Sub-leading flow modes in PbPb collisions at sNN = 2.76 TeV from the HYDJET++ model
- Received Date: 2017-02-13
- Accepted Date: 2017-03-22
- Available Online: 2017-07-05
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 calculations, the leading and 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 (v2(1)) and triangular (v3(1)) flow calculated with the HYDJET++ model reproduce rather well the v2{2} and v3{2} coefficients measured experimentally 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 the 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 the 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 the n = 3 case, there is no centrality dependence. The sub-leading flow mode results obtained from the HYDJET++ model are in rather good agreement with the experimental measurements of the CMS Collaboration.