Proton decay, neutrino oscillations and other consequences from supersymmetric SU(6) with pseudo-Goldstone Higgs Original Research Article

We suggest a new mechanism for naturally suppressing dimension five baryon number violating in supersymmetric SU(5+N) (N=0,1,…) GUTs. The mechanism is realized through suppression of qqT type couplings, and is implemented by introducing new `matterʹ multiplets belonging to symmetric representations of SU(5+N). Together with the suppression of nucleon decay, these multiplets also enable one to avoid the unwanted asymptotic mass relations ms=mμ, md/ms=me/mμ. As an example, we consider an SU(6) model with pseudo-Goldstone Higgs. By supplementing the model with an anomalous U(1) flavor symmetry, we also obtain a simple `all-orderʹ solution of the gauge hierarchy problem and natural explanation of charged fermion mass hierarchies and values of the CKM matrix elements. The proton life time τp∼102τpSU(5) yr. is compatible with experiments, with the dominant decay being p→Kνμ,τ. Thanks to the SU(6) symmetry, successful unification of the gauge couplings can be retained, and the value of the strong coupling αs(MZ) can be reduced to ≃0.12. Finally, we show how to accommodate the solar and atmospheric neutrino data through the bi-maximal neutrino mixing scenario, with maximal vacuum νe−νμ,τ and large angle νμ−ντ oscillations.