The double-beta decay of ${}^{116}\mathrm{Cd}$ has been investigated with the help of radiopure enriched ${}^{116}\mathrm{Cd}{\mathrm{WO}}_4$ crystal scintillators (mass of 1.162 kg) at the Gran Sasso underground laboratory. The half-life of ${}^{116}\mathrm{Cd}$ relative to the $2\nu 2\beta$ decay to the ground state of ${}^{116}\mathrm{Sn}$ was measured with the highest up-to-date accuracy as $T_{1/2}=(2.63_{-0.12}^{+0.11})\times {10}^{19}\mathrm{yr}$. A new improved limit on the $0\nu 2\beta$ decay of ${}^{116}\mathrm{Cd}$ to the ground state of ${}^{116}\mathrm{Sn}$ was set as $T_{1/2}\ge 2.2\times {10}^{23}\mathrm{yr}$ at 90% C.L., which is the most stringent known restriction for this isotope. It corresponds to the effective Majorana neutrino mass limit in the range $⟨m_{\nu }⟩\le (1.0–1.7)\mathrm{eV}$, depending on the nuclear matrix elements used in the estimations. New improved half-life limits for the $0\nu 2\beta$ decay with majoron(s) emission, Lorentz-violating $2\nu 2\beta$ decay, and $2\beta$ transitions to excited states of ${}^{116}\mathrm{Sn}$ were set at the level of $T_{1/2}\ge {10}^{20}–{10}^{22}\mathrm{yr}$. New limits for the hypothetical lepton-number violating parameters (right-handed currents admixtures in weak interaction, the effective majoron-neutrino coupling constants, R-parity violating parameter, Lorentz-violating parameter, heavy neutrino mass) were set.

• Received 23 July 2018

DOI:https://doi.org/10.1103/PhysRevD.98.092007