Degree of Chemical Non-equilibrium in Central Au-Au Collisions at RHIC energies

Abstract

We investigate the difference between hadron resonance gas (HRG) calculations for chemical freeze-out parameters at fully and partly chemical equilibria. To this end, the results are compared with the particle ratios measured in central Au-Au collisions at a wide range of nucleon-nucleon center-of-mass energies, \hbox{$\sqrt{s_{NN}}=7.7-200$GeV} as offered by the STAR experiment. We restrict the discussion to STAR, because of large statistics and overall homogeneity of STAR measurements (one detector) against previous experiments. We find that the matter produced at these energies is likely in fully chemical equilibrium, which is consistent with recent lattice QCD results. The possible improvements by partial chemical equilibrium (${\gamma }_S\ne 1$) are very limited. We also discuss these results with the ones deduced from $\varphi /{\pi }^{-}$ and ${\Omega }^{-}/{\pi }^{-}$ ratios. These hadron ratios are sensitive to the degree of chemical equilibrium. Accordingly, the conclusion that the matter produced reaches fully chemical equilibrium in central Au-Au at RHIC energies is confirmed.

15 pages, 5 figures and 10 eps graphs

References in corpus (4)

• Systematic Measurements of Identified Particle Spectra in pp, d+Au and Au+Au Collisions from STAR
• Measurements of $\varphi$ meson production in relativistic heavy-ion collisions at RHIC
• Strange and Multi-strange Particle Production in Au+Au Collisions at $\sqrt{s_{NN}}$ = 62.4 GeV
• Chemical freeze-out in ultra-relativistic heavy ion collisions at sqrt(s)_NN = 130 and 200 GeV

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• Nuclear system size scan for freeze-out properties in relativistic heavy-ion collisions by using a multiphase transport model
• On SU(3) effective models and chiral phase-transition
• Phenomenology of strangeness production at high energies
• Strangeness production in high-energy collisions and Hawking-Unruh radiation
• Analogy of QCD hadronization and Hawking-Unruh radiation at NICA
• Hadronization correspondence of Hawking-Unruh radiation from rotating and electrically charged black holes