Photoproduction of J/ ψ in pp and PbPb Collisions at Leading Order

The production of J/ ψ originating from photoproduction processes in pp and PbPb collisions at leading order is calculated. We use the color singlet and color octet mechanisms for heavy quarkonium production to deal with the direct photon processes, and consider fragmentation processes. The shadowing and iso-spin of the nucleus are also considered in our calculation. The numerical results show that the modification of photoproduction processes for J/ψ production becomes obvious in the large p_T region at LHC energy.