Search for Boosted Dark Matter in COSINE-100

TL;DR

This study uses the COSINE-100 detector to search for boosted dark matter signals via energetic electron recoils, setting new limits on dark photon parameters and demonstrating the detector's potential for low-mass dark matter detection.

Contribution

First to analyze COSINE-100 data for boosted dark matter signals, providing competitive dark photon limits and highlighting advantages over previous experiments for low-mass dark matter searches.

Findings

No excess events observed above background.

Set competitive limits on dark photon interactions below 4 MeV.

Demonstrated COSINE-100's potential for low-mass dark matter detection.

Abstract

We search for energetic electron recoil signals induced by boosted dark matter (BDM) from the galactic center using the COSINE-100 array of NaI(Tl) crystal detectors at the Yangyang Underground Laboratory. The signal would be an excess of events with energies above 4 MeV over the well-understood background. Because no excess of events are observed in a 97.7 kg$\cdot$years exposure, we set limits on BDM interactions under a variety of hypotheses. Notably, we explored the dark photon parameter space, leading to competitive limits compared to direct dark photon search experiments, particularly for dark photon masses below 4\,MeV and considering the invisible decay mode. Furthermore, by comparing our results with a previous BDM search conducted by the Super-Kamionkande experiment, we found that the COSINE-100 detector has advantages in searching for low-mass dark matter. This analysis demonstrates the potential of the COSINE-100 detector to search for MeV electron recoil signals produced by the dark sector particle interactions.