Natural Radioactive Background Suppression in 76Ge Neutrinoless Double-β Decay Experiments

Abstract

The observation of neutrino oscillations showed that neutrinos have mass and provides direct evidence that the Standard Model of particle physics is an incomplete theory of the universe at the fundamental scale. As a neutral fermion, the neutrino is the only known particle in the Standard Model that could have a Majorana mass. A particle with a Majorana mass is indistinguishable from its anti-particle and gives the possibility for lepton number flavor vio lating reactions to occur. The observation of a Majorana neutrino would demonstrate lepton number flavor violation of two, which is necessary to support the baryogenesis through lepto genesis model; a compelling theory that offers an explanation for the preferred production of matter over anti-matter in the early universe. The most practical way to discover a Majorana neutrino is through the observation of neutrinoless double-β decay (0νββ). 0νββ decay is a process where a nucleus that prefers to undergo double-β decay over single β decay emits two electrons and no neutrinos. Current experiments have set the largest lower half-life limits for 0νββ decay on the order of 1026 years. The next generation 76Ge experiment, LEGEND 1000, plans to be sensitive to half-lifes on the order of 1028 years. To reach these half-life sensitivities much research and development has been done on current generation, LEGEND 200, and previous generation, Majorana Demonstrator and GERDA, 76Ge experiments to determine the optimal technology and data analysis methods for LEGEND-1000. This work will discuss pulse shape analysis contributions to the Majorana Demonstrator’s final result half-life sensitivity of 8.3×1025 years and silicon photomultiplier characterization results relevant for understanding the efficiency of the LEGEND style liquid argon veto.