New results of 116Cd double β decay study with 116CdWO4 scintillators -: art. no. 045501

A new phase of a Cd-116 double beta decay experiment is in progress in the Solotvina Underground Laboratory. Four enriched (CdWO4)-Cd-116 scintillators with total mass of 339 g are used in a setup, whose active shield is made of 15 natural CdWO4 crystals (20.6 kg). The background rate in the energy interval 2.5-3.2 MeV is 0.03 counts/yr kg keV. The half-life for 2 nu 2 beta decay of Cd-116 is measured as T-1/2(2 nu) = 2.6 +/- 0.1(stat)(-0.4)(+0.7)(syst) X 10(19) yr. The T-1/2 limits for neutrinoless 2 beta decay of Cd-116 are set at T-1/2 greater than or equal to 0.7(2.5) x 10(23) yr at 90% (68%) C.L. for transition to ground state of Sn-116, while for decays to the first 2(1)(+) and second 0(1)(+) excited levels of Sn-116 at T-1/2 greater than or equal to 1.3(4.8) X 10(22) yr and greater than or equal to 0.7(2.4) X 10(22) yr with 90%(68%) C.L., respectively. For 0 nu 2 beta decay with emission df one or two Majorons, the limits are T-1/2(0 nu M1) greater than or equal to 3.7(5.8) X 10(21) yr and T-1/2(0 nu M2) greater than or equal to 5.9(9.4) X 10(20) yr at 90%(68%) C.L. Restrictions on the value of the neutrino mass, right-handed admixtures in the weak interaction, and the neutrino-Majoron coupling constant are derived as m(nu) less than or equal to 2.6(1.4) eV, eta less than or equal to 3.9 X 10(-8), lambda less than or equal to 3.4 X 10(-6), and g(M) less than or equal to 12(9.5) X 10(-5) at 90%(68%) C.L., respectively.