Oliver Fochler

Open heavy flavor in Pb+Pb collisions at √ s=2.76 TeV within a transport model

The space-time evolution of open heavy flavor is studied in Pb+Pb collisions at √ s=2.76 TeV using the partonic transport model Boltzmann Approach to MultiParton Scatterings (BAMPS). An updated version of BAMPS is presented which allows interactions among all partons: gluons, light quarks and heavy quarks. Heavy quarks, in particular, interact with the rest of the medium via binary scatterings with a running coupling and a Debye screening which is matched by comparing to hard thermal loop calculations. The lack of radiative processes in the heavy flavor sector is accounted for by scaling the binary cross section with a phenomenological factor K = 3.5, which describes well the elliptic flow v2 and nuclear modification factor RAA at RHIC. Within this framework we calculate in a comprehensive study the v2 and RAA of all interesting open heavy flavor particles at the LHC: electrons, muons, D mesons, and non-prompt J/ψ from B mesons. We compare to experimental data, where it is already available, or make predictions. To do this accurately next-to-leading order initial heavy quark distributions are employed which agree well with proton-proton data of heavy flavor at √ s=7 TeV.

Elliptic flow and energy loss of heavy quarks in ultrarelativistic heavy ion collisions

the modifications we employed to the standard leading order cross section. In Sec. IV we show our results for RHIC and LHC and compare them to the experimental data where possible. Finally, we conclude with a short summary.

Jet quenching and elliptic flow at the RHIC and the LHC within a pQCD-based partonic transport model

The description of jet quenching and elliptic flow at the RHIC and the LHC within a common dynamical framework has been notoriously difficult. In this paper, an approach using the perturbative QCD-based partonic transport model BAMPS (Boltzmann approach to multi-parton scatterings) is presented that has recently been extended to include light quarks. The investigations are complemented by a study on the suppression of D-mesons at the LHC based on elastic interactions with the medium.

Relativistic shock waves in viscous gluon matter.

We solve the relativistic Riemann problem in viscous gluon matter employing a microscopic parton cascade. We demonstrate the transition from ideal to viscous shock waves by varying the shear viscosity to entropy density ratio eta/s from zero to infinity. We show that an eta/s ratio larger than 0.2 prevents the development of well-defined shock waves on time scales typical for ultrarelativistic heavy-ion collisions. Comparisons with viscous hydrodynamic calculations confirm our findings.

Investigation of shock waves in the relativistic Riemann problem: A comparison of viscous fluid dynamics to kinetic theory

We solve the relativistic Riemann problem in viscous matter using the relativistic Boltzmann equation and the relativistic causal dissipative fluid-dynamical approach of Israel and Stewart. Comparisons between these two approaches clarify and point out the regime of validity of second-order fluid dynamics in relativistic shock phenomena. The transition from ideal to viscous shocks is demonstrated by varying the shear viscosity to entropy density ratio

Heavy-quark production in ultrarelativistic heavy-ion collisions within a partonic transport model

\ensuremath{\eta}/s

Elliptic flow and nuclear modification factor in ultrarelativistic heavy-ion collisions within a partonic transport model.

. We also find that a good agreement between these two approaches requires a Knudsen number

Radiative parton processes in perturbative QCD: An improved version of the Gunion and Bertsch cross section from comparisons to the exact result

\text{Kn}l1/2

Towards a Unified Understanding of Jet Quenching and Elliptic Flow within a Perturbative QCD Parton Transport

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Elastic and radiative heavy quark interactions in ultra-relativistic heavy-ion collisions

The production and space-time evolution of charm and bottom quarks in nucleus-nucleus collisions at RHIC and LHC are investigated with the partonic transport model BAMPS (Boltzmann Approach of MultiParton Scatterings). Heavy quarks, produced in primary hard parton scatterings during nucleon-nucleon collisions, are sampled using the Monte Carlo event generator PYTHIA or the leading order mini-jet model in conjunction with the Glauber model, revealing a strong sensitivity on the parton distribution functions, scales, and heavy quark mass. In a comprehensive study exploring different charm masses, K factors, and possible initial gluon conditions, secondary production and the evolution of heavy quarks are examined within a fully dynamic BAMPS simulation for central heavy ion collisions at RHIC and LHC. Although charm production in the quark-gluon plasma can be neglected at RHIC, it is significant at LHC but very sensitive to the initial conditions and the charm mass. Bottom production in the quark-gluon plasma, however, is negligible both at RHIC and LHC. PACS numbers: 25.75.-q, 25.75.Bh, 25.75.Cj, 12.38.Mh, 24.10.Lx ∗ E-mail: uphoff@th.physik.uni-frankfurt.de