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A Fast Hadron Freeze-out Generator  [PDF]
N. S. Amelin,R. Lednicky,T. A. Pocheptsov,I. P. Lokhtin,L. V. Malinina,A. M. Snigirev,Iu. A. Karpenko,Yu. M. Sinyukov
Physics , 2006, DOI: 10.1103/PhysRevC.74.064901
Abstract: We have developed a fast Monte Carlo procedure of hadron generation allowing one to study and analyze various observables for stable hadrons and hadron resonances produced in ultra-relativistic heavy ion collisions. Particle multiplicities are determined based on the concept of chemical freeze-out. Particles can be generated on the chemical or thermal freeze-out hypersurface represented by a parameterization or a numerical solution of relativistic hydrodynamics with given initial conditions and equation of state. Besides standard space-like sectors associated with the volume decay, the hypersurface may also include non-space-like sectors related to the emission from the surface of expanding system. For comparison with other models and experimental data we demonstrate the results based on the standard parameterizations of the hadron freeze-out hypersurface and flow velocity profile under the assumption of a common chemical and thermal freeze-out. The C++ generator code is written under the ROOT framework and is available for public use at http://uhkm.jinr.ru/.
Hadron Freeze-out and QGP Hadronization  [PDF]
Johann Rafelski,Jean Letessier
Physics , 1999,
Abstract: Abundances and $m_\bot$-spectra of strange and other hadronic particles emanating from central 158-200 A GeV reactions between nuclei are found to originate from a thermally equilibrated, deconfined source in chemical non-equilibrium. Physical freeze-out parameters and physical conditions (pressure, specific energy, entropy, and strangeness) are evaluated. Five properties of the source we obtain are as expected for direct hadron emission (hadronization) from a deconfined quark-gluon plasma phase.
Strange hadron resonances as a signature of freeze-out dynamics  [PDF]
Giorgio Torrieri,Johann Rafelski
Physics , 2001, DOI: 10.1016/S0370-2693(01)00492-0
Abstract: We study the production and the observability of Lambda*(1520), K*0(892), and Sigma*(1385), strange hadron resonances as function of the freeze-out conditions within the statistical model of hadron production. We obtain an estimate of how many decay products are rescattered in evolution towards thermal freeze-out following chemical freeze-out, and find that the resonance decay signal is strong enough to be detected. We show how a combined analysis of at least two resonances can be used to understand the chemical freeze-out temperature, and the time between chemical and thermal freeze-outs.
Fast hadron freeze-out generator, part II: noncentral collisions
Amelin, N. S.;Lednicky, R.;Lokhtin, I. P.;Malinina, L. V.;Snigirev, A. M.;Karpenko, Iu. A.;Sinyukov, Yu. M.;Arsene, I.;Bravina, L.
High Energy Physics - Phenomenology , 2007, DOI: 10.1103/PhysRevC.77.014903
Abstract: The fast Monte Carlo procedure of hadron generation developed in our previous work is extended to describe noncentral collisions of nuclei. We consider different possibilities to introduce appropriate asymmetry of the freeze-out hyper-surface and flow velocity profile. For comparison with other models and experimental data we demonstrate the results based on the standard parametrizations of the hadron freeze-out hyper-surface and flow velocity profile assuming either a common chemical and thermal freeze-out or the chemically frozen evolution from chemical to thermal freeze-out. The C++ generator code is written under the ROOT framework and is available for public use at
Strange Hadron Resonances and QGP Freeze-out  [PDF]
G. Torrieri,J. Rafelski
Physics , 2001, DOI: 10.1088/0954-3899/28/7/346
Abstract: We describe how the abundance and distribution of hyperon resonances can be used to probe freeze-out conditions. We demonstrate that resonance yields allow us to measure the time scales of chemical and thermal freeze-outs. This should permit a direct differentiation between the explosive sudden, and staged adiabatic freeze-out scenarios.
Hadron Production Ratios as Probes of Confinement and Freeze- Out  [PDF]
E. Suhonen},J. Cleymans,K. Redlich,H. Satz
Physics , 1993,
Abstract: Particle production in central S-A collisions at 200 GeV/A energy is analysed within a thermal model. Present data imply that the strange particles freeze out at a higher temperature than the non-strange particles and that the strangeness saturation is incomplete.
$Λ$ - anomaly in the hadron chemical freeze-out  [PDF]
V. V. Sagun
Physics , 2014,
Abstract: A new way to overcome the $\Lambda$ hyperon selective suppression, which is known as the $\Lambda$-anomaly, has been suggested. In particular, the additional radius of a $\Lambda$ hyperon is introduced into the model of hadron resonance gas with the multicomponent hard-core repulsion. The proposed approach allows one to describe the hadron multiplicity ratios measured at the AGS, SPS and RHIC energies with the accuracy $\chi^{2}/dof=$52/55$\simeq $0.95.
Hadron freeze-out conditions in high energy nuclear collisions  [PDF]
Nu Xu,Masashi Kaneta
Physics , 2001, DOI: 10.1016/S0375-9474(01)01377-X
Abstract: Systematic trend of the hadron freeze-out conditions from AGS/SPS to RHIC is discussed. The most interesting results from collisions at RHIC are that the system is indeed approaching net-baryon free and the transverse expansion is much stronger than that from collisions at AGS/SPS energies. In order to understand the trend of the collective velocity, an energy scan between $\sqrt{s_{NN}} = 20 - 200 GeV, is important. In addition, systematic studies on the anisotropy parameter $v_2$ and the transverse momentum distributions of $\phi, \Omega,$ and $J / \psi$ are necessary as they will help in determining whether the collectivity is developed at the partonic stage.
Particle ratios at RHIC: Effective hadron masses and chemical freeze-out  [PDF]
D. Zschiesche,S. Schramm,J. Schaffner-Bielich,H. Stoecker,W. Greiner
Physics , 2002, DOI: 10.1016/S0370-2693(02)02736-3
Abstract: The measured particle ratios in central heavy-ion collisions at RHIC-BNL are investigated within a chemical and thermal equilibrium chiral SU(3) \sigma-\omega approach. The commonly adopted noninteracting gas calculations yield temperatures close to or above the critical temperature for the chiral phase transition, but without taking into account any interactions. Contrary, the chiral SU(3) model predicts temperature and density dependent effective hadron masses and effective chemical potentials in the medium and a transition to a chirally restored phase at high temperatures or chemical potentials. Three different parametrizations of the model, which show different types of phase transition behaviour, are investigated. We show that if a chiral phase transition occured in those collisions, ''freezing'' of the relative hadron abundances in the symmetric phase is excluded by the data. Therefore, either very rapid chemical equilibration must occur in the broken phase, or the measured hadron ratios are the outcome of the dynamical symmetry breaking. Furthermore, the extracted chemical freeze-out parameters differ considerably from those obtained in simple noninteracting gas calculations. In particular, the three models yield up to 35 MeV lower temperatures than the free gas approximation. The in-medium masses turn out differ up to 150 MeV from their vacuum values.
Comparing different freeze-out scenarios in azimuthal hadron correlations induced by fast partons
Neufeld, R. Bryon
High Energy Physics - Phenomenology , 2008, DOI: 10.1140/epjc/s10052-009-0946-x
Abstract: I review the linearized hydrodynamical treatment of a fast parton traversing a perturbative quark-gluon plasma. Using numerical solutions for the medium's response to the fast parton, I obtain the medium's distribution function which is then used in a Cooper-Frye freeze-out prescription to obtain an azimuthal particle spectrum. Two different freeze-out scenarios are considered which yield significantly different results. I conclude that any meaningful comparison of azimuthal hadron correlation functions to RHIC data requires implementing a realistic freeze-out scenario in an expanding medium.
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