Exclusive dimuon production and coherent charmonium photoproduction at forward rapidity in ultra-peripheral Pb–Pb collisions at √sNN=5.36 TeV

A bstract 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 μ b − 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.