Photonic penguins at two loops and m(t)-dependence of BR[B -> X-s l(+)l(-)]

We calculate two-loop matching conditions for all the operators that are re levant 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 ma inly 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 a round 13% perturbative uncertainty in this quantity, while the non-perturba tive effects are expected to be smaller. (C) 2000 Elsevier Science B.V. All rights reserved.