Higher harmonic non-linear flow modes of charged hadrons in Pb-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ = 5.02 TeV

Abstract

Anisotropic flow coefficients, v n , non-linear flow mode coefficients, χ n,mk , and correlations among different symmetry planes, ρ n,mk are measured in Pb-Pb collisions at √ s NN = 5.02 TeV. Results obtained with multi-particle correlations are reported for the transverse momentum interval 0.2 < p T < 5.0 GeV/c within the pseudorapidity interval 0.4 < |η| < 0.8 as a function of collision centrality. The v n coefficients and χ n,mk and ρ n,mk are presented up to the ninth and seventh harmonic order, respectively. Calculations suggest that the correlations measured in different symmetry planes and the non-linear flow mode coefficients are dependent on the shear and bulk viscosity to entropy ratios of the medium created in heavy-ion collisions. The comparison between these measurements and those at lower energies and calculations from hydrodynamic models places strong constraints on the initial conditions and transport properties of the system.

Bayesian estimation of the specific shear and bulk viscosity of the quark-gluon plasma with additional flow harmonic observables

“…The most important remaining open questions in the field are the location of the critical point (T c ) in the QCD phase diagram and temperature dependence of specific shear (η) and bulk (ζ) viscosity of the QGP. The flow analysis in LHC has been very successful and provides valuable information to the field [2][3][4][5][6]. For example, the main constraints for the QGP properties using the Bayesian analysis [7] in the theory came from the AL-ICE measurements [2,8,9] with both low and high beam energy data.…”

“…There had been new observables that give much stronger constraints to the theory [3,4], where they show good sensitivities especially to η/s(T) and ζ/s(T). The correlation strength measured in [3,4] was experimentally decomposed into two components as linear and non-linear flow mode in [5,17] for the first time in the field, which gives a better understanding of our harmonic analysis and its origin both with LHC Run 1 (2009-2013) and Run 2 (2015-2018) data.…”

J/ψ elliptic and triangular flow in Pb-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ = 5.02 TeV

“…Fluctuations in the initial energy-density profile within the overlap region are thought to be the origin of the triangular flow, v 3 [8][9][10]. Higher order harmonics are strongly damped, do not depend linearly on the initial JHEP10(2020)141 anisotropy, and have significant contributions from the interplay of lower order harmonics [11][12][13][14][15]. The ALICE Collaboration published extensive studies of anisotropic flow measurements for identified light and strange particles [16,17].…”

Long- and short-range correlations and their event-scale dependence in high-multiplicity pp collisions at $$ \sqrt{s} $$ = 13 TeV

“…The origin of these observations are collective effects, which are related to the formation of a strongly interacting quark-gluon plasma (QGP), which exhibits hydrodynamic behavior (see the reviews [8][9][10]). Recent theoretical [11][12][13] and experimental [14][15][16][17] advancements have contributed significantly to the understanding of the transport properties of the QGP. Similar long-range correlations are also observed in high-multiplicity proton-proton (pp) [18][19][20][21], proton-nucleus (pA) [22][23][24][25], and light nucleus-nucleus collisions [26,27].…”