par Abreu, Pedro;Bertrand, Daniel 
;Braibant, Sylvie J.S.J. ;Bricman, Charles ;Cao, Futian;Daubie, Evelyne;De Boeck, Hugo;De Brabandere, S.;De Clercq, Catherine;Grard, Fernand ;Herquet, P. ;Huet, Kathy;Lemonne, Jacques ;Tomaradze, A.;Vander Velde, Catherine ;Van Doninck, Walter;Verbeure, F;Wickens, John H. ; [et al.]
Référence Physics letters. Section B, 327, 3-4, page (386-396)
Publication Publié, 1994-05
;Braibant, Sylvie J.S.J. ;Bricman, Charles ;Cao, Futian;Daubie, Evelyne;De Boeck, Hugo;De Brabandere, S.;De Clercq, Catherine;Grard, Fernand ;Herquet, P. ;Huet, Kathy;Lemonne, Jacques ;Tomaradze, A.;Vander Velde, Catherine ;Van Doninck, Walter;Verbeure, F;Wickens, John H. ; [et al.]Référence Physics letters. Section B, 327, 3-4, page (386-396)
Publication Publié, 1994-05
Article révisé par les pairs
| Résumé : | The total and the differential cross sections for the reaction e+e- → γγ(γ) have been measured with the DELPHI detector at LEP using an integrated luminosity of 36.9 pb-1. The results agree with the QED predictions and consequently there is no evidence for non-standard channels with the same experimental signature. The lower limits obtained on the QED cutoff parameters are Λ+ > 143 GeV and Λ- > 120 GeV, and the lower bound on the mass of an excited electron with an effective coupling constant λγ = 1 is 132 GeV/c2. Upper limits on the branching ratios for the decays Z0 → γγ, Z0 → π0γ, Z0 → ηγ and Z0 → γγγ have been determined to be 5.5 × 10-5, 5.5 × 10-5, 8.0 × 10-5, and 1.7 × 10-5 respectively. All the limits are at the 95% confidence level. © 1994. |
