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

Understand

We present a background model for dark matter searches using an array of NaI(Tl) crystals in the COSINE-100 experiment that is located in the Yangyang underground laboratory.

• The model includes background contributions from both internal and external sources, including cosmogenic radionuclides and surface $^{210}$Pb contamination.
• To build the model in the low energy region, with a threshold of 1 keV, we used a depth profile of $^{210}$Pb contamination in the surface of the NaI(Tl) crystals determined in a comparison between measured and simulated spectra.
• We also considered the effect of the energy scale errors propagated from the statistical uncertainties and the nonlinear detector response at low energies.