Scale hierarchies, symmetry breaking and particle spectra in SU(3)-family extended SUSY trinification

Abstract

A unification of left-right $\rm{SU}(3)_\rm{L}\times \rm{SU}(3)_\rm{R}$, colour $\rm{SU}(3)_\rm{C}$ and family $\rm{SU}(3)_\rm{F}$ symmetries in a maximal rank-8 subgroup of ${\rm{E}}_8$ is proposed as a landmark for future explorations beyond the Standard Model (SM). We discuss the implications of this scheme in a supersymmetric (SUSY) model based on the trinification gauge $\left[\rm{SU}(3)\right]^3$ and global $\rm{SU}(3)_\rm{F}$ family symmetries. Among the key properties of this model are the unification of SM Higgs and lepton sectors, a common Yukawa coupling for chiral fermions, the absence of the $\mu$-problem, gauge couplings unification and proton stability to all orders in perturbation theory. The minimal field content consistent with a SM-like effective theory at low energies is composed of one $\mathrm{E}_6$ $27$-plet per generation as well as three gauge and one family $\rm{SU}(3)$ octets inspired by the fundamental sector of ${\rm{E}}_8$. The details of the corresponding (SUSY and gauge) symmetry breaking scheme, multi-scale gauge couplings' evolution, and resulting effective low-energy scenarios are discussed.