MSGUT: From bloom to doom Original Research Article

By a systematic survey of the parameter space we confirm our surmise [C.S. Aulakh, MSGUTs from germ to bloom: Towards falsifiability and beyond, hep-ph/0506291] that the Minimal Supersymmetric GUT (MSGUT) based on the image Higgs system is incompatible with the generic Type I and Type II seesaw mechanisms. The incompatibility of the Type II seesaw mechanism with this MSGUT is due to its generic extreme sub-dominance with respect to the Type I contribution. The Type I mechanism although dominant over Type II is itself unable to provide neutrino masses larger than image anywhere in the parameter space. Our Renormalization Group based analysis shows the origin of these difficulties to lie in a conflict between baryon stability and neutrino oscillation. The MSGUT completed with a 120-plet Higgs is the natural next to minimal candidate. We propose a scenario where the 120-plet collaborates with the 10-plet to fit the charged fermion masses. The freed 120-plet couplings can then give sub-dominant contributions to charged fermion masses and enhance the Type I seesaw masses sufficiently to provide a viable seesaw mechanism. We give formulae required to verify this scenario.