Measurement of the $2\nu\beta\beta$ Decay Half-Life and Search for the $0\nu\beta\beta$ Decay of $^{116}$Cd with the NEMO-3 Detector

TL;DR

The NEMO-3 experiment precisely measured the two-neutrino double beta decay half-life of $^{116}$Cd and set new limits on the neutrinoless decay, constraining neutrino mass and beyond Standard Model physics.

Contribution

This work provides the most accurate measurement of $^{116}$Cd's $2 uetaeta$ decay half-life and establishes new lower bounds on the $0 uetaeta$ decay half-life, improving constraints on neutrino properties.

Findings

Measured $2 uetaeta$ half-life as $2.74 imes 10^{19}$ years.

No evidence found for $0 uetaeta$ decay, setting a half-life limit of $1.0 imes 10^{23}$ years.

Derived upper limits on effective Majorana neutrino mass and other mechanisms.

Abstract

The NEMO-3 experiment measured the half-life of the $2\nu\beta\beta$ decay and searched for the $0\nu\beta\beta$ decay of $^{116}$Cd. Using $410$ g of $^{116}$Cd installed in the detector with an exposure of $5.26$ y, ($4968\pm74$) events corresponding to the $2\nu\beta\beta$ decay of $^{116}$Cd to the ground state of $^{116}$Sn have been observed with a signal to background ratio of about $12$. The half-life of the $2\nu\beta\beta$ decay has been measured to be $ T_{1/2}^{2\nu}=[2.74\pm0.04\mbox{(stat.)}\pm0.18\mbox{(syst.)}]\times10^{19}$ y. No events have been observed above the expected background while searching for $0\nu\beta\beta$ decay. The corresponding limit on the half-life is determined to be $T_{1/2}^{0\nu} \ge 1.0 \times 10^{23}$ y at the $90$ % C.L. which corresponds to an upper limit on the effective Majorana neutrino mass of $\langle m_{\nu} \rangle \le 1.4-2.5$ eV depending on the nuclear matrix elements considered. Limits on other mechanisms generating $0\nu\beta\beta$ decay such as the exchange of R-parity violating supersymmetric particles, right-handed currents and majoron emission are also obtained.