Measurement of the double-beta decay half-life on Nd-150 and search for neutrinoless decay modes with the NEMO-3 detector

The half-life for double-beta decay of Nd-150 has been measured by the NEMO-3 experiment at the Modane Underground Laboratory. Using 924.7 days of data recorded with 36.55 g of Nd-150, we measured the half-life for 2 nu beta beta decay to be T-1/2(2 nu) = (9.11(-0.22)(+0.25)(stat.) +/- 0.63(syst.)) x 10(18) yr. The observed limit on the half-life for neutrinoless double-beta decay is found to be T-1/2(0 nu) > 1.8 x 10(22) yr at 90% confidence level. This translates into a limit on the effective Majorana neutrino mass of < m(nu)> < 4.0-6.3 eV if the nuclear deformation is taken into account. We also set limits on models involving Majoron emission, right-handed currents, and transitions to excited states.
We thank the staff at the Modane Underground Laboratory for its technical assistance in running the experiment,Vladimir Tretyak for providing the Monte Carlo event generator, and Wade Fisher for helping with the limit-setting program. We acknowledge support by the grants agencies of the Czech Republic, RFBR (Russia), STFC (UK), and NSF (USA).