Photonuclear $\mathbf{\mathrm{J/}\psi}$ production at the LHC: proton-based versus nuclear dipole scattering amplitudes

TL;DR

This paper compares two theoretical approaches for modeling J/ψ photonuclear production at the LHC, using different dipole scattering amplitudes, and assesses their agreement with experimental data to determine the more accurate method.

Contribution

It introduces and compares two distinct models for nuclear dipole scattering amplitudes in J/ψ production, highlighting their differences and alignment with LHC data.

Findings

The nuclear approach better matches current measurements.

Different models predict significantly different cross sections.

Future data can distinguish the correct theoretical framework.

Abstract

The coherent photonuclear production of a $\mathrm{J/}\psi$ vector meson at the LHC has been computed using two different sets of solutions of the impact-parameter dependent Balitsky-Kovchegov equation. The nuclear dipole scattering amplitudes are obtained either from ($i$) solutions for this process off proton targets coupled with a Glauber-Gribov prescription, or ($ii$) from solutions obtained with an initial condition representing the nucleus. These approaches predict different cross sections, which are compared with existing data from ultra-peripheral collisions at the LHC. The latter approach seems to better describe current measurements. Future LHC data should be precise enough to select one of the two approaches as the correct one.