Two-particle correlations in azimuthal angle and pseudorapidity in central 7Be+9Be collisions at the CERN Super Proton Synchrotron
Abstract
A measurement of charged hadron pair correlations in two-dimensional ηφ space is presented. The analysis is based on total 30 million central Be+Be collisions observed in the NA61/SHINE detector at the CERN SPS for incident beam momenta of 19A, 30A, 40A, 75A, and 150A GeV/c. Measurements were carried out for unlike-sign and like-sign charge hadron pairs independently. The C(η,φ) correlation functions were compared with results from a similar analysis on p+p interactions at similar beam momenta per nucleon. General trends of the back-to-back correlations are similar in central Be+Be collisions and p+p interactions, but are suppressed in magnitude due to the increased combinatorial background. Predictions from the EPOS and UrQMD models are compared to the measurements. Evolution of an enhancement around (η,φ) = (0,0) with incident energy is observed in central Be+Be collisions. It is not predicted by both models and almost non-existing in proton-proton collisions at the same momentum per nucleon.