Proton decay: flipped vs. unflipped SU(5)

We analyze nucleon decay modes in a no-scale supersymmetric flipped SU(5) GUT model, and contrast them with the predictions for proton decays via dimension-6 operators in a standard unflipped supersymmetric SU(5) GUT model. We find that these GUT models make very different predictions for the ratios Γ(p → π⁰μ⁺)/Γ(p → π⁰e⁺), Γ(p →π⁺ν¯)/Γ(p → π⁰e⁺), Γ(p → K⁰e⁺)/Γ(p → π⁰e⁺) and Γ(p → K⁰μ⁺)/Γ(p → π⁰μ⁺), and that predictions for the ratios Γ(p → π⁰μ⁺)/Γ(p → π⁰e⁺) and Γ(p →π⁺ν¯)/Γ(p → π⁰e⁺) also differ in variants of the flipped SU(5) model with normal- or inverse-ordered light neutrino masses. Upcoming large neutrino experiments may have interesting opportunities to explore both GUT and flavour physics in proton and neutron decays.