Identification of the anomalous fast bulk events in a p-type point contact germanium detector

TL;DR

This paper presents a method to identify and extract anomalous fast bulk events in p-type point-contact germanium detectors, improving background discrimination for rare-event searches like dark matter detection.

Contribution

It introduces a pulse shape simulation-based technique to distinguish fast bulk events from normal events, enhancing detector background rejection capabilities.

Findings

Successfully extracted fast bulk events using the new method

Demonstrated the detector's ability for single-hit bulk spatial resolution

Verified the method with calibration and radioactivity data

Abstract

The ultralow detection threshold, ultralow intrinsic background, and excellent energy resolution of p-type point-contact germanium detector are important for rare-event searches, in particular for the detection of direct dark matter interactions, coherent elastic neutrino-nucleus scattering, and neutrinoless double beta decay. Anomalous bulk events with an extremely fast rise time are observed in the CDEX-1B detector. We report a method of extracting fast bulk events from bulk events using a pulse shape simulation and reconstructed source experiment signature. Calibration data and the distribution of X-rays generated by intrinsic radioactivity verified that the fast bulk experienced a single hit near the passivation layer. The performance of this germanium detector indicates that it is capable of single-hit bulk spatial resolution and thus provides a background removal technique.