Determination of the Number of Light Neutrino Species

The ALEPH collaboration
Phys.Lett.B 231 (1989) 519-529, 1989.

Abstract (data abstract)
CERN-LEP. First Z0 paper by the ALEPH Collaboration. Results are based on approximately 3000 hadron events. The Z0 mass is determined to be 91.174 +- 0.070 GeV and its width 2.68 +- 0.15 GeV. This implies the number of light neutrino species is 3.27 +- 0.30. The data were analyzed from two separate triggers. The first selection was with the TPC tracks and selected hadrons. The second selection by the calorimeters selected decays of Z& apos;s into TAU pairs as well as hadrons. The two methods agreed in their measurements of the Z0. Both are presented here.

  • Table 1

    Data from T 2


    Selection from TPC tracks.

  • Table 2

    Data from T 2


    Selection by calorimeters.

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