Azimuthal anisotropies and initial-state fluctuations from SPS to LHC energies

Vinca Institute of Nuclear Sciences, M. Petrovica Alasa 12-14, 11001 Belgrade, Serbia

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

Published online: 27 March 2017

Abstract

The v₃ coefficient, obtained using the PbAu data from the CERES detector at the top SPS energy of √s_NN = 17.3 GeV, is presented. The v₂ is measured over a p_T range up to 100 GeV/c in PbPb collisions collected with the CMS detector. The v₂{2} of charged and strange particles emitted in pp collisions shows a mass ordering effect. The v₂{4} and v₂{6} are comparable to the v₂{2}, and thus supports the collective nature of the long-range correlations in high-multiplicity pp collisions at 13 TeV. Principle Component Analysis (PCA) of two-particle harmonics (V_nΔ) is studied in PbPb and high-multiplicity pPb collisions at the LHC. The factorization breaking of the V_nΔ can be attributed to the effect of initial-state fluctuations. Using a PCA, the V_nΔ are characterized through the leading and sub-leading modes. The leading modes are essentially equivalent to the v_n{2}. The sub-leading modes represent the largest sources of factorization breaking.