Measurement of Ionization Produced by 254 eVnr Nuclear Recoils in Germanium

TL;DR

This study measures ionization from low-energy nuclear recoils in germanium, revealing higher ionization yields than predicted, which could enhance dark matter and neutrino detection sensitivity.

Contribution

The paper provides a re-measurement of ionization yields for 254 eVnr recoils in germanium with improved methods, showing results that surpass theoretical predictions.

Findings

Ionization yield of 64 +/- 8 eVee for 254 eVnr recoils

Quenching factor of 25 +/- 3%, higher than Lindhard model

Potential for improved dark matter detection sensitivity

Abstract

Ionization produced by low-energy nuclear recoils is among the primary direct signatures of dark matter interactions. Despite the urgency of dark matter detection and the recent measurements of coherent elastic neutrino-nucleus scattering, detector response to nuclear recoils is not well characterized in the keVnr and sub-keVnr regime across a variety of materials. We have re-performed a measurement of the ionization produced by monoenergetic 254 eVnr nuclear recoils in Ge with improved digital electronics and additional systematic studies. Our results indicate an ionization yield of 64 +/- 8 eVee corresponding to a quenching factor of 25 +/- 3%, greater than the 14% predicted by the Lindhard model. This ionization enhancement could greatly improve the sensitivity of high-purity Ge detectors in dark matter detection and measurement of neutrinos via coherent scattering.