Event-by-event fluctuations of particle ratios in heavy-ion collisions

We have studied the event-by-event dynamical fluctuations of some particle yield ration at various incident energies. We have assumed that the particle production in the final state is due to chemical equilibrium processes. We have compared the results from the hadron resonance gas (HRG) model with the available experimental data. At energies up to SPS, the HRG model can very well reproduce the experimentally measured fluctuations. To reproduce RHIC results, the quark phase space occupancy parameter is allowed to vary. Furthermore, we have made predictions for the dynamical fluctuations of strange and non-strange particle ratios. We have found that overall energy-dependence is non-monotonic. We have also found that the fluctuations strongly depend on the various species of particle ratios. (author)