Nonequilibrium Models of Relativistic Heavy-Ion Collisions

Goethe-Universität Frankfurt am Main, Frankfurt, Hesse, Germany
Journal of Physics G Nuclear and Particle Physics (Impact Factor: 2.84). 12/2004; DOI: 10.1088/0954-3899/31/6/037
Source: arXiv

ABSTRACT We review the results from the various hydrodynamical and transport models on the collective flow observables from AGS to RHIC energies. A critical discussion of the present status of the CERN experiments on hadron collective flow is given. We emphasize the importance of the flow excitation function from 1 to 50 A$\cdot$GeV: here the hydrodynamic model has predicted the collapse of the $v_1$-flow and of the $v_2$-flow at $\sim 10$ A$\cdot$GeV; at 40 A$\cdot$GeV it has been recently observed by the NA49 collaboration. Since hadronic rescattering models predict much larger flow than observed at this energy we interpret this observation as evidence for a first order phase transition at high baryon density $\rho_B$. Moreover, the connection of the elliptic flow $v_2$ to jet suppression is examined. It is proven experimentally that the collective flow is not faked by minijet fragmentation. Additionally, detailed transport studies show that the away-side jet suppression can only partially ($<$ 50%) be due to hadronic rescattering. Furthermore, the change in sign of $v_1, v_2$ closer to beam rapidity is related to the occurence of a high density first order phase transition in the RHIC data at 62.5, 130 and 200 A$\cdot$GeV. Comment: 15 pages, 7 eps figures, to be published in J. Phys. G - Proceedings of SQM 2004

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Evolution of the elliptic flow of hadrons in heavy-ion collisions at RHIC energies is studied within the microscopic quark gluon string model. The elliptic flow is shown to have a multi-component structure caused by (i) rescattering and (ii) absorption processes in spatially asymmetric medium. Together with different freeze-out dynamics of mesons and baryons, these processes lead to the following trend in the flow formation: the later the mesons are frozen, the weaker their elliptic flow, whereas baryon fraction develops stronger elliptic flow during the late stages of the fireball evolution. The phase-space distributions of the emitted particles are studied as well. The flow is shown to be formed both in the central and in the fragmentation regions of the reaction. Comparison with the PHOBOS data demonstrates the model ability to reproduce the v2ch(η) signal in different centrality bins.
    Physics Letters B 12/2005; 631(3):109-117. DOI:10.1016/j.physletb.2005.09.085 · 6.02 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Recent data from the NA49 experiment on directed and elliptic flow for Pb+Pb reactions at CERN-SPS are compared to calculations with a hadron-string transport model, the ultrarelativistic quantum molecular dynamics (UrQMD) model. The rapidity and transverse momentum dependence of the directed and elliptic flow, i.e., v⁠and vâ, are investigated. The flow results are compared to data at three different centrality bins. Generally, a reasonable agreement between the data and the calculations is found. Furthermore, the energy excitation functions of v⁠and vâ from E{sub beam}=90A MeV to E{sub c.m.}=200A GeV are explored within the UrQMD framework and discussed in the context of the available data. It is found that, in the energy regime below E{sub beam}{
    Physical Review C 12/2006; 74(6):064908-064908. DOI:10.1103/PHYSREVC.74.064908 · 3.88 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Relativistic nonideal fluid dynamics is formulated in 3+1 space-time dimensions. The equations governing dissipative relativistic hydrodynamics are given in terms of the time and three-space quantities which correspond to those familiar from nonrelativistic physics. Dissipation is accounted for by applying the causal theory of relativistic dissipative fluid dynamics. As a special case, we consider a fluid without viscous/heat couplings in the causal system of transport/relaxation equations. For the study of physical systems, we consider pure (1+1)-dimensional expansion in planar geometry, (1+1)-dimensional spherically symmetric (fireball) expansion, (1+1)-dimensional cylindrically symmetric expansion, and a (2+1)-dimensional expansion with cylindrical symmetry in the transverse plane (firebarrel expansion). The transport/relaxation equations are given in terms of the spatial components of the dissipative fluxes, since these are not independent. The choice for the independent components is analogous to the nonrelativistic equations.
    Physical Review C 07/2007; 76(1). DOI:10.1103/PhysRevC.76.014909 · 3.88 Impact Factor


1 Download
Available from