We have studied azimuthal correlations in singly-tagged e+e- → e+e-μ+μ- events at an average Q2 of 5.2 GeV2. The data were taken with the OPAL detector at LEP at e+e- centre-of-mass energies close to the Z0 mass, with an integrated luminosity of approximately 100 pb-1. The azimuthal correlations are used to extract the ratio FB γ/F2 γ of the QED structure functions FB γ(x, Q2) and F2 γ(x, Q2) of the photon. In leading order and neglecting the muon mass FB γ is expected to be identical to the longitudinal structure function FL γ. The measurement of FB γ/F2 γ is found to be significantly different from zero and to be consistent with the QED prediction.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)