Particle multiplicities and particle ratios in excluded volume model

One of the most surprising results is to find that a consistent description of all the experimental results on particle multiplicities and particle ratios obtained from the lowest AGS to the highest RHIC energies is possible within the framework of a thermal statistical model. We propose here a thermodynamically consistent excluded-volume model involving an interacting multi-component hadron gas. We find that the energy dependence of the total multiplicities of strange and non-strange hadrons obtained in this model agrees closely with the experimental results. It indicates that the freeze out volume of the fireball is uniformly the same for all the particles. We have also compared the variation of the particle ratios such as $/, < K^{-}>/, K^{-}/K^{+}, \bar{p}/p, \bar{\Lambda}/\Lambda, \bar{\Xi}/\Xi, \bar{\Omega}/\Omega, /, /, /$ and $/$ with respect to the center-of-mass energy as predicted by our model with the recent experimental data.Comment: 15 pages, 12 figure

Fluctuations of Particle Yield Ratios in Heavy-Ion Collisions

We study the dynamical fluctuations of various particle yield ratios at different incident energies. Assuming that the particle production yields in the hydronic final state are due to equilibrium chemical processes ($\gamma=1$), the experimental results available so far are compared with the hadron resonance gas model (HRG) taking into account the limited momentum acceptance in heavy-ion collisions experiments. Degenerated light and conserved strange quarks are presumed at all incident energies. At the SPS energies, the HRG with $\gamma=1$ provides a good description for the measured dynamical fluctuations in $(K^++K^-)/(\pi^++\pi^-)$. To reproduce the RHIC results, $\gamma$ should be larger than one. We also studied the dynamical fluctuations of $(p+\bar{p})/(\pi^++\pi^-)$. It is obvious that the energy-dependence of these dynamical fluctuations is non-monotonic.Comment: 8 pages, 2 eps figures and 1 tabl