Total Hadronic Cross-Section of Photon-Photon Interactions at LEP

TL;DR

This paper measures the total hadronic cross-section of photon-photon interactions at LEP energies, providing insights into its energy dependence and comparing it with theoretical models and other hadronic interactions.

Contribution

It presents the first measurement of sigma_gg(W) over a wide energy range at LEP, using novel extrapolation techniques and comparing results with theoretical predictions.

Findings

Sigma_gg(W) increases with energy W.

Data agrees with Regge factorisation at high energies.

Models with additional hard gg interactions better fit the data.

Abstract

The total hadronic cross-section sigma_gg(W) for the interaction of real photons, gg->hadrons, is measured for gg centre-of-mass energies 10<W<110 GeV. The cross-section is extracted from a measurement of the process e+e- -> e+e-g*g* -> e+e- hardrons, using a luminosity function for the photon flux together with form factors for extrapolating to real photons (Q^2=0 GeV^2). The data were taken with the OPAL detector at LEP at e+e- centre-of-mass energies 161, 172 and 183 GeV. The cross-section sigma_gg(W) is compared with Regge factorisation and with the energy dependence observed in gp and pp interactions. The data are also compared to models which predict a faster rise of sigma_gg(W) compared to gp and pp interactions due to additional hard gg interactions not present in hadronic collisions.