Low-Mass WIMP Sensitivity and Statistical Discrimination of Electron and Nuclear Recoils by Varying Luke-Neganov Phonon Gain in Semiconductor Detectors

TL;DR

This paper demonstrates how varying Luke-Neganov phonon gain in semiconductor detectors enhances sensitivity to low-mass WIMPs and enables statistical discrimination between nuclear and electronic recoils, improving dark matter detection capabilities.

Contribution

It introduces a method to vary phonon gain via voltage bias to improve WIMP sensitivity and distinguish recoil types in semiconductor detectors.

Findings

Validated amplification up to |E|=40V/cm without leakage.

Achieved sensitivity to 8 GeV WIMPs with specific cross section.

Demonstrated statistical discrimination between recoil types.

Abstract

Amplifying the phonon signal in a semiconductor dark matter detector can be accomplished by operating at high voltage bias and converting the electrostatic potential energy into Luke-Neganov phonons. This amplification method has been validated at up to |E|=40V/cm without producing leakage in CDMSII Ge detectors, allowing sensitivity to a benchmark WIMP with mass = 8GeV and cross section 1.8e-42cm^2 assuming flat electronic recoil backgrounds near threshold. Furthermore, for the first time we show that differences in Luke-Neganov gain for nuclear and electronic recoils can be used to discriminate statistically between low-energy background and a hypothetical WIMP signal by operating at two distinct voltage biases. Specifically, 99% of events have p-value<1e-8 for a simulated 20kg-day experiment with a benchmark WIMP signal with mass =8GeV and cross section =3.3e-41cm^2.