Search for new physics with the FASER experiment at the LHC & prospects at future experiments
28 Nov 2023







Supervisors: Dr. Monika Wielers (RAL/PPD) + Dr. ​Carl Gwilliam (Liverpool University​)

FASER is a new CERN experiment designed primarily to search for light, weakly-interacting beyond Standard Model (BSM) particles with a significant lifetime in the far-forward region of the LHC.  Located 480m downstream of the proton-proton interaction point (IP) used by the ATLAS experiment, the detector is a cylindrical spectrometer, consisting primarily of a tracker and a calorimeter, immersed in a 0.6T magnetic field. It successfully started data-taking in summer 2022 during LHC run-3 and has collected approximately 40/fb of data so far, leading to the first direct observation of collider neutrinos and a first search for Dark Photons in previously unexplored phase space. For the HL-LHC, there is a proposal for a dedicated Forward Physics Facility (FPF), hosting a suite of experiments including a 10x larger FASER2 detector with a significantly expanded physics reach.  

Liverpool, the largest UK group on FASER, played a major role in the latter and currently holds the role of Physics Coordinator, overseeing the entire physics programme. RAL has experience in Heavy Neutral Leptons, using the LHC collision data collected at a centre-of-mass energy of 13TeV and has expertise in developing tracking software.

The student is expected to play a leading role in searches for long-lived BSM particles (LLPs). The decays of boosted LLPs, such as HNLs, produce a challenging experimental signature of very close-by tracks, which are difficult to resolve experimentally. In addition, the student will study and optimise the layout of the tracking detector for FASER2.  Cutting across the FASER and FASER2 activities, the student will study the FASER tracking software and play a major role in developing and improving this software, which was the limiting factor in the recent dark-photon result. On FASER, once the full run-3 dataset has been collected by the end of 2025, they will be ideally placed to play a leading role in the legacy BSM searches with the full run-3 dataset.   The increased dataset gives access to more complex BSM models than the simple dark photon and axion-like particles currently probed, in particular in the context of heavy neutral leptons (HNLs) in tau final states. The student will take a lead in this analysis and explore previously uncovered phase space.

For more details, contact Monika Wielers ( or Carl Gwilliam (​

Contact: Tomalin, Ian (STFC,RAL,PPD)