MULTIPLE COLLISIONS AND INDUCED GLUON BREMSSTRAHLUNG IN QCD

Induced soft gluon bremsstrahlung associated with multiple collisions is calculated via perturbative QCD. We derive the non-abelian analog of the Landau-Pomeranchuk effect that suppresses induced soft radiation with formation times exceeding the mean free path. The dependence of the suppression effect on the SU(N) representation of the jet parton as well as the kinematic variables is expressed through a radiation formation factor. The soft radiation with k(perpendicular-to) < mu, where mu is the infrared screening scale in the medium, is shown to lead to an approximately constant radiative energy loss per unit length.