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

Abstract

The total hadronic cross-section σγγ for the interaction of real photons, γγ → hadrons, is extracted from a measurement of the cross-section of the process e + e − → e + e − γ * γ * → (e + e − + hadrons) using a luminosity function for the photon flux and form factors for extrapolating to Q 2 = 0. The data was taken with the OPAL detector at LEP at e + e − centre-of-mass energies √ s ee = 161 GeV and 172 GeV. In the energy range 10 ≤ W ≤ 110 GeV the total hadronic γγ cross-section σγγ is consistent with the Regge behaviour of the total cross-section observed in γp and hadron-hadron interactions.

γpandγγscattering fromp¯p,

“…e e ÿ hadrons by means of both the luminosity function L for the photon flux and the hadronic cross section W ; Q 2 1 ; Q 2 2 [5,6,[25][26][27]. However, the uncertainty in the cross section extrapolation to real pho- tons (Q 2 1 Q 2 2 0) is estimated to be 5-7.5%, and this uncertainty is not included in the systematic error of the measurement [27]. In this case we can introduce a normalization factor in the data as performed in Ref.…”

“…2 ) [5,6,25,26,27]. However, the uncertainty in the cross section extrapolation to real photons (Q 2 1 = Q 2 2 = 0) is estimated to be 5-7.5%, and this uncertainty is not included in the systematic error of the measurement [27]. In this case we can introduce a normalization factor in the σ γγ data as performed in Ref.…”

QCD saturation and $\gamma^{*}$ - $\gamma^{*}$ scattering

“…Circles denote the L3 data [35] while the triangles mark OPAL data [36]. Squares label data taken from [37].…”