Antiproton production in 11.5A GeV/c Au+Pb nucleus-nucleus collisions

We present the first results from the E864 Collaboration on the production of antiprotons in 10% central 11.5A GeV/c Au + Ph nucleus collisions at the Brookhaven Alternating Gradient Synchrotron. We report invariant multiplicities for antiproton production in the kinematic region 1.4 < y < 2.2 and 50 < p(T) < 300 MeV/c, and compare our data with a first collision scaling model and previously published results from the E878 Collaboration. The differences between the E864 and E878 antiproton measurements and the implications for antihyperon production are discussed