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 $173\mathrm{kg}·\mathrm{yr}$. 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 $0.0067\pm 0.0042$ and $0.0051\pm 0.0047\mathrm{counts}/(\mathrm{day}·\mathrm{kg}·\mathrm{keV})$, respectively, with a phase fixed at 152.5 days.

• Received 17 November 2021
• Accepted 9 August 2022

DOI:https://doi.org/10.1103/PhysRevD.106.052005

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Published by the American Physical Society