QCD corrections to charged Higgs-mediated b → c τ ν decay

We calculate the O(αs) corrections to the charged Higgs mediated inclusive semi-tauonic B decay. By working in the Landau gauge, we demonstrate how to obtain the charged Higgs contributions (both direct and interference terms) from the known QCD corrections to t → bH+. Combining our results with O(1mb2) corrections to the spectator model and comparing the theoretical prediction with the recent experimental measurements, we find a model-independent 2σ upper bound on the ratio of Higgs vacuum expectation values, tan β < 0.52(mH1 GeV).