MSGUTs from Germ to Bloom: towards Falsifiability and Beyond

We review the development of minimal renormalizable SO(10) Susy GUTs. Using our $SO(10) \to G_{Pati-Salam} $ label decomposition we calculated the complete GUT scale spectra and couplings and the threshold effects therefrom. The corrections to $\alpha_G, Sin^2{\theta}_W $ and $ M_X $ are sensitive functions of the single parameter $\xi$ that controls symmetry breaking and slow funtions of the others. Scans of the parameter space to identify regions compatible with gauge unification are shown. The tight connection between the phenomenology of neutrino oscillations and exotic ($\Delta B\neq 0 $) processes predicted by Susy SO(10) GUTs is discussed in the context of the recent successful fits of all available fermion mass/mixing data using the ${\bf{10 \oplus {\bar {126}}}}$ Higgs representations and Type I/II seesaw mechanisms for neutrino mass. We emphasize that {\it{the true output of these calculations should be regarded as the unitary matrices that specify the orientation of the embedding of the MSSM within the MSGUT}}. Fermion Mass fitting constraints combined with GUT spectra can falsify/constrain the MSGUT and its near relatives. An initial survey indicates that Type I Seesaw neutrino masses dominate Type II and both are too small in the perturbative MSGUT even when the mixing and mass squared splitting ratios are as per data. This motivates a detailed study of the MSGUT constraints using the outputs of the fitting of fermion data, as well as consideration of modifications/extensions of the MSGUT scenario.