Hydrodynamic elliptic and triangular flow in Pb-Pb collisions at sNN=2.76A TeV

It is shown that a simultaneous comparison of both elliptic and triangular flow from (2+1)-dimensional viscous fluid dynamics with recent measurements in Pb + Pb collisions at the Large Hadron Collider (LHC) favors a small specific shear viscosity (η/s)QGP≈1/(4π) for the quark-gluon plasma. Using this viscosity value, the relative magnitude of the elliptic and triangular flow is well described with Monte Carlo Glauber (MC-Glauber) initial conditions while Monte Carlo Kharzeev-Levin-Nardi (MC-KLN) initial conditions require twice as large viscosity to reproduce the elliptic flow and then underpredict triangular flow by about 30%.