Limits on spin-independent couplings of WIMP dark matter with a p-type point-contact germanium detector

TL;DR

This study sets new limits on spin-independent WIMP-nucleon interactions using a p-type point-contact germanium detector, improving constraints in the low-mass WIMP parameter space through careful event discrimination and calibration.

Contribution

It introduces a novel calibration method and detailed event selection procedures to enhance sensitivity in low-energy WIMP detection with germanium detectors.

Findings

New exclusion limits on WIMP-nucleon cross-section

Effective differentiation of bulk and surface events at sub-keV energies

Probing and excluding parts of the parameter space suggested by other experiments

Abstract

We report new limits on spin-independent WIMP-nucleon interaction cross-section using 39.5 kg-days of data taken with a p-type point-contact germanium detector of 840 g fiducial mass at the Kuo-Sheng Reactor Neutrino Laboratory. Crucial to this study is the understanding of the selection procedures and, in particular, the bulk-surface events differentiation at the sub-keV range. The signal-retaining and background-rejecting efficiencies were measured with calibration gamma sources and a novel n-type point-contact germanium detector. Part of the parameter space in cross-section versus WIMP-mass implied by various experiments is probed and excluded.