A simple extension of the standard model to an SU(2${)}_{\mathrm{L}}$×U(1${)}_{\mathrm{Y}}$×U(1) gauge symmetry is considered. The symmetry is broken by vacuum expectation values of one doublet and one singlet scalar field, resulting in a second massive neutral gauge boson. Electron-positron collisions at this Z’ resonance are calculated. Aside from the possibility of Z’ decays into exotic fermions which fill out the irreducible representations of grand unified theories, there generally are important decay modes into $W^{+}$$W^{\mathrm{-}}$ and $Z^0$$H^0$ coming from mixing between the Z’ and the Z of the standard model, even after imposing the constraints from experiment on the magnitude of the mixing angle.

• Received 24 March 1987

DOI:https://doi.org/10.1103/PhysRevD.36.1337