par Abreu, Pedro;Bertrand, Daniel 
;Vander Velde, Catherine ; [et al.]
Référence Zeitschrift für Physik. C, Particles and fields, 74, page (577-586)
Publication Publié, 1997
;Vander Velde, Catherine ; [et al.]Référence Zeitschrift für Physik. C, Particles and fields, 74, page (577-586)
Publication Publié, 1997
Article révisé par les pairs
| Résumé : | Data are presented on the reaction e+e- → γ + no other detected particle at centre-of-mass energies of 89.48, 91.26 and 93.08 GeV. The cross-section for this reaction is related directly to the number of light neutrino generations which couple to the Z0 boson, and to several other possible phenomena such as the production of excited neutrinos, the production of any invisible 'X' particle, and the magnetic moment of the tau neutrino. Based on the observed number of single photon events, the number of light neutrinos that couple to the Z0 is measured to be Nν = 2.89 ± 0.38. No evidence is found for anomalous production of energetic single photons, and upper limits at 95% confidence level are determined for excited neutrino production (BR < 4 - 8 × 10-6 depending on its mass), production of an invisible 'X' particle (σ < 0.1 pb for masses below 60 GeV), and the magnetic moment of the tau neutrino (< 5.1 × 10-6μB). © Springer-Verlag 1997. |
