Abstract
We report a measurement of the branching fraction of \$B^+ \tau^+
\nu\_\tau\$ decays using a data sample of \$772 10^6 B B\$ pairs,
collected at the \$\Upsilon(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^+ \tau^+ \nu\_\tau\$ candidate in
the recoiling event. We obtain a branching fraction of \$B(B^+ \tau^+
\nu\_\tau) = 1.25 0.28 (stat.) 0.27(syst.) \times
10^-4\$. This result is in good agreement with previous measurements and the
expectation from calculations based on the Standard Model.
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