Initial-state anisotropies and their uncertainties in ultrarelativistic heavy-ion collisions from the Monte Carlo Glauber model

In hydrodynamical modeling of heavy-ion collisions, the initial-state spatial anisotropies are translated into momentum anisotropies of the final-state particle distributions. Thus, understanding the origin of the initial-state anisotropies and their uncertainties is important before extracting specific QCD matter properties, such as viscosity, from the experimental data. In this work we review the wounded nucleon approach based on the Monte Carlo Glauber model, charting in particular the uncertainties arising from modeling of the nucleon-nucleon interactions between the colliding nucleon pairs and nucleon-nucleon correlations inside the colliding nuclei. We discuss the differences between the black disk model and a probabilistic profile function approach for the inelastic nucleon-nucleon interactions and investigate the influence of initial-state correlations using state-of-the-art modeling of these.

Figure 1

Number of wounded nucleons (a) and binary collisions (b) as a function of impact parameter with different interaction models and initial-state configurations. The results shown correspond to the black disk approximation with uncorrelated configurations (green dashed line); the profile function approach $\Gamma \left(b_{ij}\right)$ with uncorrelated configurations (black solid line); the profile function approach with central $NN$ correlations (red squares); and the profile function approach with full $NN$ configurations (blue circles). The insets show the ratios of the last three cases to the black disk $+$ uncorrelated one, with corresponding notations.

Figure 2

First three harmonics ${\epsilon }_n$ as a function of the number of participants. Results shown are for the two different interaction models. In these plots no $NN$ correlations are taken into account.

Figure 3

Relative fluctuations of the first three harmonics ${\epsilon }_n$ as a function of number of participants. Results are shown with two different interaction models. In these plots, no $NN$ correlations are taken into account.

Figure 4

First three harmonics ${\epsilon }_n$ as a function of number of participants. Results are shown with different $NN$ correlations and using the $\Gamma \left(b_{ij}\right)$ collision profile function approach.

Figure 5

Relative fluctuations of the first three harmonics ${\epsilon }_n$ as a function of the number of participants. Results are shown with different $NN$ correlations and using the $\Gamma \left(b_{ij}\right)$ collision profile approach.

Figure 6

The effect of different models of realistic correlations on the relative fluctations of eccentricity; see text for explanation.