Radiative and Collisional Jet Energy Loss in a Quark-Gluon Plasma

TL;DR

This paper calculates and compares radiative and collisional energy loss mechanisms for high-energy partons in quark-gluon plasma, emphasizing the importance of probabilistic modeling for accurate nuclear modification factor predictions.

Contribution

It provides a complete leading-order treatment of both energy loss processes and demonstrates the necessity of solving the Fokker-Planck equation for accurate R_{AA} calculations.

Findings

Both collisional and radiative losses significantly affect R_{AA}

Average parton energy is less sensitive to collisional contributions

The combined formalism matches experimental pion suppression data at RHIC

Abstract

We calculate radiative and collisional energy loss of hard partons traversing the quark-gluon plasma created at RHIC and compare the respective size of these contributions. We employ the AMY formalism for radiative energy loss and include additionally energy loss by elastic collisions. Our treatment of both processes is complete at leading order in the coupling, and accounts for the probabilistic nature of jet energy loss. We find that a solution of the Fokker-Planck equation for the probability density distributions of partons is necessary for a complete calculation of the nuclear modification factor $R_{AA}$ for pion production in heavy ion collisions. It is found that the magnitude of $R_{AA}$ is sensitive to the inclusion of both collisional and radiative energy loss, while the average energy is less affected by the addition of collisional contributions. We present a calculation of $R_{AA}$ for $\pi^0$ at RHIC, combining our energy loss formalism with a relativistic (3+1)-dimensional hydrodynamic description of the thermalized medium.