Current status of LEGEND: Searching for Neutrinoless Double-Beta Decay in 76Ge: Part II

Abstract

Neutrinoless double-beta decay (0$\nu\beta\beta$) decay is a hypothetical process that violates lepton number, and whose observation would unambiguously indicate that neutrinos are Majorana fermions. In the standard inverted-ordering neutrino mass scenario, the minimum possible value of mbb corresponds to a half-life around 10$^{28}$ yr for 0$\nu\beta\beta$ decay in $^{76}$Ge, which is the target of the next generation of experiments. The current limits of GERDA and MAJORANA DEMONSTRATOR indicate a half-life higher than 10$^{26}$ yr. These experiments use high-purity germanium (HPGe) detectors that are highly enriched in $^{76}$Ge. They have achieved the best intrinsic energy resolution and the lowest background rate in the signal search region among all 0nbb experiments. Taking advantage of these successes, a new international collaboration - the Large Enriched Germanium Experiment for Neutrinoless bb Decay (LEGEND) - has been formed to build, following a phased approach, a ton-scale experiment with discovery potential covering the inverse-ordering neutrino mass range in a decade. The first part of LEGEND proceedings describes GERDA and MAJORANA DEMONSTRATOR capabilities and the general plan of LEGEND to reach the goal, while this second part is focused in the status of the first stage of LEGEND, LEGEND-200.