Two-hadron correlations in the Color Glass Condensate formalism

TL;DR

This paper investigates two-hadron correlations within the Color Glass Condensate framework, highlighting the importance of higher point Wilson line functions and deriving their evolution equations, which challenges previous approximations and aids understanding of experimental data.

Contribution

It derives the energy evolution equations for higher point Wilson line functions in the CGC formalism, revealing the breakdown of the dipole approximation used in prior analyses.

Findings

Higher point functions are essential in two-hadron production cross sections.

The dipole approximation is insufficient for accurate predictions.

Full hierarchy of JIMWLK equations is needed for precise modeling.

Abstract

Two-hadron correlations are a sensitive probe of the dynamics of gluon saturation and the Color Glass Condensate formalism where the degrees of freedom are Wilson lines of the gluon field. It is shown that unlike structure functions in DIS and single hadron production in proton-nucleus collisions, higher point functions of Wilson lines appear in two-hadron production cross section. We derive equations for the energy ($x$) evolution of these higher point functions using the JIMWLK Hamiltonian and show that dipole approximation, employed in the literature to fit the di-hadron data measured by the STAR collaboration in the forward rapidity region, breaks down. This necessitates an investigation of the full hierarchy of the JIMWLK evolution equations for these higher point functions and their solutions. This can then be used to make a quantitative analysis of the di-hadron correlations in the forward rapidity region in deuteron-gold collisions at RHIC and in the long range rapidity correlations observed in proton-proton collisions at the LHC.