Ultralow-Background Study of Neutrinoless DoubleβDecay ofGe76: New Limit on the Majorana Mass ofνe

A lower limit of 1.16×${10}^{23}$ yr ($1\sigma$) is reported for the half-life of no-neutrino ${\beta }^{-}{\beta }^{-}$ decay of ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ge}$ which results from 3763 h of counting with an ultralow-background, 135-${\mathrm{cm}}^3$ prototype detector located 1438 m underground. A limit of 1.7×${10}^{23}$ yr ($1\sigma$) results from the best combination of our data with that from other experiments. Straightforward application of shell-model matrix elements to this limit implies that $〈m_{\nu }〉<3.2\mathrm{}$ eV ($1\sigma$).