NEXT-TO-LEADING-ORDER MATCHING FOR THE MAGNETIC PHOTON-PENGUIN OPERATOR IN THE B-]X(S)Y DECAY

The initial condition at the matching scale mu(w) = O(M-w) for the Wil son coefficient of the magnetic photon-penguin operator in the decay B --> X-s gamma is calculated in the next-to-leading-order approximatio n. The technical details of the necessary two-loop calculation in the full theory are described and the matching with the corresponding resu lt in the effective theory is discussed in detail. Our outcome for the initial condition confirms the final results of Adel and Yao and Greu b and Hurth. We show that the matching procedure can be properly perfo rmed for infrared divergent amplitudes, i.e. independently of contribu tions from gluon bremsstrahlung. (C) 1998 Published by Elsevier Scienc e B.V.