Bachelor Projects

Bachelor Projects

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

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): Measurement of W boson polarisation in top quark decays ==== NOT LONGER AVAILABLE

Top quarks are produced copiously at the LHC and measured with the ATLAS detector. The top quark is the heaviest elementary particle known and decays to the W boson and the b-quark. The measurement of the decay properties allow to set limits on possible new physics effect on the Wtb vertex. New measurements of the W boson polarization in top quark pair events become available and limit several of these new physics effects. The object of this bachelor project is to install, run and understand a dedicated program, called TopFit, to study these limits. The student should have affinity with theory and programming. More information: dr Marcel Vreeswijk, h73@nikhef.nl, 020 5925088

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.

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

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. The first detection unit has been succesfully deployed in december 2015 at at depth of 3500m, 100 km of the coast of Sicily and is currently taking data.

Bachelor projects:

Data from the first detection unit of KM3NeT

Data from the first detection unit provides plenty of opportunities for analysis. Photons from atmospheric muons, potassium decay and calibration beacons can be used to quantify and monitor the quality of the taken data, to perform timing calibrations to achieve the required nanosecond accuracy and to study the detector and medium properties. Two projects are available which consist of analysis of the data in the context of timing calibration, detector and medium properties and data quality. For the data-analysis, we will make extensive use of the C++ programming language.

DOM orientation

In order to reconstruct the properties of neutrino interactions from the recorded photons, the orientation of the photomultiplier tubes has to be known at each moment in time. The position of the DOMs is determined using an acoustic positioning system. To complement that, each DOM contains an attitude and heading reference system (compass, accelerometer, gyroscopes) to determine the orientation. The project concerns an investigation of an alternative system for the DOM orientation. In this project we will be working with hardware (DOM, compass/accelerometer boards) and software (C++, Java).

Supervisors: R.Bruijn, M. Jongen, K. Melis