Missing doublet multiplet as the origin of the doublet - triplet splitting in SUSY SU(6)

Abstract In a SU (6) gauge theory we found the irreducible representation (175-plet) which does not contain the Higgs doublet. Using this representation we construct two SUSY SU (6) models in which the doublet-triplet splitting occurs naturally, without fine tuning. The crucial role is played by the “custodial” global SU (2) H in combination with discrete or continuous R symmetries.