Equation of state, spectra, and composition of hot and dense infinite hadronic matter in a microscopic transport model

Abstract

Equilibrium properties of infinite relativistic hadron matter are investigated using the Ultrarelativistic Quantum Molecular Dynamics (UrQMD) model. The simulations are performed in a box with periodic boundary conditions. Equilibration times depend critically on energy and baryon densities. Energy spectra of various hadronic species are shown to be isotropic and consistent with a single temperature in equilibrium. The variation of energy density versus temperature shows a Hagedorn-like behavior with a limiting temperature of 130±10 MeV. Comparison of abundances of different particle species to ideal hadron gas model predictions show good agreement only if detailed balance is implemented for all channels. At low energy densities, high mass resonances are not relevant; however, their importance raises with increasing energy density. The relevance of these different conceptual frameworks for any interpretation of experimental data is questioned.

Local equilibrium in heavy ion collisions: Microscopic model versus statistical model analysis

“…The simplicity of the SM has led to a very abundant literature (see, e.g. [23][24][25][26] and references therein). Therefore, we shall recall briefly some of its principle features.…”

Collective flow in heavy-ion collisions forElab=1−160GeV/nucleon

“…Thus, the flow reflects stiffness of the nuclear EoS. The collective flow observable has been extensively exploited to obtain information on the EoS [15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51]. In particular, it was expected that the transition to the quark-gluon phase results in significant reduction of the directed flow [52] (so called "softest point" effect), since the pressure in the quark-gluon phase is lower than that in the hadronic phase.…”

Analysis of particle production in ultrarelativistic heavy-ion collisions within a two-source statistical model

“…Although this idea was put forward by Fermi 50 years ago [1], up to now there is no unambiguous test to probe the degree of equilibration in the system. One of the possible approaches is to study the equilibration process within microscopic models [2,3,4,5,6,7]. The more traditional way is to fit macroscopic observables, yields and transverse spectra of particles, obtained in experiments to the statistical model (SM) of a fully equilibrated hadron gas.…”