Indications for an Extra Neutral Gauge Boson in Electroweak Precision Data

TL;DR

This paper analyzes electroweak precision data, suggesting the existence of an extra Z' boson, possibly non-universal, with properties consistent with certain grand unified and superstring theories.

Contribution

It provides a model-independent analysis of extra Z' bosons using precision data, indicating potential non-universal couplings and compatibility with theoretical models.

Findings

Data favor a Z' boson with specific couplings

Good fit achieved with a non-universal Z' model

Supports theories predicting extra gauge bosons

Abstract

A new analysis of the hadronic peak cross section at LEP 1 implies a small amount of missing invisible width in Z decays, while the effective weak charge in atomic parity violation has been determined recently to 0.6% accuracy, indicating a significantly negative S parameter. As a consequence of these two deviations, the data are described well if the presence of an additional Z' boson, such as predicted in Grand Unified Theories, is assumed. Moreover, the data are now rich enough to study an arbitrary extra Z' boson and to determine its couplings in a model independent way. An excellent best fit to the data is obtained in this case, suggesting the possibility of a family non-universal Z' with properties similar to ones predicted in a class of superstring theories.