Plasma Effects in Jet Quenching

We consider the bremsstrahlung energy loss of high energy partons moving in the quarkgluon plasma, at weak coupling. We show that the rates for these processes receive large O(g) corrections from classical (nonabelian) plasma physics effects, which are calculated. In the high-energy (deep LPM) regime these corrections can be absorbed in a change of the transverse momentum broadening coefficient q̂, which we give to the next-to-leading order. The correction is large even at relatively weak couplings αs ∼ 0.1, as is typically found for such effects, signaling difficulties with the perturbative expansion. Our approach is based on an effective “Euclideanization” property of classical physics near the light-cone, which allows an effective theory approach based on dimensional reduction and suggests new possibilities for the nonperturbative lattice study of these effects.