Two-Loop Matrix Element of the Current-Current Operator in the Decay B -> Xs gamma
Abstract
We evaluate the important two-loop matrix element <s gamma| Q2 | b> of the operator (cbar gammamu PL b) (sbar gammamu PL b) contributing to the inclusive radiative decay B -> Xs gamma. 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 0(z3). Higher-order terms are found to be numerically insignificant.
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