Excitation function of nucleon and pion elliptic flow in relativistic heavy-ion collisions

Within a relativistic transport model for heavy-ion collisions, we show that the recently observed characteristic change from out-of-plane to in-plane elliptic flow of protons in midcentral Au+Au collisions as the incident energy increases is consistent with the calculated results using a stiff nuclear equation of state (K=380MeV). We have also studied the elliptical flow of pions and the transverse momentum dependence of both the nucleon and pion elliptic flow in order to gain further insight about collision dynamics.