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

The problem of Freeze Out (FO) in relativistic heavy ion reactions is addressed. We develop and analyze an idealized one-dimensional model of FO in a finite layer, based on the covariant FO probability. The resulting post FO phase-space distributions are discussed for different FO probabilities and layer thicknesses.Comment: 16 pages, 19 figures, changed content, references adde

Quark-Gluon Plasma Freeze-out from a Supercooled State?

We consider time-scales of first-order deconfinement or chiral-symmetry restoring phase transition in high energy heavy ion collisions at RHIC and LHC energies. Recently it was shown that the system must supercool below $T_c$ before the nucleation of hadronic bubbles is sufficiently rapid to overcome the expansion rate. It is shown here that the expected time-scales of high energy heavy ion reactions are sufficiently short to prevent the reheating of the system to near $T_c$. If quark-gluon plasma is produced in these collisions, it may have to hadronize from a supercooled state and the hadrons produced during rehadronization may freeze-out almost immediately.Comment: LaTeX, 14 pages + 2 eps figures. Contribution to the Proceedings of the Workshop on Preequilibrium Parton Dynamics, LBL, Aug. 199

Kinetic description of particle emission from expanding source

The freeze out of the expanding systems, created in relativistic heavy ion collisions, is discussed. We combine kinetic freeze out equations with Bjorken type system expansion into a unified model. The important feature of the proposed scenario is that physical freeze out is completely finished in a finite time, which can be varied from 0 (freeze out hypersurface) to infinity. The dependence of the post freeze out distribution function on the freeze out time will be studied. As an example, model is completely solved and analyzed for the gas of pions. We shall see that the basic freeze out features, pointed out in the earlier works, are not smeared out by the expansion of the system. The entropy evolution in such a scenario is also studied.Comment: 8 pages, 4 figures. Accepted to Physics Letters

Instabilities in Nuclei

The evolution of dynamical perturbations is examined in nuclear multifragmentation in the frame of Vlasov equation. Both plane wave and bubble type of perturbations are investigated in the presence of surface (Yukawa) forces. An energy condition is given for the allowed type of instabilities and the time scale of the exponential growth of the instabilities is calculated. The results are compared to the mechanical spinodal region predictions. PACS: 25.70 MnComment: 22 pages, latex, with 5 PS figures, available at http://www.gsi.de/~papp