordt (meten van de hoeveelheid Higgs bosonen met een extreem hoge massa) precies werkt en kijken of we door het toevoegen van nieuwe ideeën een verbetering kunnen aanbrengen.

Specifiek: We gaan eerst in detail de eigenschappen bekijken van het Higgs signaal en de twee achtergronden die er het meest op lijken. Daarna gaan we op zoek naar de verschillen en een manier waarop we onze kennis daarover kunnen gebruiken om gevoeliger te worden voor het Higgs signaal.

Supervisors: Hella Snoek, Ivo van Vulpen

E-mail: H.Snoek_at_nikhef.nl & Ivo.van.Vulpen_at_nikhef.nl

ATLAS (6): Project ATLAS-ITk

Voor de ATLAS upgrade van de binneste detector, de tracking detector ITk zal op Nikhef een groot onderdeel worden gebouwd: de End-Cap met een doorsnede van 2meter en 1.6meter lang. De silicium detectoren worden gekoeld met CO2, waarvoor een testopstelling ontwikkeld en doorgerekend moet worden. Hier ligt een flinke uitdaging voor een bachelorstudent die kennis heeft van thermodynamica en die affiniteit heeft met technische toepassingen. De berekeningen maken gebruik van een software pakket COBRA waar eventueel nog verfijningen in zijn aan te brengen. Het werk zal onder begeleiding plaatsvinden van ir Jesse van Dongen en dr Marcel Vreeswijk. (h73_at_nikhef.nl)

KM3Net

The KM3NeT collaboration is constructing a new generation neutrino telescope with a volume of several cubic kilometers (final configuration) in the deep waters of the Mediterranean Sea. With the data, scientists will look for the astrophysical sources of neutrinos such as supernovae, colliding stars or gamma-ray bursts. In the domain of particle physics the properties of neutrinos will be investigated, in particular the unknown neutrino mass hierachy.

The KM3NeT telescope detects the Cherenkov light emitted by the secondary particles produced in neutrino interactions using an array of thousands of sensitive 3 inch photo-multiplier tubes housed in 17 inch pressure resistant glass spheres, digital-optical-modules (DOMs), together with electronics. The DOMs are oriented along 700m long vertical lines, called detection units.

The first phase of the KM3NeT neutrino telescope is currently under construction, with the first two detection units operational at 3500m depth in the Mediterranean Sea, 100 km off the coast of Sicily.

KM3NeT (1): Photon counting in KM3NeT

The details of a neutrino interaction, such as its incoming direction and energy, determine the pattern, time and amount, of recorded photons (´hits´) by the photo-multplier tubes. The time of arrival is recorded with nanosecond accuracy and the amount of photons is encoded in the length of the pulse(time-over-threshold, ToT). Currently, only the photon arrival time and the number of photo-multipliers that record a hit are used in reconstructing event properties. In this project, the distributions of the ToT mainly originating from photons from potassium-40 decays in the sea-water and from atmospheric muons passing through the water will be studied. The goals are to investigate the properties of the ToT distributions obtained from data and simulation, in particular the dependence on the photo-multiplier efficiency and atmospheric muon flux. In this project we will be extensively using the programming language C++ to analyse the data, so a reasonable proficiency is required.

Supervisors: Ronald Bruijn & Karel Melis

Email: rbruijn_at_nikhef.nl

KM3NeT (2): Acoustic detection of neutrino's (eavesdropping on whales)

The study of the cosmic neutrinos of energies above 10¹⁷ eV, the so-called ultra-high energy neutrinos, provides a unique view on the universe and may provide insight in the origin of the most violent sources, such as gamma ray bursts, supernovae or even dark matter. One proposed method of observation is the acoustic detection of neutrinos: The energy deposition of cosmic neutrinos in water induce a thermo-acoustic signal (i.e. sound) that can be detected using sensitive hydrophones. The detection of these extreme neutrinos would have far reaching consequences for astrophysics.

Using a large sensor network consisting of more than 1000 sensitive hydrophones, an acoustics neutrino telescope could be realized in the Mediterranean Sea at a depth of 2 km. While technology development is ongoing, several deep-sea recorders have been deployed off the coast of Greece to characterize the underwater acoustics at large depth in the sea. Understanding of underwater acoustics is crucial for the acoustic detection of neutrinos. An interesting feature of this new underwater experiment is that one of the largest sources of background is the sound of sperm whales and dolphins.

Student project
A position is available for a bachelor student to work on the analysis of the data that has been taken near Pylos, Greece at 800 and 1800 meters depths. Analysing the data will require (developing) signal processing algorithms in Python to extract features from the data, such as sea state noise curves, shipping noise and click sounds from whales. The goal is to get clear view of the (acoustic) environment in the deep sea and to study if, and how, we could distinguish the expected acoustic signals from cosmic neutrinos in the, literally in this case, sea of background.

Note: This project can be carried out at Nikhef or at the TNO laboratories in Delft and the Hague.

For further information, please contact:
Ernst-Jan Buis: ernst-jan.buis@tno.nl
Ivo van Vulpen: ivo.van.vulpen@nikhef.nl

VIRGO

"It is anticipated that in the next few years, Advanced LIGO and Advanced Virgo will start observing gravitational waves from binary neutron star mergers. Prior to merger, as two neutron stars spiral towards each other, the tidal field of one star will cause a deformation in the other. These deformations affect the orbital motion, which in turn gets imprinted onto the gravitational wave signal. This way we can find out how deformable a neutron star is in the first place, which will yield information about the interior of neutron stars; the latter is the main open problem in nuclear astrophysics.

To succeed in this, good models are needed for the gravitational waveforms. The best model currently available which can be generated sufficiently fast on a computer to be useful in data analysis, contains a state-of-the art description of tidal effects, but not neutron star spins. It is generally assumed that neutron stars are slowly spinning, but it needs to be determined how measurements of tides would be affected by the absence of spins in our analyses.

In practice, the project will consist of learning how to use pre-existing gravitational wave data analysis tools, setting up simulations based on them, and interpreting the results."

The VIRGO collaboration operates the advanced VIRGO gravitational waves detector in Italy, and forms together with the LIGO collaboration a consortium that analyzes the data from both VIRGO and LIGO. For projects in the Nikhef VIRGO group, please contact Jo van den Brand (jo_at_nikhef.nl) or Chris van den Broeck (vdbroeck_at_nikhef.nl)

LHCb

Begeleider: Sean Benson

Title: Searching for physics beyond the Standard Model with LHCb

The LHCb experiment is designed to study the "The Flavour Problem" in particle physics: Why is the universe dominated by matter over antimatter? Why are there three generations of elementary particles? What is the origin of quark flavour changing interactions.

To solve these riddles, LHCb performs precision measurements on b-quark particle decays. An intriguing signal has recently been observed in the decay of a B-meson to a K* and two muons: Bd→K*μμ, which does not seem to behave according to the predictions of the Standard Model In this project the bachelor student will investigate this further by studying the case where the K* particle decays to a so-called k-short particle and a π0. The observation of such a final state will provide valuable information in the search for physics beyond the Standard Model.

In this ambitious project the student is expected to study both a theory on the mechanism of CP violation with B mesons, in addition to data analysis with B decays. Programming experience in python is required.

The LHCb experiment at CERN analyzes the properties of B-hadrons produced in proton-proton collisions at the LHC. For projects in the LHCb group, please contact Marcel Mark (marcel.merk_at_nikhef.nl)