Multiparticle production in proton-nucleus collisions beyond eikonal accuracy

TL;DR

This paper investigates non-eikonal corrections in multigluon production during proton-nucleus collisions, revealing their limited impact on single particle production but significant effects on double gluon correlations, and their role in azimuthal asymmetries.

Contribution

It extends the analysis of non-eikonal effects from proton-proton to proton-nucleus collisions within the Color Glass Condensate framework, incorporating finite target size and non-eikonal corrections.

Findings

Non-eikonal effects are small (~few percent) for single inclusive production at modest energies.

Double inclusive gluon production shows larger non-eikonal effects under the same conditions.

Non-eikonal corrections enable odd azimuthal harmonics, breaking previous symmetries in the CGC.

Abstract

We study the effects on multigluon production at mid-rapidity in the Color Glass Condensate of the non-eikonal corrections that stem from relaxing the shockwave approximation and giving the target a finite size. We extend previous works performed in the dilute-dilute approximation suitable for proton-proton collisions, to the dilute-dense one applicable to proton-nucleus. We employ the McLerran-Venugopalan model for the projectile averages. For the target averages, we use the Golec-Biernat--W\"usthoff model and restrict to the leading contributions in overlap area that allow a factorization of ensembles of Wilson lines into products of dipoles. We make the connection with the jet quenching formalism and compare with previous results in the literature, providing a parametrization of the so-called decorated dipoles. We show that the non-eikonal effects on single inclusive particle production, contrary to what happens in jet quenching, are only sizable, of a few percent, for modest energies $\sqrt{s_{NN}}\leq 100$ GeV and central rapidities. On the other hand, we find that the effects on double inclusive gluon production are larger for the same kinematics. We show that, as found previously in the dilute-dilute situation, non-eikonal corrections break the accidental symmetry in the CGC, allowing for the existence of non-vanishing odd azimuthal harmonics.