Eccentricity and elliptic flow at fixed centrality in Au+Au collisions at sqrt(s_NN)=200GeV in AMPT

TL;DR

This study investigates how elliptic flow varies with participant number at fixed centrality in Au+Au collisions at 200 GeV, revealing the roles of initial geometry and particle interactions in flow development.

Contribution

It provides a detailed analysis of the dependence of elliptic flow on initial geometry and particle interactions at fixed centrality, highlighting the transition to local equilibrium.

Findings

Elliptic flow increases and then decreases with participant number at different impact parameters.

The ratio v2/ε saturates at high participant numbers, indicating local equilibrium.

Initial space anisotropy dominates in near-central and mid-central collisions.

Abstract

To reduce the effect of the fluctuations of initial geometrical shape, elliptic flow are studied at fixed centrality in Au+Au collision at $\sqrt{s_{\rm NN}}$=200GeV. It is observed with the participant increasing, elliptic flow has an increase and a decrease at different fixed impact parameter, but not a trivial fluctuation. It is analyzed that the initial space anisotropy dominates the participant dependence of elliptic flow in near-central collisions(b=5fm) and mid-central collisions(b=8fm), while the interaction between particles can mainly answer for the behavior of elliptic flow in peripheral collisions(b=12fm). To distinguish the pure geometrical effect, elliptic flow scaled by initial eccentricity is studied. It is found that the ratio $v_{2}/\epsilon$ increases with participant and reaches a saturation when the participant is large enough, indicating that the collision system reach the local equilibrium.