Final Results of GERDA on the Two-Neutrino Double-$\beta$ Decay Half-Life of $^{76}$Ge

TL;DR

This paper reports the most precise measurement to date of the two-neutrino double-beta decay half-life of $^{76}$Ge, using GERDA Phase II data, and provides an accurate nuclear matrix element value.

Contribution

It presents the most precise determination of the $^{76}$Ge two-neutrino double-beta decay half-life and extracts the nuclear matrix element from experimental data.

Findings

Half-life of $^{76}$Ge double-beta decay measured as (2.022 ± 0.018 (stat) ± 0.038 (sys))×10^{21} years.

Nuclear matrix element $M^{2 u}_{ ext{eff}}$ determined as 0.101 ± 0.001.

First precise measurement of this decay process using GERDA Phase II data.

Abstract

We present the measurement of the two-neutrino double-$\beta$ decay rate of $^{76}$Ge performed with the GERDA Phase II experiment. With a subset of the entire GERDA exposure, 11.8 kg$\cdot$yr, the half-life of the process has been determined: $T^{2\nu}_{1/2} = (2.022 \pm 0.018_{stat} \pm 0.038_{sys})\times10^{21}$ yr. This is the most precise determination of the $^{76}$Ge two-neutrino double-$\beta$ decay half-life and one of the most precise measurements of a double-$\beta$ decay process. The relevant nuclear matrix element can be extracted: $M^{2\nu}_{\text{eff}} = (0.101\pm0.001).$