Background studies for DarkSide Detectors

Direct dark matter detection experiments search for the signals from dark matter (DM) scattering off an atomic nuclei target. The DarkSide-50 experiment used a dual-phase Time Projection Chamber (TPC) with liquid argon (LAr) as the DM target. The next-generation DM detector, DarkSide-20k, will have multiple tons of liquid argon in its TPC for dark matter searches. It is expected to achieve sufficient sensitivity to detect WIMP dark matter or exclude a large parameter space for the WIMP hypothesis. The expected dark matter event rate, is at most, few per year per ton of the target. To detect such rare interactions, DM searches should be nearly "background-free". The experiments need to adopt means and techniques to suppress, mitigate, and possibly reject all backgrounds to be able to detect dark matter. All potential sources of backgrounds have to be studied, and their rates estimated or measured. In this thesis, I present the results from my study of two potential backgrounds for dark matter searches: 1) Backgrounds from 42Ar/42K radioactive decays, and 2) Backgrounds from cosmic-ray muon and neutron interactions. 42Ar and 42K decays are potential source of backgrounds in liquid argon based detectors. In this thesis, I report the results from my studies of backgrounds from 42Ar/42K decays using DarkSide-50 data. The specific radioactivity for 42Ar/42K in DarkSide-50 is found to be on the order of few tens of micro-Bq per kg of natural argon. In addition, I report my studies of possible search channels and potential signatures from the decays of 42Ar/42K isotopes in liquid argon based detectors. Neutrons produced by cosmic-ray muon interactions are a major source of backgrounds in underground dark matter detectors. In this work, I present the results of my FLUKA simulations based study of cosmogenic backgrounds for DarkSide-20k. Based on these studies, the DarkSide-20k experiment can reject cosmogenic neutron backgrounds with high efficiency.