Search for An Annual Modulation in Three Years of CoGeNT Dark Matter Detector Data

TL;DR

This study analyzes three years of CoGeNT detector data to search for annual modulation signals indicative of dark matter interactions, finding a persistent modulation with unexpected amplitude and discussing possible astrophysical explanations.

Contribution

It provides a long-term dataset and analysis of annual modulation in germanium detector data, highlighting a persistent signal with anomalously large amplitude compared to standard models.

Findings

Persistent annual modulation signal observed

Modulation amplitude exceeds standard WIMP predictions

Possible non-Maxwellian halo velocity distribution considered

Abstract

Weakly Interacting Massive Particles (WIMPs) are well-established dark matter candidates. WIMP interactions with sensitive detectors are expected to display a characteristic annual modulation in rate. We release a dataset spanning 3.4 years of operation from a low-background germanium detector, designed to search for this signature. A previously reported modulation persists, concentrated in a region of the energy spectrum populated by an exponential excess of unknown origin. Its phase and period agree with phenomenological expectations, but its amplitude is a factor $\sim$4-7 larger than predicted for a standard WIMP galactic halo. We consider the possibility of a non-Maxwellian local halo velocity distribution as a plausible explanation, able to help reconcile recently reported WIMP search anomalies.