Original scientific paper

Particle ratios in heavy-ion collisions

A. Tawfik ; University of Bielefeld, P. O. Box 100131, D-33501 Bielefeld, Germany Hiroshima University, 1-7-1 Kagami-yama, Higashi-Hiroshima, Japan

Abstract

We calculated different particle ratios in a wide range of energies 3.5 < √ sNN ≤ 200 GeV using the hadron resonance gas model, which was successfully applied in previous work to describe lattice QCD thermodynamics and characterize the phase transition and phase diagram lines. In this work, we assume that the particle production occurs along the freeze-out line, which has been defined by a constant entropy density normalized by temperature s/T3 at all collision energies. The quark phase space occupancy parameters, γi , have been allowed to take values other than one. Doing this, we are able to describe K+/π+ ratio over the whole range of energies, including the sharp peak observed at top SPS energies. The parameters resulting from this analysis have been applied in calculating K−/π−, Λ/π+ and Λ/hπi particle ratios and we found that within the statistical acceptance, the peaks in all these particle ratios occur in a very narrow range of the center-of-mass energy, √ sNN ≃ 7.5 GeV, which might be related to the baryo-chemical potential µB ≃ 0.43 GeV. We also find that the entropy per particle becomes maximum in this energy-region refering to fluctuations at QCD tricritical endpoint.

Keywords

particle production ratio; heavy-ion collision; hadron resonance gas model; freeze-out line; ratios K+/π +; K−/π −; Λ/π +; Λ/hπi

Hrčak ID:

304579

URI

https://hrcak.srce.hr/304579

Publication date:

2.8.2009.

Article data in other languages: croatian

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