Background modeling for dark matter search with 1.7 years of COSINE-100 data

Abstract We present a background model for dark matter searches using an array of NaI(Tl) crystals in the COSINE-100 experiment that is located Yangyang underground laboratory. The includes contributions from both internal and external sources, including cosmogenic radionuclides surface $$^{210}$$ 210 Pb contamination. To build low energy region, with threshold 1 keV, we used depth profile contamination determined comparison between measured simulated spectra. also considered effect scale errors propagated statistical uncertainties nonlinear detector response at energies. 1.7 years data taken October 21, 2016 July 18, 2018 were this analysis. Our Monte Carlo simulation provides non-Gaussian peak around 50 keV originating beta decays bulk good agreement background. This estimates activities $$^{3}$$ 3 H are dominating rate amounts to average level $$2.85\pm 0.15$$ 2.85 ± 0.15 counts/day/keV/kg region (1–6) total exposure 97.7 kg $$\cdot $$ · years.