New limits on spin-independent and spin-dependent couplings of low-mass WIMP dark matter with a germanium detector at a threshold of 220 eV

TL;DR

This study demonstrates a germanium detector with a 220 eV threshold that sets new constraints on low-mass WIMP dark matter, especially below 10 GeV, and enhances detection sensitivity in the sub-keV energy range.

Contribution

The paper introduces a novel ultra-low-energy germanium detector with a 220 eV threshold, enabling improved constraints on low-mass WIMPs and opening new avenues for neutrino and dark matter research.

Findings

Improved limits on spin-independent WIMP-nucleon cross-section for 3-6 GeV WIMPs.

Enhanced sensitivity in the sub-keV energy window for dark matter detection.

Demonstrated feasibility of ultra-low-threshold germanium detectors for future experiments.

Abstract

An energy threshold of (220+-10) eV was achieved at an efficiency of 50% with a four-channel ultra-low-energy germanium detector each with an active mass of 5 g. This provides a unique probe to WIMP dark matter with mass below 10 GeV. With a data acquisition live time of 0.338 kg-day at the Kuo-Sheng Laboratory, constraints on WIMPs in the galactic halo were derived. The limits improve over previous results on both the spin-independent WIMP-nucleon and the spin-dependent WIMP-neutron cross-sections for WIMP mass between 3-6 GeV. Sensitivities for full-scale experiments are projected. This detector technique makes the unexplored sub-keV energy window accessible for new neutrino and dark matter experiments. Two appendices are included after Version-3 to address questions raised on trigger and selection efficiencies as well as other issues.