A direct determination of the number of light neutrino families from [formula omitted] at LEP

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doi:10.1016/0370-2693(92)90877-7

Abstract

The L3 detector at LEP has been used to determine the number of light neutrino families by measuring the cross section of single photon even in e +e − collisions at energies near the Z 0 resonance. We have observed 61 single photon candidates with more than 1.5 GeV of deposited energy in the barrel electromagnetic calorimeter, for a total integrated luminosity of 3.0 pb −1. From a likelihood fir to the single photon cross sections, we determin N ν =3.24 ± 0.46 ( statistical) ±0.22 ( systematic).

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