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FIZIKA B 18 (2009) 3, 141-150
 
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
ECTP, MTI University, Mukattam, Cairo, Eqypt
E-mail address: drtawfik@mti.edu.eg
Received 23 September 2008; Revised manuscript received 1 May
2009
Accepted 3 June 2009 Online 7 October 2009
We calculated different particle ratios in a wide range of energies 3.5 <
Ö{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,
gi, have been allowed to take values other than one. Doing this, we
are able to describe K+/p+ 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-/p-, L/p+ and L/ápñ 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, Ö{sNN} @ 7.5 GeV, which might be related to the baryo-chemical potential
mB @ 0.43 GeV.
We also find that the entropy per particle becomes maximum in this energy-region
refering to fluctuations at QCD tricritical endpoint.
PACS numbers: 25.75.-q, 13.85.-t
UDC 539.172
Keywords: particle production ratio, heavy-ion collision, hadron resonance
gas model, freeze-out line, ratios K+/p+, K-/p-, L/p+,
L/ápñ
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