Y. Narita

Determination of the QCD scale parameter ΛMS with QCD cascade on the basis of the next-to-leading logarithmic approximation

Abstract 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.

Measurement of the differential cross sections ofe+e−→γγ ande+e−→γγγ at\(\sqrt s = 55,56,56.5\) and 57 GeV and search for unstable photino pair production

AbstractDifferential 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,

Experimental limits on extra-Z bosons from e+e− annihilation data with the VENUS detector at s=50–64 GeV

e^ + e^ - \to \tilde \gamma \tilde \gamma

Charge asymmetry of hadron jets and limits on the compositeness scales in the e+e-→qq̄ reaction at 〈√s〉 = 57.6 GeV

. No candidate events were found and a new limit on the photino mass is obtained.

Measurement of forward-backward charge asymmetry in the process of b-quark production in e+e− annihilation around √s=60 GeV

Abstract A study of single photon events, produced in association with light neutrinos or other weakly interacting neutral particlaes in e + e − collisions, has been performed at √ s =54.0–61.4 GeV with the VENUS detector at TRISTAN. No anomalous signal has been observed in a data sample corresponding to an integrated luminosity of 28.2 pb −1 . This result indicates that the upper limit on the number of light neutrinos, N ν , is 11 (15) at a 90 (95)% confidence level. Combining this with published results from other e + e − experiments, the number of light neutrinos is limited to N ν

Search for susy partners of charged leptons in e+e- collisions with s up to 60.8 GeV

Abstract We have tested extra Z models in the reactions e+e−→μ+μ−, τ+τ− and hadrons in the energy range 50 s 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 ZΨ, Zη and Zχ bosons which are expected from the E6 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.

Measurement of the forward-backward asymmetry of charm quark production in e+e- annihilations at lang; S〈 = 58.4 GeV

AbstractThe angular distributions of the reactione+e−→μ+μ− ande+e+→τ+τ− have been measured between