v4 from ideal and viscous hydrodynamic simulations of nuclear collisions at the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC)

We compute v(4)/(v(2))(2) in ideal and viscous hydrodynamics. We investigate its sensitivity to details of the hydrodynamic model and compare the results to experimental data from the BNL Relativistic Heavy Ion Collider (RHIC). Whereas v2 has a significant sensitivity only to initial eccentricity and viscosity while being insensitive to freeze-out temperature, we find that v(4)/(v(2))(2) is quite insensitive to initial eccentricity. On the other hand, it can still be sensitive to shear viscosity in addition to freeze-out temperature, although viscous effects do not universally increase v(4)/(v(2))(2) as originally predicted. Consistent with data, we find no dependence on particle species. We also make a prediction for v(4)/(v(2))(2) in heavy ion collisions at the CERN Large Hadron Collider (LHC).