Double-beta-decay experiment NEMO-3: Preliminary results of phase I (2003-2004)

The NEMO-3 detector has been taking data in the Frejus underground laboratory (LSM, France) since February 2003 and is devoted to the search for neutrinoless double-beta decay (0νββ). 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 ∼7 kg of 100Mo and ∼1 kg of 82Se. The corresponding limits for the half-lives are T1/2(0νββ) > 4.6 x 1023 yr for 100Mo and T1/2(0νββ) > 1.0 x 1023 yr for 82Se (90% C.L.). They lead to the following limits for the effective Majorana neutrino mass: < 0.7-2.8 eV for 100Mo and < 1.8-4.9 eV for 82Se. The half-lives of the two-neutrino double-beta decay (2νββ) have been measured for 100Mo, 82Se, 116Cd, 150Nd, and 96Zr and reported here as well