Suppression of the jet quenching parameter near the critical temperature

Abstract

In this work, we study the jet quenching parameter $\hat{q}$ 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 $\mathcal{Q}$. 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 $\hat{q}$. The other corresponds to the $\mathcal{Q}$-modified parton distribution function which is dominant and leads to a suppression of $\hat{q}$. Decreasing the temperature $T$, our result shows a nonmonotonic $T$ dependence of the dimensionless $\hat{q}/T^3$. In the high temperature region, $\hat{q}/T^3$ 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 $\hat{q}/T^3$ 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 $\hat{q}$ 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.

minor changes, final version appears in PRD

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Cited by in corpus (1)

• Energy Loss of a Heavy Quark in a Collisional Quark-Gluon Plasma