Modeling of heavy-ion collisions at the relativistic heavy-ion collider
In summary, we have introduced a hybrid macroscopic/microscopic transport approach, combining a newly developed relativistic 3+1 dimensional hydrodynamic model for the early deconfined stage of the reaction and the hadronization process with a microscopic non-equilibrium model for the later hadronic stage at which the hydrodynamic equilibrium assumptions are not valid anymore. Within this approach we have self-consistently calculated the freeze-out of the hadronic system, accounting for the collective flow on the hadronization hypersurface generated by the QGP expansion. We have compared the results of our hybrid model and of a calculation utilizing our hydrodynamic model for the full evolution of the reaction to experimental data. This comparison has allowed us to quantify the strength of dissipative effects prevalent in the later hadronic phase of the reaction, which cannot be properly treated in the framework of ideal hydrodynamics. Overall, the improved treatment of the hadronic phase provides a far better agreement between transport calculation and data, in particular concerning the flavor dependence of radial flow observables and the collective behavior of matter at forward/backward rapidities. We find that the hadronic phase of the heavy-ion reaction at top RHIC energy is of significant duration (at least 10 fm/c) and that hadronic freeze-out is a continuous process, strongly depending on hadron flavor and momenta. With this work we have established a base-line - both for the regular 3+1 dimensional hydrodynamic model as well as for the hybrid hydro+micro approach. In forthcoming publications we shall expand on this baseline by investigating the effects of a realistic lattice-QCD motivated equation of state containing a tri-cricital point and by performing an analysis of two particle correlations (HBT interferometry). We also plan to use our model as the medium for the propagation of jets and heavy quarks and to study the modification of our medium due to the passage of these hard probes. © World Scientific Publishing Company.
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