Nonlinear coupling of flow harmonics in heavy-ion collisions

TL;DR

This paper develops a theoretical framework to quantify nonlinear contributions to higher-order flow harmonics in heavy-ion collisions, demonstrated through analysis of hexagonal flow and its coupling to triangular flow using experimental and hydrodynamic data.

Contribution

The paper introduces a novel formalism to quantify nonlinear harmonic couplings in flow coefficients of any order, advancing understanding of anisotropic flow in heavy-ion collisions.

Findings

Effective quantification of nonlinear flow contributions.

Application to hexagonal flow ($V_6$) and its coupling to $V_3$.

Agreement between theoretical predictions and experimental/hydrodynamic data.

Abstract

Anisotropic flow coefficients beyond triangular flow receive important contributions from lower-order harmonics through nonlinear coupling. We present a theoretical framework which allows one to quantify the contribution induced by such nonlinear couplings to any flow harmonic of any order. We show the effectiveness of this formalism through an application to hexagonal flow, $V_6$. We study, in particular, the coupling of $V_6$ to triangular flow, $V_3$, in Pb+Pb collisions at $~\sqrt[]{s}=2.76$ TeV, using both Large Hadron Collider data and event-by-event hydrodynamic calculations.