Scaling behavior of anisotropic flow harmonics in the far from equilibrium regime

TL;DR

This paper investigates how anisotropic flow harmonics develop in systems with few rescatterings, deriving their scaling behaviors and predicting unique patterns for higher harmonics like v6, relevant for small-system experiments.

Contribution

It introduces a kinetic-theoretical framework to analyze anisotropic flow in near-free-streaming regimes, revealing novel scaling laws for flow harmonics, especially v6.

Findings

v_n scale with initial eccentricities and rescatterings

v_6 exhibits nontrivial behavior distinct from lower harmonics

Predictions applicable to small-system experimental data

Abstract

We consider the development of anisotropic flow in an expanding system of particles undergoing very few rescatterings, using a kinetic-theoretical description with a nonlinear collision term. We derive the scaling behaviors of the harmonic coefficients $v_n$ with the initial-state eccentricities and the mean number of rescatterings, and argue that hexagonal flow $v_6$ should follow a nontrivial behavior, different from that of the lower harmonics. Our findings should be observable in experimental data for small systems.