Beyond The Colour-Singlet Model For Inelastic J/ψ Photoproduction

Bound-state corrections to J/ψ 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(v2), where v is the relative velocity of the quarks. The internal structure of the meson is characterised by two parameters, ǫB/M 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 J/ψ 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.