R-symmetric flipped SU(5)

We construct a supersymmetric flipped SU(5) grand unified model that possesses an R symmetry. This R symmetry forbids dangerous non-renormalizable operators suppressed by a cut-off scale up to sufficiently large mass dimensions so that the SU(5)-breaking Higgs field develops a vacuum expectation value of the order of the unification scale along the F- and D-flat directions, with the help of the supersymmetry-breaking effect. The mass terms of the Higgs fields are also forbidden by the R symmetry, with which the doublet-triplet splitting problem is solved with the missing partner mechanism. The masses of right-handed neutrinos are generated by non-renormalizable operators, which then yield a light neutrino mass spectrum and mixing through the seesaw mechanism that are consistent with neutrino oscillation data. This model predicts one of the color-triplet Higgs multiplets to lie at an intermediate scale, and its mass is found to be constrained by proton decay experiments to be greater than or similar to 5 x 10(11) GeV. If it is less than or similar to 10(12) GeV, future proton decay experiments at Hyper-Kamiokande can test our model in the p -> pi (0)mu (+) and p -> K-0 mu (+) decay modes, in contrast to ordinary grand unified models where p -> pi (0)e(+) or p -> K+nu is the dominant decay mode. This characteristic prediction for the proton decay branches enables us to distinguish our model from other scenarios.