Results from a Search for Light-Mass Dark Matter with a<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi></mml:math>-Type Point Contact Germanium Detector

TLDR

By implementing a new technique to reject surface events, the detector can observe cosmogenic peaks for the first time. The detector observed several spectral features, including an irreducible excess of bulk‑like events below 3 keV that could arise from unknown backgrounds or dark‑matter interactions compatible with DAMA/LIBRA, and the study places tighter constraints on a cosmological origin for the DAMA/LIBRA signal.

Abstract

We report on several features in the energy spectrum from an ultralow-noise germanium detector operated deep underground. By implementing a new technique able to reject surface events, a number of cosmogenic peaks can be observed for the first time. We discuss an irreducible excess of bulklike events below 3 keV in ionization energy. These could be caused by unknown backgrounds, but also dark matter interactions consistent with DAMA/LIBRA. It is not yet possible to determine their origin. Improved constraints are placed on a cosmological origin for the DAMA/LIBRA effect.