Pionic Freeze-out Hypersurfaces in Relativistic Nucleus-Nucleus Collisions

Abstract

The space-time structure of the multipion system created in central relativistic heavy-ion collisions is investigated. Using the microscopic transport model UrQMD we determine the freeze-out hypersurface from equation on pion density n(t,r)=n_c. It turns out that for proper value of the critical energy density ε_c equation ε(t,r)=ε_c gives the same freeze-out hypersurface. It is shown that for big enough collision energies E_kin > 40A GeV/c (sqrt(s) > 8A GeV/c) the multipion system at a time moment τ ceases to be one connected unit but splits up into two separate spatial parts (drops), which move in opposite directions from one another with velocities which approach the speed of light with increase of collision energy. This time τ is approximately invariant of the collision energy, and the corresponding τ=const. hypersurface can serve as a benchmark for the freeze-out time or the transition time from the hydrostage in hybrid models. The properties of this hypersurface are discussed.

11 pages, 8 EPS figures, references added, minor changes to match published version

References in corpus (11)

• Microscopic Models for Ultrarelativistic Heavy Ion Collisions
• Relativistic Hadron-Hadron Collisions in the Ultra-Relativistic Quantum Molecular Dynamics Model (UrQMD)
• Fully integrated transport approach to heavy ion reactions with an intermediate hydrodynamic stage
• Pion Interferometry of $\sqrt{s_{NN}}=130$ GeV Au+Au Collisions at RHIC
• Particlization in hybrid models
• Third flow component as QGP signal
• Bose-Einstein correlations of pion pairs in central Pb+Pb collisions at CERN SPS energies
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• Hadronic Reaction Zones in Relativistic Nucleus-Nucleus Collisions
• Single-Particle Spectra in Relativistic Heavy-Ion Collisions Within the Thermal Quantum Field Theory