Evidence for B-→τ-ν̄τ with a semileptonic tagging method

We present a measurement of the decay B- -> tau(-)(nu) over bar (tau) using a data sample containing 657 x 10(6) B (B) over bar pairs collected at the gamma(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. A sample of B+B- pairs are tagged by reconstructing one B+ meson decaying semileptonically. We detect the B- -> tau(-)(nu) over bar (tau) candidate in the recoil. We obtain a signal with a significance of 3.6 standard deviations including systematic uncertainties, and measure the branching fraction to be B- -> tau(-)(nu) over bar (tau) [1.54(-0.37)(+0.38) (stat) (+0.29)(-0.31) (syst) x 10(-4). This result confirms the evidence for B- -> tau(-)(nu) over bar (tau) obtained in a previous Belle measurement that used a hadronic B tagging method.