Finite width effects on the azimuthal asymmetry in proton-nucleus collisions in the Color Glass Condensate

TL;DR

This paper investigates how finite longitudinal width effects influence azimuthal correlations in proton-nucleus collisions within the Color Glass Condensate framework, revealing subeikonal contributions to harmonic patterns.

Contribution

It introduces the inclusion of subeikonal corrections due to finite target width into the CGC calculations, extending standard models to account for these effects.

Findings

Subeikonal terms affect both even and odd harmonics in azimuthal correlations.

Effects diminish with increasing energy and forward rapidity.

Finite width corrections modify standard CGC predictions.

Abstract

We perform a numerical analysis of the two particle azimuthal correlations at central rapidities generated in $p$A collisions within the framework of the Color Glass Condensate. We extend the standard computations to include the subeikonal corrections which stem from considering the finite longitudinal width of the dense target. For practical reasons, we only consider the next-to-next-to-eikonal corrections instead of using the all-order expressions for the inclusive two gluon production cross section. We show that the subeikonal terms that we account for in the two gluon yields contribute to both even and odd harmonics, the latter being absent in the standard Color Glass Condensate calculations performed at eikonal accuracy. Our analysis confirms the vanishing of the subeikonal effects with increasing collision energy and when going to forward rapidities, as expected.