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

We study radiative p⊥p⊥-broadening of high-energy quarks passing through hot and cold QCD matter. With L   the length of the matter and l0l0 the size of constituents of the matter we find 〈p⊥2〉 has both double logarithmic terms, ln2(L/l0)ln2(L/l0), and single logarithmic terms, ln(L/l0)ln(L/l0), 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 〈p⊥2〉. 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.