Two-loop heavy top corrections to the b --> s gamma decay

Abstract

We compute the two-loop corrections to the coefficient of the b --> s gamma magnetic penguin present in the limits of heavy top and/or heavy higgs. This kind of corrections affects in a significant way the observables measured at LEP. On the contrary we find that, due to a numerical accident, the correction to BR(B --> X_s gamma) is negligible (below the 1% level for any possible value of the higgs mass) when the leading order result is expressed in the usual way in terms of the semileptonic BR(B --> X_c \bar{e}ν).