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Multi-photon production in $e^{+}e^{-}$ collisions at $\sqrt{s}$ = 189 GeV

Authors
  • Abbiendi, G.
  • Ackerstaff, K.
  • Alexander, G.
  • Allison, John
  • Anderson, K.J.
  • Anderson, S.
  • Arcelli, S.
  • Asai, S.
  • Ashby, S.F.
  • Axen, D.
  • Azuelos, G.
  • Ball, A.H.
  • Barberio, E.
  • Barlow, Roger J.
  • Batley, J.R.
  • Baumann, S.
  • Bechtluft, J.
  • Behnke, T.
  • Bell, Kenneth Watson
  • Bella, G.
  • And 297 more
Publication Date
Jul 01, 1999
Identifiers
DOI: 10.1016/S0370-2693(99)01092-8
OAI: oai:cds.cern.ch:395282
Source
CERN Document Server
Keywords
Language
English
License
Unknown
External links

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.

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