High Impact: Final Result of the MAJORANA DEMONSTRATOR's Search for Neutrinoless Double-β Decay in 76Ge

The Majorana Demonstrator searched for neutrinoless double-𝛽 decay (0⁢𝜈⁢𝛽⁢𝛽) 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 40.4 kg of detectors (27.2 kg enriched to ∼88% in 76Ge). 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 𝑄𝛽⁢𝛽 (0.12%), we set a half-life limit of 0⁢𝜈⁢𝛽⁢𝛽 in ⁷⁶Ge at 𝑇_1/2>8.3×10²⁵  yr (90% C.L.). This provides a range of upper limits on 𝑚_𝛽⁢𝛽 of (113–269) meV (90% C.L.), depending on the choice of nuclear matrix elements.