Elliptic and hexadecapole flow of charged hadrons in viscous hydrodynamics with Glauber and color glass condensate initial conditions for Pb–Pb collision at $\sqrt{s_{NN}}$ = 2.76 TeV

The experimentally measured elliptic (v2) and hexadecapole (v4) flow of charged particles as a function of transverse momentum (pT) at midrapidity in Pb?Pb collisions at = 2.76 TeV is compared with the relativistic viscous hydrodynamic model simulations. The simulations are carried out for two different initial energy density profiles obtained from (i) the Glauber model, and (ii) the color glass condensate (CGC) model. A comparison to experimental data for 10?20% to 40?50% centrality shows that a centrality dependent shear viscosity to entropy density (?/s) ratio with values ranging between 0.0 to 0.12 is needed to explain the v2 data for simulations with the Glauber based initial condition, whereas for the CGC based initial conditions a slightly higher value of ?/s is preferred, around 0.08 to 0.16. From the comparison of the v4 simulated results to the corresponding experimental measurements we observe that for the centralities 20?30% to 40?50% the ?/s values lie between 0.0 to 0.12 for both the initial conditions studied. The ?/s values obtained from our studies for Pb?Pb collisions at = 2.76 TeV are compared to other studies which use both transport and hydrodynamic approaches.