Suppression of the jet quenching parameter near the critical temperature

In this work, we study the jet quenching parameter q ^ by using a background field effective theory. Particular attention is paid to its behavior near the critical temperature where nonperturbative effects induced by the deconfining phase transition are taken into account through a self-consistently introduced background field Q . We adopt a theoretical approach in which the interaction rate between the energetic jet and medium partons is computed diagrammatically and the hard-thermal-loop resummed propagator is used to regulate the infrared divergence. In the presence of a background field, its influence on the jet quenching parameter manifests in two aspects. One is the modification on the screening mass in the resummed propagator, which leads to an enhanced q ^ . The other corresponds to the Q -modified parton distribution function which is dominant and leads to a suppression of q ^ . Decreasing the temperature T , our result shows a nonmonotonic T dependence of the dimensionless q ^ / T 3 . In the high temperature region, q ^ / T 3 shows an increase with decreasing T due to the running coupling effect. Near the critical temperature, the background field plays a significant role and a dramatic suppression of q ^ / T 3 is found which qualitatively agrees with the lattice simulation. In addition, the background field modification on the jet quenching parameter which is characterized by the q ^ ratio can be simply parametrized by a polynomial expression depending only on the background field. This expression is expected to be useful for phenomenological applications in jet physics.