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

TL;DR

This study investigates the double beta decay of $^{116}$Cd using enriched crystal scintillators, providing precise measurements of decay half-lives and setting new limits on neutrinoless decay modes, advancing understanding of neutrino properties.

Contribution

The paper presents the most accurate measurement of $^{116}$Cd's two-neutrino double beta decay half-life and establishes new, more stringent limits on neutrinoless decay modes using enriched scintillators.

Findings

Measured $^{116}$Cd two-neutrino decay half-life as 2.69e19 yr.

Set a new lower limit on neutrinoless decay half-life at 2.4e23 yr.

Derived effective Majorana neutrino mass limit between 1.1 and 1.6 eV.

Abstract

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 $T_{1/2}$ = [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 $\langle$$m_\nu$$\rangle$ $\le$ $(1.1-1.6)$ 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 $T_{1/2}\geq 10^{21}-10^{22}$ yr.