Energy loss in a partonic transport model including bremsstrahlung processes

TL;DR

This paper investigates gluon energy loss in a thermal medium using a transport model, highlighting the dominance of radiative processes and analyzing effects on jet quenching and flow in heavy-ion collisions.

Contribution

It introduces a detailed comparison of elastic and radiative energy loss mechanisms, emphasizing the role of gluon multiplication in a perturbative QCD transport model.

Findings

Gluon multiplication gg -> ggg is the main energy loss process.

Radiative processes significantly increase gluon energy loss.

Results show decreased quenching in non-central collisions with similar shape.

Abstract

A detailed investigation of the energy loss of gluons that traverse a thermal gluonic medium simulated within the perturbative QCD--based transport model BAMPS (a Boltzmann approach to multiparton scatterings) is presented in the first part of this work. For simplicity the medium response is neglected in these calculations. The energy loss from purely elastic interactions is compared to the case where radiative processes are consistently included based on the matrix element by Gunion and Bertsch. From this comparison gluon multiplication processes gg -> ggg are found to be the dominant source of energy loss within the approach employed here. The consequences for the quenching of gluons with high transverse momentum in fully dynamic simulations of Au+Au collisions at the RHIC energy of sqrt(s) = 200 AGeV are discussed in the second major part of this work. The results for central collisions as discussed in a previous publication are revisited and first results on the nuclear modification factor R_AA for non-central Au+Au collisions are presented. They show a decreased quenching compared to central collisions while retaining the same shape. The investigation of the elliptic flow v2 is extended up to non-thermal transverse momenta of 10 GeV, exhibiting a maximum v2 at roughly 4 to 5 GeV and a subsequent decrease. Finally the sensitivity of the aforementioned results on the specific implementation of the effective modeling of the Landau-Pomeranchuk-Migdal (LPM) effect via a formation time based cut-off is explored.