Experimental physics

The European Physical Journal C - Particles and Fields

, Volume 14, Issue 2, pp 199-212

Total hadronic cross-section of photon-photon interactions at LEP

  • The OPAL Collaboration
  • , G. Abbiendi et al.Affiliated withDipartimento di Fisica dell' Università di Bologna and INFN, 40126 Bologna, Italy

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The total hadronic cross-section \(\sigma_{\gamma \gamma }(W)\) for the interaction of real photons, \(\gamma\gamma\rightarrow\) hadrons, is measured for \(\gamma\gamma\) centre-of-mass energies \(10\le W \le 110\) GeV. The cross-section is extracted from a measurement of the process \({\rm e}^+{\rm e}^-\rightarrow{\rm e}^+{\rm e}^-\gamma^*\gamma^*\rightarrow{\rm e}^+{\rm e}^-+\) hadrons, 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 \({\rm e}^+{\rm e}^-\) centre-of-mass energies \(\sqrt{s}_{\rm ee}=161\), 172$ and 183 GeV. The cross-section \(\sigma_{\gamma\gamma}(W)\) is compared with Regge factorisation and with the energy dependence observed in \(\gamma\)p and pp interactions. The data are also compared to models which predict a faster rise of \(\sigma_{\gamma\gamma}(W)\) compared to \(\gamma\)p and pp interactions due to additional hard \(\gamma\gamma\) interactions not present in hadronic collisions.