Forward di-hadron back-to-back correlations in $\boldsymbol{pA}$ collisions from rcBK evolution

TL;DR

This paper improves the theoretical understanding of di-hadron correlations in proton-nucleus collisions using the CGC framework, specifically through rcBK evolution, and predicts observable suppression effects at RHIC energies.

Contribution

It introduces a numerical solution of the rcBK equation for gluon distributions to describe di-hadron correlations, enhancing the CGC approach's accuracy in this context.

Findings

Good description of away-side correlation disappearance at RHIC

Prediction of a factor 2 suppression in p+Au at 200 GeV

Proposal to study rapidity dependence as evidence of gluon saturation

Abstract

We study the disappearance of the away-side peak of the di-hadron correlation function in p+A vs p+p collisions at forward rapidities, when the scaterring process presents a manifest dilute-dense asymmetry. We improve the state-of-the-art description of this phenomenon in the framework of the Color Glass Condensate (CGC), for hadrons produced nearly back-to-back. In that case, the gluon content of the saturated nuclear target can be described with transverse-momentum-dependent gluon distributions, whose small-$x$ evolution we calculate numerically by solving the Balitsky-Kovchegov equation with running coupling corrections. We first show that our formalism provides a good description of the disappearance of the away-side azimuthal correlations in d+Au collisions observed at BNL Relativistic Heavy Ion Collider (RHIC) energies. Then, we predict the away-side peak of upcoming p+Au data at $~\sqrt[]{s}=200$ GeV to be suppressed by about a factor 2 with respect to p+p collisions, and we propose to study the rapidity dependence of that suppression as a complementary strong evidence of gluon saturation in experimental data.