Semi-perturbative unification with extra vector-like families Original Research Article

We make a comprehensive analysis of an extended supersymmetric model (ESSM) obtained by adding a pair of vector-like families to the minimal supersymmetric standard model and having specific forms of 5×5 fermion mass matrices. The singlet Higgs couplings which link the ordinary to vector-like generations do not have the renormalization effects of the gauge interactions and hence the “quasi-infrared fixed point” near the scale of the top quark mass. The two-loop Yukawa effects on gauge couplings lead to an unified coupling αX around 0.2 with an unification scale MX of 1016.9 GeV. Large Yukawa effects in the high energy region arrest the growth of the QCD coupling near MX making the evolution flat. The renormalization effects of the vector-like generations on soft mass parameters has important effects on the charge and color breaking (CCB) minima. We will show that there exists parameter space where there is no charge and color breaking. We will also demonstrate that there exists minima of the Higgs potential which satisfies the mass of the Z boson but avoid CCB. Upper limits on the mass of the lightest Higgs boson from the one-loop effective scalar potential is obtained for sets of universal soft supersymmetry breaking mass parameters.