A Precision Measurement of the Z{sup 0} Lineshape Parameters for the Process Z{sup 0} {r_arrow} {tau}{sup +}{tau}{sup {minus}}
A Precision Measurement of the Z{sup 0} Lineshape Parameters for the Process Z{sup 0} {r_arrow} {tau}{sup +}{tau}{sup {minus}}

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Published: 1996

Total Pages: 284

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In this dissertation, a measurement of the partial decay width of the process Z° →??{sup −} using data collected during 1993 and 1994 at the OPAL detector at CERN is described. The cross sections of this process at three center-of-mass energies near the Z° resonance were determined, and from a fit to those cross sections, the mass of the Z°, its total decay width and its partial decay width into?+?{sup −} final states were determined as M{sub Z} = 91.183 ± 0.020 GeV,?{sub tot} = 2.514 ± 0.018 GeV and?{sub??} = 84.54 ± 0.59 MeV. Using published results for M{sub Z}, and?{sub tot} with higher accuracy, a value for the partial decay width of?{sub??} = 84.02 ± 0.20 MeV was obtained. Further using published results for the decay width of the Z° into quark pair final states, the invisible decay width of the Z° was determined as?{sub inv} = 496.9 ± 4.1 MeV, and the number of neutrino generations was determined as N{sub?} = 2.974 ± 0.025(exp) ± 0.007 (m{sub top}, M{sub Higgs}). All results were found to be in good agreement with the Standard Model predictions and were consistent with the assumption of lepton universality within the Standard Model framework.

Measurements of the Decays Tau−. --]. Rho−. Nu. /sub Tau/, Tau−. --]. Pi. −. Nu. /sub Tau/ and Tau−. --]. K*-(892). Nu. /sub Tau/ Using the MARK II Detector at SPEAR.
Measurements of the Decays Tau−. --]. Rho−. Nu. /sub Tau/, Tau−. --]. Pi. −. Nu. /sub Tau/ and Tau−. --]. K*-(892). Nu. /sub Tau/ Using the MARK II Detector at SPEAR.

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Published: 1981

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Measurements of the branching fractions for the Cabibbo favored decays tau− .-->. rho− .-->. .pi.−.nu./sub tau/ and the Cabibbo suppressed decay mode tau− .-->. K*− (892).nu./sub tau/ are presented. The energy dependence of the tautau− production cross section is obtained for the decays tau− .-->. rho−.nu./sub tau/ and these spectra agree well with the classification of the tau− as a spin-1/2 point particle. Fits to the production cross section yield a measurement of M/sub tau/ = (1787 +- 10) MeV/c2 for the tau mass. Ninety-five percent confidence upper limits for the forbidden decay tau− .-->. K*−(1430).nu./sub tau/ and the tau neutrino mass are presented.

The Decay Tau. --]. Rho Nu (and Rho. --]. Pi. Eta Nu.).
The Decay Tau. --]. Rho Nu (and Rho. --]. Pi. Eta Nu.).

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Published: 1987

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Motivated by the question of missing exclusive branching fractions in tau decays, mostly suspected to be in one prong decays with neutrals, we have studied the decay tau .-->. rho nu in tau pair production by ee− annihilation at .sqrt.s = 3.77 GeV. The branching fraction is measured to be B(tau .-->. rho nu) = (23.0 +- 1.3 +- 1.7)% consistent with known measurements and not offering a solution to the branching ratio question. No eta signal in the .gamma gamma. mass spectrum pointing to a decay tau .-->. eta .pi. nu is obvious. An upper limit on this branching fraction is given.

Measurements of the Decays Tau−. --]. Rho−. Nu
Measurements of the Decays Tau−. --]. Rho−. Nu

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Published: 1981

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Measurements of the branching fractions for the Cabibbo favored decays tau− .-->. rho− .-->. .pi.−.nu./sub tau/ and the Cabibbo suppressed decay mode tau− .-->. K*− (892).nu./sub tau/ are presented. The energy dependence of the tautau− production cross section is obtained for the decays tau− .-->. rho−.nu./sub tau/ and these spectra agree well with the classification of the tau− as a spin-1/2 point particle. Fits to the production cross section yield a measurement of M/sub tau/ = (1787 +- 10) MeV/c2 for the tau mass. Ninety-five percent confidence upper limits for the forbidden decay tau− .-->. K*−(1430).nu./sub tau/ and the tau neutrino mass are presented.

Evidence for the Decay Tau−. --]. Pi. −eta Nu
Evidence for the Decay Tau−. --]. Pi. −eta Nu

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Published: 1987

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The inclusive production of eta mesons in tau lepton decay has been studied using the High Resolution Spectrometer at the PEP ee− facility. The data sample corresponds to an integrated luminosity of 300 pb−1 and the storage ring was operated at .sqrt.s = 29 GeV. The eta production appears to be only compatible with the decay tau− .-->. .pi.−eta nu, which violates isospin and G-parity conservation. The branching ratio of 5.1 +- 1.5% explains much of the current discrepancy between the one-prong topological branching ratio and the sum of the individual one-prong modes. Various checks to test the validity of the signal are described.

Measurement of the Decays Tau−. --]. Rho−. Nu
Measurement of the Decays Tau−. --]. Rho−. Nu

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Published: 1980

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Measurements of the branching fractions for the Cabibbo-favored decay tau− .-->. rho−.nu./sub tau/ and the Cabibbo-suppressed decay tau− .-->. K*−(892).nu./sub tau/ are presented. The energy dependence of the tautau− production cross section is measured with the aid of the decay tau− .-->. rho−.nu./sub tau/, which yields a measurement M/sub tau/ = (1790 +- 40) MeV. A 2 sigma upper limit for the forbidden decay tau− .-->. K*−(1430).nu./sub tau/ is also presented. 3 figures.