Final results on 82Se double beta decay to the ground state of 82Kr from the NEMO-3 experiment

Using data from the NEMO-3 experiment, we have measured the two-neutrino double beta decay (2νββ) half-life of 82Se as T1/22ν=9.39±0.17stat±0.58syst×1019 y under the single-state dominance hypothesis for this nuclear transition. The corresponding nuclear matrix element is M2ν=0.0498±0.0016. In addition, a search for neutrinoless double beta decay (0νββ) using 0.93 kg of 82Se 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 T1/20ν>2.5×1023y(90%C.L.) for the light neutrino exchange mechanism leads to a constraint on the effective Majorana neutrino mass of ⟨mν⟩<1.2-3.0eV, where the range reflects 0νββ nuclear matrix element values from different calculations. Furthermore, constraints on lepton number violating parameters for other 0νββ mechanisms, such as right-handed currents, majoron emission and R-parity violating supersymmetry modes have been set.