Elliptic Flow, Initial Eccentricity and Elliptic Flow fluctuations in Heavy Ion Collisions at RHIC

TL;DR

This paper reports measurements of elliptic flow and its fluctuations in heavy ion collisions at RHIC, showing that initial geometry influences final particle distributions and that matter formation occurs early with similar transverse granularity.

Contribution

It demonstrates that elliptic flow scaled by participant eccentricity is consistent across different collision systems, linking initial geometry to final state fluctuations.

Findings

Elliptic flow scaled by participant eccentricity is similar for different systems.

Initial collision geometry is reflected in final azimuthal particle distribution.

Event-by-event fluctuations correlate initial eccentricity with elliptic flow.

Abstract

We present measurements of elliptic flow and event-by-event fluctuations established by the PHOBOS experiment. Elliptic flow scaled by participant eccentricity is found to be similar for both systems when collisions with the same number of participants or the same particle area density are compared. The agreement of elliptic flow between Au+Au and Cu+Cu collisions provides evidence that the matter is created in the initial stage of relativistic heavy ion collisions with transverse granularity similar to that of the participant nucleons. The event-by-event fluctuation results reveal that the initial collision geometry is translated into the final state azimuthal particle distribution, leading to an event-by-event proportionality between the observed elliptic flow and initial eccentricity.