Exclusive dimuon production and coherent charmonium photoproduction at forward rapidity in ultra-peripheral Pb–Pb collisions at $$\sqrt{{s}_{\text{NN}}}=5.36$$ TeV

This Paper presents rapidity-differential measurements of coherent J/ψ and ψ(2S) photoproduction, as well as rapidity- and mass-differential measurements of exclusive dimuon production, in the forward rapidity region −4 < y < −2.5 in ultra-peripheral Pb–Pb collisions at √ sNN = 5.36 TeV using data recorded by the ALICE detector at the LHC in 2023, corresponding to an integrated luminosity of L = 1170 ± 50 µb −1 . The J/ψ and ψ(2S) results reveal the significant role of nuclear shadowing effects. The square root of the ratio of the measured quarkonium cross section to the impulse approximation prediction is about 0.76 for J/ψ and 0.71 for ψ(2S), at y ≈ −3, corresponding to typical Bjorken-x values of 10−2. The exclusive dimuon results highlight the sensitivity of such measurements to precise modeling of the photon flux, particularly at impact parameters near the nuclear radius.