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

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|=40 V/cm without producing leakage in CDMS II Ge detectors, allowing sensitivity to a benchmark WIMP with mass M=8 GeV/c and σ=1.8×10 cm (with significant sensitivity for M>2 GeV/c) 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 <10 for a simulated 20 kg-day experiment with a benchmark WIMP signal with M=8 GeV/c and σ=3.3×10 cm. [ABSTRACT FROM AUTHOR]