MSGUT : from Futility to Precision

We computed the complete gauge and chiral superheavy spectra and couplings in the Minimal Susy GUT and therefrom evaluated the dependence of 1-loop threshold corrections to the Weinberg angle and Unification scale as functions of the single complex parameter $\xi$ that controls MSGUT symmetry breaking. The corrections are generically within 10% showing that contrary to longstanding conjectures,{\it{high precision calculations are not futile but necessary and feasible in the SO(10) MSGUT.}} Effective superpotentials for $B-L$ violation and mass formulae of the MSSM matter supermultiplets including neutrino Type I and II seesaws were derived.