Multiphoton production in e+ e- collisions at S**(1/2) = 189-GeV
Collaboration
23 pages
Published in:
- Phys.Lett.B 465 (1999) 303-314
e-Print:
- hep-ex/9907064 [hep-ex]
PDG: Mass Limits on
Report number:
- CERN-EP-99-088
Experiments:
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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.Note:
- 22 pages, 7 figures, submitted to Phys. Lett Report-no: CERN-EP/99-08
- electron positron: colliding beams
- electron positron: annihilation
- photon: multiple production
- mass spectrum: two-photon
- quantum electrodynamics: validity test
- angular distribution
- e*
- heavy lepton: mass
- lower limit
- exchange: graviton
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