Current status of LEGEND: Searching for Neutrinoless Double-Beta Decay in ${}^{76}$Ge: Part I

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 m${}_{\beta \beta }$ 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 \textsc{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 $0\nu \beta \beta$ experiments. Taking advantage of these successes, a new international collaboration - the Large Enriched Germanium Experiment for Neutrinoless $\beta \beta$ Decay (LEGEND) - has been formed to build a ton-scale experiment with discovery potential covering the inverse-ordering neutrino mass range in a decade, following a phased approach. This first part of LEGEND proceedings describes GERDA and \textsc{Majorana Demonstrator} capabilities and the general plan of LEGEND to reach the goal, while the second part is focused in the status of the first stage of LEGEND, LEGEND-200.

XXIX International Symposium on Lepton Photon Interactions at High Energies - LeptonPhoton2019 August 5-10, 2019, Toronto, Canada