Measurement of the branching fraction of B+ →τ+ντ decays with the semileptonic tagging method

Abstract

We report a measurement of the branching fraction of B+→τ+ντ decays using a data sample of 772×106BB¯ pairs, collected at the (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 recoiling B candidate in the decay channel B+→τ+ντ. We obtain a branching fraction of B(B+→τ+ντ)=[1.25±0.28(stat.)±0.27(syst.)]×10-4. This result is in good agreement with previous measurements and the expectation from the calculation based on the Standard Model.