We present the first study of coherent exclusive quarkonium (J/ψ,
Υ) photoproduction in ultraperipheral nucleus-nucleus collisions
(UPCs) at the LHC in the framework of collinear factorization and
next-to-leading order (NLO) perturbative QCD (pQCD). We make NLO predictions
for the J/ψ and Υ rapidity distributions for lead (Pb) and oxygen
(O) beams, and quantify their dependence on the factorization/renormalization
scale, nuclear parton distribution functions (PDFs) and their uncertainties,
and on differences between nuclear PDFs and generalized parton distribution
functions (GPDs). We show that within the PDF-originating uncertainties our
approach provides a good description of the available J/ψ photoproduction
data in Pb+Pb UPCs at the LHC but that the scale uncertainty is significant. We
demonstrate that at NLO pQCD the quark contributions are important in the
J/ψ case but that gluons clearly dominate the Υ cross sections.
We also study how the scale dependence could be tamed by considering O+O/Pb+Pb
ratios of the exclusive J/ψ UPC cross sections, and how HERA and p+p/Pb
LHC data can help in obtaining better-controlled NLO predictions in the
Υ case.Comment: 6 pages, 5 figures, contributed talk by K.J.E. at the 11th
International Conference on Hard and Electromagnetic Probes of High-Energy
Nuclear Collisions, Hard Probes 2023, 26-31 March 2023, Aschaffenburg,
German