Beyond the colour-singlet model for inelastic JΨ photoproduction

Bound-state corrections to Jψ production from almost real photons are calculated in the colour-singlet model. A systematic, gauge-invariant, theory of hard quarkonium processes is used upto O(ν2) where ν is the relative velocity of the quarks. The internal structure of the mesoon is characterised by two parameters, ϵBM and ∇2φ(0)M2φ(0), in addition to the usual wavefunction at the origin φ(0). These parameters are constrained to be consistent with measured leptonic decay of the Jψ and hadronic and radiative decays of ηc. The calculated corrections to the colour-singlet model, which include radiative effects, improve agreement with the experimental data.