Testing the Standard Model Versus a Composite Structure of Weak Interactions in High Precision Experiments at LEP and SLC

Abstract Models with a composite structure of the weak interactions usually contain an isoscalar weak vector boson Y or Y L which is coupled to the weak hypercharge current, or its left-handed part. We study the impact of Y and Y L on the Z-boson parameters and other measurables at future high energy e + e − colliders and discuss the corresponding standard model predictions. An analysis of the forward-backward and left-right asymmetry for the general case of two massive vector bosons with arbitrary vector and axial vector coupling constants is undertaken which may be applied to any other model containing additional weak vector bosons. If experiments at LEPI/SLC and LEPII agree with the standard model predictions within the possible experimental accuracies, Y(Y L ) bosons with a mass of up to 1 TeV (0.9 TeV) could be excluded.