Constraints on models for the initial collision geometry in ultrarelativistic heavy ion collisions

Monte Carlo simulations are used to compute the centrality dependence of the collision zone eccentricities (ε2,4), for both spherical and deformed ground state nuclei, for different model scenarios. Sizable model dependent differences are observed. They indicate that measurements of the second and fourth order Fourier flow coefficients v2,4, expressed as the ratio v4(v2)2, can provide robust constraints for distinguishing between different theoretical models for the initial-state eccentricity. Such constraints could remove one of the largest impediments to a more precise determination of the specific viscosity from precision v2,4 measurements at the Relativistic Heavy Ion Collider (RHIC).