New Limits on Double Electron Capture of ${}^{40}$Ca and ${}^{180}$W

Abstract

We analyzed low-background data from the CRESST-II experiment with a total net exposure of 730 kg days to extract limits on double electron capture processes. We established new limits for ${}^{40}$Ca with $T_{1/2}^{2v2K}>9.9\times 10^{21}$ y and $T_{1/2}^{0v2EC}>1.4\times 10^{22}$ y and for ${}^{180}$W with T${}_{1/2}^{2v2K}>3.1\times 10^{19}$ y and $T_{1/2}^{0v2EC}>9.4\times 10^{18}$ y at 90% CL. Depending on the process, these values improve the currently best limits by a factor of $\sim$1.4-30.