Momentum transfer squared dependence of exclusive quarkonia photoproduction in UPCs

TL;DR

This study investigates how the squared momentum transfer affects exclusive quarkonia photoproduction in ultraperipheral collisions, using dipole models and wave functions, providing predictions consistent with existing data and new forecasts for nuclear targets.

Contribution

It introduces a detailed analysis of momentum transfer dependence in quarkonia photoproduction using advanced dipole models and wave functions, with comprehensive uncertainty estimates and predictions for nuclear collisions.

Findings

Results agree with HERA data for proton targets.

Predictions for nuclear targets at LHC energies are provided.

Uncertainty estimates are based on two different saturation models.

Abstract

In this paper, we study fully differential quarkonia photoproduction observables in ultraperipheral collisions (UPCs) as functions of momentum transfer squared. We employ the dipole picture of the QCD part of the scattering with proton and nucleus targets, with the projectile being a quasi-real photon flux emitted by an incoming hadron. We analyse such observables for ground $J/\psi$, $\Upsilon(1S)$ and excited $\psi'$, $\Upsilon(2S)$ states whose light-front wave functions are obtained in the framework of interquark potential model incorporating the Melosh spin transformation. Two different low-$x$ saturation models, one obtained by solving the Balitsky--Kovchegov equation with the collinearly improved kernel and the other with a Gaussian impact-parameter dependent profile, are used to estimate the underlined theoretical uncertainties of our calculations. The results for the proton target and with charmonium in the final state are in agreement with the available HERA data, while in the case of nucleus target we make predictions for $\gamma A$ and $AA$ differential cross sections at different $W$ and at $\sqrt{s}=5.02$ TeV, respectively.