Search for 2β decay of 116Cd with the help of enriched 116CdWO4 crystal scintillators

Abstract

Cadmium tungstate crystal scintillators enriched in ${}^{116}$Cd to 82% (${}^{116}$CdWO${}_4$, total mass of $\approx$1.2 kg) are used to search for 2${\hat{I}}^2$ decay of ${}^{116}$Cd deep underground at the Gran Sasso National Laboratory of the INFN (Italy). The radioactive contamination of the ${}^{116}$CdWO${}_4$ crystals has been studied carefully to reconstruct the background of the detector. The measured half-life of ${}^{116}$Cd relatively to 2$\hat{I}½$2${\hat{I}}^2$ decay is $T_{1/2}^{2\nu 2{\hat{I}}^2}$ = [2.8 $\pm$ 0.05(stat.) $\pm$ 0.4(syst.)] $\times$ 10${}^{19}$ yr, in agreement with the results of previous experiments. The obtained limit on the 0$\hat{I}½$2${\hat{I}}^2$ decay of ${}^{116}$Cd (considering the data of the last 8696 h run with an advanced background 0.12(2) counts/yr/kg/keV in the energy interval 2.7-2.9 MeV) is $T_{1/2}\ge 1.0\times 10^{23}$ yr at 90% C.L. The sensitivity of the experiment to the $0\nu 2{\hat{I}}^2$ process is $\lim T_{1/2}=3\times 10^{23}$ yr at 90% C.L. over 5 years of the measurements and it can be advanced (by further reduction of the background by a factor 3-30) to the level of $\lim T_{1/2}=(0.5-1.5)\times 10^{24}$ yr for the same period of the data taking.

Contribution to Proc. of Int. Workshop on Radiopure Scintillators RPSCINT 2013, 17-20.09.2013, Kyiv, Ukraine; to be published in EPJ Web of Conferences; 4 pages, 1 figure and 3 tables