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 _χ =8 GeV/c² and σ=1.8×10⁻⁴² cm² (with significant sensitivity for M _χ >2 GeV/c²) 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 <10⁻⁸ for a simulated 20 kg-day experiment with a benchmark WIMP signal with M _χ =8 GeV/c² and σ=3.3×10⁻⁴¹ cm².

We would like to thank D. Moore and J. Filippini for valuable discussions. This work is supported by the Department of Energy contract DE-FG02-04ER41295, and in part by the National Science Foundation Grant No. PHY-0855525.

Authors and Affiliations

1. Department of Physics, Stanford University, Stanford, Ca, 94110, USA

   M. Pyle, B. Cabrera & S. Yellin

2. Fermi National Accelerator Laboratory, Batavia, IL, 60510, USA

   D. A. Bauer, J. Hall & R. Basu Thakur

3. Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA

   R. Basu Thakur

4. Department of Physics, Syracuse University, Syracuse, NY, 13244, USA

   R. W. Schnee

Corresponding author

Correspondence to M. Pyle.

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