Constraints on the mass and mixing of Z-prime bosons

We tested several models in which the Standard Model (SM) gauge group is extended by an additional U (1) gauge symmetry against available electroweak precision data to impose limits on the mass of the neutral Z ′ boson, M Z ′ , predicted in all such models, and on the Z − Z ′ mixing angle, θ ZZ ′ , at 95% C.L. We found lower limits on M Z ′ of order 1 TeV in most cases, while θ ZZ ′ was found to be constrained to very small values