Demonstration of Surface Electron Rejection with Interleaved Germanium Detectors for Dark Matter Searches

TL;DR

This paper demonstrates that interleaved germanium detectors effectively reject surface electron events in dark matter searches, significantly reducing background noise and improving detection sensitivity.

Contribution

It introduces a novel detector configuration that achieves near-zero surface event leakage, enhancing dark matter detection capabilities in cryogenic germanium detectors.

Findings

No surface events leaked into the signal region in 800 hours

Leakage fraction limited to 1.7 x 10^-5 at 90% C.L.

Projected less than 0.6 background events in future large-scale experiment

Abstract

The SuperCDMS experiment in the Soudan Underground Laboratory searches for dark matter with a 9-kg array of cryogenic germanium detectors. Symmetric sensors on opposite sides measure both charge and phonons from each particle interaction, providing excellent discrimination between electron and nuclear recoils, and between surface and interior events. Surface event rejection capabilities were tested with two $^{210}$Pb sources producing $\sim$130 beta decays/hr. In $\sim$800 live hours, no events leaked into the 8--115 keV signal region, giving upper limit leakage fraction $1.7 \times 10^{-5}$ at 90% C.L., corresponding to $< 0.6$ surface event background in the future 200-kg SuperCDMS SNOLAB experiment.