Improved Constraints on Z' Bosons from Electroweak Precision Data

TL;DR

This paper constrains the mass and mixing angle of hypothetical Z' bosons in models with extra U(1) symmetry using electroweak precision data, setting lower mass limits around 1 TeV and exploring potential better fits than the Standard Model.

Contribution

It provides updated bounds on Z' boson parameters from electroweak data, including a case with a marginally better fit than the Standard Model.

Findings

Lower limit on Z' mass around 1 TeV for most models

Electroweak data constrains Z-Z' mixing angle to very small values

One model shows a marginally better fit than the Standard Model

Abstract

We analyze various models with an extra U(1) gauge symmetry in addition to the Standard Model (SM) gauge group at low energies, and impose limits on the mass of the neutral Z' boson, M_Z', predicted in all such models, and on the Z-Z' mixing angle, theta_ZZ'. The precision electroweak data strongly constrain theta_ZZ' to very small values and for most models we find lower limits on M_Z' of order 1 TeV. In one case we obtain a somewhat better fit than in the SM (although this is only marginally statistically significant) and here we find a weak upper limit at the 90% C.L.