The Migdal Effect in LZ

LZ is a two phase xenon time projection chamber with 7 tonnes active and 5.6 tonnes fiducial volume designed to achieve a spin-independent cross section sensitivity of 1.4 x 10^-48 cm² for a 40 GeV/c² WIMP mass. For lighter WIMP masses, below about 5 GeV/c², this sensitivity is diminished due to the small energy transfer in elastic collisions of dark matter and xenon nuclei. Sensitivity to WIMPs in this mass range can be extended by searching for the ionization electrons concurrently produced in nuclear collisions, in an inelastic process called the Migdal effect. These recoiling electrons can carry more experimentally detectable energy than corresponding nuclear recoils, providing sensitivity to dark matter particles that would otherwise produce sub-threshold recoils. I will discuss the expected signature of the Migdal effect in LZ and the sensitivity enhancement to low mass dark matter that can be expected from searching for these types of events.