Evolution of structures in two particle correlations in RHIC Cu+Cu collisions as a function of centrality and momentum

Abstract

Two particle correlation measurements in heavy ion collisions at RHIC have shown an extended near side correlation in $\Delta\eta$ relative to p+p for both, momentum triggered and untriggered analyses. This phenomenon is also known as the "ridge". An investigation into the momentum and centrality dependence of two particle correlations is presented for Cu+Cu 200 GeV collisions from the STAR experiment. We extract the amplitude, $\Delta\eta$ and $\Delta\phi$ widths from the near side correlation structure, and show how its parameters depend on centrality and the lower transverse momentum cut-off. Implications for the origin of the ridge will be discussed.