Speaker
Description
Two-neutrino double beta (2$\nu\beta\beta$) decays are amongst the rarest nuclear processes ever observed. Precision studies of the electron sum energies require ultra-low background and an excellent understanding of the experiment’s response. Both are key features of the Germanium Detector Array (GERDA) experiment, which searched for neutrinoless double beta (0$\nu\beta\beta$) decay with enriched high purity germanium detectors in Liquid Argon at Laboratori Nazionali del Gran Sasso (LNGS) in Italy. The measurement of the Standard Model 2$\nu\beta\beta$ decay half-life of $^{76}$Ge was performed with unprecedented precision, profiting from the high signal-to-background ratio and the small systematic uncertainties. It provides essential inputs for nuclear structure calculations, that benefit the interpretation of 0$\nu\beta\beta$ decay results. Furthermore, the search for distortions of the 2$\nu\beta\beta$ decay spectrum allows exploring new physics, like 0$\nu\beta\beta$ decay with Majorons emission, Lorentz invariance, or search for sterile neutrinos.
The new results of the $^{76}$Ge 2$\nu\beta\beta$ decay half-life and improved limits on exotic decay modes will be presented in this talk.