Abstract
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 → {pi}^{+}overline{nu} )/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 → {pi}^{+}overline{nu} )/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.
Highlights
Proton decay is high enough to put pressure on minimal supersymmetric SU(5) [16, 17]
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+) differ in variants of the flipped SU(5) model with normal- or inverse-ordered light neutrino masses
This problem is mitigated by the higher sparticle masses [13, 18,19,20,21,22,23,24,25,26,27,28,29] required by fruitless LHC searches [30,31,32,33,34,35], and dimension-5 proton decay may be suppressed by a discrete symmetry such as the hexality [36] appearing in some stringy extra-dimensional models with local grand unification
Summary
We note that the singlet φ3 can acquire a VEV without spontaneously breaking the modified Rparity In this case, the coupling λ37, which is allowed by the modified R-parity, generates an effective μ term for h and h, μ = λ37 φ3 , just as in the next-to-minimal supersymmetric extension of the SM. The first equation in eq (2.5) is only an approximate expression, since in general renormalization-group effects and threshold corrections cause λ2 to deviate from the up-type Yukawa couplings at low energies Since these effects are at most O(10)% and depend on the mass spectrum of the theory, we neglect them in the following analysis. The GUT scale, the effects of SU(5) gauge boson exchanges are in general described by the dimension-six effective operators
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