Speaker
Mr
Christian Wittweg
(WWU Münster)
Description
Two-neutrino double electron capture ($2\nu$ECEC) is a second-order Weak process with predicted half-lives that surpass the age of the Universe by many orders of magnitude. Indications for $2\nu$ECEC decays have only been seen for two isotopes, $^{78}$Kr and $^{130}$Ba, and instruments with very low background levels are needed to detect them directly with high statistical significance. The $2\nu$ECEC half-life provides an important input for nuclear structure models and its measurement represents a first step in the search for the neutrinoless double electron capture processes ($0\nu$ECEC). A detection of the latter would imply the existence of lepton number violation and the Majorana nature of neutrinos. The XENON1T dark matter experiment located at Laboratori Nazionali del Gran Sasso recently achieved the first direct observation of the Standard Model $2\nu$ECEC in $^{124}$Xe. The significance of the signal is $4.4\sigma$ and the corresponding half-life $T_{1/2}^{2\nu\rm{ECEC}} = (1.8\pm 0.5_{\rm{stat}}\pm 0.1_{\rm{sys}})\times 10^{22}\;\rm{yr}$ is the longest ever measured directly [[XENON Collaboration. Nature 568, 532-535 (2019)]][1]. This demonstrates that the low background and large target mass of xenon-based Dark Matter detectors make them well suited to measuring other rare processes and it highlights the broad physics reach for the next-generation of experiments currently under construction.
This talk will give a general introduction to XENON1T. It will then shift to double electron capture processes, their signatures, and their connection to nuclear theory as well as neutrino physics. It will present all analysis steps with a focus on energy calibration and background modelling, and discuss prospects for future $0\nu$ECEC searches. The work of the author is supported by Deutsche Forschungsgemeinschaft (DFG) through the Research Training Group *GRK 2149: Strong and Weak Interactions - from Hadrons to Dark Matter*.
[1]: https://www.nature.com/articles/s41586-019-1124-4
Primary author
Mr
Christian Wittweg
(WWU Münster)
Co-author
E. Aprile et al.
(XENON Collaboration)
