On the strong-coupling effects in jet bremsstrahlung in the heavy flavor decays

We address the strong-coupling regime effects in the light-like quark jets where the radiated gluons are hard but highly collinear. These may lead to additional contributions in the invariant mass (or recoil energy) spectra, on top of the Fermi motion of the initial heavy quark in decays like b->s+\gamma. It is shown that the integer moments are nevertheless free from such effects; perturbation theory corrections for the moments are driven by \alpha_s in the small coupling regime. They are modified nonperturbatively by the soft modes but not by the collinear modes.