Elliptic flow v2 measurements of charged (pions and protons) and strange (Lambda and K0 Short) particles from Pb+Au collisions at the highest SPS energy are presented. Also, measurements of phi and K0 Short meson production at the same energy are reported. The data have been collected by the CERES experiment, which covers a narrow midrapidity region (2.05-2.70) with full azimuthal acceptance and pT sensitivity up to 4 GeV/c.
The value of v2 as a function of centrality, rapidity, pseudorapidity and pT is presented for different particle species. A mass ordering effect was observed: v2(Lambda)<v2 (K0 Short)<v2 (pion) at small pT, while at high pT it is opposite. In order to get better insight into the origin of collective flow, scaling to the number of constituent quarks and flavor transverse rapidity scaling predicted by hydrodynamics will be presented. The obtained measurements are compared with results from the NA49 and the STAR experiments and with hydrodynamical calculations.
For the first time in heavy-ion collisions, phi mesons were reconstructed in the same experiment both in the K+K- and in the e+e- decay channel. The yield and the inverse slope parameter in both decay modes agree within errors. The data do not support a possible enhancement of the phi yield in the dilepton over the hadronic channel by a factor larger than 1.6 at 95\% CL. The obtained measurements are compared with results from the NA49 and NA50 experiments.
The yield and the inverse slope parameter of the K0 Short mesons, reconstructed from two independent analyses, are in good agreement. The obtained results are compared with results from the NA49 and NA57 experiments.