$γp$ and $γγ$ scattering from $\bar{p}p$, $pp$ forward amplitudes in a QCD eikonal model with a dynamical gluon mass

Abstract

We examine the $γp$ photoproduction and the hadronic $γγ$ total cross sections by means of a QCD eikonal model with a dynamical infrared mass scale. In this model, where the dynamical gluon mass is the natural regulator for the tree level gluon-gluon scattering, the $γp$ and $γγ$ total cross sections are derived from the $pp$ and $\bar{p}p$ forward scattering amplitudes assuming vector meson dominance and the additive quark model. We show that the validity of the cross section factorization relation $σ_{pp}/σ_{γp}=σ_{γp}/σ_{γγ}$ is fulfilled depending on the Monte Carlo model used to unfold the hadronic $γγ$ cross section data, and we discuss in detail the case of $σ(γγ\to hadrons)$ data with $W_{γγ} > 10$ GeV unfolded by the Monte Carlo generators PYTHIA and PHOJET. The data seems to favor a mild dependence with the energy of the probability ($P_{had}$) that the photon interacts as a hadron.

16 pages, 3 figures; misprints corrected; to appear in Phys. Rev. D