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 calculations, 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 ($v_2^{(1)}$) and triangular ($v_3^{(1)}$) flow calculated within the HYDJET++ model reproduce rather well the $v_2\{2\}$ and $v_3\{2\}$ coefficients experimentally measured using the two-particle correlations. Within the $p_T\le$~3~GeV/c range where hydrodynamics dominates, the sub-leading flow effects are greatest at the highest $p_T$ 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 ($v_3^{(2)}$), 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 sub-leading flow mode results obtained from the HYDJET++ model are in a rather good agreement with the experimental measurements of the CMS Collaboration.

10 pages, 7 figures

References in corpus (8)

• PYTHIA 6.4 Physics and Manual
• Anisotropic flow of charged particles in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV
• Elliptic flow of identified hadrons in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV
• Heavy ion event generator HYDJET++ (HYDrodynamics plus JETs)
• Breaking of factorization of two-particle correlations in hydrodynamics
• Principal component analysis of event-by-event fluctuations
• Principal-component analysis of two-particle azimuthal correlations in PbPb and pPb collisions at CMS
• Searches for $p_{\mathrm{T}}$ dependent fluctuations of flow angle and magnitude in Pb--Pb and p--Pb collisions

Cited by in corpus (3)

• Principal component analysis of the nonlinear coupling of harmonic modes in heavy-ion collisions
• Measuring Momentum-Dependent Flow Fluctuations in Heavy-Ion Collisions
• Probing the structure of the initial state of heavy-ion collisions with $p_T$-dependent flow fluctuations