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Abstract |
The study of exclusive vector meson photoproduction in ultra-peripheral lead-lead collisions is essential to understand physics at low Bjorken $x$. In particular, coherent $J/\psi$ and $\psi(2S)$ mesons are promising probes of nuclear shadowing due to their sensitivity to the nuclear parton distribution function of gluons. In this study, coherent productions of $J/\psi$ and $\psi(2S)$ mesons, as well as their ratio, are studied in ultra-peripheral PbPb collisions at a nucleon-nucleon centre-of-mass energy of 5TeV. The $J/\psi$ and $\psi(2S)$ mesons are reconstructed in the dimuon decay channel using a data sample collected by the LHCb experiment in 2018, corresponding to an integrated luminosity of 228 $\pm$ 10 $\mu b^{-1}$. The differential cross-sections and their ratio are measured in five rapidity intervals. Comparisons with theoretical predictions are also presented.
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