New results on event-by-event ratio fluctuations in Pb+Pb collisions at CERN SPS energies

Abstract

Event-by-event fluctuations of produced particle multiplicities are believed to be sensitive to a deconfinement phase transition and the critical point of strongly interacting matter. The NA49 collaboration has conducted a systematic study of various fluctuation observables. In this contribution, recent results on hadron ratio fluctuations in central Pb+Pb collisions at sqrt(s_NN) = 6.3 to 17.3 GeV are reported. These results are complemented by the centrality dependence of hadron ratio fluctuations at sqrt(s_NN) = 17.3 GeV. A universal scaling was found, describing the energy and centrality dependence of the (K++ K-)/(π++ π-) and (p + pbar)/(π++ π-) ratio fluctuations purely by a change in the observed average hadron multiplicities. This scaling is broken for the fluctuations of the (K+ + K-)/(p + pbar) and K+/p ratios, possibly hinting at a change in the baryon number-strangeness correlation.

4 pages, 7 figures. To appear in the proceedings of Quark Matter 2011, the XXII International Conference on Ultrarelativistic Nucleus-Nucleus Collisions