Lowering the energy threshold in COSINE-100 dark matter searches

TL;DR

COSINE-100, a dark matter detection experiment, lowered its energy threshold to 1 keV to better compare with DAMA/LIBRA and explore low-mass dark matter particles, validating its event selection methods.

Contribution

This paper presents the development and validation of a new event selection algorithm enabling COSINE-100 to operate effectively at a 1 keV energy threshold.

Findings

Validated event selection efficiency near 1 keV

Enabled model-independent comparison with DAMA/LIBRA

Accessed potential signals from sub-GeV dark matter particles

Abstract

COSINE-100 is a dark matter detection experiment that uses NaI(Tl) crystal detectors operating at the Yangyang underground laboratory in Korea since September 2016. Its main goal is to test the annual modulation observed by the DAMA/LIBRA experiment with the same target medium. Recently DAMA/LIBRA has released data with an energy threshold lowered to 1 keV, and the persistent annual modulation behavior is still observed at 9.5$\sigma$. By lowering the energy threshold for electron recoils to 1 keV, COSINE-100 annual modulation results can be compared to those of DAMA/LIBRA in a model-independent way. Additionally, the event selection methods provide an access to a few to sub-GeV dark matter particles using constant rate studies. In this article, we discuss the COSINE-100 event selection algorithm, its validation, and efficiencies near the threshold.