PNNL

Abstract

The Majorana Demonstrator searched for neutrinoless double-ßß decay (0?ßß) of 76Ge using modular arrays of high-purity Ge detectors operated in vacuum cryostats in a low-background shield. The arrays operated with up to 45.4 kg of detectors (30.9 kg enriched to ~88% in 76Ge). The Demonstrator has completed enriched detector operation with 64:5 kg yr of enriched active exposure. With a world-leading energy resolution of 2.52 keV FWHM at the 2039 keV Qßß (0.12%), we measured a half-life limit of 0?ßß was measured at 76Ge T1=2 > 8:3 x 1025 yr (90% C.L.). This produces a range of upper limits on mßß of (113 - 269) meV (90% C.L.), depending on the choice of nuclear matrix elements.