Radiative image-broadening of high-energy quarks and gluons in QCD matter

We study radiative image-broadening of high-energy quarks passing through hot and cold QCD matter. With L the length of the matter and image the size of constituents of the matter we find image has both double logarithmic terms, image, and single logarithmic terms, image, coming from gluon radiation induced by the matter. We use a (slight) extension of a formalism developed by B. Zakharov for studying energy loss, a formalism which, for much of our calculation, reduces to a simple dipole scattering analysis. We estimate the radiative contribution to be a sizable correction to the nonradiative value of image. We also carry out a resummation of the double logarithmic terms that we find, and we briefly discuss running coupling effects which appear here in a rather unusual way.