New results of116Cddouble β decay study with116CdWO4scintillators

A new phase of a ${}^{116}\mathrm{Cd}$ double \ensuremath{\beta} decay experiment is in progress in the Solotvina Underground Laboratory. Four enriched ${}^{116}{\mathrm{CdWO}}_{4}$ scintillators with total mass of 339 g are used in a setup, whose active shield is made of 15 natural ${\mathrm{CdWO}}_{4}$ 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\ensuremath{\nu}2\ensuremath{\beta} decay of ${}^{116}\mathrm{Cd}$ is measured as ${T}_{1/2}(2\ensuremath{\nu})=2.6\ifmmode\pm\else\textpm\fi{}0.1(\mathrm{stat}{)}_{\ensuremath{-}0.4}^{+0.7}(\mathrm{syst})\ifmmode\times\else\texttimes\fi{}{10}^{19}$ yr. The ${T}_{1/2}$ limits for neutrinoless 2\ensuremath{\beta} decay of ${}^{116}\mathrm{Cd}$ are set at ${T}_{1/2}g~0.7(2.5)\ifmmode\times\else\texttimes\fi{}{10}^{23}$ yr at 90%(68%) C.L. for transition to ground state of ${}^{116}\mathrm{Sn},$ while for decays to the first ${2}_{1}^{+}$ and second ${0}_{1}^{+}$ excited levels of ${}^{116}\mathrm{Sn}$ at ${T}_{1/2}g~1.3(4.8)\ifmmode\times\else\texttimes\fi{}{10}^{22}$ yr and $g~0.7(2.4)\ifmmode\times\else\texttimes\fi{}{10}^{22}$ yr with 90%(68%) C.L., respectively. For 0\ensuremath{\nu}2\ensuremath{\beta} decay with emission of one or two Majorons, the limits are ${T}_{1/2}(0\ensuremath{\nu}M1)g~3.7(5.8)\ifmmode\times\else\texttimes\fi{}{10}^{21}$ yr and ${T}_{1/2}(0\ensuremath{\nu}M2)g~5.9(9.4)\ifmmode\times\else\texttimes\fi{}{10}^{20}$ 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 ${m}_{\ensuremath{\nu}}l~2.6(1.4)$ eV, $\ensuremath{\eta}l~3.9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8},$ $\ensuremath{\lambda}l~3.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6},$ and ${g}_{M}l~12(9.5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ at 90%(68%) C.L., respectively.