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

Abstract

We study radiative $p_{\perp }$-broadening of high energy quarks passing through hot and cold QCD matter. With $L$ the length of the matter and $l_0$ the size of constituents of the matter we find $\text{avg}{p}_{\perp }^2$ has both double logarithmic terms, ${\ln }^2(L/l_0)$, and single logarithmic terms, $\ln (L/l_0)$, 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 $\text{avg}{p}_{\perp }^2$. 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.

Comments: 24 pages, 13 figures. v2: typos corrected, discussion extended