Half-life limits on the zero-neutrino and two-neutrino double-β decay of 76Ge

Data obtained from four Ge detectors in an active NaI shield yield a maximum-likelihood 68%-C.L. lower limit of 2.5×1023 yr for the half-life of the 0+-->0+ transition, and 5×1022 yr for the 0+-->2+ transition, for zero-neutrino double-β decay of 76Ge. They also set a 90%-C.L. lower limit of 8×1019 yr for the two-neutrino decay, and 6×1020 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.