Azimuthal Correlations as a Test for Centrality in Heavy Ion Collisions

Azimuthal correlations of particles emitted in collisions between 197Au target nuclei and projectiles 36Ar (at and 129Xe (at have been measured with the MSU Miniball, a 4π phoswich array with a low detection threshold. Various impact parameter filters, based on the charge-particle multiplicity, transverse energy and midrapidity charge are tested by their ability to suppress collective motion as measured by the azimuthal correlations. The usefulness of a directivity cut in selecting central collisions for these systems is evaluated