A comprehensive program in neutrino-less double-beta decay is very timely. A principal conclusion of the APS Multidivisional Study stated: "We recommend, as a high priority, a phased program of sensitive searches for neutrino-less nuclear double-beta decay." The intellectual merit of this project derives from the fact that neutrino-less nuclear double-beta-decay "is the only practical way to determine if neutrinos are Majorana particles (their own antiparticles)". This exotic nuclear decay is the most sensitive test of lepton-number conservation, an important symmetry in elementary-particle physics. In fact, if neutrinos are Majorana particles, an accurate measurement of the neutrino-less nuclear double-beta-decay half-life might well be possible; it would yield the effective Majorana mass of the electron neutrino. When combined with neutrino oscillation data, it would determine all three neutrino-mass eigenvalues.
This award provides funding to support a major Task in the MAJORANA R&D Project to establish the feasibility and cost of a one-ton 76Ge neutrino-less nuclear double-beta-decay experiment. The purification and recycling of the quantity of enriched germanium required for a one-ton experiment will have to be done efficiently to significantly reduce the cost of the experiment. The plan involves purchasing the needed equipment, setting it up, hiring and training personnel, testing the operation with natural abundance germanium, and processing the enriched 76Ge for the MAJORANA Demonstrator Module, and optimizing the efficiency.
Among the broader impacts is, and has been, new detector technology for national and homeland security and new detector technology for other basic/applied sciences.
