Evidence for B-→τ-ν̄τ with a hadronic tagging method using the full data sample of belle

Abstract

We measure the branching fraction of B-→τ -ν̄τ using the full Υ(4S) data sample containing 772×106 BB̄ pairs collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. Events with BB̄ pairs are tagged by reconstructing one of the B mesons decaying into hadronic final states, and B-→τ -ν̄τ candidates are detected in the recoil. We find evidence for B-→τ -ν̄τ with a significance of 3.0 standard deviations including systematic errors and measure a branching fraction B(B -→τ-ν̄τ)=[0.72-0.25+0. 27(stat)±0.11(syst)]×10-4. © 2013 American Physical Society.