Data are presented on the reaction e(+)e(-) --> gamma + 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 Z(0) 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 Z(0) is measured to be N-nu = 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 x 10(-6) depending on its mass), production of an invisible 'X' particle (sigma < 0.1 pb for masses below 60 GeV), and the magnetic moment of the tall neutrino (< 5.1 x 10(-6) mu(B)).

Search for new phenomena using single photon events at LEP1

GASPARINI, UGO;MARGONI, MARTINO;RONCHESE, PAOLO;SIMONETTO, FRANCO;ZUMERLE, GIANNI
1997

Abstract

Data are presented on the reaction e(+)e(-) --> gamma + 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 Z(0) 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 Z(0) is measured to be N-nu = 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 x 10(-6) depending on its mass), production of an invisible 'X' particle (sigma < 0.1 pb for masses below 60 GeV), and the magnetic moment of the tall neutrino (< 5.1 x 10(-6) mu(B)).
File in questo prodotto:
Non ci sono file associati a questo prodotto.
Pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/2500425
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 54
  • ???jsp.display-item.citation.isi??? 55
social impact