Latest ALICE results on J/$\psi$ photoproduction in ultra-peripheral collisions at the LHC

TL;DR

This paper presents new measurements of J/ψ photoproduction in ultra-peripheral Pb-Pb collisions at the LHC, providing insights into gluon distributions and nuclear shadowing effects at low Bjorken-x.

Contribution

It introduces the first measurement of the |t|-dependence of the cross section and a rapidity-differential measurement, offering new tools to study gluonic structure and constrain models.

Findings

First |t|-dependence measurement of J/ψ photoproduction cross section.

Rapidity-differential measurement constrains nuclear gluon shadowing.

Prospects for future measurements in LHC Run 3 and 4.

Abstract

Ultra-peripheral collisions (UPCs), studied using the ALICE detector, allow us to investigate the low-$x$ behavior of the gluon distribution of the colliding particles. Two new measurements of coherent J/$\psi$ photoproduction cross section from Pb-Pb UPCs at $\sqrt{s_{\rm NN}}=5.02$ TeV are presented: the first measurement of the $|t|$-dependence of the cross section providing a new tool to investigate the transverse gluonic structure at low Bjorken-$x$ and a rapidity-differential measurement at midrapidity allowing us to provide stringent constraints on nuclear gluon shadowing and saturation models. In addition, prospects for heavy vector meson photoproduction measurements in LHC Run 3 and 4 are presented.