Two distinct components of the delayed single electron background signals in liquid xenon emission detectors

Abstract: Single electron background signals with millisecond timescales are known to follow ionizing events in liquid/gas xenon emission detectors. Due to the long timescale, these signals can present a limiting background to the low-energy threshold of dark matter searches, and prevent discovery-class searches for MeV scale hidden sector dark matter. A systematic study reveals a fast (tau_1) and slow (tau_2) component to the background. The fast component is compatible with electrons which were trapped at the liquid surface, and can be reduced by increasing the electric field. However, the slow component increases linearly with electric field. Hypotheses for the origin of the effect are discussed, and techniques for mitigation are suggested.