Grand Unification and Intermediate Scale Supersymmetry

Understand

With minimal field content and for an interesting range of the supersymmetric Higgs mixing parameter, 0.5 < tan^2 \beta < 2, the superpartner mass scale, \tilde{m}, is found to be at the intermediate scale, ~ 10^{10 \pm 1} GeV, near where the Standard Model Higgs quartic coupling passes through zero.

• For any 4d supersymmetric grand unified symmetry spontaneously broken by a vacuum expectation value <\Sigma>, if superpotential interactions for \Sigma are forbidden e.g.
• by R symmetries, the uneaten color octet, \Sigma_8, and weak triplet, \Sigma_3, have masses of order \tilde{m}.
• The combination of superpartner and \Sigma_{8,3} states leads to successful gauge coupling unification, removing the disastrously high proton decay rate of minimal Standard Model unification.