Sub-leading flow modes in PbPb collisions at √sNN =2.76 TeV from HYDJET++ model

Abstract

The LHC results on the 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 calculations, the leading and the sub-leading flow modes are studied as a function of the transverse momentum (pT) over a wide centrality range. The leading modes of the elliptic (v(1) 2 ) and triangular (v(1) 3 ) flow calculated within the HYDJET++ model reproduce rather well the v2{2} and v3{2} coefficients experimentally measured using the two-particle correlations. Within the pT ≤3 GeV/c range where hydrodynamics dominates, the sub-leading flow effects are greatest at the highest pT of around 3 GeV/c. The sub-leading elliptic flow mode (v(2) 2 ), which corresponds to n =2 harmonic, has a small non-zero value and slowly increases from central to peripheral collisions, while the sub-leading triangular flow mode (v(2) 3 ), which corresponds to n =3 harmonic, 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 sub-leading flow mode results obtained from the HYDJET++ model are in a rather good agreement with the experimental measurements of the CMS Collaboration. © The Authors, published by EDP Sciences.