The Majorana Demonstrator searched for neutrinoless double-$\beta$ decay ($0\nu \beta \beta$) of ${}^{76}\mathrm{Ge}$ using modular arrays of high-purity Ge detectors operated in vacuum cryostats in a low-background shield. The arrays operated with up to 40.4 kg of detectors (27.2 kg enriched to $\sim 88\%$ in ${}^{76}\mathrm{Ge}$). 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 $Q_{\beta \beta }$ (0.12%), we set a half-life limit of $0\nu \beta \beta$ in ${}^{76}\mathrm{Ge}$ at $T_{1/2}>8.3\times {10}^{25}\mathrm{yr}$ (90% C.L.). This provides a range of upper limits on $m_{\beta \beta }$ of (113–269) meV (90% C.L.), depending on the choice of nuclear matrix elements.

• Received 15 July 2022
• Revised 9 November 2022
• Accepted 16 December 2022

DOI:https://doi.org/10.1103/PhysRevLett.130.062501

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Published by the American Physical Society