Global Bayesian Analysis of $\mathrm{J}/\psi$ Photoproduction on Proton and Lead Targets

TL;DR

This paper conducts a Bayesian analysis of diffractive J/ψ production in gamma-proton and gamma-lead collisions using a CGC framework, highlighting challenges in simultaneously fitting data from both targets.

Contribution

It investigates the feasibility of a unified CGC-based model to describe J/ψ photoproduction across different collision systems and energies.

Findings

Simultaneous description of gamma+p and gamma+Pb data is difficult.

Introducing a K-factor improves the fit to both datasets.

Model uncertainties can be partially absorbed by scaling factors.

Abstract

We perform a global Bayesian analysis of diffractive $\mathrm{J}/\psi$ production in $\gamma+p$ and $\gamma+\mathrm{Pb}$ collisions using a color glass condensate (CGC) based calculation framework. As past calculations have shown that CGC-based models typically overpredict the $\mathrm{J}/\psi$ production in $\gamma+\mathrm{Pb}$ collisions at high center of mass energy, we address the question of whether it is possible to describe coherent and incoherent diffractive $\mathrm{J}/\psi$ data from $\gamma+p$ collisions at HERA and the LHC, and from $\gamma+\mathrm{Pb}$ collisions at the LHC simultaneously. Our results indicate that a simultaneous description of $\gamma+p$ and $\gamma+\mathrm{Pb}$ data is challenging, with results improving when an overall $K$-factor -- scaling $\gamma+p$ and $\gamma+\mathrm{Pb}$ cross sections to absorb model uncertainties -- is introduced.