Multi-photon production in e+e- collisions at sqrt(s)= 189 geV
Abstract
The process e+e- to 2 (or 3) gammas is studied using data recorded with the OPAL detector at LEP. The data sample taken at a centre-of-mass energy of 189 GeV corresponds to a total integrated luminosity of 178 pb-1. 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: Lambda+ > 304 GeV and Lambda- > 295 GeV as well as a mass limit for an excited electron, Me* > 306 GeV assuming equal e*egamma and eegamma couplings. Graviton exchange in the context of theories with higher dimensions is excluded for scales G+ < 660 GeV and G- < 634 GeV. 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 and produced in association with another photon.
Keywords
Cite
@article{arxiv.hep-ex/9907064,
title = {Multi-photon production in e+e- collisions at sqrt(s)= 189 geV},
author = {The OPAL collaboration and G. Abbiendi},
journal= {arXiv preprint arXiv:hep-ex/9907064},
year = {2008}
}
Comments
22 pages, 7 figures, submitted to Phys. Lett