Measurement of Event Plane Correlations in Pb-Pb Collisions at $\sqrt{s_{\mathrm{NN}}}$=2.76 TeV with the ATLAS Detector

TL;DR

This paper measures correlations between event-plane angles in Pb-Pb collisions at 2.76 TeV to understand initial state fluctuations and hydrodynamic evolution of the created matter.

Contribution

It provides the first detailed measurement of event-plane angle correlations in Pb-Pb collisions at this energy, revealing patterns of initial state fluctuations and collective flow.

Findings

Significant positive correlations observed for certain event-plane combinations.

Negative correlations found for specific other combinations.

Results inform models of initial state fluctuations and hydrodynamic evolution.

Abstract

A measurement of correlations between event-plane angles $\Phi_n$ is presented as a function of centrality for Pb-Pb collisions at $\sqrt{s_{_{\mathrm{NN}}}}=2.76$ TeV. These correlations are estimated from observed event-plane angles $\Psi_n$ obtained from charged particle or transverse energy flow measured over a large pseudorapidity range $|\eta|<4.8$, followed by a resolution correction that accounts for the dispersion of $\Psi_n$ relative to $\Phi_n$. Various correlators involving two or three event planes with acceptable resolution are measured. Significant positive correlations are observed for $4(\Phi_2-\Phi_4)$, $6(\Phi_2-\Phi_6)$, $6(\Phi_3-\Phi_6)$, $2\Phi_2+3\Phi_3-5\Phi_5$, $2\Phi_2+4\Phi_4-6\Phi_6$ and $-10\Phi_2+4\Phi_4+6\Phi_6$. However, the measured correlations for $2\Phi_2-6\Phi_3+4\Phi_4$ are negative. These results may shed light on the patterns of the fluctuation of the created matter in the initial state as well as the subsequent hydrodynamic evolution.