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First Search for Neutrinoless Double Beta Decay in 76Ge with the Majorana Demonstrator

Walter Pettus, University of Washington
Thursday, April 19, 2018 - 3:45pm to 4:45pm
NPL Conference Room, Rm 178

​Neutrinoless double-beta decay (0νββ) is a hypothetical lepton-number violating process that would establish the Majorana nature of neutrinos and serve as an indirect probe of the absolute neutrino mass. The Majorana Demonstrator is an array of high purity Ge detectors at the 4850’ level of the Sanford Underground Research Facility in South Dakota searching for 0νββ in 76 Ge. The experiment consists of two modules totaling 44 kg of p-type point contact detectors; the first module began data taking in June 2015, with the entire array operational since August 2016. I will report the analysis of the first 9.95 kg*yr of exposure from the MAJORANA DEMONSTRATOR, achieving a half-life limit of >1.9×10 25 yr for 0νββ decay of 76 Ge. The experiment has also demonstrated the best energy resolution and a background consistent with the best achieved of any 0νββ experiment. These results strongly position 76 Ge for a future tonne-scale 0νββ experiment.

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