The QGP shear viscosity–elusive goal or just around the corner?

Abstract

With the new viscous hydrodynamic + hadron cascade hybrid code VISHNU, a\nrather precise (O(25%)) extraction of the QGP shear viscosity (eta/s)_QGP from\nheavy-ion elliptic flow data is possible if the initial eccentricity of the\ncollision fireball is known with <5% accuracy. At this point, eccentricities\nfrom initial state models differ by up to 20%, leading to an O(100%)\nuncertainty for (eta/s)_QGP. It is shown that a simultaneous comparison of\nelliptic and triangular flow, v_2 and v_3, puts strong constraints on initial\nstate models and can largely eliminate the present uncertainty in (eta/s)_QGP.\nThe variation of the differential elliptic flow v_2(p_T) for identified hadrons\nbetween RHIC and LHC energies provides additional tests of the evolution model.\n