Proton decay and fermion mass hierarchy

In supersymmetry, there are gauge invariant dimension five proton decay operators which must be suppressed by a mass scale much large than the Planck scale. It is natural to expect that the mechanism which explains the fermion mass hierarchy also suppresses proton decay operators generatedat the cutoff scale. We apply this argument to certain supersymmetric models which generate realistic fermion masses and mixing.

1) In supersymmetric models with U(1) flavor symmetry, we show that unlike the minimal supersymmetric SU(5) model the proton decay mode containing charged lepton can have large branching ratios if the dimension five operators of left-handed type dominate. Measuring the branching ratio of the electron mode to the muon mode may reveal the mechanism of the neutrino mass generation.

2) In the framework of higher dimensional SU(5) theory where chiral multiplets are localized under a kink background, we found a configuration whic yields realistic values of quark masses, mixing angles, CP violation and charged lepton masses and sufficiently small dimension five proton decay operators. Inclusion of SU(5) breaking effects is essential in order to obtain non-vanishing CP phase as well as correct lepton masses.

Refs.:
1) JHEP 0206 (2002) 032, [hep-ph/0203192]
2) hep-ph/0110266