The effect of H^\pm on B^\pm -> \tau^\pm \nu and B^\pm -> \mu^\pm \nu

The hitherto unobserved purely leptonic decays B^\pm -> \tau^\pm \nu and B^\pm -> \mu^\pm \nu are of much interest at current and future runs of the e+e- B factories. Such decays are sensitive to charged Higgs bosons (H^\pm) at the tree-level and provide essentially model independent constraints on \tan\beta/m_{H^\pm}. We include the large corrections to the H^\pm-ub coupling induced by virtual SUSY effects and show that the bounds on \tan\beta/m_{H^\pm} can be significantly weakened or strengthened.