Speaker
Description
In recent years xenon-based dark matter direct detection experiments have reached large enough target masses and low enough background levels to additionally probe rare double beta decays. Among these decays are the two-neutrino double electron capture ($2\nu$ECEC) of $^{124}$Xe as well as the hypothetical neutrinoless double beta decay ($0\nu\beta\beta$) of $^{136}$Xe. An observation of $0\nu\beta\beta$ would provide definite proof of the neutrino’s theorized Majorana nature and indicate lepton number violation. The measurement of the Standard Model $2\nu$ECEC – first detected by XENON1T in 2018 – provides nuclear structure information that could provide crucial input for the nuclear models used to interpret $0\nu\beta\beta$ experiments. This contribution will present the $^{124}$Xe $2\nu$ECEC results and the search for $0\nu\beta\beta$ of $^{136}$Xe in XENON1T. Moreover, the sensitivity projection for a $^{136}$Xe $0\nu\beta\beta$ search in XENONnT will be discussed.
