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The total cross section for the process of the e + e - annihilation into hadrons has been measured at the centre-of-mass energies of 50 GeV and 52 GeV and a search has been made for new heavy quarks. The ratios R = σ ( e + e - → hadrons )/ σ point ( e + e - → μ + μ - ) obtained are 4.4±0.5 at 50 GeV and 4.7±0.3 at 52 GeV, respectively. An additional systematic uncertainty is 10%. From the event shape analysis we found no evidence for a new quark with charge 2 3 e .
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A search for sequential charged leptons decaying into massive neutrinos has been performed at Ec.m.=56 GeV at the KEK colliding-beam accelerator TRISTAN. We have found no evidence for the production of the charged heavy leptons for an integrated luminosity of 5.3 pb−1. A search for stable charged leptons was also conducted yielding null results. A new mass limit on the charged heavy leptons was obtained as a function of the mass of the associated neutrinos.
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The polarization parameters for the π + +p→K + +∑ + reaction have been measured at 13 laboratory momenta between 1490 and 2069 MeV/ c in the angular range of −0.1⩽ cos θ K ∗ ⩽0.7 with higher statistics than previous experiments. In general, the present results agree well with the results at the Rutherford Appleton Laboratory. It is found, however, that there exist small but systematic differences which can be attributed to certain coefficients in Legendre expansions. The physical significance of these differences is discussed.
ALPHA0 is the decay asymmetry parameter (=0.980 +- 0.015 PDG tables).
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We have studied inclusive lepton production in e + e − annihilations into multihadrons in the energy range between √ s =50 and 55 GeV using the VENUS detector at TRISTAN, KEK. Though MARK-J and JADE groups at PETRA found an excess of isolated muon events at √ s ⩾46.3 GeV, we have not observed such an anomaly in muon nor in electron production. The observed rates of isolated leptons are consistent with the production and decay of five known quarks.
Observed rates for whole event sample.
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Differential cross sections fore+e−→γγ have been measured at center-of-mass energies of 55, 56, 56.5 and 57 GeV. The results are in good agreement with those predicted by QED. Possible deviations from QED are studied in terms of contact interactions, and the limits on compositeness scales are obtained. Using events with a gramma pair in the final state, a search is made for the pair production of unstable photons,\(e^ +e^ -\to \tilde \gamma\tilde \gamma \). No candidate events were found and a new limit on the photino mass is obtained.
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A charge asymmetry has been measured in hadron jets from e + e − annihilation at energies between 52 and 61.4 geV (〈√ s 〉=57.6 GeV). The measured asymmetry is A =11.4%±2.2%±2.1% and is consistent with the prediction of the standard model of the electroweak theory. By using the differential cross section, lower limits of the compositeness scale in eeqq contact interactions have been determined to be typically a few TeV at 95% CL.
Data are fully corrected for detector effects, resolution and radiative effects.
We accumulated e + e − annihilations into multi-hadrons at CM energies between 54.0 and 61.4 GeV with the VENUS detector at TRISTAN. Measured R -ratios are consistent with the standard model using the Z-boson mass; 91.1 GeV/ c 2 . Using two new observables, we searched for a planar four-jet and other multi-jet events resulting from the decay of a charge — 1 3 e b ' quark. Having observed no positive signals, we excluded b' masses between 19.4 and 28.2 GeV/ c 2 with a 95% confidence level, regardless of branching into charged current and loop-induced flavor-changing neutral current decay, including a possible Higgs decay process. The charge + 2 3 e top quark was excluded below f30.2 GeV/ c 2 .
R value measurements.
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.
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The relative production ratio of 3-jet events to the total number of hadronic events was studied in e + e − annihilations at centre-of-mass energies between 54 and 61.4 GeV. The QCD scale parameter has been determined to be Λ MS =254 −47 +55 ±56 MeV on the basis of a QCD cascade with the next-to-leading logarithmic approximation.
Data are uncorrected for initial radiation, detector effects, and quark hadronization.
LAMBDA-MSBAR determined from the 3-jet ratio.
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