OPUS 4 Latest Documents RSS FeedLatest documents
http://publikationen.stub.uni-frankfurt.de/index/index/
Fri, 14 Jul 2006 10:20:20 +0200Fri, 14 Jul 2006 10:20:20 +0200Cluster description of cold (neutronless) alpha ternary fission of 252Cf
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2387
A coplanar three body cluster model (two deformed fragments and an alpha particle) similar to the model used for the description of cold binary fission was employed for the description of cold (neutronless) alpha accompanied fission of 252Cf. No preformation factors were considered. The three body potential was computed with the help of a double folding potential generated by the M3Y-NN effective interaction and realistic fragment ground state deformations. From the minimum action principle, the alpha particle trajectory equations, the corresponding ternary barriers, and an approximate WKB expression for the barrier penetrability are obtained. The relative cold ternary yields were calculated as the ratio of the penetrability of a given ternary fragmentation and the sum of the penetrabilities of all possible cold ternary fragmentations. Different scenarios were considered depending on the trajectories of the fragments. It was shown that two regions of cold fragmentation exist, a deformed one corresponding to large fragment deformations and a spherical one around 132Sn, similarly to the case of the cold binary fission of 252Cf. We have shown that for the scenario corresponding to the Lagrange point, where all forces acting on the alpha particle are in equilibrium, the cold alpha ternary yields of 252Cf are strongly correlated with the cold binary yields of the daughter nucleus 248Cm into the same heavy fragments. For all other scenarios only the spherical splittings are favored. We concluded that due to the present available experimental data on cold alpha ternary yields only the Lagrange scenario could describe the cold alpha ternary fission of 252Cf.Aurel Săndulescu; F. Carstoiu; Ionel Bulboaca; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2387Fri, 14 Jul 2006 10:20:20 +0200Coulomb effects on electromagnetic pair production in ultrarelativistic heavy-ion collisions
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2391
We calculate the asymptotic high-energy amplitude for electrons scattering at one ion, as well as at two colliding ions, by means of perturbation theory. We show that the interaction with one ion eikonalizes and that the interaction with two ions causally decouples. We are able to put previous results on perturbative grounds and propose further applications for the obtained rules for interactions on the light cone. We discuss the implications of the eikonal amplitude on the pair production probability in ultrarelativistic peripheral heavy-ion collisions. In this context the Weizsäcker-Williams method is shown to be exact in the ultrarelativistic limit, irrespective of the produced particles’ mass. A new equivalent single-photon distribution is derived, which correctly accounts for Coulomb distortions. The impact on single-photon induced processes is discussed.U. Eichmann; Joachim Reinhardt; Stefan Schramm; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2391Fri, 14 Jul 2006 10:12:20 +0200Shell structure of superheavy nuclei in self-consistent mean-field models
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2390
We study the extrapolation of nuclear shell structure to the region of superheavy nuclei in self-consistent mean-field models—the Skyrme-Hartree-Fock approach and the relativistic mean-field model—using a large number of parametrizations which give similar results for stable nuclei but differ in detail. Results obtained with the folded-Yukawa potential which is widely used in macroscopic-macroscopic models are shown for comparison. We focus on differences in the isospin dependence of the spin-orbit interaction and the effective mass between the models and their influence on single-particle spectra. The predictive power of the mean-field models concerning single-particle spectra is discussed for the examples of 208Pb and the spin-orbit splittings of selected neutron and proton levels in 16O, 132Sn, and 208Pb. While all relativistic models give a reasonable description of spin-orbit splittings, all Skyrme interactions show a wrong trend with mass number. The spin-orbit splitting of heavy nuclei might be overestimated by 40%–80%, which exposes a fundamental deficiency of the current nonrelativistic models. In most cases the occurrence of spherical shell closures is found to be nucleon-number dependent. Spherical doubly magic superheavy nuclei are found at 184298114, 172292120, or 184310126 depending on the parametrization. The Z=114 proton shell closure, which is related to a large spin-orbit splitting of proton 2f states, is predicted only by forces which by far overestimate the proton spin-orbit splitting in 208Pb. The Z=120 and N=172 shell closures predicted by the relativistic models and some Skyrme interactions are found to be related to a central depression of the nuclear density distribution. This effect cannot appear in macroscopic-microscopic models or semiclassical approaches like the extended Thomas-Fermi-Strutinski integral approach which have a limited freedom for the density distribution only. In summary, our findings give a strong argument for 172292120 to be the next spherical doubly magic superheavy nucleus.Michael Bender; Klemens Rutz; Paul-Gerhard Reinhard; Joachim A. Maruhn; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2390Fri, 14 Jul 2006 10:11:29 +0200Kaon effective mass and energy from a novel chiral SU(3) symmetric Lagrangian
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3098
A new chiral SU(3) Lagrangian is proposed to describe the properties of kaons and antikaons in the nuclear medium, the ground state of dense matter and the kaon-nuclear interactions consistently. The saturation properties of nuclear matter are reproduced as well as the results of the Dirac-Brückner theory. After taking into account the coupling between the omega meson and the kaon, we obtain similar results for the e ective kaon and antikaon energies as calculated in the one-boson-exchange model while in our model the parameters of the kaon-nuclear interactions are constrained by the SU(3) chiral symmetry. PACS number(s): 14.40.Aq, 12.39.Fe, 21.30.FeGuangjun Mao; Panajotis Papazoglou; Stefan Hofmann; Stefan Schramm; Horst Stöcker; Walter Greinerpreprinthttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3098Mon, 12 Dec 2005 10:10:27 +0100Freeze out in hydrodynamical models
http://publikationen.stub.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.-qCsaba Anderlik; László Pal Csernai; Frederique Grassi; Walter Greiner; Yogiro Hama; Takeshi Kodama; Zsolt Iosif Lazar; Volodymyr K. Magas; Horst Stöckerpreprinthttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3097Mon, 12 Dec 2005 10:00:25 +0100Rho meson broadening in hot and dense hadronic matter
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3112
The modification of the width of rho mesons due to in-medium decays and collisions is evaluated. The decay width is calculated from the imaginary part of the one-loop selfenergy at finite temperature. The collision width is related to the cross sections of the rho + pion and the rho + nucleon reactions. A calculation based on an e ective Lagrangian shows the importance of including the direct pho pi - > pho pi scattering which is dominated by the a1 exchange. A large broadening of the spectral function is found, accompanied by a strength suppression at the pole. http://www.arxiv.org/abs/nucl-th/9812059Song Gao; Charles Gale; Christoph Ernst; Horst Stöcker; Walter Greinerpreprinthttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3112Thu, 08 Dec 2005 11:08:29 +0100Equilibrium and nonequilibrium effects in nucleus nucleus collisions
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3108
Abstract: Local thermal and chemical equilibration is studied for central AqA collisions at 10.7 160 AGeV in the Ultrarelativis- . tic Quantum Molecular Dynamics model UrQMD . The UrQMD model exhibits strong deviations from local equilibrium at the high density hadron string phase formed during the early stage of the collision. Equilibration of the hadron resonance matter is established in the central cell of volume Vs125 fm3 at later stages, tG10 fmrc, of the resulting quasi-isentropic expansion. The thermodynamical functions in the cell and their time evolution are presented. Deviations of the UrQMD quasi-equilibrium state from the statistical mechanics equilibrium are found. They increase with energy per baryon and lead to a strong enhancement of the pion number density as compared to statistical mechanics estimates at SPS energies. PACS: 25.75.-q; 24.10.Lx; 24.10.Pa; 64.30.qtLarissa V. Bravina; Mark I. Gorenstein; Eugene E. Zabrodin; Steffen A. Bass; Mohamed Belkacem; Marcus Bleicher; Mathias Brandstetter; Markus Hofmann; Sven Soff; Christian Spieles; H. Weber; Horst Stöcker; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3108Wed, 07 Dec 2005 13:22:18 +0100Critical review of quark gluon plasma signatures
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3110
Noneequilibrium models (three-fluid hydrodynamics and UrQMD) use to discuss the uniqueness of often proposed experimental signatures for quark matter formation in relativistic heavy ion collisions. It is demonstrated that these two models - although they do treat the most interesting early phase of the collisions quite differently(thermalizing QGP vs. coherent color fields with virtual particles) - both yields a reasonable agreement with a large variety of the available heavy ion data.Stefan Scherer; Steffen A. Bass; Marcus Bleicher; Mohamed Belkacem; Larissa V. Bravina; Jörg Brachmann; Adrian Dumitru; Christoph Ernst; Lars Gerland; Markus Hofmann; Ludwig Neise; Manuel Reiter; Sven Soff; Christian Spieles; Henning Weber; Eugene E. Zabrodin; Detlef Zschiesche; Joachim A. Maruhn; Horst Stöcker; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3110Wed, 07 Dec 2005 10:33:38 +0100Dissociation of expanding c anti-c states in heavy ion collisions
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3123
We study J/psi suppression in AB collisions assuming that the charmonium states evolve from small, color transparent configurations. Their interaction with nucleons and nonequilibrated, secondary hadrons is simulated using the microscopic model UrQMD. The Drell-Yan lepton pair yield and the J/psi Drell-Yan ratio are calculated as a function of the neutral transverse energy in Pb+Pb collisions at 160 GeV and found to be in reasonable agreement with existing data.Christian Spieles; Ramona Vogt; Lars Gerland; Steffen A. Bass; Marcus Bleicher; Leonid Frankfurt; Mark Strikman; Horst Stöcker; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3123Wed, 07 Dec 2005 09:42:32 +0100Relativistic quantum transport theory of hadronic matter : the coupled nucleon, Delta, and pion system
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3122
We derive the relativistic quantum transport equation for the pion distribution function based on an effective Lagrangian of the QHD-II model. The closed-time-path Green s function technique and the semiclassical, quasiparticle, and Born approximations are employed in the derivation. Both the mean field and collision term are derived from the same Lagrangian and presented analytically. The dynamical equation for the pions is consistent with that for the nucleons and Delta's which we developed before. Thus, we obtain a relativistic transport model which describes the hadronic matter with N,Delta, and pi degrees of freedom simultaneously. Within this approach, we investigate the medium effects on the pion dispersion relation as well as the pion absorption and pion production channels in cold nuclear matter. In contrast to the results of the nonrelativistic model, the pion dispersion relation becomes harder at low momenta and softer at high momenta as compared to the free one, which is mainly caused by the relativistic kinetics. The theoretically predicted free piN->Delta cross section is in agreement with the experimental data. Medium effects on the piN->Delta cross section and momentum-dependent Delta-decay width are shown to be substantial. PACS-numbers: 24.10.Jv, 13.75.Cs, 21.65.1f, 25.75.2qGuangjun Mao; Ludwig Neise; Horst Stöcker; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3122Tue, 06 Dec 2005 11:40:47 +0100Gluon versus sea quark shadowing
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3121
We calculate the shadowing of sea quarks and gluons and show that the shadowing of gluons is not simply given by the sea quark shadowing, especially at small x. The calculations are done in the lab frame approach by using the generalized vector meson dominance model. Here the virtual photon turns into a hadronic fluctuation long before the nucleus. The subsequent coherent interaction with more than one nucleon in the nucleus leads to the depletion sigma(gamma*A )< A*sigma(gamma * N) known as shadowing. A comparison of the shadowing of quarks to E665 data for 40Ca and 207Pb shows good agreement.Nils Hammon; Horst Stöcker; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3121Tue, 06 Dec 2005 11:37:12 +0100Irreversibility, steady state, and nonequilibrium physics in relativistic heavy ion collisions
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3120
Heavy ion collisions at ultrarelativistic energies offer the opportunity to study the irreversibility of multiparticle processes. Together with the many-body decays of resonances, the multiparticle processes cause the system to evolve according to Prigogine s steady states rather than towards statistical equilibrium. These results are general and can be easily checked by any microscopic string-, transport-, or cascade model for heavy ion collisions. The absence of pure equilibrium states sheds light on the di culties of thermal models in describing the yields and spectra of hadrons, especially mesons, in heavy ion collisions at bombarding energies above 10 GeV/nucleon. PACS numbers: 25.75.-q, 05.70.Ln, 24.10.LxEugene E. Zabrodin; Larissa V. Bravina; Horst Stöcker; Walter Greinerpreprinthttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3120Tue, 06 Dec 2005 11:33:33 +0100Direct emission of multiple strange baryons in ultrarelativistic heavy-ion collisions from the phase boundary
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3119
We discuss a model for the space-time evolution of ultrarelativistic heavy-ion collisions which employs relativistic hydrodynamics within one region of the forward light-cone, and microscopic transport theory (i.e. UrQMD) in the complement. Our initial condition consists of a quark-gluon plasma which expands hydrodynamically and hadronizes. After hadronization the solution eventually changes from expansion in local equilibrium to free streaming, as determined selfconsistently by the interaction rates between the hadrons and the local expansion rate. We show that in such a scenario the inverse slopes of the mT -spectra of multiple strange baryons ( Xi,Omega) are practically una ected by the purely hadronic stage of the reaction, while the flow of p's and Lambda's increases. Moreover, we find that the rather soft transverse expansion at RHIC energies (due to a first-order phase transition) is not washed out by strong rescattering in the hadronic stage. The earlier kinetic freeze-out as compared to SPS-energies results in similar inverse slopes (of the mT -spectra of the hadrons in the final state) at RHIC and SPS energies.Adrian Dumitru; Steffen A. Bass; Marcus Bleicher; Horst Stöcker; Walter Greinerpreprinthttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3119Tue, 06 Dec 2005 11:29:47 +0100Hot hypernuclear matter in the modified quark meson coupling model
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3128
Hot hypernuclear matter is investigated in an explicit SU(3) quark model based on a mean field description of nonoverlapping baryon bags bound by the self-consistent exchange of scalar sigma, zeta and vector omega,phi mesons. The sigma, omega mean fields are assumed to couple to the u, d-quarks while the zeta ,phi mean fields are coupled to the s-quark. The coupling constants of the mean fields with the quarks are assumed to satisfy SU(6) symmetry. The calculations take into account the medium dependence of the bag parameter on the scalar fields sigma, zeta. We consider only the octet baryons N,Lambda,Sigma, Xi in hypernuclear matter. An ideal gas of the strange mesons K and K is introduced to keep zero net strangeness density. Our results for symmetric hypernuclear matter show that a phase transition takes place at a critical temperature around 180 MeV in which the scalar mean fields sigma, zeta take nonzero values at zero baryon density. Furthermore, the bag contants of the baryons decrease significantly at and above this critical temperature indicating the onset of quark deconfinement. The present results imply that the onset of quark deconfinement in SU(3) hypernuclear matter is much stronger than in SU(2) nuclear matter. PACS:21.65.+f, 24.85.+p, 12.39BaIsmail A. I. Zakout; Henry R. Jaqaman; Subrata Pal; Horst Stöcker; Walter Greinerpreprinthttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3128Tue, 06 Dec 2005 11:26:05 +0100Analysis of reaction dynamics at RHIC in a combined parton/hadron transport approach
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3129
We introduce a transport approach which combines partonic and hadronic degrees of freedom on an equal footing and discuss the resulting reaction dynamics. The initial parton dynamics is modeled in the framework of the parton cascade model, hadronization is performed via a cluster hadronization model and configuration space coalescence, and the hadronic phase is described by a microscopic hadronic transport approach. The resulting reaction dynamics indicates a strong influence of hadronic rescattering on the space-time pattern of hadronic freeze-out and on the shape of transverse mass spectra. Freeze-out times and transverse radii increase by factors of 2 3 depending on the hadron species.Steffen A. Bass; Markus Hofmann; Marcus Bleicher; Larissa V. Bravina; Eugene E. Zabrodin; Horst Stöcker; Walter Greinerpreprinthttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3129Mon, 05 Dec 2005 13:45:48 +0100Hadronic freeze-out following a first order hadronization phase transition in ultrarelativistic heavy-ion collisions
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3127
We analyze the hadronic freeze-out in ultra-relativistic heavy ion collisions at RHIC in a transport approach which combines hydrodynamics for the early, dense, deconfined stage of the reaction with a microscopic non-equilibrium model for the later hadronic stage at which the hydrodynamic equilibrium assumptions are not valid. With this ansatz we are able to self-consistently calculate the freeze-out of the system and determine space-time hypersurfaces for individual hadron species. The space-time domains of the freeze-out for several hadron species are found to be actually four-dimensional, and di er drastically for the individual hadrons species. Freeze-out radii distributions are similar in width for most hadron species, even though the is found to be emitted rather close to the phase boundary and shows the smallest freeze- out radii and times among all baryon species. The total lifetime of the system does not change by more than 10% when going from SPS to RHIC energies.Steffen A. Bass; Adrian Dumitru; Marcus Bleicher; Larissa V. Bravina; Eugene E. Zabrodin; Horst Stöcker; Walter Greinerpreprinthttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3127Mon, 05 Dec 2005 13:41:48 +0100Modeling J /Psi production and absorption in a microscopic nonequilibrium approach
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3126
Charmonium production and absorption in heavy ion collisions is studied with the Ultrarelativisitic Quantum Molecular Dynamics model. We compare the scenario of universal and time independent color-octet dissociation cross sections with one of distinct color-singlet J/psi, psi 2 and CHIc states, evolving from small, color transparent configurations to their asymptotic sizes. The measured J/psi production cross sections in pA and AB collisions at SPS energies are consistent with both purely hadronic scenarios. The predicted rapidity dependence of J/psi suppression can be used to discriminate between the two experimentally. The importance of interactions with secondary hadrons and the applicability of thermal reaction kinetics to J/psi absorption are in- vestigated. We discuss the e ect of nuclear stopping and the role of leading hadrons. The dependence of the 2/J/psi ratio on the model assumptions and the possible influence of refeeding processes is also studied.Christian Spieles; Ramona Vogt; Lars Gerland; Steffen A. Bass; Marcus Bleicher; Horst Stöcker; Walter Greinerpreprinthttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3126Mon, 05 Dec 2005 10:49:23 +0100Non-equilibrium initial conditions from pQCD for RHIC and LHC
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3131
We calculate the initial non-equilibrium conditions from perturbative QCD (pQCD) within Glauber multiple scattering theory for s = 200 AGeV and s = 5.5 ATeV. At the soon available collider energies one will particularly test the small x region of the parton distributions entering the cross sections. Therefore shadowing effects, previously more or less unimportant, will lead to new e ects on variables such as particle multiplicities dN/dy, transverse energy production d T /dy, and the initial temperature Ti. In this paper we will have a closer look on the effects of shadowing by employing di erent parametrizations for the shadowing effect for valence quarks, sea quarks and gluons. Since the cross sections at midrapidity are dominated by processes involving gluons the amount of their depletion is particularly important. We will therefore have a closer look on the results for dN/dy, d ¯E T /dy, and Ti by using two different gluon shadowing ratios, di ering strongly in size. As a matter of fact, the calculated quantities di er significantly.Nils Hammon; Horst Stöcker; Walter Greinerpreprinthttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3131Thu, 01 Dec 2005 13:02:20 +0100Relativistic Hartree approach including both positive- and negative-energy bound states
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3138
We develop a relativistic model to describe the bound states of positive energy and negative energy in finite nuclei at the same time. Instead of searching for the negative-energy solution of the nucleon's Dirac equation, we solve the Dirac equations for the nucleon and the anti-nucleon simultaneously. The single-particle energies of negative-energy nucleons are obtained through changing the sign of the single-particle energies of positive-energy anti-nucleons. The contributions of the Dirac sea to the source terms of the meson fields are evaluated by means of the derivative expansion up to the leading derivative order for the one-meson loop and one-nucleon loop. After refitting the parameters of the model to the properties of spherical nuclei, the results of positive-energy sector are similar to that calculated within the commonly used relativistic mean field theory under the no-sea approximation. However, the bound levels of negative-energy nucleons vary drastically when the vacuum contributions are taken into account. It implies that the negative-energy spectra deserve a sensitive probe to the effective interactions in addition to the positive-energy spectra.Guangjun Mao; Horst Stöcker; Walter Greinerpreprinthttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3138Thu, 01 Dec 2005 12:55:44 +0100Relativistic Hartree approach including negative energy-bound states
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3137
We develop a relativistic model to describe the bound states of positive energy and negative energy in finite nuclei at the same time. Instead of searching for the negative-energy solution of the nucleon s Dirac equation, we solve the Dirac equations for the nucleon and the anti-nucleon simultaneously. The single-particle energies of negative-energy nucleons are obtained through changing the sign of the single-particle energies of positive-energy anti-nucleons. The contributions of the Dirac sea to the source terms of the meson fields are evaluated by means of the derivative expansion up to the leading derivative order for the one-meson loop and one-nucleon loop. After refitting the parameters of the model to the properties of spherical nuclei, the results of positive-energy sector are similar to that calculated within the commonly used relativistic mean field theory under the no-sea approximation. However, the bound levels of negative-energy nucleons vary drastically when the vacuum contributions are taken into account. It implies that the negative-energy spectra deserve a sensitive probe to the e ective interactions in addition to the positive-energy spectra.Guangjun Mao; Horst Stöcker; Walter Greinerpreprinthttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3137Thu, 01 Dec 2005 12:50:14 +0100Kinetic freeze out models
http://publikationen.stub.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.-qVolodymyr K. Magas; Csaba Anderlik; László Pal Csernai; Frederique Grassi; Walter Greiner; Yogiro Hama; Takeshi Kodama; Zsolt Iosif Lazar; Horst Stöckerpreprinthttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3136Thu, 01 Dec 2005 12:44:15 +0100Moments of event observable distributions and many-body correlations
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3133
We investigate event-by-event fluctuations for ensembles with non-fixed multiplicity. Moments of event observable distributions, like total energy distribution, total transverse momentum distribution, etc, are shown to be related to the multi-body correlations present in the system. For classical systems, these moments reduce in the absence of any correlations to the mo- ments of particle inclusive momentum distribution. As a consequence, a zero value for the recently introduced Phi-variable is shown to indicate the van- ishing of two-body correlations from one part, and of correlations between multiplicity and momentum distributions from the other part. It is often misunderstood as a measure of the degree of equilibration in the system.Mohamed Belkacem; Zoheir Aouissat; Marcus Bleicher; Horst Stöcker; Walter Greinerpreprinthttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3133Thu, 01 Dec 2005 10:28:43 +0100Nonequilibrium dynamics of a hadronizing quark gluon plasma
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3132
We investigate the hadronic cooling of a quark droplet within a microscopic model. The color flux tube approach is used to describe the hadronization of the quark phase. The model reproduces experimental particle ratios equally well compared to a static thermal hadronic source. Furthermore, the dynamics of the decomposition of a quark-gluon plasma is investigated and time dependent particle ratios are found.Markus Hofmann; Judah M. Eisenberg; Stefan Scherer; Marcus Bleicher; Ludwig Neise; Horst Stöcker; Walter Greinerpreprinthttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3132Thu, 01 Dec 2005 10:24:26 +0100Deuterons and space-momentum correlations in high energy nuclear collisions
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3143
Using a microscopic transport model together with a coalescence after-burner, we study the formation of deuterons in Au + Au central collisions at s = 200 AGeV . It is found that the deuteron transverse momentum distributions are strongly a ected by the nucleon space-momentum correlations, at the moment of freeze-out, which are mostly determined by the number of rescatterings. This feature is useful for studying collision dynamics at ultrarelativistic energies.B. Monreal; Steffen A. Bass; Marcus Bleicher; S. Esumi; Walter Greiner; Qingfeng Li; H. Liu; W.J. Llope; Raffaele Mattiello; Sergey Y. Panitkin; I. Sakrejda; Raimond Snellings; Heinz Sorge; Christian Spieles; Horst Stöcker; J. Thomas; S. Voloshin; F. Wang; Nu Xupreprinthttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3143Thu, 01 Dec 2005 10:14:29 +0100Freeze-out in hydrodynamical models in relativistic heavy ion collisions
http://publikationen.stub.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 Stöckerpreprinthttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/3142Thu, 01 Dec 2005 09:56:09 +0100