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The European Physical Journal C
ISSN: 1434-6044 (printed version)
ISSN: 1434-6052 (electronic version)
Abstract Volume 1 Issue 1/2 (1998) pp 21-30
experimental physics:
Multi-photon final states in ${\rm e^+e^-}$ collisions at $\sqrt{\vec s} = $130-172 GeV
The OPAL Collaboration
, K. Ackerstaff et al. (8)
(8) CERN, European Organisation for Particle Physics, CH-1211 Geneva 23, Switzerland
Received: 11 August 1997
Abstract. The process ${\rm e^+e^-}\to \gamma \gamma (\gamma)$ 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 ${\rm e^+e^-}\gamma$ couplings and contact interactions, as well as a 95% CL mass limit for an excited electron, $M_{\mathrm{e^{\ast}}} > 194$ GeV for an ${\rm e^+e^-}\gamma$ coupling $\kappa = 1$, are determined.
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Online publication: December 11, 1997
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