QCD corrections to tb-bar H$^{–}$ associated production in e+e– annihilation

We calculate the QCD corrections to the cross section of e+e–-->tb-bar H– and its charge-conjugate counterpart within the minimal supersymmetric extension of the standard model. This process is particularly important if mt<mH + mb and sqrt(s)<2mH, so that t-->bH+ and e+e–-->H+H– are not allowed kinematically. Large logarithmic corrections that arise in the on-mass-shell scheme of quark mass renormalization, especially from the tb-bar H– Yukawa coupling for large values of tan beta, are resummed by adopting the modified minimal-subtraction scheme, so that the convergence behavior of the perturbative expansion is improved. The inclusion of the QCD corrections leads to a significant reduction of the theoretical uncertainties due to scheme and scale dependences.