Event-by-event hadron ratio fluctuations from Au+Au collisions at RHIC-STAR

We present measurements of event-by-event fluctuations on hadron multiplicity ratios (K/π, p/π, K/p) in Au+Au collisions at $\sqrt {s_{NN} }$ and 200 GeV using the STAR detector at RHIC. The magnitude of dynamical fluctuations σ dyn for p/π and K/p ratios change smoothly from a large negative value at 7.7 GeV to a smaller negative value at 200 GeV while that for the K/π ratios exhibits no significant beam energy dependence. The dynamical fluctuations related to pair production σ dynpair dyn for the p/K, K/p, K −/K + and p/p ratios at 200 GeV all exhibit a maximum at the mid-central collisions and decrease at the most peripheral and most central collisions.