Dr Holly Pacey

Dr Pacey is a Research Fellow in particle physics, working on the ATLAS experiment at CERN's LHC. Prior to this she held an Eric and Wendy Schmidt AI in Science Postdoctoral Research Fellowship at Oxford, and a Research Fellowship at Peterhouse, Cambridge. Dr Pacey completed her PhD searching for new physics with leptons at the ATLAS experiment at King's College, Cambridge, in 2020.

I am interested in studying the Higgs boson through multi-Higgs production, and searching for new particles beyond the Standard Model of particle physics being produced in our unprecedently high energy proton collisions at the LHC. Most recently my focus is on searching for dark matter and extended Higgs sector models, and developing new graphical Machine Learning analysis methods to represent our dataset and enhance sensitivity. I also work in optimising ATLAS's ability to detect invisible particles through complex missing transverse momentum reconstruction and triggers.

I tutor the 2nd year Mathematical Methods course and A3 Quantum and Further Quantum courses.

ATLAS Collaboration. A search for dark matter produced in association with a dark Higgs boson decaying into a Higgs boson pair in 3b or 4b final states using pp collisions at sqrt(s)=13TeV with the ATLAS detector. JHEP 09 (2025) 067;
ATLAS Collaboration. A search for triple Higgs boson production in the 6⁢b final state using pp collisions at sqrt(s) =13 TeV with the ATLAS detector. PRD 111 (2025) 032006;
FCC Collaboration. Future Circular Collider Feasibility Study Report. EPJC 85 (2025) 12 1468;
ATLAS Collaboration. The performance of missing transverse momentum reconstruction and its significance with the ATLAS detector using 140 fb-1 of sqrt(s)=13 TeV pp collisions. EPJC 85 606 (2025);
ATLAS Collaboration. The ATLAS trigger system for LHC Run 3 and trigger performance in 2022. JINST 19 (2024) P06029;
ATLAS Collaboration. A search for an unexpected asymmetry in the production of e+μ− and e−μ+ pairs in proton–proton collisions recorded by the ATLAS detector at sqrt(s)=13 TeV. PLB 830 (2022) 137106.
A. Mullins, S. Nicholls, H. Pacey et al. Does SUSY have friends? A new approach for LHC event analysis. JHEP 02 (2021) 160;
ATLAS Collaboration. Search for electroweak production of charginos and sleptons decaying into final states with two leptons and missing transverse momentum in sqrt(s)=13 TeV pp collisions using the ATLAS detector. EPJC 80 (2020) 2, 123.