ar X iv : h ep - p h / 05 06 29 1 v 1 2 8 Ju n 20 05 MSGUTs from Germ to Bloom : towards Falsifiability and Beyond

We review the development of renormalizable SO(10) Susy GUTs based on the 210 ⊕⊕126 ⊕ 126 ⊕ 10 Higgs system. These GUTs are minimal by parameter counting. Using the SO(10) → SU(4) × SU(2)L × SU(2)R label decomposition developed by us we calculated the complete GUT scale spectra and couplings and the threshold effects therefrom. The corrections to αG, Sin θW and MX are sensitive functions of the single parameter ξ that controls symmetry breaking and slow funtions of the other parameters. 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 (∆B 6= 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 10 ⊕ 126 Higgs representations and Type I/II seesaw mechanisms for neutrino mass. We emphasize that 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. The ∆B 6= 0 , d=5 effective Lagrangian is written down using these embedding matrices. We show how Fermion Mass fitting constraints can be combined with GUT spectra to 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. Expanded version of Plenary talks at THEP I , IIT Roorkee, March 16-20 and Planck05, ICTP, Trieste 23-28 May, 2005. E-Mail: [email protected] ; [email protected]