Study of charmonium photoproduction in ultra-peripheral lead-lead collisions at LHCb

The LHCb detector is a single-arm forward spectrometer covering the pseudorapidity range 2 < 𝜂 < 5, designed for the study of particles containing bottom or charm quark. 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 charmonium mesons are promising probes of nuclear shadowing due to their sensitivity to the nuclear parton distribution function of gluons. In this presentation, we report the measurements of the differential coherent cross section productions as a function of rapidity for J/ψ meson in ultra-peripheral PbPb collisions at a nucleon-nucleon centre-of-mass energy of 5.02TeV. The J/ψ mesons are reconstructed in the dimuon decay channel using a data sample collected by the LHCb experiment in 2015, corresponding to an integrated luminosity about 10𝜇𝑏^(−1). The comparisons with theoretical predictions are also presented. More precise result from 2018 would come soon !