XENON FUTURES: R&D FOR A GLOBAL RARE EVENT OBSERVATORY (PHASE 2)

This proposal describes a 3-year programme of research and development into some of the most important challenges to be faced by next-generation liquid xenon-based dark matter detectors, and will enable the UK to maintain and enhance its global reputation. Astrophysical and cosmological evidence has established the Standard Model of Cosmology, which indicates that dark matter contributes ~27% to the total density of the universe.

The ZEPLIN programme of experiments, operated at Boulby (UK), pioneered the LXe technology for dark matter searches. The design is inherently scalable and, with sizes large enough to benefit maximally from self-shielding, LXe detectors have been the world-leading technology in searches for dark matter scattering ever since. The proponents of this proposal successfully delivered major contributions to the current state-of-the-art 'Generation 2' LUX-ZEPLIN (LZ) experiment.

With LZ entering its data-taking and exploitation phase in late 2020, it is timely to start research and development for future liquid xenon detectors now. This 3-year R&D project is for developing and preparing UK contributions for a future liquid xenon Generation 3 (G3) Global Rare Event Observatory. This will extend the search sensitivity right down to where new neutrino backgrounds will become dominant for masses of dark matter candidates >5 GeV, and also to lower masses, for which candidates are less well-constrained but equally well-motivated.

The main aims of this R&D phase are to enhance the scientific reach of a G3 experiment through demonstrating sensitivity via the Migdal effect and developing scalable low background VUV-SiPM photosensor arrays and their readout systems.