Estimate of 42Ar production underground

I will present our estimate of the rate of 42Ar production underground by nuclear processes. Radioactive decays from 42Ar, and its progeny 42K, are potential background sources in large-scale liquid-argon-based neutrino and dark matter experiments. In the atmosphere, 42Ar is produced primarily by cosmogenic activation on 40Ar. DarkSide-20k, the only experiment to use underground argon (UAr), found no conclusive evidence of 42Ar in UAr. There has been little study on underground production mechanisms of 42Ar and the expected production rates. In this talk, I will discuss 42Ar production underground by nuclear reactions induced by natural radioactivity and cosmic-ray muon interactions. I will present our estimate of the 42Ar production rate at various depths in the continental crust.