PhD projects available for self-funded students

These projects are available for students that are able to self-fund their PhD studies, or have an externally funded scholarship. Applications for these studentships are welcome at any time of year.

ATLAS: Investigating the fundamentals of the Universe by measuring the properties the top quark and Higgs boson

Probing the Higgs boson, the most recently discovered fundamental particle, and one unlike anything else in the SM, is a critical priority in the search for new physics at the LHC. The Higgs boson is responsible for giving fundamental particles their mass and has the strongest interaction with the largest mass particles. The top quark is the heaviest fundamental particle in the SM and therefore has the strongest coupling to the Higgs. This makes LHC collisions where a Higgs is produced with a top-quark pair (ttH) one of the most exciting places to look for signs of new physics. The candidate will play a leading role in new differential measurements of ttH in the H->leptons decay mode using the Run 3 data. This will provide fresh sensitivity to the top quark-Higgs interaction and the Higgs boson’s interaction with itself that will lead to world-leading sensitivity to new physics. The importance of this work goes beyond understanding the Higgs boson. The interplay between the strength of the top-Higgs interaction and the Higgs self-interaction is directly related to the stability of the Universe at a quantum level and the exact (CP) nature of the top-Higgs interaction could hold the answer to why we exist at all - why the Universe is matter-dominated.

The interaction of top quarks and leptons (ttll) as well as being an important background to ttH measurements is also of extremely high priority in its own right as it gives a window into one of the strongest hints of new physics to come out of the LHC, the flavour anomalies. The candidate will also investigate a measurement of ttll (where l=e,mu,tau) to test the universality of lepton couplings in the top sector. This measurement will add a vital additional piece of information in our attempts to understand the flavour anomalies seen in the B-sector.

The ATLAS-Sussex group has made significant contributions measurements of ttH, ttW and ttll production in multi-lepton final states performed so far in ATLAS: profiting from this experience in the group, the candidate will be ideally positioned to make large impact in this sector, also through close contact with CERN-based experts. (Supervisor: Dr Josh McFayden)

FASER(2): Looking forward to new physics

FASER stands for “ForwArd Search ExpeRiment” and is one the newest experiments based at the Large Hadron Collider (LHC) at CERN. It is a novel experiment searching for exotic long-lived and weakly-interacting new particles. Such particles are excellent candidates to explain the existence of Dark Matter. If they exist, these exotic particles would be produced in collisions inside the ATLAS detector and detected nearly 500m away in FASER.
The Sussex Experimental Particle Physics group has had involvement in the construction and commissioning of the FASER detector that is now installed underground at CERN. FASER is currently taking data during LHC Run 3 and the candidate will make major contributions to the analysis of this data with a view to probing brand new areas of phase-space that have until now been experimentally out of reach. The analysis of the data will involve understanding the performance of the detector and backgrounds to be then be able to search for possible signs of new particles.

In addition, R&D studies are underway for a significantly upgraded detector to FASER, known as FASER2. This detector would be housed in the Forward Physics Facility and would be installed in next, high-luminosity (HL), phase of running for the LHC (Run 4) and would take data until the end of HL-LHC. It has a strong neutrino physics measurement programme in addition to the searches for new physics. The candidate will investigate different designs of FASER2 to determine what layouts and detector technologies will be required to get the best sensitivity to neutrinos and long-lived new particles.

The Sussex Collider physics group has made significant contributions to the construction, commissioning and operation of FASER and is leading R&D efforts on FASER2: profiting from this experience in the group, the candidate will be ideally positioned to make large impact in this sector, also through close contact with CERN-based experts. (Supervisor: Dr Josh McFayden)

Searching for new sources of CP violation with the n2EDM experiment

Searches for a neutron Electric Dipole Moment (nEDM) provide an extremely sensitive probe for new physics that violates combined charge and parity symmetries (CP). Additional CP violation is required to explain why there is more matter than antimatter in the universe, and the measurement of a nonzero EDM could be the key to this important puzzle, and would have profound implications for particle physics and cosmology. The Paul Scherrer Institute (PSI) in Switzerland hosts the collaboration that holds the world record in sensitivity in nEDM measurement, and is currently commissioning a new experimental apparatus (n2EDM) which should improve the nEDM sensitivity by more than an order of magnitude. An interested self-funded student would be welcome to join the Sussex group working on the n2EDM experiment, where they would have the opportunity to analyse new data from the n2EDM apparatus, with a focus on analysing and optimising signals from the optical atomic magnetometry subsystems (Hg and Cs), which are crucial for studying and understanding systematic effects. (Supervisor: Dr W Clark Griffith)