Measurements of the QED structure of the photon
The OPAL Collaboration
G.Abbiendi - et al.
2 Dipartimento di Fisica dell' Università di Bologna and INFN,
40126 Bologna, Italy
Received: 8 February 1999 / Published online: 28 September 1999
The structure of both quasi-real and highly virtual photons is investigated using the reaction , proceeding via the exchange of two photons. The results are based on the complete OPAL dataset taken at centre-of-mass energies close to the mass of the boson. The QED structure function and the differential cross-section 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 ranging from 1.5 to 400 . The differential cross-section for highly virtual photons is measured for and , where and are the negative values of the four-momentum squared of the two photons such that . Based on azimuthal correlations the QED structure functions and for quasi-real photons are determined for an average of 5.4 .