BOSE-EINSTEIN CORRELATIONS OF SOFT PIONS IN ULTRARELATIVISTIC NUCLEUS-NUCLEUS COLLISIONS

A detailed analysis of pair correlations of positive pions in the targ et fragmentation region is presented. Data on nuclear collisions at 20 0 GeV per nucleon were measured with the Plastic Ball in the WA80 expe riment at the CERN SPS, The correlation functions are compared with an alytical functions and with simulations incorporating Bose-Einstein sy mmetrization, final-state interactions and detector resolution. Source radii are shown to increase with increasing target size and with cent rality. For central collisions the radii are larger than the geometric al sizes of the involved nuclei.