Figure 1

$v_{2}\{2\}$ with $|\Delta\eta|>$ 0 (circles), $|\Delta\eta| >$ 0.4 (diamonds) and $|\Delta\eta| >$ 0.8 (squares) for various centrality classes in Pb--Pb collisions at $\sqrt{s_{_{\rm NN}}} = 2.76$ TeV. Hydrodynamic calculations with MC-Glauber initial conditions and $\eta/s =$ 0.08~, with MC-KLN initial conditions and $\eta/s =$ 0.20~, with Trento initial conditions and temperature dependent $\eta/s$~ and AMPT initial conditions and $\eta/s =$ 0.08~ are shown in green dot-dash, orange dashed curves, and magenta and grey shaded areas, respectively.
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