An Investigation of the Hard Contribution to phi Photoproduction

Abstract

We investigate the possibility that the process of phi photoproduction may have a significant hard perturbative QCD component. This suggestion is based on a study of the energy dependence of the forward phi photoproduction cross section followed by a calculation where we show that a coherent sum of the pQCD and conventional soft Pomeron contributions provides an excellent reproduction of the experimental data. Our results suggest that the transition from the predominantly soft photoproduction of light rho and omega vector mesons to the predominantly hard photoproduction of heavy J/psi and upsilon is smooth and gradual, similar to the transition observed in deep inelastic scattering studies of the proton structure function in the small x limit. Our predictions for higher HERA energies are presented.

14 pages including 5 postscript figures

References in corpus (6)

• Small x: Two Pomerons!
• Measurement of the Proton Structure Function F_2 and σ_{tot}^{γ^* p} at Low Q^2 and Very Low x at HERA
• Measurement of Elastic $J/\psi$ Photoproduction at HERA
• Upsilon photoproduction at HERA compared to estimates of perturbative QCD
• The effect of screening on the $x$ and $Q^2$ bhaviour of $F_2$ slopes
• Evidence for no shrinkage in elastic photoproduction of J/Psi