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Measurements of the QED structure of the photon

  • The OPAL Collaboration
  • G. Abbiendi et al.
Experimental physics

Abstract.

The structure of both quasi-real and highly virtual photons is investigated using the reaction \({\rm e^+e^-}\rightarrow{\rm e^+e^-}\mu^+\mu^-\), proceeding via the exchange of two photons. The results are based on the complete OPAL dataset taken at \({\rm e^+e^-}\) centre-of-mass energies close to the mass of the Z boson. The QED structure function \(F^\gamma _2\) and the differential cross-section \({\rm d}\sigma/{\rm d}x\) for quasi-real photons are obtained as functions of the fractional momentum x from the muon momentum which is carried by the struck muon in the quasi-real photon for values of \(Q^2\) ranging from 1.5 to 400 GeV\(^2\). The differential cross-section \({\rm d}\sigma/{\rm d}x\) for highly virtual photons is measured for \(1.5< Q^2 < 30\) GeV\(^2\) and \(1.5< P^2 < 20\) GeV\(^2\), where \(Q^2\) and \(P^2\) are the negative values of the four-momentum squared of the two photons such that \(Q^2>P^2\). Based on azimuthal correlations the QED structure functions \(F^\gamma _{\rm A}\) and \(F^\gamma _{\rm B}\) for quasi-real photons are determined for an average \(Q^2\) of 5.4 GeV\(^2\).

Keywords

Structure Function Virtual Photon Fractional Momentum Azimuthal Correlation Complete Opal 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • The OPAL Collaboration
  • G. Abbiendi et al.
    • 1
  1. 1.Dipartimento di Fisica dell' Università di Bologna and INFN, 40126 Bologna, Italy IT

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