Measurement of double-${\hat{I}}^2$ decay of ${}^{150}$Nd to the 0${}_1^{+}$ excited state of ${}^{150}$Sm in NEMO-3

Abstract

The NEMO-3 results for the double-${\hat{I}}^2$ decay of ${}^{150}$Nd to the 0${}_1^{+}$ and 2${}_1^{+}$ excited states of ${}^{150}$Sm are reported. The data recorded during 5.25 yr with 36.6 g of the isotope ${}^{150}$Nd are used in the analysis. For the first time, the signal of the $2\hat{I}½{\hat{I}}^2{\hat{I}}^2$ transition to the 0${}_1^{+}$ excited state is detected with a statistical significance exceeding 5$\ddot{I}ƒ$. The half-life is measured to be $T_{1/2}^{2νββ}(0^+_1) = \left[ 1.11 ^{+0.19}_{-0.14} \,\left(\mbox{stat}\right) ^{+0.17}_{-0.15}\, \left(\mbox{syst}\right) \right] \times10^{20}\,\mbox{yr}$. The limits are set on the $2\hat{I}½{\hat{I}}^2{\hat{I}}^2$ decay to the 2${}_1^{+}$ level and on the $0\hat{I}½{\hat{I}}^2{\hat{I}}^2$ decay to the 0${}_1^{+}$ and 2${}_1^{+}$ levels of ${}^{150}$Sm.

Minor corrections