Constraints on leptophobic Z ′ models from electroweak experiments

We study the constraints from updated electroweak data on the three leptophobic Z ′ models, the η model with an appropriate U(1)U(1)Y kinetic mixing, a Z ′ model motivated by the flipped SU(5) × U(1) unification, and the phenomenological Z ′ model of Agashe, Graesser, and Hinchliffe. The Z-Z ′ mixing effects are parametrized in terms of a positive contribution to the T parameter, Tnew, and the effective mass mixing parameter, ξ̄. All the theoretical predictions for the Z boson parameters, the W boson mass and the observables in low-energy neutral current experiments are presented together with the standard model radiative corrections. The allowed region in the ( ξ̄, Tnew) plane is shown for the three models. The 95% CL lower limit on the heavier mass eigenstate Z2 is given as a function of the effective Z-Z ′ mixing parameter ζ . PACS: 12.60.Cn; 12.60.Jv; 14.70.Pw