2024/04/26 by Guzey, V., Strikman, M.
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #High Energy Physics - Phenomenology (hep-ph) #Nuclear Experiment (nucl-ex)
paper · doi:10.48550/arxiv.2404.17476
We determine the nuclear suppression factor SPb(x), where x=MJ/ψ2/Wγp2 with MJ/ψ the J/ψ mass and Wγp the photon-nucleon energy, for the cross section of coherent J/ψ photoproduction in heavy-ion ultraperipheral collisions (UPCs) at the Large Hadron Collider (LHC) and Relativistic Heavy Ion Collider (RHIC) by performing the χ2 fit to all available data on the cross section dσAA → J/ψAA/dy as a function of the J/ψ rapidity y and the photoproduction cross section σγA → J/ψA(Wγp) as a function of Wγp. We find that while the dσAA → J/ψAA/dy data alone constrain SPb(x) for x ≥ 10-3, the combined dσAA → J/ψAA/dy and σγA → J/ψA(Wγp) data allow us to determine SPb(x) in the wide interval 10-5 < x < 0.05. In particular, the data favor SPb(x), which decreases with a decrease of x in the 10-4 < x < 0.01 interval, and can be both decreasing or constant for x< 10-4. Identifying SPb(x) with the ratio of the gluon distributions in Pb and the proton Rg(x,Q02)=gA(x,Q02)/[A gp(x,Q02)], we demonstrate that the leading twist approximation (LTA) for nuclear shadowing provides a good description of all the data on dσAA → J/ψAA/dy and σγA → J/ψA(Wγp) as well as on the experimental values for SPb(x) derived from σγA → J/ψA(Wγp). We also show that modern nuclear PDFs reasonably reproduce SPb(x) as well.