Sub-leading flow modes in PbPb collisions at \(\sqrt{s_{NN}}\) = 2.76 TeV from HYDJET++ model

Abstract

Recent LHC results on the appearance of sub-leading flow modes in PbPb collisions at 2.76 TeV, related to initial-state fluctuations, are analyzed and interpreted within the HYDJET++ model. Using the newly introduced Principal Component Analysis (PCA) method applied to two-particle azimuthal correlations extracted from the model data, the leading and the sub-leading flow modes are studied as a function of the transverse momentum (\(p_{T}\)) over a wide centrality range. The leading modes of the elliptic and triangular flow reproduce rather well the \(v_{2}\) and \(v_{3}\) coefficients experimentally measured using the two-particle correlations. At high-\(p_{T}\) region, where the effect is greatest, the sub-leading flow mode which corresponds to \(n = 2\) has a small non-zero value and slowly increases from central to peripheral collisions, while the one which corresponds to \(n = 3\) is even smaller and does not depend on centrality. For \(n = \)~2, the relative magnitude of the effect measured with respect to the leading flow mode shows a shallow minimum for semi-central collisions and increases for very central and for peripheral collisions. For \(n = \)~3 case, there is no centrality dependence. The obtained results are in a rather good agreement with the experimental findings recently presented by the CMS Collaboration.