Two-loop matrix element of the current-current operator in the decay B -> X-S gamma

We evaluate important two-loop matrix element (S gamma \Q(2)\b) of the oper ator ((c) over bar gamma (mu)P(L)b)((s)over bar gamma muPLB) contributing t o the inclusive radiative decay B --> X(s)gamma. The calculation is perform ed in the NDR scheme, by means of asymptotic expansions method. The result is given as a series in z equivalent to m(c)(2)/m(b)(2) up to O(z(6)). We c onfirm the result of Greub. Hurth and Wyler obtained by a different method up to O(z(3)). Higher-order terms are found to be numerically insignificant . (C) 2001 Elsevier Science B.V. All rights reserved.