AZIMUTHAL CORRELATIONS IN THE TARGET FRAGMENTATION REGION OF HIGH-ENERGY NUCLEAR COLLISIONS

Results on the target mass dependence of proton and pion pseudorapidit y distributions and of their azimuthal correlations in the target rapi dity range -1.73 less than or equal to eta less than or equal to 1.32 are presented. The data have been taken with the Plastic-Ball detector set-up for 4.9 GeV p+Au collisions at the Berkeley BEVALAC acid for 2 00 A . GeV/c p-, O-, and S-induced reactions on different nuclei at th e CERN-SPS. The yield of protons at backward rapidities is found to be proportional to the target mass. Although protons show a typical ''ba ck-to-back'' correlation, a ''side-by-side'' correlation is observed f or positive pions, which increases both with target mass and with impa ct parameter of a collision. The data can consistently be described by assuming strong rescattering phenomena including pion absorption effe cts in the entire excited target nucleus.