Exclusive $J/\psi$ production in ultraperipheral Pb+Pb collisions to NLO pQCD

TL;DR

This paper provides the first NLO pQCD analysis of exclusive $J// ext{psi}$ production in ultraperipheral Pb+Pb collisions at the LHC, highlighting the importance of NLO contributions and the sensitivity to nuclear quark PDFs.

Contribution

It introduces a comprehensive NLO pQCD framework for coherent exclusive $J// ext{psi}$ photoproduction in heavy-ion collisions, including uncertainties and comparison with experimental data.

Findings

NLO contributions significantly affect the cross section.

The real part of the amplitude is essential for accurate predictions.

The process is more sensitive to nuclear quark PDFs than previously thought.

Abstract

We present the first NLO pQCD study of coherent exclusive $J/\psi$ photoproduction in ultraperipheral heavy-ion collisions (UPCs) at the LHC. Taking the generalized parton distributions (GPDs) in their forward limit, as parton distribution functions (PDFs), we quantify the NLO contributions in the rapidity-differential cross section, show that the real part of the amplitude must not be neglected, study the gluon and quark contributions, chart the scale-choice and PDF uncertainties, and compare the NLO results with LHC and HERA data. We show that the scale dependence is significant but a scale choice can be found with which we reproduce the 2.76 and 5.02 TeV UPC data. In particular, we show that the process is clearly more sensitive to the nuclear quark PDFs than thought before.