Multi-harmonic correlations of different flow amplitudes in Pb-Pb collisions at $\sqrt{s_{_{\rm NN}}}=2.76$ TeV

TL;DR

This paper measures event-by-event three-harmonic flow correlations in Pb-Pb collisions at 2.76 TeV, revealing new insights into the medium's collective evolution and initial state conditions.

Contribution

It introduces higher-order Symmetric Cumulants to analyze three-harmonic correlations, providing novel constraints on initial conditions and medium properties.

Findings

Three-harmonic correlations develop during medium evolution.

New correlations differ from initial state predictions.

Results constrain initial conditions and system properties.

Abstract

The event-by-event correlations between three flow amplitudes are measured for the first time in Pb--Pb collisions, using higher-order Symmetric Cumulants. We find that different three-harmonic correlations develop during the collective evolution of the medium, when compared with correlations that exist in the initial state. These new results cannot be interpreted in terms of previous lower-order flow measurements, since contributions from two-harmonic correlations are explicitly removed in the new observables. Comparison with Monte Carlo simulations provides new and independent constraints for the initial conditions and system properties of nuclear matter created in heavy-ion collisions.