Two-loop matrix element of the current–current operator in the decay B→Xsγ Original Research Article

We evaluate important two-loop matrix element 〈sγ|Q2|b〉 of the operator (c̄γμPLb)(s̄γμPLb) contributing to the inclusive radiative decay B→Xsγ. The calculation is performed in the NDR scheme, by means of asymptotic expansions method. The result is given as a series in z≡mc2/mb2 up to O(z6). We confirm the result of Greub, Hurth and Wyler obtained by a different method up to O(z3). Higher-order terms are found to be numerically insignificant.