Coherent photoproduction of J/ψ mesons in ultraperipheral Pb–Pb collisions at CMS

In this contribution, we briefly describe the CMS results on J/ψ photoproduction in Pb–Pb collisions, in which the coherent J/ψ photoproduction cross section as a function of the photon-nucleus center-of-mass energy (WγN^Pb) was measured up to 400 GeV. The cross section is observed to plateau above WγN^Pb ≈ 40 GeV and up to 400 GeV, accessing very small Bjorken-x values of ≈ 6 × 10⁻⁵.