Latest documents http://publikationen.ub.uni-frankfurt.de/index/index/ Fri, 29 Apr 2011 17:25:31 +0200 Fri, 29 Apr 2011 17:25:31 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/17209 NCQ scaling of elliptic flow is studied in a non-equilibrium hadronization and freeze-out model from ideal, deconfined and chirally symmetric Quark Gluon Plasma (QGP), to final non-interacting hadrons. In this transition the quarks gain constituent quark mass while the background Bag-field breaks up. The constituent quarks then recombine into simplified hadron states, while chemical, thermal and flow equilibrium break down. Then the resulting temperatures and flow velocities of baryons and mesons will be different. In a simplified model, we reproduce the constituent quark number scaling. László Pal Csernai; Yun Cheng; Szabolcs Horvat; Igor Mishustin; Sven Zschocke article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/17209 Fri, 29 Apr 2011 17:25:31 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2470 The collision process is described by hydrodynamical equations. The escape of nucleons which do not take part in the thermal equilibrium is considered by including drain terms in these equations. The energy spectra of the escaped nucleons and of nucleons evaporated after the breakup of the fluid are compared. NUCLEAR REACTIONS Relativistic heavy ion reactions, nuclear hydrodynamics, nucleon spectra. H. W. Barz; László Pal Csernai; Walter Greiner article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2470 Fri, 30 Jun 2006 12:54:49 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2469 The nucleons taking part in heavy ion reaction are considered as a three-component fluid. The first and second components correspond to the nucleons of the target and the projectile, while the thermalized nucleons produced in the course of the collision belong to the third component. Making use of the Boltzmann equation, hydrodynamical equations are derived. An equation of state for anisotropic nuclear matter obtained from a field theoretical model in mean field approximation is applied in a one dimensional version of the three-component fluid model. The speed of thermalization is analyzed and compared to the results of cascade and kinetic models. NUCLEAR REACTIONS Relativistic heavy-ion reactions, hydrodynamic description. László Pal Csernai; I. Lovas; Joachim A. Maruhn; A. J Rosenhauer; J. Zimányi; Walter Greiner article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2469 Fri, 30 Jun 2006 12:51:03 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2584 We present an analysis of high energy heavy ion collisions at intermediate impact parameters, using a two-dimensional fluid-dynamical model including shear and bulk viscosity, heat conduction, a realistic treatment of the nuclear binding, and an analysis of the final thermal emission of free nucleons. We find large collective momentum transfer to projectile and target residues (the highly inelastic bounce-off effect) and explosion of the hot compressed shock zones formed during the impact. As the calculated azimuthal dependence of energy spectra and angular distributions of emitted nucleons depends strongly on the coefficients of viscosity and thermal conductivity, future exclusive measurements may allow for an experimental determination of these transport coefficients. The importance of 4π measurements with full azimuthal information is pointed out. Gerd Buchwald; László Pal Csernai; Joachim A. Maruhn; Walter Greiner; Horst Stöcker article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2584 Tue, 20 Jun 2006 10:41:14 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2583 Problems arising in viscous nuclear fluid dynamical models of high-energy heavy-ion collisions are discussed. The importance of an accurate treatment of the transport properties of the hot and dense nuclear matter is pointed out. László Pal Csernai; Horst Stöcker article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2583 Tue, 20 Jun 2006 10:34:24 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2613 Two-particle correlation data are presented for the reaction Ar (800 MeV/ nucleon) + Pb. The experimental results are analyzed in the nuclear fluid dynamical and in a linear cascade model. We demonstrate that the collective hydrodynamical correlations dominate the measured two-particle correlation function for the heavy system studied. We discuss the transition from the early stages of the reaction which are governed by few nucleon correlations, to the later stages with their macroscopic flow which can only be reached using heavy colliding systems. The sensitivity of the correlation data on the underlying compressional dissipative processes is analyzed. László Pal Csernai; Walter Greiner; Horst Stöcker; Isao Tanihata; Shoji Nagamiya; Jörn Knoll article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2613 Tue, 13 Jun 2006 12:56:53 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2625 The fluid dynamical model is used to study the reactions 20Ne+238U and 40Ar+40Ca at Elab=390 MeV/nucleon. The calculated double differential cross sections d2σ/dΩdE exhibit sidewards maxima in agreement with recent experimental data. The azimuthal dependence of the triple differential distributions, to be obtained from an event-by-event analysis of 4π exclusive experiments, can yield deeper insight into the collision process: Jets of nuclear matter are predicted with a strongly impact-parameter-dependent thrust angle θjet(b). NUCLEAR REACTIONS Ar+Ca, Ne+U, Elab=393 MeV/nucleon, fluid dynamics with thermal breakup, double differential cross sections, azimuthal dependence of triple differential cross sections, event-by-event thrust analysis of 4π exclusive experiments. Horst Stöcker; László Pal Csernai; Gerhard Graebner; Gerd Buchwald; Hans Kruse; R. Y. Cusson; Joachim A. Maruhn; Walter Greiner article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2625 Tue, 13 Jun 2006 12:52:18 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2646 We present a theoretical description of nuclear collisions which consists of a three-dimensional fluid-dynamical model, a chemical equilibrium breakup calculation for local light fragment (i.e., p, n, d, t, 3He, and 4He) production, and a final thermal evaporation of these particles. The light fragment cross sections and some properties of the heavy target residues are calculated for the asymmetric system Ne+U at 400 MeV/N. The results of the model calculations are compared with recent experimental data. Several observable signatures of the collective hydrodynamical processes are consistent with the present data. An event-by-event analysis of the flow patterns of the various clusters is proposed which can yield deeper insight into the collision dynamics. László Pal Csernai; Horst Stöcker; Pal R. Subramanian; Gerd Buchwald; Gerhard Graebner; Albrecht Rosenhauer; Joachim A. Maruhn; Walter Greiner article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2646 Mon, 12 Jun 2006 10:51:42 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2649 The final states of central Ca + Ca and Nb + Nb collisions at 400 and 1050 MeV/nucleon and at 400 and 650 MeV/nucleon, respectively, are studied with two independently developed statistical models, namely the classical microcanonical model and the quantum-statistical grand canonical model. It is shown that these models are in agreement with each other for these systems. Furthermore, it is demonstrated that there is essentially a one-to-one relationship between the observed relative abundances of the light fragments p, d, t, 3He, and α and the entropy per nucleon, for breakup temperatures greater than 30 MeV. Entropy values of 3.5–4 are deduced from high-multiplicity selected fragment yield data. László Pal Csernai; Joseph I. Kapusta; George I. Fai; D. Hahn; Jørgen Randrup; Horst Stöcker article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2649 Fri, 09 Jun 2006 10:36:30 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3100 We reexamine the scenario of homogeneous nucleation of the quark-gluon plasma produced in ultra-relativistic heavy ion collisions. A generalization of the standard nucleation theory to rapidly expanding system is proposed. The nucleation rate is derived via the new scaling parameter Z. It is shown that the size distribution of hadronic clusters plays an important role in the dynamics of the phase transition. The longitudinally expanding system is supercooled to about 3 6%, then it is reheated, and the hadronization is completed within 6 10 fm/c, i.e. 5 10 times faster than it was estimated earlier, in a strongly nonequilibrium way. PACS: 12.38.Mh; 12.39.Ba; 25.75.-q; 64.60.Qb Eugene E. Zabrodin; Larissa V. Bravina; László Pal Csernai; Horst Stöcker; Walter Greiner preprint http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3100 Mon, 12 Dec 2005 10:47:57 +0100 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3097 We study the effects of strict conservation laws and the problem of negative contributions to final momentum distribution during the freeze out through 3-dimensional hypersurfaces with space-like normal. We study some suggested solutions for this problem, and demonstrate it on one example. PACS: 24.10.Nz, 25.75.-q Csaba Anderlik; László Pal Csernai; Frederique Grassi; Walter Greiner; Yogiro Hama; Takeshi Kodama; Zsolt Iosif Lazar; Volodymyr K. Magas; Horst Stöcker preprint http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3097 Mon, 12 Dec 2005 10:00:25 +0100 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3095 In fluid dynamical models the freeze out of particles across a three dimensional space-time hypersurface is discussed. The calculation of final momentum distribution of emitted particles is described for freeze out surfaces, with both space-like and time-like normals, taking into account conservation laws across the freeze out discontinuity. Csaba Anderlik; Zsolt Iosif Lazar; Volodymyr K. Magas; László Pal Csernai; Horst Stöcker; Walter Greiner preprint http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3095 Fri, 09 Dec 2005 14:11:17 +0100 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3136 Freeze out of particles across a space-time hypersurface is discussed in kinetic models. The calculation of final momentum distribution of emitted particles is described for freeze out surfaces, with spacelike normals. The resulting non-equilibrium distribution does not resemble, the previously proposed, cut Jüttner distribution, and shows non-exponential pt-spectra similar to the ones observed in experiments. PACS: 24.10.Nz, 25.75.-q Volodymyr K. Magas; Csaba Anderlik; László Pal Csernai; Frederique Grassi; Walter Greiner; Yogiro Hama; Takeshi Kodama; Zsolt Iosif Lazar; Horst Stöcker preprint http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3136 Thu, 01 Dec 2005 12:44:15 +0100 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3142 In continuum and fluid dynamical models, particles, which leave the system and reach the detectors, can be taken into account via freeze-out (FO) or final break-up schemes, where the frozen out particles are formed on a 3-dimensional hypersurface in space-time. Such FO descriptions are important ingredients of evaluations of two-particle correlation data, transverse-, longitudinal-, radial- and cylindrical- flow analyses, transverse momentum and transverse mass spectra and many other observables. The FO on a hypersurface is a discontinuity, where the pre FO equilibrated and interacting matter abruptly changes to non-interacting particles, showing an ideal gas type of behavior. Volodymyr K. Magas; Csaba Anderlik; László Pal Csernai; Frederique Grassi; Walter Greiner; Yogiro Hama; Takeshi Kodama; Zsolt Iosif Lazar; Horst Stöcker preprint http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3142 Thu, 01 Dec 2005 09:56:09 +0100 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3140 Freeze out of particles across three dimensional space-time hypersurface is discussed in a simple kinetic model. The final momentum distribution of emitted particles, for freeze out surfaces with space-like normal, shows a non-exponential transverse momentum spectrum. The slope parameter of the pt distribution increases with increasing pt, in agreement with recently measured SPS pion and h spectra. Volodymyr K. Magas; Csaba Anderlik; László Pal Csernai; Frederique Grassi; Walter Greiner; Yogiro Hama; Takeshi Kodama; Zsolt Iosif Lazar; Horst Stöcker preprint http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3140 Tue, 29 Nov 2005 11:25:33 +0100