2020 Impact factor 4.590
Particles and Fields
Eur. Phys. J. C 26, 331-344 (2003)
DOI: 10.1140/epjc/s2002-01074-5

Multi-photon production in e +e - collisions at $\sqrt{s} = $181-209 GeV

The OPAL Collaboration

(Received: 22 July 2002 / Published online: 8 November 2002 )

The process $\mathrm{e}^+\mathrm{e}^- \to\gamma\gamma(\gamma)$ is studied using data collected by the OPAL detector at LEP between the years 1997 and 2000. The data set corresponds to an integrated luminosity of 672.3 pb -1 at centre-of-mass energies lying between 181 GeV and 209 GeV. Total and differential cross-sections are determined and found to be in good agreement with the predictions of QED. Fits to the observed angular distributions are used to set limits on parameters from several models of physics beyond the Standard Model such as cut-off parameters, contact interactions of the type $\mathrm{e}^+\mathrm{e}^- \gamma\gamma$, gravity in extra spatial dimensions and excited electrons. In events with three photons in the final state the mass spectrum of photon pairs is investigated. No narrow resonance $X\to\gamma\gamma$ is found and limits are placed on the product of the $\rm X \gamma$ production cross-section and branching ratio.

© Società Italiana di Fisica, Springer-Verlag 2003