Neutrinoless Double Beta Decay Search with $^{76}$Ge: Status and Prospect with LEGEND

Abstract

The search for neutrinoless double beta ($0\nu\beta\beta$) decay is the best way to test lepton number violation and Majorana nature of neutrinos. One of the most promising techniques to discover $0\nu\beta\beta$ decay is by operating High-Purity Ge detectors enriched in $^{76}$Ge. The current generation of $^{76}$Ge experiments, GERDA and MAJORANA, lead the field in the achieved energy resolution and ultra-low background. These are two of the most important characteristics for sensitive searches of this undiscovered decay. The next generation of $0\nu\beta\beta$ decay experiments requires more mass and further reduction of backgrounds to maximize the discovery potential. Building on the successes of GERDA and MAJORANA, the LEGEND collaboration has been formed to pursue a tonne-scale $^{76}$Ge experiment, with a discovery potential projected to be a half-life beyond 10^{28} years. The collaboration aims to develop a phased experimental program, starting with a 200 kg measurement by repurposing the existing Gerda infrastructure.