Abstract
Using data from the NEMO-3 experiment, we have measured the two-neutrino double beta decay (2 nu beta beta) half-life of Se-82 as T-1/2(2 nu) = [9.39 +/- 0.17 (stat) +/- 0.58 (syst)] x 10(19) y under the single-state dominance hypothesis for this nuclear transition. The corresponding nuclear matrix element is vertical bar M-2 nu vertical bar = 0.0498 +/- 0.0016.
In addition, a search for neutrinoless double beta decay (0 nu beta beta) using 0.93 kg of Se-82 observed for a total of 5.25 y has been conducted and no evidence for a signal has been found. The resulting half-life limit of T-1/2(0 nu) > 2.5 x 10(23) y (90% C.L.) for the light neutrino exchange mechanism leads to a constraint on the effective Majorana neutrino mass of < (1.2-3.0) eV, where the range reflects 0 nu beta beta nuclear matrix element values from different calculations.
Furthermore, constraints on lepton number violating parameters for other 0 nu beta beta mechanisms, such as right-handed currents, majoron emission and R-parity violating supersymmetry modes have been set.