Bonn 2020 – wissenschaftliches Programm
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HK: Fachverband Physik der Hadronen und Kerne
HK 28: Astroparticle Physics I
HK 28.2: Vortrag
Mittwoch, 1. April 2020, 14:30–14:45, J-HS B
Observation of two-neutrino double electron capture in 124Xe with XENON1T — •Christian Wittweg for the XENON collaboration — Institut für Kernphysik, WWU Münster
Two-neutrino double electron capture (2νECEC) is a second-order weak process with predicted half-lives that surpass the age of the Universe by far. After indications of 2νECEC in 78Kr and 130Ba, the XENON1T dark matter experiment achieved the first direct observation of 2νECEC in 124Xe with a significance 4.4σ. The corresponding half-life T1/22νECEC = (1.8± 0.5stat± 0.1sys)× 1022 yr is the longest ever measured directly [XENON Collaboration. Nature 568, 532–535 (2019)] and agrees well with recent matrix element calculations [Coello Pérez et al., PLB 797 (2019) 134885]. It provides an important input for nuclear structure models from the proton-rich side of the nuclide chart and is a first step in the search for 0νECEC.
Moreover, decay modes involving positrons such as 0νECβ+ are energetically allowed, would provide coincidence signatures, and could exhibit half-lives accessible to future detectors. Experimental proof of neutrinoless decays would imply lepton number violation and the Majorana nature of neutrinos. This talk will present the XENON1T result and discuss detection prospects for 124Xe decays involving positrons, both with and without neutrino emission, in the next-generation of xenon-based experiments currently under construction. 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".