Elliptic emission of K+ and π+ in 158 A·GeV Pb + Pb collisions

An event-by-event analysis of the azimuthal angular correlation with respect to the reaction plane has been carried out for K+ and π+ emission near mid-rapidity in 158 A·GeV Pb + Pb collisions. In semi-central collisions, K+ mesons are found to be preferentially emitted out of the reaction plane, while π+ mesons are emitted in the reaction plane. The results suggest that the kaon emission is influenced by in-medium potential effects in addition to collective flow effects.