HAL : in2p3-00000026, version 1
 Physics Letters B 431 (1998) 199-208
 Determination of the Number of Light Neutrino Species from Single Photon Production at LEP
 L3 Collaboration(s)
 (1998)
 A determination of the number of light neutrino families performed by measuring the cross section of single photon production in \ee\ collision near the \Zo\ resonance is reported. From an integrated luminosity of $100~\mathrm{pb^{-1}}$, collected during the years 1991--94, we have observed 2091 single photon candidates with an energy above 1~\GeV\ in the polar angular region $45^\circ \theta_\gamma 135^\circ$. From a maximum likelihood fit to the single photon cross section, the \Zo\ decay width into invisible particles is measured to be $\Ginv = 498 \pm 12 \mathrm{(stat)} \pm 12 \mathrm{(sys)~MeV}$. Using the Standard Model couplings of neutrinos to the \Zo, the number of light neutrino species is determined to be $N_\nu = 2.98 \pm 0.07 (\mathrm{stat}) \pm 0.07 (\mathrm{sys}).$
 équipe(s) de recherche : CMS
 Thème(s) : Physique/Physique des Hautes Energies - Expérience
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 in2p3-00000026, version 1 http://hal.in2p3.fr/in2p3-00000026 oai:hal.in2p3.fr:in2p3-00000026 Contributeur : Sylvie Florès <> Soumis le : Jeudi 5 Novembre 1998, 16:15:16 Dernière modification le : Jeudi 21 Avril 2005, 09:41:35