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

Abstract

Monte Carlo simulations are used to compute the centrality dependence of the collision zone eccentricities (ε 2,4 ), 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 v 2,4 , expressed as the ratio v 4 (v 2 ) 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 v 2,4 measurements at the Relativistic Heavy Ion Collider (RHIC).

Heavy ion initial conditions and correlations between higher moments in the spatial anisotropy

“…This conclusion is repeated in [3] where it is stated that the orientation of triangular overlap shape due to fluctuations is random relative to the event-plane direction as determined by the elliptic anisotropy. This conclusion is then generalized in [4] where these authors state that the angles for the odd and even harmonics are uncorrelated. * jamie.nagle@colorado.edu There have been many initial studies for how this spatial anisotropy translates into the final momentum space distribution of particles (e.g.…”

Dissipative hydrodynamics coupled to chiral fields

“…in viscous hydrodynamic simulations, which may provide further crucial constraints on η/s and on 044904-6 models used to calculate QGP initial conditions (see, e.g., Refs. [75,[82][83][84][85][86][87]). …”

Glauber-based evaluations of the odd moments of the initial eccentricity relative to the even order participant planes

“…Experimental measurements of this eccentricity have not been possible to date. The necessary theoretical estimates can be obtained from Glauber-based models [30,31] via the two-dimensional profile S of the density of sources in the transverse plane ρ s (r ⊥ ) of the overlap collision geometry specified by the impact parameter b, or the number of participants N part [18,30,[32][33][34][35][36][37][38][39][40]:…”

“…ε * n = cos n(φ − m ) , n = m, are the nth-order moments of the eccentricity obtained relative to n and m , respectively [34,37,41]; the brackets denote averaging over sources, as well as events belonging to a particular centrality or impact parameter range. Note that n is restricted to the range 0.0-π/n radians due to its n-fold symmetry (separated by 2π/n).…”

“…Monte Carlo (MC) calculations were performed following the implementation scheme outlined in Refs. [37,41] for the Glauber (MC-Glauber) [30,32] and the factorized Kharzeev-Levin-Nardi (MC-KLN) models [31,44]. A subset of the results from these calculations is shown in Fig.…”