Measurement of the branching fraction of $B^{+}\to {\tau }^{+}{\nu }_{\tau }$ decays with the semileptonic tagging method and the full Belle data sample

We report a measurement of the branching fraction of $B^+ \to \tau^+ \nu_\tau$decaysusingadatasampleof$772 \times 10^6 B \bar{B}$ pairs, collected at the $\mathrm{{\rm Y}}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We reconstruct the accompanying $B$ meson in a semileptonic decay and detect the $B^{+}\to {\tau }^{+}{\nu }_{\tau }$ candidate in the recoiling event. We obtain a branching fraction of ${\cal B}(B^+ \to \tau^+ \nu_\tau) = [1.25 \pm 0.28 ({\rm stat.}) \pm 0.27({\rm syst.})] \times 10^{-4}$. This result is in good agreement with previous measurements and the expectation from calculations based on the Standard Model.