Comparative study of ratio and spectral shape discrimination technique in case of physics event selection for point contact germanium detector in sub-$keV_{ee}$ range

Abstract

As a result of the p-type point contact germanium detectors’ ability to produce kg-scale radiation sensors with sub-$keV_{ee}$ (electron equivalent energy) sensitivity, they have been preferred for light dark matter WIMP searches and the study of low energy neutrino physics. These detectors display anomalous behavior to events placed at the surface layer. The spectral shape and ratio methods are utilized to separate the bulk–surface events. The spectral shape technique relies on spectral shape assumptions and the use of external calibration sources to discriminate bulk–surface events. Whereas in ratio method to distinguish between bulk–surface events by employing ratios between several in situ event sample types as calibration sources. Here in this article we will present the comparison study of the two improved methods to separate the bulk–surface events. The bulk–surface separation results for both techniques are found to be comparable, but the main advantage of the ratio technique is its ability to calibrate systems using on-site data; this property makes it easier to collect long-term data and conduct large-scale multidetector research by reducing or eliminating the need for external $\gamma$-ray sources for calibration.