DELTA-RESONANCE PRODUCTION IN NI-58+CU COLLISIONS AT E=1.97A GEV

Invariant mass analyses of (p, pi(+/-)) pairs in Ni-58 + Cu collisions at 1.97A GeV have been performed and show correlations resulting from the decays of the Delta resonance, the Lambda baryon, and possibly th e N(1440) resonance. A reduction in the Delta mass is observed and th e mass reduction increases with collision centrality. Events generated by the relativistic cascade model (ARC) also reveal a mass reduction. The mass reduction is related to the size of the reaction volume and the details of Delta production mechanisms in heavy ion collisions.