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Multi-photon final states in e+e- collisions at sqrts = 130-172 GeV

The OPAL Collaboration, K. Ackerstaff et al

hep-exarXiv:hep-ex/9709002

Abstract

The process e+e- -> gamma gamma (gamma) is studied using data recorded with the OPAL detector at LEP. The data sample corresponds to a total integrated luminosity of 25.38 pb-1 taken at centre-of-mass energies of 130-172 GeV. The measured cross-sections agree well with the expectation from QED. In a combined fit using data from all centre-of-mass energies, the angular distribution is used to obtain improved limits on the cut-off parameters: Lambda+ > 195 GeV and Lambda- > 210 GeV (95% CL). In addition, limits on non-standard e+e-gamma couplings and contact interactions, as well as a 95% CL mass limit for an excited electron, Me* > 194 GeV for an e+e-gamma coupling kappa = 1, are determined.

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