Thermalization of dense hadronic matter in Au + Au collisions at energies available at the Facility for Antiproton and Ion Research

Abstract

The conditions of local thermodynamic equilibrium of baryons (non-strange, strange) and mesons (strange) are presented for central Au + Au collisions at FAIR energies using the microscopic transport model UrQMD. The net particle density, longitudinal-to-transverse pressure anisotropy and inverse slope parameters of the energy spectra of non-strange and strange hadrons are calculated inside a cell in the central region within rapidity window |y| < 1.0 at different time steps after the collisions. We observed that the strangeness content is dominated by baryons at all energies, however contribution from mesons become significant at higher energies. The time scale obtained from local pressure (momentum) isotropization and thermalization of energy spectra are nearly equal and found to decrease with increase in laboratory energy. The equilibrium thermodynamic properties of the system are obtained with statistical thermal model. The time evolution of the entropy densities at FAIR energies are found very similar with the ideal hydrodynamic behaviour at top RHIC energy.

Total and Partial Shear Viscosity in Heavy-Ion Collisions at Energies of BES, FAIR and NICA

“…As was shown in previous studies within the UrQMD [44][45][46][47], there is no global equilibrium within the whole volume of the fireball, even in very central heavy-ion collisions because, for instance, the net baryon charge and net strangeness are not uniformly distributed. A local equilibrium, however, is very likely [46,[48][49][50][51] at least in the central zone of a rapidly expanding fireball. The investigations revealed that the central cubic cell with volume V = 5 × 5 × 5 = 125 fm 3 is appropriate for investigating the process of relaxation to equilibrium of hot and dense nuclear matter produced in relativistic heavy-ion collisions.…”