Multi-photon production in e+e- collisions at √s = 183 GeV

Abstract The process e + e − → γγ ( γ ) is studied using data recorded with the OPAL detector at LEP. The data sample corresponds to a total integrated luminosity of 56.2 pb −1 taken at a centre-of-mass energy of 183 GeV. The measured cross-section agrees well with the expectation from QED. A fit to the angular distribution is used to obtain improved limits at 95% CL on the QED cut-off parameters: Λ + > 233 GeV and Λ − > 265 GeV as well as a mass limit for an excited electron, M e ∗ > 227 GeV assuming equal e ∗ eγ and eeγ couplings. No evidence for resonance production is found in the invariant mass spectrum of photon pairs. Limits are obtained for the cross-section times branching ratio for a resonance decaying into two photons.