Macroscopic nucleon-nucleon correlations caused by the bounce-off process in energetic collisions of heavy nuclei

Two-particle correlation data are presented for the reaction Ar (800 MeV/nucleon)+Pb. The experimental results are analyzed in the nuclear fluid dynamical and in a linear cascade model. We demonstrate that the collective hydrodynamical correlations dominate the measured two-particle correlation function for the heavy system studied. We discuss the transition from the early stages of the reaction which are governed by few nucleon correlations, to the later stages with their macroscopic flow which can only be reached using heavy colliding systems. The sensitivity of the correlation data on the underlying compressional and dissipative processes is analyzed