Final Results of GERDA on the Two-Neutrino Double- β Decay Half-Life of Ge 76

Abstract

We present the measurement of the two-neutrino double-β decay rate of Ge76 performed with the GERDA Phase II experiment. With a subset of the entire GERDA exposure, 11.8 kg yr, the half-life of the process has been determined: T1/22ν=(2.022±0.018stat±0.038syst)×1021 yr. This is the most precise determination of the Ge76 two-neutrino double-β decay half-life and one of the most precise measurements of a double-β decay process. The relevant nuclear matrix element can be extracted: Meff2ν=(0.101±0.001).