M. Belkacem

Microscopic models for ultrarelativistic heavy ion collisions

In this paper, the concepts of microscopic transport theory are introduced and the features and shortcomings of the most commonly used ansatzes are discussed. In particular, the Ultrarelativistic Quantum Molecular Dynamics (UrQMD) transport model is described in great detail. Based on the same principles as QMD and RQMD, it incorporates a vastly extended collision term with full baryon-antibaryon symmetry, 55 baryon and 32 meson species. Isospin is explicitly treated for all hadrons. The range of applicability stretches from

Relativistic hadron-hadron collisions in the ultra-relativistic quantum molecular dynamics model

E_{lab} 200

Equation of State, Spectra and Composition of Hot and Dense Infinite Hadronic Matter in a Microscopic Transport Model ∗

GeV/nucleon, allowing for a consistent calculation of excitation functions from the intermediate energy domain up to ultrarelativistic energies. The main physics topics under discussion are stopping, particle production and collective flow.

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

Hadron-hadron (h-h) collisions at high energies are investigated in the ultra-relativistic quantum molecular dynamics (UrQMD) approach. This microscopic transport model describes the phenomenology of hadronic interactions at low and intermediate energies ( 5 GeV, the excitation of colour strings and their subsequent fragmentation into hadrons dominates the multiple production of particles in the UrQMD model. The model shows a fair overall agreement with a large body of experimental h-h data over a wide range of h-h centre-of-mass energies. Hadronic reaction data with higher precision would be useful to support the use of the UrQMD model for relativistic heavy-ion collisions.

Critical review of quark gluon plasma signatures

Bogolyubov Institute for Theoretical Physics, Kiev, Ukraine(February 9, 2008)Equilibrium properties of infinite relativistic hadron matter are investi-gated using the Ultrarelativistic Quantum Molecular Dynamics (UrQMD)model. The simulations are performed in a box with periodic boundary con-ditions. Equilibration times depend critically on energy and baryon densities.Energy spectra of various hadronic species are shown to be isotropic andconsistent with a single temperature in equilibrium. The variation of energydensity versus temperature shows a Hagedorn-like behavior with a limitingtemperature of 130±10 MeV. Comparison of abundances of different particlespecies to ideal hadron gas model predictions show good agreement only ifdetailed balance is implemented for all channels. At low energy densities,high mass resonances are not relevant; however, their importance raises withincreasing energy density. The relevance of these different conceptual frame-works for any interpretation of experimental data is questioned.

CAN MOMENTUM CORRELATIONS PROVE KINETIC EQUILIBRATION IN HEAVY ION COLLISIONS AT 160 AGEV

The assumption of local equilibrium in relativistic heavy ion collisions at energies from 10.7 AGeV (AGS) up to 160 AGeV (SPS) is checked in the microscopic transport model. Dynamical calculations performed for a central cell in the reaction are compared to the predictions of the thermal statistical model. We find that kinetic, thermal and chemical equilibration of the expanding hadronic matter are nearly approached late in central collisions at AGS energy for

Local thermal and chemical equilibration and the equation of state in relativistic heavy ion collisions

t \geq 10

ARE WE CLOSE TO AN EQUILIBRATED QUARK-GLUON PLASMA? NONEQUILIBRIUM ANALYSIS OF PARTICLE PRODUCTION IN ULTRARELATIVISTIC HEAVY ION COLLISIONS

fm/

Local thermodynamical equilibrium and the equation of state of hot, dense matter created in Au+Au collisions at AGS

c

Reaction dynamics in Pb + Pb at the CERN/SPS: From partonic degrees of freedom to freeze-out

in a central cell. At these times the equation of state may be approximated by a simple dependence