We measure the branching fraction of $B^{-}\to {\tau }^{-}{\overline{\nu }}_{\tau }$ using the full ${\rm Y}(4S)$ data sample containing $772\times {10}^6$ $B\overline{B}$ pairs collected with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. Events with $B\overline{B}$ pairs are tagged by reconstructing one of the $B$ mesons decaying into hadronic final states, and $B^{-}\to {\tau }^{-}{\overline{\nu }}_{\tau }$ candidates are detected in the recoil. We find evidence for $B^{-}\to {\tau }^{-}{\overline{\nu }}_{\tau }$ with a significance of 3.0 standard deviations including systematic errors and measure a branching fraction $\mathcal{B}(B^{-}\to {\tau }^{-}{\overline{\nu }}_{\tau })=[{0.72}_{-0.25}^{+0.27}(\mathrm{stat})\pm 0.11(\mathrm{syst})]\times {10}^{-4}$.

• Received 16 November 2012

DOI:https://doi.org/10.1103/PhysRevLett.110.131801