Final Result of the Majorana Demonstrator’s Search for Neutrinoless Double- β Decay in Ge76

Abstract

The Majorana Demonstrator searched for neutrinoless double-β decay (0νββ) of ^{76}Ge using modular arrays of high-purity Ge detectors operated in vacuum cryostats in a low-background shield. The arrays operated with up to 40.4kg of detectors (27.2kg enriched to ∼88% in ^{76}Ge). From these measurements, the Demonstrator has accumulated 64.5kg yr of enriched active exposure. With a world-leading energy resolution of 2.52keV FWHM at the 2039keV Q_{ββ} (0.12%), we set a half-life limit of 0νββ in ^{76}Ge at T_{1/2}>8.3×10^{25} yr (90%C.L.). This provides a range of upper limits on m_{ββ} of (113-269)meV (90%C.L.), depending on the choice of nuclear matrix elements.