Coherent final state interaction in jet production in nucleus-nucleus collisions

The coherent final state interaction of an energetic parton produced in AA collisions is studied. This interaction is due to the change in the cutoff scale and in the running coupling constant when the parton passes from a vacuum to a quark-gluon plasma. It is demonstrated that the contribution of this new mechanism to the energy loss may be of the same order of magnitude as the induced gluon radiation. However, an accurate evaluation of this medium effect is a difficult task, because there is a strong cancellation between the cutoff and running coupling constant effects. The uncertainties in the contribution of the coherent final state interaction restrict strongly the accuracy of jet tomographic analyses of the matter density produced in AA reactions.