We compute the virtual (αs2) fermionic contributions to the charm quark mass dependent matrix elements of the X sγ decay. In the case of a massless quark loop insertion into the gluon propagator, our result obtained as an expansion in z ≤ m c2/mb2 and an exact expression in terms of multi-fold MB integrals, confirms the findings of Bieri, Greub and Steinhauser . In the case of a b-quark loop insertion, we observe large differences between the actual massive case and the massless approximation. These turn out, as expected, to be less pronounced for the charm quark.
- Rare decays
ASJC Scopus subject areas
- Nuclear and High Energy Physics