PHENOMENOLOGY OF WEAK ISOSCALAR VECTOR BOSONS

Abstract Motivated by the hypothesis of compositeness of leptons, quarks and vector bosons the effects of a weak isoscalar vector boson Y coupled to the weak hypercharge current, and, alternatively, the effects of an isoscalar vector boson Y L coupled to the left-handed part of the weak hypercharge current only, are investigated within the framework of an effective electroweak lagrangian theory incorporating W(Y) dominance. We discuss experimental implications for the neutral current phenomenology at presently available as well as at LEP and SLC energies. From the experimental data in neutrino scattering we deduce that the Y(Y L ) can hardly have a mass below 250 GeV. An enhanced forward-backward asymmetry A FB in e + e − → μ + μ − is expected at PETRA and TRISTAN energies. In fact, the one standard deviation effect seen at PETRA in A FB (e + e − → μ + μ − ) can naturally be explained through the existence of such an isoscalar boson.