Energy loss and p⊥ - broadening of high energy partons in hot and cold QCD matter

Recent work on jet p_⊥-broadening and induced gluon radiation from jets passing through hot and cold QCD matter is reviewed. The basic assumption used is that multiple scattering of a high energy parton in a QCD medium can be viewed as a series of independent scatterings, exactly as in the standard Glauber theory. We show that p_{⊥ w}² grows as L, the length of the nuclear matter, as does - {dE}/{dz} the energy loss of the parton per unit length. We find - {dE}/{dz} = - {αN _c}/{8}p _⊥w², a generalization of an earlier result of Brodsky and Hoyer. Numerical estimates suggest that p_⊥-broadening and induced energy loss may be significantly enhanced in hot matter as compared to cold matter.