Radiative energy loss of high energy partons traversing an expanding QCD plasma

Abstract

We study analytically the medium-induced energy loss of a high energy parton passing through a finite size QCD plasma, which is expanding longitudinally according to Bjorken's model. We extend the Baier-Dokshitzer-Mueller-Peign\'e-Schiff formalism already applied to static media to the case of a quark which hits successive layers of matter of decreasing temperature, and we show that the resulting radiative energy loss can be as large as 6 times the corresponding one in a static plasma at the reference temperature $T=T(L)$, which is reached after the quark propagates a distance $L$.