Precision Tests of the Standard Model

TL;DR

This paper reviews recent precision electroweak measurements, analyzing their implications for the Standard Model and its extensions, including constraints on the top quark and Higgs boson masses, and testing grand unification theories.

Contribution

It provides updated fits to electroweak data, predicts top quark mass ranges in the Standard Model and MSSM, and discusses the impact of these measurements on testing the Standard Model's validity.

Findings

Electroweak data constrains \

Predicted top quark mass ranges in SM and MSSM are consistent with experimental bounds.

No significant constraint on Higgs mass until independent top mass measurement.

Abstract

The implications of recent precision $Z$-pole, $W$ mass, and weak neutral current data for testing the standard electroweak model, constraining the $t$ quark and Higgs masses, \alsz, and grand unification are discussed. A fit to all data yields $\siz = 0.2328 \pm 0.0007$ (\msb) or $\sinn \equiv 1 - \mw^2/\mz^2 = 0.2267 \pm 0.0024$ (on-shell), where the uncertainties are mainly from \mt. In the standard model one predicts $\mt = 150^{+19 + 15}_{-24 - 20}$ GeV, where the central value assumes \mh = 300 GeV and the second uncertainty is for \mh $\ra$ 60 GeV ($-$) or 1 TeV (+). In the minimal supersymmetric extension of the standard model (MSSM) one predicts $\mt = 134^{+23}_{-28} \pm 5$ GeV, where the difference is due the light Higgs scalar expected in the MSSM. There is no significant constraint on \mh \ until \mt \ is known independently.