Completing the NLO QCD calculation of (B)over-bar→Xsγ

We evaluate two-loop b --> sgamma matrix elements of all the four-quark operators containing no derivatives. Contrary to previous calculations, no expansion in the mass ratio m(c)/m(b) is performed, and all the possible Dirac and flavor structures are included. Consequently, we are able to provide the last item in the NLO analysis of (B) over bar --> X(s)gamma that has been missing so far, namely the two-loop matrix elements of the QCD-penguin operators. Due to smallness of the Wilson coefficients of those operators in the Standard Model, their effect on the branching ratio is small: a reduction by roughly 1%. We find BR[(B) over bar --> X(s)gamma]E-gamma > 1.6 GeV = (3.57 +/- 0.30) x 10(-4). (C) 2002 Elsevier Science B.V. All rights reserved.