350 research outputs found

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

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    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?

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    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 TcT_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 TcT_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

    Differential Hanbury-Brown-Twiss for an exact hydrodynamic model with rotation

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    We study an exact rotating and expanding solution of the fluid dynamical model of heavy ion reactions, that take into account the rate of slowing down of the rotation due to the longitudinal and transverse expansion of the system. The parameters of the model are set on the basis of realistic 3+1D fluid dynamical calculation at TeV energies, where the rotation is enhanced by the build up of the Kelvin Helmholtz Instability in the flow.Comment: 4 Pages, 7 figures, to be published in PR

    Study of vorticity in an exact rotating hydro model

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    We study a semianalytic exact solution of the fluid dynamical model of heavy ion reactions, and evaluate some observable signs of the rotation.Comment: 19 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:1406.101

    Kinetic description of particle emission from expanding source

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    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

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    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

    Time dependence of partition into spectators and participants in relativistic heavy-ion collisions

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    The process of formation of the participant system in heavy-ion collisions is investigated in the framework of a simplified analytic Glauber-like model, which is based on the relativistic Boltzmann transport equation. The key point lies in the time-dependent partition of the nucleon system into two groups: nucleons, which did not take part in any interaction before a given time and nucleons, which already have interacted. In the framework of the proposed model we introduce a natural energy-dependent temporal scale tct_c, which allows us to remove all dependencies of the model on the collision energy except for the energy dependence of the nucleon-nucleon cross-section. By investigating the time dependence of the total number of participants we conclude that the formation process of the participant system becomes complete at t‚ČÉ1.5tct\simeq1.5 t_c. Time dependencies of participant total angular momentum and vorticity are also considered and used to describe the emergence of rotation in the reaction plane.Comment: 24 pages, 10 figures, minor changes to match published versio
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