$K/\pi$ and $p/\pi$ Fluctuations in Au+Au Collisions in STAR

The freeze-out of an extended, strongly-interacting system created in a relativistic heavy ion collision near the QCD critical endpoint could create observable non-statistical fluctuations in net charge, strangeness and baryon number. We present results for $K/\pi$ and $p/\pi$ fluctuations from central Au+Au collisions at $\sqrt{s_{NN}}$ = 20, 62.4, 130, and 200 GeV in terms of the variable $\sigma_{\rm dyn}$. We compare these results with recent data from NA49 [1] for central Pb-Pb collisions. The energy dependence of the present data for central collisions extends smoothly from the NA49 measurements. We present the centrality dependence of $K/\pi$ and $p/\pi$ fluctuations from Au+Au collisions at $\sqrt{s_{NN}}$ = 62.4 and 200 GeV in terms of the variable $\nu_{{\rm dyn},K\pi}$ . To minimize contributions from background protons, we restrict our measurements for $p$ and $\overline{p}$ to the transverse momentum range $0.4 < p_{t} < 1.0$ GeV/c. We present results for $K/\pi$ and $p/\pi$ fluctuations separated by sign as a function of centrality. In addition, we present results for net charge fluctuations ($\pi^+/\pi^-$), net strangeness fluctuations ($K^+/K^-$), and net baryon fluctuations ($p/\overline{p}$). We compare our results with the predictions of the Statistical Hadronization, HIJING, UrQMD, and HSD models.\\[4pt] [1] T. Anticic et al., Phys. Rev. C {\bf 79}, 044910 (2009).