Two-loop QCD corrections to charged-Higgs-mediated b -> s gamma decay

The charged-Higgs-mediated contribution to the Wilson coefficient of the b --> s gamma magnetic penguin is expected to be one of the more promising candidates for a supersymmetric effect in B physics, probably the only one in gauge-mediated models. We compute the two-loop QCD correction to it. With naive dimensional regularization and <(MS)over bar> subtraction, for reasonable values of the charged Higgs mass and for <(mu)over bar> = m(t), we find a (10-20) % reduction of the corresponding one-loop effect. (C) 1998 Elsevier Science B.V.