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ABRAMS 1989B

MARK-II Collaboration; Abrams, G.S. et al.
Measurements of Z^o-Boson Resonance Parameters in e⁺ e^– Annihilation
Phys. Rev. Lett. 63 (1989) 2173;

Abstracts
We have measured the mass of the Z^o boson to be 91.14 ± 0.12 GeV/c², and its width to be 2.42^+0.45_-0.35 GeV. If we constrain the visible width to its standard-model value, we find the partial width to invisible decay modes to be 0.46 ± 0.10 GeV, corresponding to 2.8 ± 0.6 neutrino species, with a 95% confidence-level upper limit of 3.9.

Accelerator SLAC-SLC Detectors MARK-II

Related references
More (earlier) information appears in
G. S. Abrams et al., Phys. Rev. Lett. 63 (1989) 724;

Experiment comments
Total integrated luminosity of 19 nb-1.

Reactions

	e+ e– Zo	91.3 GeV (Ecm)	cs
	Zo μ– μ+
	Zo τ– τ+
	Zo 2hadron (hadrons)

Particles studied

	Zo	mass, w, pw
	ν	ex

Record comments
First evidence that the number of light neutrinos = 3. MARK-II Collaboration.

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