Sensitivity projections for hidden photons and axion-like particles in the LUX-ZEPLIN experiment

Abstract

The particle nature of dark matter is one of the yet unresolved puzzles in contemporary physics. The properties of dark matter, as revealed by several types of cosmological evidence, are inconsistent with the Standard Model of particle physics and imply a new physics beyond. The multi-ton scale, low threshold LUX−ZEPLIN (LZ) experiment aims to detect prospective dark matter particles, particularly the weakly interacting massive particles (WIMPs), by their interactions with liquid xenon nuclei. Apart from WIMPs, LZ is also sensitive to dark matter candidates that may interact with atomic electrons, e.g. the hidden photons (HPs) and the axion-like particles (ALPs). The sensitivity of rare dark matter searches, however, is critically limited by the unavoidable detector backgrounds – the majority of which sit in the electron recoil (ER) band. An accurate modelling of ER backgrounds with a proper treatment of the atomic binding is thus crucial, particularly for the low energy ER searches. The present work addresses some of these exciting issues (e.g. the studies of solar neutrino and low energy electromagnetic backgrounds) in the context of the LZ detector and evaluates the sensitivity reach of the experiment (for 5600 kg fiducial volume and a 1000 live-day run) for HPs and ALPs in the 2 − 70 keV/c^2 mass range.