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 ( χ2 NDf= 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 pp collider experiments, although there have been some combined analyses reporting the limits better than those obtained in the present analysis.
ASJC Scopus subject areas
- Nuclear and High Energy Physics