CoGeNT: A Search for Low-Mass Dark Matter using p-type Point Contact Germanium Detectors

TL;DR

CoGeNT uses specialized germanium detectors with low energy thresholds to search for low-mass dark matter particles, analyzing background events and potential annual modulation signals to support dark matter detection efforts.

Contribution

This paper demonstrates the suitability of p-type point-contact germanium detectors for low-mass dark matter searches and provides detailed background modeling and analysis of event characteristics.

Findings

Extensive background simulations do not explain the low-energy excess.

The detector effectively rejects surface background events.

Data shows potential for detecting annual modulation signals.

Abstract

CoGeNT employs p-type point-contact (PPC) germanium detectors to search for Weakly Interacting Massive Particles (WIMPs). By virtue of its low energy threshold and ability to reject surface backgrounds, this type of device allows an emphasis on low-mass dark matter candidates (wimp mass of about 10 GeV/c2). We report on the characteristics of the PPC detector presently taking data at the Soudan Underground Laboratory, elaborating on aspects of shielding, data acquisition, instrumental stability, data analysis, and background estimation. A detailed background model is used to investigate the low energy excess of events previously reported, and to assess the possibility of temporal modulations in the low-energy event rate. Extensive simulations of all presently known backgrounds do not provide a viable background explanation for the excess of low-energy events in the CoGeNT data, or the previously observed temporal variation in the event rate. Also reported on for the first time is a determination of the surface (slow pulse rise time) event contamination in the data as a function of energy. We conclude that the CoGeNT detector technology is well suited to search for the annual modulation signature expected from dark matter particle interactions in the region of WIMP mass and coupling favored by the DAMA/LIBRA results