We attempt to describe the rapidity and transverse momentum spectra of strange as well as non-strange hadrons e.g.-and their ratios in the ultra-relativistic collisions of gold nuclei at √ s = 200 GeV. This is done by using a statistical thermal freeze-out model which incorporates the rapidity (collision) axis as well as transverse direction boosts developed within an expanding hot and dense hadronic fluid (fireball) till the final freeze-out. We determine the thermo-chemical freeze-out conditions particularly in terms of the temperature, baryon chemical potential and collective flow effect parameters for different particle species. The parameters indicate occurrence of freeze-out of the singly and doubly strange hyperon species at somewhat earlier times during the evolution of the fireball. The experimental data of the transverse momentum and rapidity distribution are well reproduced. The contribution of heavier hadronic resonance decay is taken into account.

The transverse momentum spectra of identified particles at midrapidity in Pb + Pb

The transverse momentum spectra of several types of hadrons,p,p̅,K+,K-,Ks0,Λ,Ω,Ω̅,Ξ-, andΞ̅produced in most central Pb-Pb collisions at LHC energysNN=2.76 TeV have been studied at midrapidity (|y|<0.5) using an earlier proposed unified statistical thermal freeze-out model. The calculated results are found to be in good agreement with the experimental data measured by the ALICE experiment at LHC. The model calculation fits provide the thermal freeze-out conditions in terms of the temperature and collective flow effect parameters for different particle species. Interestingly the model parameter fits to the experimental data reveal stronger collective flow in the system and lesser freeze-out temperatures of the different particle species as compared to Au-Au collisions at RHIC. The strong increase of the collective flow appears to be a consequence of the increasing particle density at LHC. The model used incorporates a longitudinal as well as transverse hydrodynamic flow. The chemical potential has been assumed to be nearly equal to zero for the bulk of the matter owing to high degree of nuclear transparency effect at such collision energies. The contributions from heavier decay resonances are also taken into account.

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