Double beta decay of $^{100}$Mo

Two-neutrino double beta decay of $^{100}$Mo with half-life $T_{1/2}=[7.2\pm0.9(stat)\pm1.8(syst)]\times10^{18}$ yr was detected using a liquid argon ionization chamber. With a C.L. of $68\%\, (90\%)$, the bounds on neutrinoless decay and decay with majoron emission were found to be $8.4\,(4.9)\times10^{21}$ and $4.1\,(3.2)\times10^{20}$ yr, respectively. An analysis of all available results provides the average «world» value $T_{1/2}=(8.0\pm0.7)\times10^{18}$ yr for the two-neutrino decay of $^{100}$Mo, and the corresponding nuclear matrix element is $M_{GT}=0.118\pm0.005$.