Z′-bosons in supersymmetric E6 models confront electroweak data

We study constraints on additional Z'-bosons predicted in the supersymmetric (SUSY) E-6 models by using the updated results of electroweak experiments - Z-pole experiments, mw measurements and low-energy neutral current (LENC) experiments. We find that the effects of Z-Z' mixing are parametrized by (i) a tree-level contribution to the T-parameter, (ii) the effective Z-Z' mass mixing angle <(xi)over bar>. In addition, the effect of the direct exchange of the heavier mass eigenstate Z(2) in the LENC processes is parametrized by (iii) a contact term g(E)(2)/c(chi)(2)m(Z2)(2). We give the theoretical predictions for the observables in the electroweak experiments together with the standard model radiative corrections. Constraints on T-new and <(xi)over bar> from the Z-pole and m(W) experiments and those on g(E)(2)/c(chi)(2)m(Z2)(2) from the LENC experiments are separately shown. Impacts of the kinetic mixing between the U(1)(Y) and U(1)' gauge bosons on the chi(2)-analysis are studied. We show the 95% CL lower mass limit of Z(2) as a function of the effective Z-Z' mixing parameter zeta, a combination of the mass and kinetic mixings. A theoretical prediction on zeta and g(E) is given for the chi-, psi-, eta- and nu-models by assuming the minimal particle content of the SUSY E-6 models. In a certain region of the parameter space, the Z(2)-boson mass in the detectable range of LHC is still allowed. (C) 1998 Elsevier Science B.V.