Two-Proton Correlations Relative to the Reaction Plane

Abstract

Studies of the collective flow of hadrons in all of its forms - directed, elliptic, radial is an important direction in the understanding of the physics of heavy-ion collisions¹. The asymmetries observed in azimuthal distributions in momentum space imply underlying asymmetries in configuration space. But the experimental information about spatial properties of the flowing nuclear systems is at best sparse and is mostly obtained with pion measurements. The E877 collaboration reported² that the parameters of the pion source created in Au+Au collisions at 10.8 AGeV/c appear to be different for particles emitted at different angles relative to the reaction plane. The information about space-time properties of the proton effective source involved in directed flow is totally absent. Since nucleons are the main carriers of the directed flow in nucleus nucleus collisions at the AGS energies, it is interesting to check whether the parameters of the nucleon source, probed with the help of two-proton correlations, exhibit any dependencies or asymmetries related to the reaction plane orientation. In this paper we present the preliminary results of the first study of the proton correlation function’s dependence on the orientation of the reaction plane.