Search for Neutrinoless Double-Beta Decay of ${}^{100}$Mo with the NEMO-3 Detector

Abstract

We report the results of a search for the neutrinoless double-${\hat{I}}^2$ decay (0$\hat{I}½{\hat{I}}^2{\hat{I}}^2$) of ${}^{100}$Mo, using the NEMO-3 detector to reconstruct the full topology of the final state events. With an exposure of 34.7 kg.y, no evidence for the 0$\hat{I}½{\hat{I}}^2{\hat{I}}^2$ signal has been found, yielding a limit for the light Majorana neutrino mass mechanism of $T_{1/2}(0\hat{I}½{\hat{I}}^2{\hat{I}}^2)>1.1\times 10^{24}$ years (90% C.L.) once both statistical and systematic uncertainties are taken into account. Depending on the Nuclear Matrix Elements this corresponds to an upper limit on the Majorana effective neutrino mass of $<m_{\hat{I}}½><0.3-0.9$ eV (90% C.L.). Constraints on other lepton number violating mechanisms of 0$\hat{I}½{\hat{I}}^2{\hat{I}}^2$ decays are also given. Searching for high-energy double electron events in all suitable sources of the detector, no event in the energy region [3.2-10] MeV is observed for an exposure of 47 kg.y.