$2\nu \beta \beta$ decay of ${}^{76}$Ge into excited states with GERDA Phase I

Abstract

Two neutrino double beta decay of ${}^{76}$Ge to excited states of ${}^{76}$Se has been studied using data from Phase I of the GERDA experiment. An array composed of up to 14 germanium detectors including detectors that have been isotopically enriched in ${}^{76}$Ge was deployed in liquid argon. The analysis of various possible transitions to excited final states is based on coincidence events between pairs of detectors where a de-excitation $\gamma$ ray is detected in one detector and the two electrons in the other. No signal has been observed and an event counting profile likelihood analysis has been used to determine Frequentist 90\,\% C.L. bounds for three transitions: $0_{g.s.}^{+}-2_1^{+}$: $T_{1/2}^{2\nu }>$1.6$\cdot 10^{23}$ yr, $0_{g.s.}^{+}-0_1^{+}$: $T_{1/2}^{2\nu }>$3.7$\cdot 10^{23}$ yr and $0_{g.s.}^{+}-2_2^{+}$: $T_{1/2}^{2\nu }>$2.3$\cdot 10^{23}$ yr. These bounds are more than two orders of magnitude larger than those reported previously. Bayesian 90\,\% credibility bounds were extracted and used to exclude several models for the $0_{g.s.}^{+}-0_1^{+}$ transition.

References in corpus (8)

• Double Beta Decay, Majorana Neutrinos, and Neutrino Mass
• Phase space factors for double-$\beta$ decay
• Disassembling the Nuclear Matrix Elements of the Neutrinoless double beta Decay
• Nuclear matrix elements for double-β decay
• The GERDA experiment for the search of 0νββ decay in ^{76}Ge
• \textsc{MaGe} - a {\sc Geant4}-based Monte Carlo Application Framework for Low-background Germanium Experiments
• Results on $\beta \beta$ decay with emission of two neutrinos or Majorons in ${}^{76}$Ge from GERDA Phase I
• Production, characterization and operation of ${}^{76}$Ge enriched BEGe detectors in GERDA

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• The Majorana Demonstrator's Search for Double-Beta Decay of ${}^{76}$Ge to Excited States of ${}^{76}$Se
• Final Results of the MAJORANA DEMONSTRATOR's Search for Double-Beta Decay of ${}^{76}$Ge to Excited States of ${}^{76}$Se
• New limit for the half-life of double beta decay of ${}^{94}$Zr to the first excited state of ${}^{94}$Mo
• Systematic shell-model analysis of $2\nu \beta \beta$ decay of ${}^{76}$Ge and ${}^{96}$Zr to the ground and excited states of ${}^{76}$Se and ${}^{96}$Mo
• Status Report of the GERDA Phase II Startup
• Two-neutrino $\beta \beta$ decay to excited states at next-to-leading order