Investigation of 2$\beta$ Decay of ${}^{116}$Cd with the Help of Enriched ${}^{116}$CdWO${}_4$ Crystal Scintillators

Double beta decay of ${}^{116}$Cd has been investigated with the help of radiopure enriched ${}^{116}$CdWO${}_4$ crystal scintillators in the experiment Aurora. The half-life of ${}^{116}$Cd relatively to the 2$\nu$2$\beta$ decay of ${}^{116}$Cd to the ground level of ${}^{116}$Sn is measured with the highest up-to-date accuracy as $T_{1\mathrm{/}2}$ = [2.69 $\pm$ 0.02 (stat.) $\pm$ 0.14 (syst.)] $\times$ 10${}^{19}$ yr. A new improved limit on the 0$\nu$2$\beta$ decay of ${}^{116}$Cd to the ground state of ${}^{116}$Sn is set as $T_{1/2}\geq 2.4 \times 10^{23}$ yr at 90% C.L., that corresponds to the effective Majorana neutrino mass limit in the range $⟨$$m_{\nu }$$⟩$ $\le$ $(1.1-1.6)$ eV, depending on the nuclear matrix elements used in the estimations. New improved limits on other $2\beta$ processes in ${}^{116}$Cd (decays with majoron emission, transitions to excited levels of ${}^{116}$Sn) were set at the level of $T_{1\mathrm{/}2}\ge {10}^{21}-{10}^{22}$ yr.