Accueil du site > Publications récentes > Systematic studies of correlations between different order flow harmonics in Pb-Pb collisions at √sNN=2.76 TeV
S. Acharya et al. (ALICE Collaboration)
The correlations between event-by-event fluctuations of anisotropic flow
harmonic amplitudes have been measured in Pb-Pb collisions at √sNN=2.76
TeV with the ALICE detector at the Large Hadron Collider. The results
are reported in terms of multiparticle correlation observables dubbed
symmetric cumulants. These observables are robust against biases
originating from nonflow effects. The centrality dependence of
correlations between the higher order harmonics (the quadrangular v4 and pentagonal v5 flow) and the lower order harmonics (the elliptic v2 and triangular v3 flow) is presented. The transverse momentum dependences of correlations between v3 and v2 and between v4 and v2
are also reported. The results are compared to calculations from
viscous hydrodynamics and a multiphase transport (AMPT) model
calculations. The comparisons to viscous hydrodynamic models demonstrate
that the different order harmonic correlations respond differently to
the initial conditions and the temperature dependence of the ratio of
shear viscosity to entropy density (η/s). A small average value of η/s
is favored independent of the specific choice of initial conditions in
the models. The calculations with the AMPT initial conditions yield
results closest to the measurements. Correlations among the magnitudes
of v2, v3, and v4 show moderate pT
dependence in midcentral collisions. This might be an indication of
possible viscous corrections to the equilibrium distribution at hadronic
freeze-out, which might help to understand the possible contribution of
bulk viscosity in the hadronic phase of the system. Together with
existing measurements of individual flow harmonics, the presented
results provide further constraints on the initial conditions and the
transport properties of the system produced in heavy-ion collisions.
Voir en ligne : Phys. Rev. C 97, 024906 (2018)
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