Large R-parity Violating Couplings and Grand Unification

الأصل · EN

We consider a possibility that R-parity violating interactions of particles which do not involve the first generation have large (up to 1) coupling constants, Λ. Such couplings, if exist, could have a number of phenomenological consequences: renormalization of b-τ mass ratio, generation of ντ mass in MeV region, etc.. In Grand Unified models, where B- and L-violating couplings appear simultaneously, the proton decay can be forbidden in virtue of hierarchical flavor structure of Λ. However, due to Cabibbo-Kobayashi-Maskawa mixing this decay is induced already in one-loop. Present experimental data give the upper bound Λ 10⁻⁸ (or |λ' λ''| 7· 10⁻¹⁶, on products of certain L- and B-violating coupling constants, in more general context). The bound can be avoided, if there is an asymmetry between the L- and B-violating couplings of usual matter fields. In the SU(5) model the asymmetry can be related to the doublet-triplet splitting.