New experimental limits on double-beta decay of osmium

Abstract

Double-beta processes in ${}^{184}$Os and ${}^{192}$Os were searched for over 15851 h at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. by using a 118 g ultra-pure osmium sample installed on the endcap of a 112 cm${}^3$ ultra-low-background broad-energy germanium detector. New limits on double-electron capture and electron capture with positron emission in ${}^{184}$Os were set at the level of $\lim T_{1/2}\sim 10^{16}-10^{17}$ yr. In particular the $2\hat{I}½$2K and $2\hat{I}½$KL decays of ${}^{184}$Os to the ground state of ${}^{184}$W are restricted as $T_{1/2}\ge 3.0\times 10^{16}$ yr and $T_{1/2}\ge 2.0\times 10^{16}$ yr, respectively. A lower limit on the half-life for the double-beta decay of ${}^{192}$Os to the first excited level of ${}^{192}$Pt was set as $\lim T_{1/2}=2.0\times 10^{20}$ yr at 90\% C.L.

22 pages, 9 figures, 2 tables