Proton Decay, Neutrino Oscillations And Other Consequences From Supersymmetric SU(6) With Pseudo-Goldstone Higgs

Abstract

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 `matter' 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 $m_s=m_{\mu }$, $\frac{m_d}{m_s}=\frac{m_e}{m_{\mu }}$. As an example, we consider a SU(6) model with pseudo-Goldstone Higgs. By supplementing the model with an anomalous $\mathcal{U}(1)$ flavor symmetry, we also obtain a simple `all-order' 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 ${\tau }_p\sim 10^2{\tau }_p^{SU(5)}$~yr. is compatible with experiments, with the dominant decay being $p\to K{\nu }_{\mu ,\tau }$. Thanks to the SU(6) symmetry, successful unification of the gauge couplings can be retained, and the value of the strong coupling ${\alpha }_s(M_Z)$ can be reduced to $\simeq 0.12$. Finally, we show how to accommodate the solar and atmospheric neutrino data through the bi-maximal neutrino mixing scenario, with maximal vacuum ${\nu }_e-{\nu }_{\mu ,\tau }$ and large angle ${\nu }_{\mu }-{\nu }_{\tau }$ oscillations.

Comments: 20 pp. LATEX. Version with minor corrections accepted for Nucl. Phys. B