I am a Graduate student at the Particle Physics sub-department at the University of Oxford. I work as a member of the LUX-ZEPLIN (LZ) experiment, with the primary physics goal of discovery of dark matter particle candidates via direct detection methods. LZ is an international collaboration that consists of over 200 students, researchers and engineers across the UK, US, Portugal and Korea that all work together to achieve this goal. The LZ experiment itself is located at the 4850' level of the Sanford Underground Research Facility, South Dakota, US. We will use 7 tonnes of liquid xenon in a Dual Phase Time Projection Chamber (TPC) to detect recoils with the xenon nuclei at the keV energy scale. We expect to achieve world leading sensitivity to multiple exciting physics signals, including possible detection of solar axions and observations of neutrinoless double beta decay to name just a few.
Before coming to Oxford, I graduated with a First Class Physics with Astrophysics MPhys (Hons) from the University of Manchester. For my MPhys project during my final year, I worked with Dr. Darren Price and Dr. Andrzej Slezc on the DarkSide-20k experiment. The DarkSide collaboration are also hoping to detect dark matter particle candidates using liquid argon as the detection medium.
Niamh Fearon
Graduate student
Research theme
Sub department
Astroparticle Physics
Dark Matter
Low Background Experiments
J.Phys.G 50 (2023) 1, 013001
The nature of dark matter and properties of neutrinos are among the most pressing issues in contemporary particle physics. The dual-phase xenon time-projection chamber is the leading technology to cover the available parameter space for weakly interacting massive particles, while featuring extensive sensitivity to many alternative dark matter candidates. These detectors can also study neutrinos through neutrinoless double-beta decay and through a variety of astrophysical sources. A next-generation xenon-based detector will therefore be a true multi-purpose observatory to significantly advance particle physics, nuclear physics, astrophysics, solar physics, and cosmology. This review article presents the science cases for such a detector.
Phys.Rev.Lett. 131 (2023) 4, 041002
The LUX-ZEPLIN experiment is a dark matter detector centered on a dual-phase xenon time projection chamber operating at the Sanford Underground Research Facility in Lead, South Dakota, USA. This Letter reports results from LUX-ZEPLIN’s first search for weakly interacting massive particles (WIMPs) with an exposure of 60 live days using a fiducial mass of 5.5 t. A profile-likelihood ratio analysis shows the data to be consistent with a background-only hypothesis, setting new limits on spin-independent WIMP-nucleon, spin-dependent WIMP-neutron, and spin-dependent WIMP-proton cross sections for WIMP masses above 9 GeV/c2. The most stringent limit is set for spin-independent scattering at 36 GeV/c2, rejecting cross sections above 9.2×10-48 cm at the 90% confidence level.
Phys.Rev.D 108 (2023) 1, 012010
The LUX-ZEPLIN experiment recently reported limits on WIMP-nucleus interactions from its initial science run, down to 9.2×10-48 cm2 for the spin-independent interaction of a 36 GeV/c2 WIMP at 90% confidence level. In this paper, we present a comprehensive analysis of the backgrounds important for this result and for other upcoming physics analyses, including neutrinoless double-beta decay searches and effective field theory interpretations of LUX-ZEPLIN data. We confirm that the in-situ determinations of bulk and fixed radioactive backgrounds are consistent with expectations from the ex-situ assays. The observed background rate after WIMP search criteria were applied was (6.3±0.5)×10-5 events/keVee/kg/day in the low-energy region, approximately 60 times lower than the equivalent rate reported by the LUX experiment.
Phys.Rev.D 108 (2023) 7, 072006
The LUX-ZEPLIN (LZ) experiment is a dark matter detector centered on a dual-phase xenon time projection chamber. We report searches for new physics appearing through few-keV-scale electron recoils, using the experiment’s first exposure of 60 live days and a fiducial mass of 5.5 t. The data are found to be consistent with a background-only hypothesis, and limits are set on models for new physics including solar axion electron coupling, solar neutrino magnetic moment and millicharge, and electron couplings to galactic axionlike particles and hidden photons. Similar limits are set on weakly interacting massive particle (WIMP) dark matter producing signals through ionized atomic states from the Migdal effect.