We present measurements of $B^{+}\to {\overline{D}}^{*0}{\tau }^{+}{\nu }_{\tau }$ and $B^{+}\to {\overline{D}}^0{\tau }^{+}{\nu }_{\tau }$ decays in a data sample of $657\times {10}^6$ $B\overline{B}$ pairs collected with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We find ${446}_{-56}^{+58}$ $B^{+}\to {\overline{D}}^{*0}{\tau }^{+}{\nu }_{\tau }$ events with a significance of 8.1 standard deviations, and ${146}_{-41}^{+42}$ $B^{+}\to {\overline{D}}^0{\tau }^{+}{\nu }_{\tau }$ events with a significance of 3.5 standard deviations. The latter signal provides the first evidence for this decay mode. The measured branching fractions are $\mathcal{B}(B^{+}\to {\overline{D}}^{*0}{\tau }^{+}{\nu }_{\tau })=({2.12}_{-0.27}^{+0.28}(\mathrm{stat})\pm 0.29(\mathrm{syst}))\%$ and $\mathcal{B}(B^{+}\to {\overline{D}}^0{\tau }^{+}{\nu }_{\tau })=(0.77\pm 0.22(\mathrm{stat})\pm 0.12(\mathrm{syst}))\%$.

• Received 13 May 2010

DOI:https://doi.org/10.1103/PhysRevD.82.072005