The Impact Parameter Dependence of the Disappearance of Flow

The Michigan State University 4π Array has been recently upgraded to include the High Rate Array (HRA), a close-packed 45 element phoswich array which covers laboratory polar angles from ≈ 3° to ≈ 18°. The HRA subtends all solid angle between the Maryland Forward Array and the detectors of the main Ball resulting in ≈ 90% geometric efficiency for the entire array. With this improved detector configuration, we studied the reaction 40Ar + 45Sc at beam energies from 35 to 115 MeV/nucleon. We present preliminary results on the impact parameter dependence of the disappearance of flow in nuclear collisions, extending the systematics of our previous work.