Energy Dependence of Particle Ratios in High Energy Nucleus-Nucleus Collisions: A USTFM Approach

Abstract

We study the identified particle ratios produced at mid-rapidity in heavy ion collisions, along with their correlations with the collision energy. We employ our earlier proposed Unified Statistical Thermal Freeze-out Model (USTFM), which incorporates the effects of both longitudinal as well as transverse hydrodynamic flow in the hot hadronic system. A fair agreement seen between the experimental data and our model results confirms that the particle production in these collisions is of statistical nature. The variation of the chemical freeze-out temperature and the baryon chemical potential with respect to collision energies is studied. The chemical freeze-out temperature is found to be almost constant beyond the RHIC energy and is found to be close to the QCD predicted phase transition temperature suggesting that the chemical freeze-out occurs soon after the hadronization takes place. The vanishing value of chemical potential at LHC indicates very high degree of nuclear transparency in the collision.*saeed_jmi@yahoo.co.in ==================================================================================

Particle Ratios in a Multicomponent Nonideal Hadron Resonance Gas

“…In the light of the above and the freeze-out temperature values obtained in our as well as other analyses, which are in generally the range of 155-165 MeV, it appears that if the critical end point exists at all, then it might be located above this temperature range for a reasonably baryon-rich system (μ B ≈200-300 MeV) [91]. From the analysis, it further appears that the hadrons freeze out shortly after the phase transition [30,100]. The kinetic freeze-out temperatures reported in the analysis of the experimental p T spectra in various works are also in the vicinity of the temperature range mentioned above.…”

“…It has been highlighted earlier that the point-like hadrons do not reproduce the ground state properties of the nuclear matter. Further, no reasonable first-order QGP-HRG phase transition within the framework of a thermal model can be constructed with suitably large number of degrees of freedom in the HRG phase [29][30][31][32]. This essentially happens because a large number of point-like hadronic resonances can be thermally excited at high temperatures in absence of any repulsive interaction in a given physical volume of the system.…”