Proceedings of XXI International Workshop on Deep-Inelastic Scattering and Related Subjects — PoS(DIS 2013)
DOI: 10.22323/1.191.0173
The cross sections for inelastic photoproduction of J/ψ and ψ′ mesons have been measured in ep collisions with the ZEUS detector at HERA, using an integrated luminosity of 468 pb -1 collected in the period 1996-2007. The ψ′ to J/ψ cross section ratio was measured in the range 0.55 1 GeV. Theoretical predictions within the non-relativistic QCD framework including NLO colour-singlet and colour-octet contributions were compared to the data, as were predictions based on the k T -factorisation approach. © 2013 SISSA.