The VII-th International Conference on the Initial Stages of High-Energy Nuclear Collisions : Initial Stages 2023

NLO pQCD predictions for exclusive J/Psi and Upsilon photoproduction in A+A UPCs at the LHC

Not scheduled

20m

Copenhagen

Oral Partonic structure of protons and nuclei

Speaker

Prof. Kari J. Eskola (University of Jyväskylä (FI))

Description

We present the first study of coherent exclusive quarkonium (J/Psi, Upsilon) 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) [1-3]. We make NLO predictions for the J/Psi [1,2] and Upsilon [3] rapidity distributions for lead (Pb) and oxygen (O) beams, and quantify their dependence on the factorization/renormalization scale, nuclear PDFs and their uncertainties, and on differences between nuclear PDFs and generalized parton distribution functions (GPDs). We show that our approach provides a good description of the available J/Psi photoproduction data in Pb+Pb UPCs at the LHC. We demonstrate that, at NLO pQCD, the quark contributions are important in the J/Psi case but that gluons clearly dominate the Upsilon cross sections. We also study how the significant scale dependence could be tamed by considering O+O/Pb+Pb ratios of the exclusive J/Psi UPC cross sections, and how HERA and p+p/Pb LHC data can help in obtaining better-controlled NLO predictions in the Upsilon case.

[1] K.J. Eskola, C.A. Flett, V. Guzey, T. Loytainen, H. Paukkunen, Phys. Rev. C 106 (2022) 3, 035202, arXiv:2203.11613 [hep-ph]

[2] K.J. Eskola, C.A. Flett, V. Guzey, T. Loytainen, H. Paukkunen, arXiv:2210.16048 [hep-ph], submitted to Phys. Rev. C

[3] K.J. Eskola, C.A. Flett, V. Guzey, T. Loytainen, H. Paukkunen, arXiv:2303.03007 [hep-ph], submitted to Eur. Phys. J. C