arXiv subjects

Oliver Fochler

Publications and source records attributed to Oliver Fochler.

23 records · Page 2Linked to original sources

arXiv2010

Relativistic Shock Waves and Mach Cones in Viscous Gluon Matter

To investigate the formation and the propagation of relativistic shock waves in viscous gluon matter we solve the relativistic Riemann problem using a microscopic parton cascade. We demonstrate the transition from ideal to viscous shock waves by varying the shear viscosity to entropy density ratio $η/s$. Furthermore we compare our results with those obtained by solving the relativistic causal dissipative fluid equations of Israel and Stewart (IS), in order to show the validity of the IS hydrodynamics. Employing the parton cascade we also investigate the formation of Mach shocks induced by a high-energy gluon traversing viscous gluon matter. For $η/s = 0.08$ a Mach cone structure is observed, whereas the signal smears out for $η/s \geq 0.32$.

hep-ph↗

arXiv2010

Production and elliptic flow of heavy quarks at RHIC and LHC within a partonic transport model

Production and elliptic flow of heavy quarks are investigated in nucleus-nucleus collisions at RHIC and LHC within the Boltzmann Approach of MultiParton Scatterings (BAMPS). The initial heavy quark yield is estimated with the leading order mini-jet model and compared to PYTHIA for several parton distribution functions. Secondary production of heavy quarks in the quark-gluon plasma is examined within the full 3+1 dimensional BAMPS simulation of heavy ion collisions. At RHIC this yield is negligible, but for LHC charm production in the QGP plays a significant role. In addition, we study the elliptic flow of charm quarks at RHIC with the result that leading order processes are not sufficient to describe the experimental data.

hep-ph↗

arXiv2010

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.

hep-ph↗

arXiv2010

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.

hep-ph↗

arXiv2008

QCD plasma equilibration, elliptic flow and jet-quenching - phenomena of common origin

Fast thermalization, a subsequent strong buildup of elliptic flow of QCD matter and jet-quenching as found at the Relativistic Heavy Ion Collider (RHIC) are understood as the consequence of perturbative QCD (pQCD) interactions within the 3+1 dimensional parton cascade BAMPS. The main contributions stem from pQCD inspired bremsstrahlung. Comparisons to Au+Au data of the flow parameter v_2 as a function of participation number as well as the gluonic contribution to the nuclear modification factor R_AA for most central collisions are given. Also the shear viscosity to entropy ratio is dynamically extracted, which lies in the range of 0.08-0.15, depending on the chosen coupling constant.

hep-ph↗