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 am currently ramping up my involvement in the silicon tracker replacement for the High-Luminosity LHC upgrade, where I am involved in the production database.

FASER2020 - Current

Liverpool joined the FASER experiment to search for new light, weakly-interacting particles (such as dark photons and ALPs) down-stream of ATLAS in summer 2020. I am currently working on the simulation and digitisation of the FASER calorimeter, comparing the results with test-beam data. With the start of run-3 LHC data-taking, I am leading the FASER physics exploitation as joint Physics Convener.

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.

• Lottie Cavanagh: FASER2020--present
• Conor McPartland: τ → 3μ2020--present
• Zhiyuan (Jordan) Li: HH → bbττ2018--2022
• Emily Graham: HH → bbττ2015--2019
• Ellis Kay: W' → eν 2014--2018

Roles

• Deputy Physics Department Disability Contact 2022--present