Neutral current and LEP constraints on an extra E6 neutral gauge boson. A global fit to electroweak parameters
We perform an analysis of the laboratory constraints on the parameters of an additional neutral gauge boson from the E6 gauge group. We combine the recent constraints on the mass of the Z as well as its leptonic, hadronic and total decay widths obtained by the four LEP collaborations, with those that follow from deep-inelastic νμN scattering and other low energy neutral current experiments, in a global fit. The constraints on the mass and mixing of the Z' are given for the general unconstrained E6 model as well as for the case of constrained string models.