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

We study the coherent final state interaction of an energetic parton produced in $AA$ collisions caused by the change in the cutoff scale and running coupling constant from the vacuum to quark-gluon plasma. We demonstrate that the contribution of this new mechanism to the energy loss may be of the order of magnitude of 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.