The NEMO 3 detector, which has been operating in the Fréjus underground laboratory since February 2003, is devoted to the search for neutrinoless double-beta decay (beta beta 0v). The half-lives of the two neutrino double-beta decay (beta beta 2v) have been measured for 100Mo and 82Se. After 389 effective days of data collection from February 2003 until September 2004 (phase I), no evidence for neutrinoless double-beta decay was found from approximately 7 kg of 100Mo and approximately 1 kg of 82Se. The corresponding limits are T1/2(beta beta0v) > 4.6 x 10(23) yr for 100Mo and T1/2(beta beta 0v) > 1.0 x 10(23) yr for 82Se (90% C.L.). Depending on the nuclear matrix element calculation, the limits for the effective Majorana neutrino mass are < 0.7-2.8 e/v for 100Mo and < 1.7-4.9 eV for 82Se.

The NEMO-3 detector, which had been operating in the Modane Underground Laboratory from 2003 to 2010, was designed to search for neutrinoless double-β (0νββ) decay. We report the final results of a search for 0νββ decays with 6.914 kg of 100 Mo using the entire NEMO-3 data set with a detector live time of 4.96 yr, which corresponds to an exposure of 34.3 kg · yr. We perform a detailed study of the expected background in the 0νββ signal region and find no evidence of 0νββ decays in the data. The level of observed background in the 0νββ signal region [2.8-3.2] MeV is 0.44 AE 0.13 counts=yr=kg, and no events are observed in the interval [3.2-10] MeV. We therefore derive a lower limit on the half-life of 0νββ decays in 100 Mo of * Deceased PHYSICAL REVIEW D 92, 072011 (2015) 1550-7998=2015=92 (7)=072011 (23) 072011-1 © 2015 American Physical Society T 1=2 ð0νββÞ > 1.1 × 10 24 yr at the 90% confidence level, under the hypothesis of decay kinematics similar to that for light Majorana neutrino exchange. Depending on the model used for calculating nuclear matrix elements, the limit for the effective Majorana neutrino mass lies in the range hm ν i < 0.33-0.62 eV. We also report constraints on other lepton-number violating mechanisms for 0νββ decays.

The development of the NEMO3 detector, which is now running in the Frejus Underground Laboratory (L.S.M. Laboratoire Souterrain de Modane), was begun more than ten years ago. The NEMO3 detector uses a tracking-calorimeter technique in order to investigate double beta decay processes for several isotopes. The technical description of the detector is followed by the presentation of its performance