Photonic penguins at two loops and mt-dependence of BR[B → Xs l+l-]

We calculate two-loop matching conditions for all the operators that are relevant to B --> X(s)l(+)l(-) decay in the Standard Model. In effect, we are able to remove the +/- 16% uncertainty in the decay spectrum, which was mainly due to the renormalization-scale dependence of the top-quark mass. We find 1.46 x 10(-6) for the branching ratio integrated in the domain m(l+l-)(2)/m(b)(2) is an element of [0.05, 0.25], for l = e or mu. There remains around 13% perturbative uncertainty in this quantity, while the non-perturbative effects are expected to be smaller. (C) 2000 Elsevier Science B.V. All rights reserved.