EXPERIMENTAL LIMITS ON EXTRA-Z BOSONS FROM E+E- ANNIHILATION DATA WITH THE VENUS DETECTOR AT SQUARE-ROOT-S=50-64 GEV

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. © 1990.