Supersymmetry and Unification: Heavy Top Was the Key

TL;DR

This paper reviews gauge coupling unification within supersymmetric GUTs, emphasizing how a heavy top quark was crucial for accurate predictions, and discusses experimental prospects for testing these theories at the LHC.

Contribution

It provides an updated analysis of minimal supersymmetric GUTs, highlighting the role of a heavy top quark in unification and exploring potential experimental signatures.

Findings

Minimal SU(5) aligns with experimental data.

A light fermion triplet may be detectable at the LHC.

Heavy top quark was key to successful unification.

Abstract

I review the unification of gauge couplings of strong, weak and electro-magnetic interactions. I start by recalling the history of the most important prediction of low-energy supersymmetry: the correct value of the weak mixing angle tied to a large top quark mass. I then turn to the discussion of the present day situation of the minimal supersymmetric Grand Unified Theories based on SU(5) and SO(10) groups, and I show why the minimal SU(5) is in accord with experiment. For the sake of completeness I also summarize the problems and possible solutions of the minimal ordinary SU(5). One version, based on the minimal Georgi-Glashow model, augmented by the adjoint fermion, predicts a light fermion triplet to lie below TeV or so. Its (lepton number violating) decays offer a hope of probing neutrino (Majorana) masses and mixings at the LHC.