Author/Authors :
OPAL Collaboration، نويسنده , , G. Alexander، نويسنده , , J. Allison، نويسنده , , N. Altekamp، نويسنده , , K. Ametewee، نويسنده , , K.J. Anderson، نويسنده , , S. Anderson، نويسنده , , S. Arcelli، نويسنده , , S. Asai، نويسنده , , D. Axen، نويسنده , , G. Azuelos، نويسنده , , A.H. Ball، نويسنده , , E. Barberio، نويسنده , , R.J. Barlow، نويسنده , , R. Bartoldus، نويسنده , , J.R. Batley، نويسنده , , G. Beaudoin، نويسنده , , J. Bechtluft، نويسنده , , C. Beeston، نويسنده , , T. Behnke، نويسنده , , et al.، نويسنده ,
Abstract :
Cross-sections and angular distributions for the production of events with single and multiple photons are measured from data recorded with the OPAL detector at the recently upgraded LEP collider. The measured cross-sections are generally consistent with Standard Model expectations for the e+e− → νvγ(γ) and e+e− → γγ(γ) processes. Six events with an acoplanar photon pair and large missing mass are found. The observed number of events is larger than expected from e+e− → ννγγ; however, the missing mass distribution is compatible with the Z0 resonance. Deviations from QED are constrained by the data on e+e− → γγ(γ). Lower limits are set at 95% confidence level on the QED cut-off parameters Λ+ and Λ− of 152 GeV and 142 GeV, respectively, and also on the mass of an excited electron of 147 GeV.
