Freeze-out in hydrodynamical models in relativistic heavy ion collisions

Abstract

Freeze-out of particles across 3-dimensional space-time hypersurface with space-like normal is discussed in a simple kinetic model. The final momentum distribution of emitted particles shows a non-exponential transverse momentum spectrum, which is in quantitative agreement with recently measured SPS pion and $h^-$ spectra.Comment: 4 pages, 1 figure. Quark Matter'99 Proceeding

Covariant description of kinetic freeze-out through a finite time-like layer

“…This special Post FO distribution leads to a curved "p t -spectrum". Here, we can also demonstrate (as in earlier works [1,5,6,7]) that non-equilibrium processes in kinetic FO lead to observable effects.…”

Cancelling Jüttner distributions for space-like freeze-out

“…In figure 1, the schematic way of making the CJ distribution is shown. The distribution obtained this way (figure 2) resembles strongly the one obtained numerically in a kinetic FO model [5]. In the following we demonstrate the use of the Cancelling Jüttner distribution.…”

Modified Boltzmann Transport Equation and Freeze Out

“…The emission or freeze out probability may depend on physical processes, cross sections, transition rates, and the actual PS distributions. Furthermore, f i can be space-time dependent, and must be determined selfconsistently during the detonation, deflagration or FO process [3,4,5,6,16].…”

“…Earlier such kinetic FO calculations were performed in one-dimensional models [3,4,5,6], where the dynamics was governed by two constants: a re-thermalization parameter and a FO parameter. This latter one is governed by the phase-space FO probability, which was constructed recently in a fully covariant form [7].…”