Final results of the Aurora experiment to study 2β decay of 116Cd with enriched 116CdWO4 crystal scintillators.

The double-beta decay of 116Cd has been investigated with the help of radiopure enriched 116CdWO4 crystal scintillators (mass of 1.162 kg) at the Gran Sasso underground laboratory. The half-life of 116Cd relative to the 2ν2β decay to the ground state of 116Sn was measured with the highest up-to-date accuracy as T1/2=(2.63+0.11-0.12)×1019 yr. A new improved limit on the 0ν2β decay of 116Cd to the ground state of 116Sn was set as T1/2≥2.2×1023 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 ⟨mν⟩≤(1.0-1.7) eV, depending on the nuclear matrix elements used in the estimations. New improved half-life limits for the 0ν2β decay with majoron(s) emission, Lorentz-violating 2ν2β decay, and 2β transitions to excited states of 116Sn were set at the level of T1/2≥1020-1022 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. [ABSTRACT FROM AUTHOR]