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Nobel prize to M. Perl awarded in 1995 "for the discovery of the τ lepton''. Co-winner F. Reines "for the detection of the neutrino''

PERL 1977F

Perl, M.L. et al.
Properties of the Proposed τ Charged Lepton
Phys. Lett. 70B (1977) 487;

Abstracts
The anomalous eμ and 2-prong μx events produced in e⁺e^– annihilation are used to determine the properties of the proposed τ charged lepton. We find the τ mass is 1.90 ± 0.10 GeV/c²; the mass of the associated neutrino, ν_τ, is less than 0.6 GeV/c² with 95% confidence; V-A coupling is favored over V+A coupling for the τ - ν_τ current and the leptonic branching ratios are 0.186 ± 0.010 ± 0.028 from the eμ events and 0.175 ± 0.027 ± 0.030 from the μx events where the first error is statistical and the second is systematic.

Accelerator SLAC-SPEAR Detectors SMAG

Related references
More (earlier) information appears in
M. L. Perl et al., Phys. Lett. 63B (1976) 466;
M. L. Perl et al., Phys. Rev. Lett. 35 (1975) 1489;

Reactions

	e+ e– μ– e+ (neutrals)	3.8-7.8 GeV (Ecm)	pt, cs
	e+ e– μ+ e– (neutrals)	3.8-7.8 GeV (Ecm)	pt, cs
	e+ e– τ– X	3.8-7.8 GeV (Ecm)	cs
	e+ e– τ+ X	3.8-7.8 GeV (Ecm)	cs

Particles studied

	τ+	mass, w, qn, ex, pw
	τ–	mass, w, qn, ex, pw
	ντ	ex, mass

Record comments
Firm establishment of the τ lepton properties.

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