Danevich F. Experimental research of double beta decay of atomic nuclei

Results of experiments to search for double beta decay are presented. The half-life of the two neutrino double beta decay of 116Cd has been measured as T1/2 = 2.9+0.4-0.3 by 10 to 19 yr with the help of enriched CdWO4 crystal scintillators. The new half-life limits on different channels and modes of double beta decay of 116Cd have been established, particularly the half-life limit at the level of T1/2 > 1.7 by 10 to 23 yr was set for the neutrinoless double beta-decay of 116Cd to the ground state of 116Sn at 90% CL. The restriction on the Majorana neutrino mass m < 1.7 eV and other parameters of theory were obtained. New half-life bounds at the level of 10 to 17 10 to 21 yr were obtained for various double beta processes in 64Zn, 70Zn, 106Cd, 108Cd, 114Cd, 136Ce, 138Ce, 142Ce, 160Gd, 180W, and 186W. The new constraint on the Majorana neutrino mass m < 0.24 eV was set by analysis of double beta experiments with 76Ge. Scintillation properties, pulse-shape, and radioactive contamination were studied with CaWO4, ZnWO4, CdWO4, PbWO4, GSO, CeF3, yttrium-aluminum garnet doped with neodymium (YAG:Nd) crystal scintillators as promising detectors for double beta decay experiments.