Exclusive J/{\psi} production in ultraperipheral collisions at the LHC: constrains on the gluon distributions in the proton and nuclei

TL;DR

This paper uses perturbative QCD to analyze LHC data on exclusive J/ψ production in ultraperipheral collisions, constraining gluon distributions in protons and nuclei at small x.

Contribution

It provides a combined analysis of proton and nuclear data to better constrain gluon distributions using collinear factorization in pQCD.

Findings

Reduced ambiguity in gluon distribution models.

Constraints on gluon PDFs at small x.

Predictions for J/ψ production in nuclear ultraperipheral collisions.

Abstract

Using the framework of collinear factorization in perturbative QCD (pQCD), we analyze the recent data of the LHCb and ALICE collaborations on exclusive photoproduction of J/{\psi} in ultraperipheral pp and AA collisions, respectively. We demonstrate that the simultaneous analysis of the proton and Pb data allows us to reduce the ambiguity of the pQCD description of the $\gamma p \to J/\psi p$ and $\gamma A \to J/\psi p$ cross sections and, hence, to place additional constraints on the gluon distributions in the nucleon and nuclei at small x. We also make predictions for the cross section of coherent exclusive photoproduction of J/{\psi} in nucleus-nucleus ultraperipheral collisions accompanied by the electromagnetic excitation of nuclei and the subsequent neutron emission.