Final Result of the Majorana Demonstrator 's Search for Neutrinoless Double- β Decay in Ge 76

Abstract

The Majorana Demonstrator searched for neutrinoless double-β decay (0νββ) of Ge76 using modular arrays of high-purity Ge detectors operated in vacuum cryostats in a low-background shield. The arrays operated with up to 40.4 kg of detectors (27.2 kg enriched to ∼88% in Ge76). From these measurements, the Demonstrator has accumulated 64.5 kg yr of enriched active exposure. With a world-leading energy resolution of 2.52 keV FWHM at the 2039 keV Qββ (0.12%), we set a half-life limit of 0νββ in Ge76 at T1/2>8.3×1025 yr (90% C.L.). This provides a range of upper limits on mββ of (113-269) meV (90% C.L.), depending on the choice of nuclear matrix elements.