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 → π$^{0}$μ$^{+}$)/Γ(p → π$^{0}$e$^{+}$), Γ(p →$ {\pi}^{+}\overline{\nu} $)/Γ(p → π$^{0}$e$^{+}$), Γ(p → K$^{0}$e$^{+}$)/Γ(p → π$^{0}$e$^{+}$) and Γ(p → K$^{0}$μ$^{+}$)/Γ(p → π$^{0}$μ$^{+}$), and that predictions for the ratios Γ(p → π$^{0}$μ$^{+}$)/Γ(p → π$^{0}$e$^{+}$) and Γ(p →$ {\pi}^{+}\overline{\nu} $)/Γ(p → π$^{0}$e$^{+}$) 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.