Decomposition of flow and nonflow in relativistic heavy-ion collisions

Abstract

We propose a method to separate Δη-dependent and Δη-independent azimuthal correlations using two- and four-particle cumulants between pseudo-rapidity (η) bins in symmetric heavy-ion collisions. The Δη-independent correlation may be dominated by harmonic flows, a global correlation to the common collision geometry. The Δη-dependent correlation can be identified as nonflow, particle correlations unrelated to the common geometry. Our method exploits the ηsymmetry of the average harmonic flows and is "data-driven." We use the AMPT and HIJING event generators to illustrate our method. We discuss the decomposed Δη-independent and Δη-dependent correlations regarding flow and nonflow in the models.

16 pages, 15 figures, 1 table