ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2010, vol. 82, p. -
Evidence for B-→τ-ν̄τ with a semileptonic tagging method
We present a measurement of the decay B-→τ -ν̄τ using a data sample containing 657×106 BB̄ pairs collected at the Υ(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-→τ -ν̄τ 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(B-→τ -ν̄τ)=[1.54-0.37+0.38(stat)-0.31+0.29(syst)] ×10-4. This result confirms the evidence for B -→τ-ν̄τ obtained in a previous Belle measurement that used a hadronic B tagging method. © 2010 The American Physical Society.