N ov 2 01 7 Spectral analysis for the Majorana Demonstrator experiment

The Majorana Demonstrator is an experiment constructed to search for neutrinoless double-beta decays in germanium-76 and to demonstrate the feasibility to deploy a ton-scale experiment in a phased and modular fashion. It consists of two modular arrays of natural and Ge-enriched germanium detectors totaling 44.1 kg (29.7 kg enriched detectors), located at the 4850’ level of the Sanford Underground Research Facility in Lead, South Dakota, USA. Data taken with this setup since summer 2015 at different construction stages of the experiment show a clear reduction of the observed background index around the ROI for 0νββdecay search due to improvements in shielding. We discuss the statistical approaches to search for a 0νββ-signal and derive the physics sensitivity for an expected exposure of 10 kg·y from enriched detectors using a profile likelihood based hypothesis test in combination with toy Monte Carlo data.