Three-year annual modulation search with COSINE-100

Abstract

COSINE-100 is a direct detection dark matter experiment that aims to test DAMA/LIBRA's claim of dark matter discovery by searching for a dark-matter-induced annual modulation signal with NaI(Tl) detectors. We present new constraints on the annual modulation signal from a dataset with a 2.82 yr livetime utilizing an active mass of 61.3 kg for a total exposure of 173 kg·yr. This new result features an improved event selection that allows for both lowering the energy threshold to 1 keV and a more precise time-dependent background model. In the 1-6 and 2-6 keV energy intervals, we observe best-fit values for the modulation amplitude of 0.0067±0.0042 and 0.0051±0.0047 counts/(day·kg·keV), respectively, with a phase fixed at 152.5 days.