Measurement of the branching ratio for the process →τ

The inclusive branching ratio for the process b→τ−ν̄τX has been measured using hadronic Z decays collected by the OPAL experiment at LEP in the years 1992–2000. The result is: BR(b→τ−ν̄τX)=(2.78±0.18±0.51)%. This measurement is consistent with the Standard Model expectation and puts a constraint of tanβ/MH±<0.53 GeV−1 at the 95% confidence level on Type II Two Higgs Doublet Models.