Investigation of jet quenching and elliptic flow within a pQCD-based partonic transport model

The partonic transport model BAMPS (a Boltzmann approach to multiparton scatterings) is employed to investigate different aspects of heavy ion collisions within a common framework based on perturbative QCD. This report focuses on the joint investigation of the collective behavior of the created medium and the energy loss of high-pT gluons traversing this medium. To this end the elliptic flow and the nuclear modification factor of gluons in heavy ion collisions at 200 AGeV are simulated with BAMPS. The mechanism for the energy loss of high energy gluons within BAMPS is studied in detail. For this, purely elastic interactions are compared to radiative processes, gg -> ggg, that are implemented based on the matrix element by Gunion and Bertsch. The latter are found to be the dominant source of energy loss within the framework employed in this work.Comment: To appear in the proceedings of the 26th Winter Workshop on Nuclear Dynamics (2010)

Untersuchung von Phänomenen bei hohen Transversalimpulsen im Rahmen eines partonischen Transportmodells

In the work presented herein the microscopic transport model BAMPS (Boltzmann Approach to Multi-Parton Scatterings) is applied to simulate the time evolution of the hot partonic medium that is created in Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC) and in Pb+Pb collisions at the recently started Large Hadron Collider (LHC). The study is especially focused on the investigation of the nuclear modification factor R_{AA}, that quantifies the suppression of particle yields at large transverse momentum with respect to a scaled proton+proton reference, and the simultaneous description of the collective properties of the medium in terms of the elliptic flow v_{2} within a common framework.In der vorliegenden Arbeit wird das mikroskopische Transportmodell BAMPS (Boltzmann Approach to Multi-Parton Scatterings) eingesetzt um die Eigenschaften des heißen partonischen Mediums - des sogenannten Quark-Gluon-Plasmas - zu untersuchen, wie es in hochenergetischen Schwerionenkollisionen erzeugt wird. Die Verwendung eines mikroskopischen Transportmodells ermöglicht die detaillierte Untersuchung der zeitlichen Entwicklung des Systems unter Berücksichtigung der vollen Dynamik. Der Schwerpunkt dieser Arbeit liegt dabei auf der Untersuchung des nuklearen Modifizierungsfaktors, R_{AA}, und des elliptischen Flusses, v_{2}, im Rahmen eines gemeinsamen und konsistenten Modells. Betrachtet werden Au+Au-Kollisionen bei einer Schwerpunktsenergie pro Nukleon-Nukleon-Paar von 200 AGeV, wie sie am Relativistic Heavy Ion Collider (RHIC) experimentell erforscht werden. Zudem werden erste Ergebnisse für Pb+Pb-Kollisionen bei 2760 ATeV präsentiert, wie sie seit Kurzem am Large Hadron Collider (LHC) untersucht werden

Energy loss in a partonic transport model including bremsstrahlung processes

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.Comment: 40 pages, 20 figures, 1 tabl