Abstract
Single electron noise which persists for many milliseconds is known to follow ionizing events in liquid/gas xenon emission detectors. Due to the long timescale, this noise can be mistaken for a genuine signal. Therefore, it is a limiting background to the low-energy threshold of dark matter searches, and could prevent discovery-class searches for MeV scale hidden sector dark matter. A systematic study reveals distinct fast and slow components to the noise. The fast component is compatible with the hypothesis of electrons which were trapped below the liquid surface, and can be reduced by increasing the electric field across the liquid/gas interface. However, the slow component increases linearly with electric field. Hypotheses for the origin of this effect are discussed, and techniques for mitigation are suggested.
Highlights
Liquid xenon emission detectors [1,2,3] have proven extremely useful for rare-event searches, such as for galactic dark matter
In this article we report results of R&D towards that end, from a systematic study of electron trains in a small liquid xenon emission detector
The fast component decreases with El and appears to be due to thermalized electrons which were not emitted in the primary S2 signal
Summary
Liquid xenon emission detectors [1,2,3] have proven extremely useful for rare-event searches, such as for galactic dark matter. In a search for low-mass dark matter, the XENON10 Collaboration identified a single electron background which they referred to as an “electron train,” with a time scale at least as long as the putative thermalized component [6]. This background is thought to have been responsible for a significant number of the one, two and three electron signals reported in that analysis. It may be due to fluorescence photons which photo-ionize impurities in the liquid xenon
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