Azimuthal harmonics of color fields in a high energy nucleus

TL;DR

This paper investigates azimuthal anisotropies in high energy proton-nucleus collisions by analyzing Wilson line distributions, revealing initial state fluctuations significantly contribute to observed multiparticle correlations.

Contribution

It provides a first-principles calculation of azimuthal anisotropy coefficients using Wilson lines, highlighting differences from models and emphasizing initial state effects.

Findings

Wilson line distributions differ between MV model and JIMWLK evolution.

Initial state fluctuations significantly influence azimuthal anisotropies.

Results match experimental momentum dependence of flow coefficients.

Abstract

Recent experimental results have revealed a surprisingly rich structure of multiparticle azimuthal correlations in high energy proton-nucleus collisions. Final state collective effects can be responsible for many of the observed effects, but it has recently been argued that a part of these correlations are present already in the wavefunctions of the colliding particles. We evaluate the momentum space 2-particle cumulant azimuthal anisotropy coefficients v_n{2}, n=2,3,4 from fundamental representation Wilson line distributions describing the high energy nucleus. These would correspond to the flow coefficients in very forward proton nucleus scattering. We find significant differences beteen Wilson lines from the MV model and from JIMWLK evolution. The magnitude and transverse momentum dependence of the v_n{2} values suggest that the fluctuations present in the initial fields are a significant contribution to the observed anisotropies.