Supersymmetric Grand Unification with Light Color-Triplet

TL;DR

This paper presents a supersymmetric SU(6) unification model featuring light color-triplet pseudo-Nambu-Goldstone superfields, which are compatible with proton decay constraints and could be detectable as long-lived particles in experiments.

Contribution

The authors develop a natural SU(6) unification model with light color-triplet pseudo-Nambu-Goldstone superfields arising from symmetry breaking, avoiding fine-tuning and experimental conflicts.

Findings

Light color-triplet states can have lifetimes from 1 second to 1 day.

Proton decay constraints are satisfied due to suppressed Yukawa couplings.

The model supports SU(6) unification without fine-tuning.

Abstract

We construct a natural model of the supersymmetric SU(6) unification, in which the symmetry breaking, down to the standard model gauge group, results in the number of pseudo-Nambu-Goldstone superfields with interesting properties. Namely, besides the Higgs doublet-antidoublet pair which is responsible for the electroweak phase transition, the Nambu-Goldstone sector consists of multiplets in the anti- and fundamental representations of SU(5). While being strictly massless in the supersymmetric limit, they acquire the weak scale masses as a result of its breaking. The color-triplet components of this light sector could, in principle, mediate an unacceptably fast proton decay; however, because of the natural $\text{TeV}/M_{\text{GUT}}$ suppression of the Yukawa couplings to the light quarks and leptons, their existence is compatible with the experimental bound on proton lifetime. This suppression is made further interesting, since it results in the lifetime, of the lightest of the above-mentioned colored particles from 1 sec to 1 day, long enough for it to appear stable in the detector. Furthermore, we argue that the accommodation of the color-triplet pseudo-Nambu-Goldstones, without fine-tuning or contradicting observations, implies SU(6) unification.