Hard Excluseive $\Phi$ and $J/\Psi$ Photoproduction off a Proton

TL;DR

This paper investigates the photoproduction of $\

Contribution

It applies perturbative QCD's hard scattering approach to predict vector meson production off protons at high energies and angles, highlighting dominant scattering mechanisms.

Findings

Unpolarized cross sections are dominated by Compton-like graphs.

Vector-meson-dominance-like graphs have minor contributions.

Explicit cross section predictions are provided and compared with data.

Abstract

We study the photoproduction of the vector mesons $\Phi$ and $J/\Psi$ off a proton in the kinematical regime of large energies and scattering angles within the framework of perturbative QCD. Our investigations are based on the hard scattering approach. This means that the hadrons are replaced by their valence Fock states and scattering on the partonic level is described by tree graphs in which the large transferred momentum is redistributed between the valence partons via the exchange of hard gluons. We find that the unpolarized photoproduction cross sections are dominated by Compton-scattering-like graphs in which the photon couples to the proton, whereas vector-meson-dominance-like graphs, in which the photon fluctuates into the heavy quark-antiquark pair which then exchanges two gluons with the proton, play a minor role. We give explicit predictions for unpolarized scattering cross sections and compare them with experimental data where possible.