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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 ($γ=1$), 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 $γ=1$ provides a good description for the measured dynamical fluctuations in $(K^++K^-)/(π^++π^-)$. To reproduce the RHIC results, $γ$ should be larger than one. We also studied the dynamical fluctuations of $(p+\bar{p})/(π^++π^-)$. It is obvious that the energy-dependence of these dynamical fluctuations is non-monotonic.