Gamma*Gamma* Reactions at High Energies

TL;DR

This paper models high-energy gamma*gamma* interactions using a combination of Regge theory, quark box diagrams, and pomeron exchanges, achieving good data agreement for some observables but underestimating the gamma* gamma* cross section.

Contribution

It introduces a combined model for gamma*gamma* reactions incorporating Regge exchange, quark box, and pomeron contributions, and refines the hard pomeron parametrization.

Findings

Model agrees with real gamma-gamma cross section data.

Model underestimates gamma* gamma* cross section due to Q^2 extrapolation issues.

A simple Regge pole with intercept ~1.3 effectively describes the hard pomeron.

Abstract

The total hadronic gamma*gamma* cross sections at high energy are calculated as a function of energy and photon virtuality in a model combining Regge exchange, the quark box diagram (a fixed pole in Regge language) and soft and hard pomeron exchanges evaluated in the context of dipole-dipole scattering. Good agreement is obtained with the data for the real gamma-gamma cross section and for the real photon structure function. However the model prediction for the gamma* gamma* cross section is too small. This is attributed to an incorrect extrapolation of the Q^2 dependence of the hard pomeron adopted here. Parametrising it independently shows that the hard part of the cross section can be well represented by a simple Regge pole with intercept ~ 1.3.