Half-life limits on the zero-neutrino and two-neutrino double-β decay ofGe76

Abstract

Data obtained from four Ge detectors in an active NaI shield yield a maximum-likelihood 68%-C.L. lower limit of 2.5×${10}^{23}$ yr for the half-life of the $0^{+}$→$0^{+}$ transition, and 5×${10}^{22}$ yr for the $0^{+}$→$2^{+}$ transition, for zero-neutrino double-β decay of ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ge}$. They also set a 90%-C.L. lower limit of 8×${10}^{19}$ yr for the two-neutrino decay, and 6×${10}^{20}$ yr for the mode in which a light boson (Majoron) is emitted with no neutrinos. These results are used to set limits on light and very heavy neutrino masses, on Majoron-neutrino coupling, and on right-handed currents.