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

¹ University of Belgrade and Vinca Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade, Serbia
² University of Belgrade and Institute of physics, P.O. Box 68, 11081 Belgrade, Serbia
³ University of Oslo, Department of Physics, Oslo, Norway

^a e-mail: Jovan.Milosevic@cern.ch

Published online: 3 August 2018

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 (v₃⁽¹⁾3) flow calculated within the HYDJET++ model reproduce rather well the v₂{2} and v₃{2} coeffcients 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 (v₂⁽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 (v₃⁽²⁾), 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 subleading flow mode results obtained from the HYDJET++ model are in a rather good agreement with the experimental measurements of the CMS Collaboration.