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Background and sensitivity studies for the LUX-ZEPLIN dark matter experiment

Utku, Umit; (2021) Background and sensitivity studies for the LUX-ZEPLIN dark matter experiment. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

The existence of dark matter is now supported by a wide range of physical observations, ranging from galactic to cosmological scales. Our cosmological models predict dark matter to make up approximately 85% of the matter-content of the universe. One of the leading particle candidates that can effectively explain cosmological observations is the Weakly Interacting Massive Particles (WIMPS), the presence of which can be directly searched for by rare-event underground experiments via its scattering off atomic nuclei. By deploying a multi-tonne dual-phase liquid xenon (LXe) detector, the LUX-ZEPLIN (LZ) experiment, currently under construction in the Davis Campus at the Sanford Underground Research Facility (SURF) (South Dakota, USA) is projected to reach unprecedented sensitivities in search for WIMPs. In probing deeper into the WIMP landscape, an extensive screening and cleanliness campaign was envisioned, selecting some of the most radio-pure material for the construction of LZ. This work highlights some of the cutting-edge techniques used in understanding and modelling a wide range of backgrounds, focusing primarily on measuring and modeling the radon emanation background projections. By using the LZ simulation and statistical inference frameworks, the impact of radon emanation across different background scenarios are examined, where the 90% CL sensitivity is determined to vary from a cross-section of 1.34x10^{-48} cm^{2} to 1.76x10^{-48} cm^2 at best and worst case radon activities of 11.0 mBq and 60.4 mBq for a 40 GeV/c^{2}, respectively—remaining well below LZ requirement of 3.0x10^{-48} cm^{2}. The projected LZ sensitivity for a WIMP mass of 40 GeV/c^{2}, at a 90% CL and the 3 discovery potential was determined to be 1.43x10^{-48} cm^{2} and 3.4x10^{-48} cm^{2}. The projected limits from second-generation detectors, such as LZ and XENONnT, leave a significant amount of the parameter space above the cosmic neutrino floor (~10^{-49} cm^{2}) unexplored. In envisioning what a future third-generation (G3) detector may offer and the background necessities of such a detector, a toy G3 experiment is presented. A cryogenic radon facility currently under construction is outlined to pave the way for achieving the background requirements of a G3 dual-phase LXe observatory.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Background and sensitivity studies for the LUX-ZEPLIN dark matter experiment
Event: University College London
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2021. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10126479
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