UCL

Physics and Astronomy » High Energy Physics »

Postgraduate Opportunities

16 Apr 2024

PhD projects Offered

Click for individual project details.

Experimental: 3-lepton production with ATLAS

PhD project: An inclusive measurement of three-lepton production in pp collisions with ATLAS

Supervisor: Prof. Jon Butterworth

The three-lepton final state is a powerful probe of several important physics processes. In the Standard Model, it can arise from WZ production and top-Z production, as well as continuum processes which do not involve an on-shell Z boson. A precise inclusive and model-independent measurement will extend knowledge of these processes both in precision and into the off-shell regions. It will also be a powerful input to Effective Field Theory fits searching for signs of physics beyond the Standard Model above the LHC energy scale, and will be directly sensitive to models which have mass states within reach. We will make such a measurement, unfolded to particle level, and use it to probe the Standard Model as well as physics beyond it.

Contact: Prof. Jon Butterworth

Experimental: Multi-messenger neutrino astronomy

PhD project: New frontiers in multi-messenger neutrino astronomy with the P-ONE experiment

Supervisor: Dr. Matteo Agostini

Neutrinos from the edge of the observable universe are reshaping our understanding of astrophysical systems at the highest energy and gravitational frontiers. Several massive neutrino telescopes are soon coming online, presenting extraordinary challenges in analysis and computation, primarily involving the extraction of signals from experimental data and their comparison with astrophysical theories. This project aims at addressing these challenges by employing leading-edge analysis and computational techniques developed within a cross-disciplinary framework, ultimately applying them to the analysis of data from the Pacific Ocean Neutrino Experiment (P-ONE).

Contact: Dr. Matteo Agostini

Experimental: Neutrinoless double-beta decay with LEGEND

PhD project: LEGEND Neutrinoless Double-Beta Decay Experiment

Supervisor: Prof. David Waters

Neutrinoless double-beta decay (0vbb) is a process often predicted in theories of physics beyond the Standard Model. Two electrons are produced in the decay process but no neutrinos are emitted: in effect a neutrino is created and re-absorbed inside the nucleus, and this can only happen if they are Majorana particles. The 0νbb process is manifestly lepton number violating, and would shine a light on the mechanism underlying the cosmological matter-antimatter asymmetry that we observe today.

The most sensitive experiment in the world searching for 0νbb is LEGEND, using high-purity germanium (HPGe) solid-state detectors fabricated with the double-beta isotope Ge-76. The first phase of LEGEND, using 200kg of isotope, has now started taking data at the Gran Sasso underground laboratory in Italy. Over the next few years, LEGEND has the potential to make a ground-breaking discovery of 0νbb, and the UCL group is at the forefront of the analysis effort.

A PhD project on the LEGEND experiment will include:
  • Analysis of data from LEGEND-200, including the development of novel techniques to maximise the discovery potential of the experiment.
  • Analysis of the performance and backgrounds of LEGEND-200, to inform the preparation of the next phase of the project (LEGEND-1000) that will be entering construction later this decade.
  • The operation and development of HPGe detectors onsite at UCL.
This PhD project will mostly be computational, with significant opportunities for the development of novel analysis techniques. There will also be opportunities to get involved in practical and experimental aspects of the LEGEND experiment.

Contact: Prof. David Waters

Experimental: Plasma wakefield acceleration at FLASHForward

PhD project: Plasma Wakefield Acceleration on the FLASHForward Experiment

Supervisor: Prof. Matthew Wing

A studentship is offered jointly funded by DESY and UCL to work on plasma wakefield acceleration which could lead to future machines that are shorter and less costly than when using conventional accelerator techniques. The student will work on the FLASHForward experiment at DESY which is investigating electron-driven plasma wakefield acceleration. Research at the FLASHForward experiment focuses on energy gain of witness electron bunches, their beam quality, efficiency of the process, etc. The student would work on understanding the repetition frequency of the acceleration process, crucial to the luminosity of future colliders or brightness of future light sources. Up to megahertz rates are required and the dynamics of the plasma and beams needs to be understood in detail for a range of parameters with a combination of experiment and simulation. The student would also have the opportunity to work on designs for future colliders such as the recently proposed HALHF collider. The student would spend a significant period of about 2 years based in DESY, Hamburg, working directly on the experiment and closely with the rest of the collaboration.

Contact: Prof. Matthew Wing

Experimental: Anomaly detection with ATLAS

PhD project: Anomaly detection in ATLAS using machine learning

Supervisor: Prof. Mario Campanelli

After over a decade of unsuccessful searches for new physics at the LHC, the attention is shifting more and more towards model-independent approaches that exploit the rapid advancement of machine learning from last years. Detecting anomalies means searching for events that differ from the bulk of Standard Model collisions recorded by the detector, in a novel and model-independent way. Instead of searching for a specific model of new physics, the events are classified into classes using unsupervised techniques, mapping the emitted particles to a lower-dimensional space the various regions corresponding to known physics identified using Monte Carlo simulations. Anomalous events laying outside of the known boundaries may indicate unforeseen phenomena. The work will also explore the possibility to perform this searches online at trigger level, for the high-luminosity upgrade program.
The student will be expected to spend an extended period (up to 1 year) at the CERN laboratory in Geneva.

Contact: Prof. Mario Campanelli

Experimental: Vector boson measurements with ATLAS

PhD project: Measuring WZ events in the semi-leptonic channel using ML-based taggers

Supervisor: Prof.Mario Campanelli

Several new physics models predict particles that interact with vector bosons, notably W and Z bosons. Albeit measurements of WZ production already exist in ATLAS, they are not optimised to the kinematic regime that could indicate presence of new physics. This project aims at measuring the production of W and Z boson in the case when one of them decays in the clean leptonic channel, and the other in the hadronic one, giving rise to a hadronic jet with characteristic 2-prong signature. These decay modes are identified using specific Machine-Learning based algorithms, that have been developed by the UCL group and other collaborators over the years. During the course of this project the student will work on further improvements and in the design of new techniques for multi-particle tagging. The final results will be interpreted in the context of various new physics models, and unfolded to particle level using modern ML-based techniques.
The student will be expected to spend an extended period (up to 1 year) at the CERN laboratory in Geneva.

Contact: Prof. Mario Campanelli

Experimental: Dark matter searches with LZ

PhD project: Dark Matter searches with the LZ experiment

Supervisor: Dr. Amy Cottle

Despite accounting for 85% of the mass of the Universe, the nature of dark matter remains a mystery. The LZ experiment is at the forefront in the quest to observe galactic dark matter, having recently published world-leading limits on dark matter interactions from its engineering run. LZ is now probing uncharted electroweak parameter space, with the ability to discover or provide constraints on the foremost dark matter theories.

This studentship represents an exciting opportunity to participate in the analysis of new science data from LZ. The candidate will play an active role in the flagship dark matter search, currently being led by the UCL group, and will have the chance to explore the sensitivity of LZ to more physics beyond the Standard Model, including neutrinoless double beta decay. In addition to data analysis, the project will involve the use and development of Monte Carlo simulations and statistical inference techniques.

There is the potential for the successful applicant to travel to site to assist in the operation of LZ’s 7 active-tonne dual-phase xenon time projection chamber, the world’s largest detector of its kind, as well as to spend extended time at one of our collaborating US institutions. There will also be the opportunity for the student to engage with R&D and design efforts being pursued UK-wide towards a future, global xenon-based rare-event search observatory, should they wish.

Contact: Dr. Amy Cottle

Experimental: The Mu2e experiment

PhD project: The Mu2e experiment

Supervisor: Dr. Becky Chislett

Muons are a unique probe in the search for new physics, offering large increases in sensitivity (4 orders of magnitude) due to the availability of intense muon beams combined with the properties of muon production and decay. There are also hints at muons behaving differently to the theoretical prediction coming from the g-2 experiment at Fermilab. This has now finished running and the beam transferred to the Mu2e experiment, which searches for charged lepton flavour violation i.e a muon turning into an electron. More specifically, looking for the neutrinoless conversion of a muon to an electron in the field of a nucleus. Lepton flavour violation has been observed in the neutral sector through neutrino oscillations but it has not yet been observed in the charged sector. The rate allowed in the Standard Model is well below the level that experiments can currently reach, so any observation would be a sign of new physics.

The experiment is currently under construction with the various systems being commissioned and data taking expected to start in 2025. The PhD project would involve work on the installation and commissioning of the experiment with a focus on the stopping target monitor (the detector being provided by the UK), followed by analysis of the first data taken by the experiment.

Contact: Dr. Becky Chislett

Theory: Parton Distribution Functions

PhD project: Improving the MSHT Parton Distribution Functions

Supervisor: Prof. Robert Thorne

The project would be based on the updating and improvement of the MSHT parton distribution functions (PDFs). It would revolve around the theory of the strong force, QCD, and the extraction of the PDFs, describing the composition of the proton in terms of quarks, antiquarks and gluons, and the use of these in collider physics. This is a very large-scale, on going project and all LHC and high-energy neutrino cross-sections rely on our understanding of these partons. The extraction relies on comparing all relevant data with the most up-to-date theoretical calculations in order to obtain information on the the uncalculable components of the predictions, which depends on nonperturbative physics. As well as the uses of the obtained PDFs in making predictions for Standard Model physics, and potentially investigating discrepancies which might be a signal for Beyond the Standard Model physics, the study is an excellent test of precision QCD and the strong coupling. In recent years the data has become exceptionally precise and constraining, and recent work has involved improving the precision of theoretical descriptions and predictions by going to higher order in perturbative QCD, and also in making a full investigation of the statistical tools used in comparable data and theory and developing techniques for non-standard uncertainty analyses.

Contact: Prof. Robert Thorne

There will also be 4-5 HEP studentship projects available via the Data Intensive Science (DIS) Centre for Doctoral Training (CDT) covering similar topics on a similar range of experiments. To be considered for these projects, an application will also need to be made directly to the CDT.