New Limits on the Neutrino Mass, Lepton Conservation, and No-Neutrino Double Beta Decay ofGe76

A continuing search for the no-neutrino mode of the double beta decay of ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ge}$ has resulted in a new lower limit ${T_{\frac{1}{2}}}^{0\nu }>~1.7\times {10}^{22}$ yr. This value corresponds to a 90% confidence level determined with a maximum-likelihood analysis of the energy interval 2041±2 keV. Combined with recent shell-model calculations, the data imply $m_{\nu }<~10$ eV and a limit on lepton nonconservation $\left|\eta \right|<~2.4\times {10}^{-5\mathrm{}}$. In the context of the shell model, the data imply that the electron neutrino is not a Majorana mass eigenstate.