Constraints on Extended Neutral Gauge Structures

TL;DR

This paper uses precision data to set limits on the masses and mixings of hypothetical Z' bosons in various theoretical models, finding that most are constrained to be several hundred GeV or higher, with some pushed into the TeV range.

Contribution

It provides comprehensive constraints on Z' bosons across multiple models, including E6, left-right, and string-inspired theories, using indirect precision measurements.

Findings

Mixing angles constrained to sin θ < 0.01

Mass limits typically several hundred GeV, some in the TeV range

Weaker limits for Z_psi due to vanishing vector couplings

Abstract

Indirect precision data are used to constrain the masses of possible extra Z^prime bosons and their mixings with the ordinary Z. We study a variety of Z^prime bosons as they appear in E_6 and left-right unification models, the sequential Z boson, and the example of an additional U(1) in a concrete model from heterotic string theory. In all cases the mixings are severely constrained (sin theta < 0.01). The lower mass limits are generally of the order of several hundred GeV and competitive with collider bounds. The exception is the Z_psi boson, whose vector couplings vanish and whose limits are weaker. The results change little when the rho parameter is allowed, which corresponds to a completely arbitrary Higgs sector. On the other hand, in specific models with minimal Higgs structures the limits are generally pushed into the TeV region.