Electroweak radiative corrections to b→sγ

Two loop electroweak corrections to b --> s gamma decays are computed. Fermion and photonic loop effects are found to reduce R = B (b --> s gamma)/B(b --> ce nu) by similar to(8 +/- 2)% and lead to the standard model prediction B(B --> X-s gamma) = (3.28 +/- 0.30) X 10(-4) for inclusive B meson decays. Comparison of R-theory = (3.04 +/- 0.25) X 10(-3)(1 + 0.10 rho), where rho is a Wolfenstein Cabibbo-Kobayashi-Maskawa parameter, with the current experimental average R-exp = (2.52 +/- 0.52) X 10-3 gives rho = -1.7 +/- 1.9 which is consistent with -0.21 less than or equal to rho less than or equal to 0.27 obtained from other B and K physics constraints. [S0031-9007(98)06553-3].