On Angular Correlations and High Energy Evolution

TL;DR

This paper investigates the capability of JIMWLK evolution to account for angular correlations in high energy hadronic wave functions, highlighting the necessity of Pomeron loops for accurate calculations and analyzing the rapid decay of correlations with energy.

Contribution

It demonstrates that angular correlations cannot be reliably computed without Pomeron loops and provides numerical analysis within the large N_c approximation of JIMWLK evolution.

Findings

Correlations vanish quickly with rapidity outside saturation radius

Target correlations should remain sizable at any rapidity

Pomeron loops are essential for accurate angular correlation calculations

Abstract

We address the question to what extent JIMWLK evolution is capable of taking into account angular correlations in a high energy hadronic wave function. Our conclusion is that angular (and indeed other) correlations in the wave function cannot be reliably calculated without taking into account Pomeron loops in the evolution. As an example we study numerically the energy evolution of angular correlations between dipole scattering amplitudes in the framework of the large $N_c$ approximation to JIMWLK evolution (the "`projectile dipole model"'). Target correlations are introduced via averaging over (isotropic) ensemble of anisotropic initial conditions. We find that correlations disappear very quickly with rapidity even inside the saturation radius. This is in accordance with our physical picture of JIMWLK evolution. The actual correlations inside the saturation radius in the target QCD wave function, on the other hand should remain sizable at any rapidity.