Measurement of the 2νββ decay half-life and search for the 0νββ decay of 116Cd with the NEMO-3 detector

Abstract

The NEMO-3 experiment measured the half-life of the 2νββ decay and searched for the 0νββ decay of 116Cd. Using 410 g of 116Cd installed in the detector with an exposure of 5.26 y, (4968±74) events corresponding to the 2νββ decay of 116Cd to the ground state of 116Sn have been observed with a signal to background ratio of about 12. The half-life of the 2νββ decay has been measured to be T2ν1/2=[2.74±0.04(stat)±0.18(syst)]×1019 y. No events have been observed above the expected background while searching for 0νββ decay. The corresponding limit on the half-life is determined to be T0ν1/2≥1.0×1023 y at the 90% C.L. which corresponds to an upper limit on the effective Majorana neutrino mass of ⟨mν⟩≤1.4–2.5 eV depending on the nuclear matrix elements considered. Limits on other mechanisms generating 0νββ decay such as the exchange of R-parity violating supersymmetric particles, right-handed currents and majoron emission are also obtained.