# A Search for Neutrinoless Double-Beta Decay in $^{76}$Ge with 26 kg-yr of Exposure from the MAJORANA DEMONSTRATOR

## TL;DR

The MAJORANA DEMONSTRATOR searched for neutrinoless double-beta decay in $^{76}$Ge using 26 kg-yr of data, achieving high energy resolution and setting new lower limits on the decay half-life and neutrino mass.

## Contribution

This work provides the most sensitive search to date with the MAJORANA DEMONSTRATOR, demonstrating ultra-clean detector technology and low-background techniques for future neutrinoless double-beta decay experiments.

## Key findings

- Lower limit on decay half-life: 2.7×10^25 years
- Background rate: 11.9 counts/(FWHM·t·yr)
- Effective neutrino mass upper limit: 200-433 meV

## Abstract

The MAJORANA Collaboration is operating an array of high purity Ge detectors to search for the neutrinoless double-beta decay of $^{76}$Ge. The MAJORANA DEMONSTRATOR consists of 44.1 kg of Ge detectors (29.7 kg enriched to 88% in $^{76}$Ge) split between two modules constructed from ultra-clean materials. Both modules are contained in a low-background shield at the Sanford Underground Research Facility in Lead, South Dakota. We present updated results on the search for neutrinoless double-beta decay in $^{76}$Ge with $26.0\pm0.5$ kg-yr of enriched exposure. With the DEMONSTRATOR's unprecedented energy resolution of 2.53 keV FWHM at $Q_{\beta\beta}$, we observe one event in the region of interest with 0.65 events expected from the estimated background, resulting in a lower limit on the $^{76}$Ge neutrinoless double-beta decay half-life of $2.7\times10^{25}$ yr (90% CL) with a median sensitivity of $4.8\times10^{25}$ yr (90% CL). Depending on the matrix elements used, a 90% CL upper limit on the effective Majorana neutrino mass in the range of 200-433 meV is obtained. The measured background in the low-background configurations is $11.9\pm2.0$ counts/(FWHM t yr).