Search for a Dark Matter-Induced Annual Modulation Signal in NaI(Tl) with the COSINE-100 Experiment

Abstract

We present new constraints on the dark matter-induced annual modulation signal using 1.7 years of COSINE-100 data with a total exposure of 97.7 kg yr. The COSINE-100 experiment, consisting of 106 kg of NaI(Tl) target material, is designed to carry out a model-independent test of DAMA/LIBRA's claim of WIMP discovery by searching for the same annual modulation signal using the same NaI(Tl) target. The crystal data show a $2.7\text{ }\text{ }\text{cpd/kg/keV}$ background rate on average in the 2--6 keV energy region of interest. Using a $\ensuremath{\chi}$-squared minimization method we observe best fit values for modulation amplitude and phase of $0.0092\ifmmode\pm\else\textpm\fi{}0.0067\text{ }\text{ }\text{cpd/kg/keV}$ and $127.2\ifmmode\pm\else\textpm\fi{}45.9\text{ }\text{ }\mathrm{d}$, respectively.