Article

# Nonequilibrium Models of Relativistic Heavy-Ion Collisions

Journal of Physics G Nuclear and Particle Physics (Impact Factor: 5.33). 12/2004; DOI: 10.1088/0954-3899/31/6/037

Source: arXiv

- [Show abstract] [Hide abstract]

**ABSTRACT:**We investigate the relativistic equation of state of hadronic matter and quark-gluon plasma at finite temperature and baryon density in the framework of the non-extensive statistical mechanics, characterized by power-law quantum distributions. We impose the Gibbs conditions on the global conservation of baryon number, electric charge and strangeness number. For the hadronic phase, we study an extended relativistic mean-field theoretical model with the inclusion of strange particles (hyperons and mesons). For the quark sector, we employ an extended MIT-Bag model. In this context we focus on the relevance of non-extensive effects in the presence of strange matter.Central European Journal of Physics 02/2012; 10(3). · 0.91 Impact Factor - [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., vâ and 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 vâ and 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 01/2006; 74(6):064908-064908. · 3.72 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**The energy excitation functions of directed flow (v1) and elliptic flow (v2) from Ebeam=90A MeV to Ecm=200A GeV are explored within the UrQMD framework and discussed in the context of the available data. The radial and the elliptic flow of the particles produced in a relativistic heavy-ion collision are intimately connected to the pressure and its gradients in the early stage of the reaction. Therefore, these observables should also be sensitive to changes in the equation of state. To prove this connection, the temporal evolution of the pressure, pressure gradients and elliptic flow are shown. For the flow excitation functions it is found that, in the energy regime below Ebeam≤10A GeV, the inclusion of nuclear potentials is necessary to describe the data. Above 40A GeV beam energy, the UrQMD model starts to underestimate the elliptic flow. Around the same energy the slope of the rapidity spectra of the proton directed flow develops negative values. This effect is known as the third flow component (“antiflow”) and cannot be reproduced by the transport model. The difference between the data and the UrQMD model can possibly be explained by assuming a phase transition from hadron gas to quark–gluon plasma around Elab=40A GeV. This would be consistent with the model calculations, indicating a transition from hadronic matter to “string matter” in this energy range. Thus, we speculate that the missing pressure might be generated by strong interactions in the early pre-hadronic/partonic phase of central Au + Au (Pb + Pb) collisions already at lower SPS energies.European Physical Journal C 12/2006; 49(1):91-96. · 5.25 Impact Factor

Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.