Directed flow in Au+Au collisions at the AGS

Studies of anisotropic transverse flow at AGS are presented. With the reconstruction of the reaction plane event by event, how signals of the global variables transverse energy (E-T) and charged multiplicities (N-ch), and as well as, protons and charged pions are quantified by Fourier moments of the azimuthal distributions. The analysis shows that protons (or nucleons) exhibit a strong directed flow while pions collectively move in the opposite direction. The excitation functions of the directed how and elliptical flow shows an interesting change of flow behavior as a function of beam energy.