skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Energy and system size dependence of chemical freeze-out in relativistic nuclear collisions

Abstract

We present a detailed study of chemical freeze-out in p-p, C-C, Si-Si, and Pb-Pb collisions at beam momenta of 158A GeV as well as Pb-Pb collisions at beam momenta of 20A, 30A, 40A, and 80A GeV. By analyzing hadronic multiplicities within the statistical hadronization model, we studied the parameters of the source as a function of the number of participating nucleons and the beam energy. We observe a nice smooth behavior of temperature, baryon chemical potential, and strangeness under-saturation parameter as a function of energy and nucleus size. Interpolating formulas are provided which allow us to predict the chemical freeze-out parameters in central collisions at center-of-mass energies {radical}(s){sub NN} > or approx. 4.5 GeV and for any colliding ions. Specific discrepancies between data and the model emerge in particle ratios in Pb-Pb collisions at beam energies between 20A and 40A GeV which cannot be accounted for in the considered model schemes.

Authors:
; ;  [1];  [2];  [3]
  1. Universita di Firenze and INFN Sezione di Firenze, Florence (Italy)
  2. (Finland)
  3. (Germany) and Swietokrzyska Academy, Kielce (Poland)
Publication Date:
OSTI Identifier:
20771471
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 73; Journal Issue: 4; Other Information: DOI: 10.1103/PhysRevC.73.044905; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; CARBON 12 REACTIONS; CARBON 12 TARGET; ENERGY DEPENDENCE; GEV RANGE; LEAD 208 REACTIONS; LEAD 208 TARGET; MULTIPLICITY; NUCLEONS; POTENTIALS; PROTON-PROTON INTERACTIONS; RELATIVISTIC RANGE; SILICON 28 REACTIONS; SILICON 28 TARGET; STRANGENESS

Citation Formats

Becattini, F., Manninen, J., Gazdzicki, M., University of Oulu, Oulu, and Institut fuer Kernphysik, Universitaet Frankfurt, Frankfurt. Energy and system size dependence of chemical freeze-out in relativistic nuclear collisions. United States: N. p., 2006. Web. doi:10.1103/PhysRevC.73.044905.
Becattini, F., Manninen, J., Gazdzicki, M., University of Oulu, Oulu, & Institut fuer Kernphysik, Universitaet Frankfurt, Frankfurt. Energy and system size dependence of chemical freeze-out in relativistic nuclear collisions. United States. doi:10.1103/PhysRevC.73.044905.
Becattini, F., Manninen, J., Gazdzicki, M., University of Oulu, Oulu, and Institut fuer Kernphysik, Universitaet Frankfurt, Frankfurt. Sat . "Energy and system size dependence of chemical freeze-out in relativistic nuclear collisions". United States. doi:10.1103/PhysRevC.73.044905.
@article{osti_20771471,
title = {Energy and system size dependence of chemical freeze-out in relativistic nuclear collisions},
author = {Becattini, F. and Manninen, J. and Gazdzicki, M. and University of Oulu, Oulu and Institut fuer Kernphysik, Universitaet Frankfurt, Frankfurt},
abstractNote = {We present a detailed study of chemical freeze-out in p-p, C-C, Si-Si, and Pb-Pb collisions at beam momenta of 158A GeV as well as Pb-Pb collisions at beam momenta of 20A, 30A, 40A, and 80A GeV. By analyzing hadronic multiplicities within the statistical hadronization model, we studied the parameters of the source as a function of the number of participating nucleons and the beam energy. We observe a nice smooth behavior of temperature, baryon chemical potential, and strangeness under-saturation parameter as a function of energy and nucleus size. Interpolating formulas are provided which allow us to predict the chemical freeze-out parameters in central collisions at center-of-mass energies {radical}(s){sub NN} > or approx. 4.5 GeV and for any colliding ions. Specific discrepancies between data and the model emerge in particle ratios in Pb-Pb collisions at beam energies between 20A and 40A GeV which cannot be accounted for in the considered model schemes.},
doi = {10.1103/PhysRevC.73.044905},
journal = {Physical Review. C, Nuclear Physics},
number = 4,
volume = 73,
place = {United States},
year = {Sat Apr 15 00:00:00 EDT 2006},
month = {Sat Apr 15 00:00:00 EDT 2006}
}
  • One surprising result in relativistic heavy-ion collisions is that the abundance of various particles measured in experiments is consistent with the picture that they reach chemical equilibrium at a temperature much higher than the temperature they freeze out kinetically. Using a multiphase transport model to study particle production in these collisions, we find, as an example, that the effective pion to nucleon ratio, which includes those from resonance decays, indeed changes very little during the evolution of the hadronic matter from the chemical to the kinetic freeze-out, and it is also accompanied by an almost constant specific entropy. Finally, wemore » further use a hadron resonance gas model to illustrate the results from the transport model study.« less
  • We propose a parameter-free method to determine the temperature of a thermalized state in relativistic nuclear interactions, using the experimental {mu}{sub {ital q}}/{ital T} and {mu}{sub {ital s}}/{ital T} values, obtained from strange particle ratios. The hadron gas formalism and strangeness neutrality are employed to relate the quark-chemical potential {mu}{sub {ital q}} and {mu}{sub {ital s}} to the temperature and thus determine its value at chemical freeze-out. This temperature, together with the inverse slope parameter from {ital m}{sub {ital T}} distributions, enable the determination of the transverse flow velocity of the fireball matter, thus disentangling the thermal and flow effects.more » We study several nucleus-nucleus interactions from AGS and SPS and obtain the temperature, transverse flow velocity, and quark-chemical potentials. Extrapolating the systematics we predict the values of these quantities for ongoing and future experiments at AGS, SPS, and RHIC. We discuss the possibility of reaching the conditions for quark deconfinement and QGP formation and give distinct and identifiable signature. {copyright} {ital 1996 The American Physical Society.}« less
  • We present the first measurements of the pseudorapidity distribution of primary charged particles in Cu+Cu collisions as a function of collision centrality and energy, {radical}(s{sub NN})=22.4, 62.4, and 200 GeV, over a wide range of pseudorapidity, using the PHOBOS detector. A comparison of Cu+Cu and Au+Au results shows that the total number of produced charged particles and the rough shape (height and width) of the pseudorapidity distributions are determined by the number of nucleon participants. More detailed studies reveal that a more precise matching of the shape of the Cu+Cu and Au+Au pseudorapidity distributions over the full range of pseudorapiditymore » occurs for the same N{sub part}/2A rather than the same N{sub part}. In other words, it is the collision geometry rather than just the number of nucleon participants that drives the detailed shape of the pseudorapidity distribution and its centrality dependence at RHIC energies.« less
  • Recently reported transverse momentum distributions of strange hadrons produced in Pb(158A GeV ) on Pb collisions and corresponding results from the relativistic quantum molecular dynamics approach are examined. We argue that the experimental observations favor a scenario in which multi-strange hadrons are formed and decouple from the system rather early at large energy densities (at about 1 GeV/fm{sup 3} ). The systematics of the strange and nonstrange particle spectra indicate that the observed transverse flow develops mainly in the late hadronic stages of these reactions. {copyright} {ital 1998} {ital The American Physical Society}
  • No abstract prepared.