Multi-Photon Production in e+e- collisions at sqrt(s) = 181 - 209 GeV

TL;DR

This study measures multi-photon production in electron-positron collisions at energies between 181 and 209 GeV, confirming QED predictions and setting limits on new physics models through angular distribution analysis.

Contribution

It provides precise cross-section measurements and explores potential signals of physics beyond the Standard Model using LEP data.

Findings

Good agreement with QED predictions

No evidence of narrow resonance X-> gamma gamma

Limits set on models of extra dimensions and excited electrons

Abstract

The process e+e- -> 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 672.3pb-1 at centre-of-mass energies lying between 181 GeV and 209 GeV. Total and differential cross- sections are determined and found to be 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 e+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-> gamma gamma is found and limits are placed on the product of the Xgamma production cross-section and branching ratio.