We calculate and compare bremsstrahlung and collisional energy loss of hard partons traversing a quark-gluon plasma. Our treatment of both processes is complete at leading order in the coupling and accounts for the probabilistic nature of the jet energy loss. We find that the nuclear modification factor $R_{AA}$ for neutral ${\pi }^0$ production in heavy ion collisions is sensitive to the inclusion of collisional and radiative energy loss contributions while the averaged energy loss only slightly increases if collisional energy loss is included for parent parton energies $E\gg T$. These results are important for the understanding of jet quenching in $\mathrm{Au}+\mathrm{Au}$ collisions at $200A\mathrm{GeV}$ at the Relativistic Heavy Ion Collider (RHIC). Comparison with data is performed applying the energy loss calculation to a relativistic ideal ($3+1$)-dimensional hydrodynamic description of the thermalized medium formed at RHIC.

• Received 9 October 2007

DOI:https://doi.org/10.1103/PhysRevLett.100.072301