The polarization of tau leptons in the reaction e+ e- --> tau+ tau- has been measured using a e+e- collider, TRISTAN, at the center-of-mass energy of 58 GeV. From the kinematical distributions of daughter particles in tau --> e nu nu-bar, mu nu nu-bar, rho nu or pi(K) nu decays, the average polarization of tau- and its forward-backward asymmetry have been evaluated to be 0.012 +- 0.058 and 0.029 +- 0.057, respectively.
Charged-conjugated states are included. The polarization is measured from final charged-particle energy spectrum. The last value is the combination of the results for all decay modes. The systematic error is not given.
Charged-conjugated states are included. The forward-backward asymmetry of the polarization is defined as (SIG(F)*POL-SIG(B)*POL)/(SIG(F)*POL+SIG(B)*POL). The last value is the combination of the results for all decay modes. The systematic error is not given.
The angular distributions of the reactione+e−→μ+μ− ande+e+→τ+τ− have been measured between\(\sqrt s= 50\) and 60.8 GeV with the VENUS detector at TRISTAN. The average total cross section and the forward-backward charge asymmetry for μ-pair production are observed to be 28.3±1.4±0.8 pb and (−29.0−4.8+5.0±0.5)%, and those for τ-pair production are 27.6±1.7±1.0 pb and (−32.8−6.2+6.4±1.5)% at\(\langle \sqrt s \rangle \). These values are consistent with the predictions of the standard model of electroweak interactions.
No description provided.
No description provided.
No description provided.
We have tested extra Z models in the reactions e + e − → μ + μ − , τ + τ − and hadrons in the energy range 50< s <64 GeV using the VENUS detector at the TRISTAN e + e − storage ring. Our data are in good agreement with the standard model prediction ( χ 2 N Df = 2.9 31 ) ). We have obtained 90% confidence-level lower limits of 105, 125 and 231 GeV for the masses of Z Ψ , Z η and Z χ bosons which are expected from the E 6 grand unified theory. We also place a 90% confidence-level lower limit of 426 GeV for the mass of an extra-Z boson whose couplings to quarks and leptons are assumed to be the same as those for the standard Z boson. Our results exceed the previous experimental limits from the p p collider experiments, although there have been some combined analyses reporting the limits better than those obtained in the present analysis.
New measurements.
New measurements. Statistical and systematic errors combined in quadrature.
New measurements.
Forum