Nuclear Recoil Migdal Effect in Liquid Xenon Dark Matter Experiments

Abstract

The Migdal effect predicts that a nuclear recoil can be accompanied by detectable atomic ionization or excitation signals, even at the low energies expected from interactions of sub-GeV dark matter particles with atomic nuclei. Liquid xenon-based dark matter experiments have projected substantial sensitivity gains to light dark matter based on this effect, underscoring the importance of its direct characterization in xenon. In this Letter, we draw on our theoretical and experimental studies of nuclear recoil Migdal interactions to discuss their predicted characteristics and corresponding observable signatures in liquid xenon detectors. We examine the challenges of directly observing Migdal signals using neutron-induced xenon recoils and outline possible measurement strategies and necessary background mitigation measures to allow a definitive confirmation of the Migdal effect in liquid xenon.