Harmonic decomposition of two-particle angular correlations in Pb-Pb collisions at √sNN = 2.76 TeV

Abstract

Angular correlations between unidentified charged trigger (t) and associated (a) particles are measured by the ALICE experiment in Pb–Pb collisions at for transverse momenta , where . The shapes of the pair correlation distributions are studied in a variety of collision centrality classes between 0 and 50% of the total hadronic cross section for particles in the pseudorapidity interval . Distributions in relative azimuth are analyzed for , and are referred to as “long-range correlations”. Fourier components are extracted from the long-range azimuthal correlation functions. If particle pairs are correlated to one another through their individual correlation to a common symmetry plane, then the pair anisotropy is fully described in terms of single-particle anisotropies as . This expectation is tested for by applying a global fit of all to obtain the best values . It is found that for , the fit agrees well with data up to , with a trend of increasing deviation as and are increased or as collisions become more peripheral. This suggests that no pair correlation harmonic can be described over the full range using a single curve; such a description is however approximately possible for when . For the harmonic, however, a single curve is not obtained even within the reduced range .