Speaker
Summary
Neutrinoless Double-Beta Decay ($0\nu\beta\beta$) is a hypothetical process that violates lepton number, and whose observation would unambiguously indicate that neutrinos are Majorana fermions. Because of the long half-life of the decay--current experimental limits indicate $T_{1/2}^{0\nu\beta\beta}>10^{26}$~yr--at least a tonne-year of isotopic exposure with ultra-low background index of $<0.1$~counts/(FWHM-t-yr) in the region of interest of the decay are required. GERDA and the \textsc{Majorana Demonstrator} are currently operating experiments searching for $0\nu\beta\beta$ in $^76$Ge. Both experiments consist of arrays of P-type Point Contact (PPC) High-Purity Germanium (HPGe) detectors enriched in $^76$Ge and operating underground. These experiments have achieved the lowest background indexes and best energy resolution of any current-generation $0\nu\beta\beta$ search. By combining the techniques and technologies developed by these experiments, LEGEND (Large Enriched Germanium Experiment for Neutrinoless $\beta\beta$ Decay) will continue the search for $0\nu\beta\beta$ in $^76$Ge. LEGEND-200 is a 200-kg array of PPC HPGe detectors that will begin operating at LNGS with repurposed GERDA infrastructure in 2021, with a background goal of $<0.6$~counts/(FWHM-t-yr). LEGEND-1000 is a planned tonne-scale array that is currently undergoing R\&D.
