The Majorana project: 76Ge 0ν ββ-decay neutrino mass measurement

Abstract

Interest in, and the relevance of, next-generation 0ν ββ-decay experiments is increasing. Even with nonzero neutrino mass strongly suggested by SNO, Super Kamiokande, and similar experiments sensitive to δm 2, 0ν ββ-decay experiments are still the only way to establish the Dirac or Majorana nature of neutrinos by measuring effective electron neutrino mass, 〈m ν〉. Various theorists have recently argued in favor of a neutrino mass between 0.01 and 1 eV. The Majorana Project aims to probe this effective neutrino mass range, reaching a sensitivity of 0.02–0.07 eV. The experiment relies entirely on proven technology and has been devised based upon the materials, technology, and data analysis demonstrated to produce the lowest background per kilogram of fiducial germanium. The project plan includes 500 kg of germanium detector material enriched to 85% in 76Ge, specialized pulse-acquisition electronics and detector segmentation for background rejection, and underground electroformed copper support hardware.