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Title: Rapidity-dependent spectra from a single-freeze-out model of relativistic heavy-ion collisions

Abstract

An extension of the single-freeze-out model with thermal and geometric parameters dependent on the spatial rapidity, {alpha}{sub parallel}, is used to describe the rapidity and transverse-momentum spectra of pions, kaons, protons, and antiprotons measured at the Relativistic Heavy Ion Collider at {radical}(s{sub NN})=200 GeV by the BRAHMS Collaboration. THERMINATOR is used to perform the necessary simulation, which includes all resonance decays. The result of the fit to the rapidity spectra in the range of the BRAHMS data is the expected growth of the baryon and strange chemical potentials with the magnitude of {alpha}{sub parallel}, whereas the freeze-out temperature is kept fixed. The value of the baryon chemical potential at {alpha}{sub parallel}{approx}3, which is the relevant region for particles detected at the BRAHMS forward rapidity y{approx}3, is about 200 GeV, i.e., lies in the range of the values obtained for the highest SPS energy. The chosen geometry of the fireball has a decreasing transverse size as the magnitude of {alpha}{sub parallel} is increased, which also corresponds to decreasing transverse flow. This feature is verified by reproducing the transverse momentum spectra of pions and kaons at various rapidities. The strange chemical potential obtained from the fit to the K{sup +}/K{sup -} ratiomore » is such that the local strangeness density in the fireball is compatible with zero. The resulting rapidity spectra of net protons are described qualitatively in the model. As a result of the study, the knowledge of the 'topography' of the fireball is achieved, making other calculations possible. As an example, we give predictions for the rapidity spectra of hyperons.« less

Authors:
;  [1];  [2];  [2]
  1. AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Cracow (Poland)
  2. (Poland)
Publication Date:
OSTI Identifier:
20995309
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevC.75.054905; (c) 2007 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; ANTIPROTONS; BROOKHAVEN RHIC; FREEZING OUT; GEV RANGE 100-1000; HEAVY ION REACTIONS; HYPERONS; KAONS; PARTICLE RAPIDITY; PIONS; POTASSIUM IONS; POTENTIALS; RELATIVISTIC RANGE; SPECTRA; TRANSVERSE MOMENTUM

Citation Formats

Biedron, Bartlomiej, Broniowski, Wojciech, Institute of Physics, Swietokrzyska Academy, ul. Swietokrzyska 15, PL-25406 Kielce, and H. Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Cracow. Rapidity-dependent spectra from a single-freeze-out model of relativistic heavy-ion collisions. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.054905.
Biedron, Bartlomiej, Broniowski, Wojciech, Institute of Physics, Swietokrzyska Academy, ul. Swietokrzyska 15, PL-25406 Kielce, & H. Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Cracow. Rapidity-dependent spectra from a single-freeze-out model of relativistic heavy-ion collisions. United States. doi:10.1103/PHYSREVC.75.054905.
Biedron, Bartlomiej, Broniowski, Wojciech, Institute of Physics, Swietokrzyska Academy, ul. Swietokrzyska 15, PL-25406 Kielce, and H. Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Cracow. Tue . "Rapidity-dependent spectra from a single-freeze-out model of relativistic heavy-ion collisions". United States. doi:10.1103/PHYSREVC.75.054905.
@article{osti_20995309,
title = {Rapidity-dependent spectra from a single-freeze-out model of relativistic heavy-ion collisions},
author = {Biedron, Bartlomiej and Broniowski, Wojciech and Institute of Physics, Swietokrzyska Academy, ul. Swietokrzyska 15, PL-25406 Kielce and H. Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Cracow},
abstractNote = {An extension of the single-freeze-out model with thermal and geometric parameters dependent on the spatial rapidity, {alpha}{sub parallel}, is used to describe the rapidity and transverse-momentum spectra of pions, kaons, protons, and antiprotons measured at the Relativistic Heavy Ion Collider at {radical}(s{sub NN})=200 GeV by the BRAHMS Collaboration. THERMINATOR is used to perform the necessary simulation, which includes all resonance decays. The result of the fit to the rapidity spectra in the range of the BRAHMS data is the expected growth of the baryon and strange chemical potentials with the magnitude of {alpha}{sub parallel}, whereas the freeze-out temperature is kept fixed. The value of the baryon chemical potential at {alpha}{sub parallel}{approx}3, which is the relevant region for particles detected at the BRAHMS forward rapidity y{approx}3, is about 200 GeV, i.e., lies in the range of the values obtained for the highest SPS energy. The chosen geometry of the fireball has a decreasing transverse size as the magnitude of {alpha}{sub parallel} is increased, which also corresponds to decreasing transverse flow. This feature is verified by reproducing the transverse momentum spectra of pions and kaons at various rapidities. The strange chemical potential obtained from the fit to the K{sup +}/K{sup -} ratio is such that the local strangeness density in the fireball is compatible with zero. The resulting rapidity spectra of net protons are described qualitatively in the model. As a result of the study, the knowledge of the 'topography' of the fireball is achieved, making other calculations possible. As an example, we give predictions for the rapidity spectra of hyperons.},
doi = {10.1103/PHYSREVC.75.054905},
journal = {Physical Review. C, Nuclear Physics},
number = 5,
volume = 75,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • The influence of the nuclear Coulomb field on transverse spectra of {pi}{sup +} and {pi}{sup {minus}} measured in Pb+Pb reactions at 158A GeV has been investigated. Pion trajectories are calculated in the field of an expanding fireball. The observed enhancement of the {pi}{sup {minus}}/{pi}{sup +} ratio at small momenta depends on the temperature and transverse expansion velocity of the source, the rapidity distribution of the net positive charge, and mainly the time of the freeze-out. {copyright} {ital 1997} {ital The American Physical Society}
  • In this study, we present results of analyses of two-pion interferometry in Au+Au collisions at √s NN = 7.7, 11.5, 19.6, 27, 39, 62.4, and 200 GeV measured in the STAR detector as part of the RHIC Beam Energy Scan program. The extracted correlation lengths (HBT radii) are studied as a function of beam energy, azimuthal angle relative to the reaction plane, centrality, and transverse mass ( mT) of the particles. The azimuthal analysis allows extraction of the eccentricity of the entire fireball at kinetic freeze-out. The energy dependence of this observable is expected to be sensitive to changes inmore » the equation of state. A new global fit method is studied as an alternate method to directly measure the parameters in the azimuthal analysis. The eccentricity shows a monotonic decrease with beam energy that is qualitatively consistent with the trend from all model predictions and quantitatively consistent with a hadronic transport model.« less
  • On the basis of a nine-parameter expanding source model that includes special relativity, quantum statistics, resonance decays, and freeze-out on a realistic hypersurface in spacetime, we analyze in detail invariant {pi}{sup +}, {pi}{sup {minus}}, K{sup +}, and K{sup {minus}} one-particle multiplicity distributions and {pi}{sup +} and K{sup +} two-particle correlations in nearly central collisions of Si+Au at p{sub lab}/A=14.6thinspGeV/c. By considering separately the one-particle data and the correlation data, we find that the central baryon density, nuclear temperature, transverse collective velocity, longitudinal collective velocity, and source velocity are determined primarily by one-particle multiplicity distributions and that the transverse radius, longitudinalmore » proper time, width in proper time, and pion incoherence fraction are determined primarily by two-particle correlations. By considering separately the pion data and the kaon data, we find that although the pion freeze-out occurs somewhat later than the kaon freeze-out, the 99{percent} confidence-level error bars associated with the two freeze-outs overlap. By constraining the transverse freeze-out to the same source time for all points with the same longitudinal position and by allowing a more flexible freeze-out in the longitudinal direction, we find that the precise shape of the freeze-out hypersurface is relatively unimportant. By regarding the pion and kaon one-particle data to be unnormalized, we find that the nuclear temperature increases slightly, but that its uncertainty increases substantially. By including proton one-particle data (which are contaminated by spectator protons), we find that the nuclear temperature increases slightly. These detailed studies confirm our earlier conclusion based on the simultaneous consideration of the pion and kaon one-particle and correlation data that the freeze-out temperature is less than 100 MeV and that both the longitudinal and transverse collective velocities{emdash}which are anticorrelated with the temperature{emdash}are substantial. We also discuss the flaws in several previous analyses that yielded a much higher freeze-out temperature of approximately 140 MeV for both this reaction and other reactions involving heavier projectiles and/or higher bombarding energies. thinsp {copyright} {ital 1998} {ital The American Physical Society}« less
  • Identified charged pion, kaon, and proton spectra are used to explore the system size dependence of bulk freeze-out properties in Cu+Cu collisions at {radical}s{sub NN} = 200 and 62.4 GeV. The data are studied with hydrodynamically motivated blast-wave and statistical model frameworks in order to characterize the freeze-out properties of the system. The dependence of freeze-out parameters on beam energy and collision centrality is discussed. Using the existing results from Au + Au and pp collisions, the dependence of freeze-out parameters on the system size is also explored. This multidimensional systematic study furthers our understanding of the QCD phase diagrammore » revealing the importance of the initial geometrical overlap of the colliding ions. The analysis of Cu+Cu collisions expands the system size dependence studies from Au+Au data with detailed measurements in the smaller system. The systematic trends of the bulk freeze-out properties of charged particles is studied with respect to the total charged particle multiplicity at midrapidity, exploring the influence of initial state effects.« less