Single electron backgrounds with millisecond timescales are known to follow ionizing events in liquid/gas xenon emission detectors. These backgrounds can limit 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. This is consistent with electron impact excitation of higher-energy molecular excited states.
P. Sorensen and K. Kamdin
Tue, 21 Nov 17