  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.
