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

TL;DR

This study identifies two components of delayed single electron background signals in liquid xenon detectors, with implications for improving dark matter search sensitivity by understanding their origins and mitigation strategies.

Contribution

It reveals the existence of fast and slow components in the background signals and explores their origins and how they can be mitigated in xenon emission detectors.

Findings

Fast component linked to electrons trapped at the liquid surface

Slow component increases linearly with electric field

Increasing electric field reduces the fast component

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.