Unification and low-energy supersymmetry at one and two-loop orders

TL;DR

This paper examines the unification of coupling constants and Yukawa couplings within supersymmetric grand unified theories, analyzing two-loop effects, theoretical uncertainties, and low-energy predictions, including Higgs mass constraints.

Contribution

It provides a detailed analysis of coupling unification and Yukawa relations at one and two-loop orders, highlighting the impact of theoretical uncertainties and model embeddings.

Findings

Bottom-tau unification suggests a Higgs lighter than 110 GeV

Embedding in GUTs influences soft supersymmetry breaking parameters

Theoretical uncertainties significantly affect unification predictions

Abstract

The status of coupling constant unification -- assuming the validity of the standard model or of its minimal supersymmetric extension at high energies -- and of relations between various Yukawa couplings (assuming the supersymmetri extension) which are implied in certain grand-unified theories, are studied in detail. Theoretical uncertainties in the calculations are emphasized, and low-energy constraints and predictions are derived. In particular, we find that bottom-tau unification favors a Higgs boson lighter than 110 GeV. The structure of the vacuum in the model studied is also discussed. Implications of embedding supersymmetric models in grand-unified theories are further explored and are shown to affect the soft supersymmetry breaking mass parameters of the models, and thus the spectrum at low-energy.