E. O’Brien

Two-proton correlations from 14.6A GeV/c Si+Pb and 11.5A GeV/c Au+Au central collisions

Two-proton correlation functions have been measured in Si+Pb collisions at 14.6A GeV/c and Au+Au collisions at 11.5A GeV/c by the E814/E877 collaboration. Data are compared with predictions of the transport model RQMD and the source size is inferred from this comparison. Our analysis shows that, for both reactions, the characteristic size of the system at freeze-out exceeds the size of the projectile, suggesting that the fireball created in the collision has expanded. For Au+Au reactions, the observed centrality dependence of the two-proton correlation function implies that more central collisions lead to a larger source sizes.

Flow in Ultrarelativistic Heavy Ion Collisions at the AGS

The azimuthal distributions of produced transverse energy from the reaction Au + Au at 10.8 AGeV/c have been studied with the nearly 4π calorimetric coverage of the E877-setup at the AGS. A Fourier analysis of these distributions has been performed in different regions of pseudorapidity as a function of centrality. The extracted sideward flow is found to be maximal in semi-central collisions. This analysis has also been employed to extract the orientation of the reaction plane. Spectra of particles identified in the forward spectrometer are then analyzed with respect to the reaction plane and their triple differential cross sections are determined. The nucleons are found to be the carriers of the sideward flow identified in the calorimeters. While the pions are also preferentially emitted into the reaction plane they show a slight tendency for emission to the opposite side of where the nucleons are found.