Aspects of Grand Unified Models with Softly Broken Supersymmetry

Abstract

The minimal SU(3)× SU(2)× U(1) gauge model with softly broken supersymmetry is studied in the framework of the standard grand unification. It is assumed that the supersymmetry is left intact at an energy scale μ≃ MX, the grand unification mass scale, except for Majorana masses of gauge fermions. The other soft breaking parameters at low energies are shown to be generated by renormalization effects. The gauge symmetry breaking SU(2)× U(1)→ U(1)em is also caused through radiative corrections. The super-GIM mechanism apparently works well to suppress flavor changing neutral interactions. The mass of the top quark is remarkably found to be constrained as 60 GeV ≾ mt ≾ 180 GeV. Futhermore various mass relations for unconventional particles are obtained as well as crude estimates for numerical masses of them. It is found that there is a plethola of new particles in a mass range from a few tens of GeV to a few hundred GeV.