Carl Gwilliam

ATLAS 2006 - Current

My early ATLAS research focused on searching for the much-sought Higgs boson. I used the first LHC data to search for a heavy SM Higgs boson not accessible at previous colliders, significantly constraining the allowed mass range. Following this, I made a significant contribution to the first LHC search for the dominant low-mass H → bb decay using the 7 TeV ATLAS data.

Since the Higgs discovery, I have focused on searching for physics beyond the SM (BSM). I initiated and led searches for additional BSM Higgs bosons, predicted in many models, in the lepton + jet final state using the 8 TeV ATLAS data. I then spearheaded the first run-2 ATLAS Higgs searches as ATLAS BSM Higgs subgroup convener, probing several BSM models.

I have subsequently utilised the SM Higgs boson as a new-physics probe. With the early 13 TeV data, I played a major role in the novel search for dark matter recoiling against a Higgs boson decaying to two b-jets. As ATLAS Exotics Diboson and Multilepton (DBL) subgroup convener, I oversaw the searches for new diboson resonances with the 2015+16 data, probing uncharted masses. I led the search for Higgs pair production in the HH → bbττ decay, establishing the world's best limit on the SM non-resonant di-Higgs cross section

From 2018-2020, I led the ATLAS BSM search programme as Exotics Working group convener, overseeing over 500 international physicists producing a wide-range of new phublications using the full run-2 LHC data.

I currently study the Higgs mechanism by continuing to search for the as-yet-unobserved HH production, which provides a unique probe of the Higgs potential and hence the underlying mechanism for mass generation. I also search generically for new physics and have particular interests in Dark Matter and Lepton Flavour Violation.

Besides physics analysis, I have contributed significantly to ATLAS track reconstruction software and the identification and calibration of jets originating from b-quarks; I currently contribute to the prodcution database for the ITk silicon tracker replacement for the High-Luminosity LHC upgrade. Nationally, I was ATLAS UK Physics Coordinator from 2020-2022 and I am currently Liverpool ATLAS Team Leader.

FASER2020 - Current

I joined the FASER experiment to search for long-lived particles (LLPs) downstream of ATLAS in 2020, where I have published searches for dark photons and axion like particles (ALPs) probing previously unexplored phase space. From 2022-2024, I was FASER Physics Coordinator, where I wa responsible for defining and overseeing the physics program of the FASER Experiment, coordinating the work of 90+ international physicists across different analysis teams, leading to timely delivery of the first FASER physics publications, which (in addition to the above LLP searches) provided the first direct detection of collider neutrinos that open a new avenue to study the Universe. In addition to physics analysis, I have contributed significantly to the simulation and digitisation of the scintillators and EM calorimeter. Looking forward, I am studying the physics potential of the proposed CERN Forward Physics Facility (FPF), in particular the optimisation of the tracking detector.

SHiP2024 - Current

I have recently joined the newly-approved SHiP experiment at the CERN SPS as an associate member, investigating ways Liverpool can contribute.

LUX/LUX-Zeplin 2017 - 2020

My LUX/LZ focus was on using EFTs to extend the classic spin-(in)depndent results to probe more complext dark sectors and allow direct detection results to be better compared with colliders. I contributed to the LUX run-4 EFT analysis. On LUX-Zeplin, I originated the analysis software framework and provided support for the UK Data Centre to prepare for first data.

H1 2002 - 2006

I wrote my thesis on the "Diffractive Photproduction of ρ mesons with Large Momentum Transfer at HERA". This was the first H1 measurement in this kinematic regieme and probed perturbative QCD modeles via mesurements of the differential cross-sections and spin density matrix elements.

• Pawan: FASER2024--present
• Sinead Eley: FASER2023--present
• Bhupesh Dixit: HH → bbττ2022--present
• Conor McPartland: τ → 3μ2020--present
• Lottie Cavanagh: FASER γ_dark and ALPS2020--2024
• Zhiyuan (Jordan) Li: HH → bbττ2018--2022
• Emily Graham: HH → bbττ2015--2019
• Ellis Kay: W' → eν 2014--2018

Roles

• Physics Department Disability Coordinator 2022--present