PHENIX measurements of higher order flow harmonics in Au plus Au collisions at √sNN=200 GeV

Flow coefficients upsilon(n) for n = 2, 3, 4, characterizing the anisotropic collective flow in Au+Au collisions at root s(NN) = 200 GeV, are presented. They indicate the expected growth of viscous damping for sound propagation in the quark-gluon plasma (QGP) produced in these collisions. Hydrodynamical model comparisons which include the effects of initial state geometry fluctuations highlight the role of higher harmonics (upsilon(n),(n>2)) as a constraint for disentangling the effects of viscosity and initial conditions and suggest a small specific viscosity for the QGP.