2012/07/10 by Kokulu, Ahmet
#FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph)
paper · doi:10.48550/arxiv.1207.2397
We calculate the set of O(αs) corrections to the double differential decay width dΓ77/(ds1 ds2) for the process B → Xs γγoriginating from diagrams involving the electromagnetic dipole operator O7. The kinematical variables s1 and s2 are defined as si=(pb - qi)2/mb2, where pb, q1, q2 are the momenta of b-quark and two photons. While the (renormalized) virtual corrections are worked out exactly for a certain range of s1 and s2, we retain in the gluon bremsstrahlung process only the leading power w.r.t. the (normalized) hadronic mass s3=(pb-q1-q2)2/mb2 in the underlying triple differential decay width dΓ77/(ds1 ds2 ds3). The double differential decay width, based on this approximation, is free of infrared- and collinear singularities when combining virtual- and bremsstrahlung corrections. The corresponding results are obtained analytically. When retaining all powers in s3, the sum of virtual- and bremstrahlung corrections contains uncanceled 1/εsingularities (which are due to collinear photon emission from the s-quark) and other concepts, which go beyond perturbation theory, like parton fragmentation functions of a quark or a gluon into a photon, are needed which is beyond the scope of our paper.