Related papers: Flavour structure and proton decay in 6D orbifold …
After we study the 6-dimensional ${\cal N} = (1, 1)$ supersymmetry breaking and $R$ symmetry breaking on $M^4\times T^2/Z_n$, we construct two ${\cal N} = (1, 1)$ supersymmetric $E_6$ models on $M^4\times T^2/Z_3$ where $E_6$ is broken down…
Supersymmetric SO(10) grand unified models with renormalizable Yukawa couplings involving {\bf 10}, {\bf 126} and {\bf 120} Higgs fields have been shown to give a very economical theory for understanding quark-lepton flavor in a unified…
We reconsider dimension-five proton decay operators, making semi-quantitative remarks which apply to a large class of supersymmetric GUTs in which the short-distance operators are correlated with the fermion Yukawa couplings. In these GUTs,…
Model building based on abelian quiver gauge theories gives models which resemble trinification, originally proposed with yottavolt unification. However, unification occurs in the teravolt range so proton decay must be completely excluded…
Extensions of the standard model with low-energy supersymmetry generically allow baryon- and lepton-number violating operators of dimension four and five, yielding rapid proton decay. The dimension-four operators are usually forbidden by…
We show that grand unified theories based on SO(10) generate quite naturally baryon number violating dimension seven operators that violate (B-L), and lead to novel nucleon decay modes such as n \to e^-K^+, e^- \pi^+ and p \to \nu \pi^+. We…
We probe the unification of down quarks and leptons in a supersymmetric SO(10) GUT. The large atmospheric neutrino mixing angle induces bR-sR transitions, which can account for the sizeable CP phase measured in Bs-Bsbar mixing. Corrections…
Realistic models based on the renormalizable grand unified theories have varieties of scalars, many of which are capable of mediating baryon ($B$) and lepton ($L$) number non-conserving processes. We identify all such scalar fields residing…
It is shown that by a simple extension of the fermion sector of flipped SU(5) models and other flipped models proton decay coming from dimension-6 operators can be suppressed by fermion mixing angles by an arbitrary amount in a natural way.
We discuss the first string theory examples of three generation non-supersymmetric SU(5) and {\em flipped} SU(5) GUTS, which break to the Standard model at low energy, without extra matter and/or gauge group factors. Our GUT examples are…
After a brief review of the motivations for grand unification, I discuss the main challenges facing realistic SUSY GUT model building. Achieving doublet-triplet splitting without fine--tuning is chief among them. Symmetry breaking should…
We review the current status of the minimal non-supersymmetric SO(10) grand unified theory and perform a detailed next-to-leading-order analysis of the gauge unification and proton lifetime constraints on the part of its parameter space…
I discuss the problem of proton decay, from dimension four, five and six operators, in superstring derived standard--like models. I classify the sectors that produce color triplet superfields which may generate proton decay from dimension…
We provide detailed estimates of the proton lifetime in the context of simple supersymmetric SU(5) grand unified models with an extra compact spatial dimension, described by the orbifold S/(Z_2 x Z_2') and by a large compactification scale…
In a model of supersymmetric SU(5) Grand Unification with a spatial dimension described by the orbifold $S^1/(Z_2 \times Z_2')$, proton decay is naturally suppressed at all orders. This is achieved by a suitable implementation of the…
In the minimal SUSY SU(5) GUT with $O(1)$ TeV SUSY particles and $O(1)$ or below self-coupling for the GUT-breaking Higgs field, the width of the dimension-6 proton decay is suppressed below the reach of Hyper-Kamiokande. In this paper, we…
Orbifold grand unified theories (GUTs) solve several problems in GUT model building. Therefore, it is intriguing to investigate similar constructions in the flavor context. In this paper, we propose that a flavor symmetry might emerge due…
We calculate the high and low scale threshold corrections to the D=6 proton decay mode in supersymmetric SU(5) grand unified theories with higher-dimensional representation Higgs multiplets. In particular, we focus on a missing-partner…
We discuss the proton decay problem in theories with low gravity and/or GUT scales. We pointed out that the gravity induced proton decay can be indeed suppressed up to a desired level, while the GUT origin of the proton instability is…
We propose a natural framework of SU(5) supersymmetric grand unified theory with the minimal particle contents, which does not contain dimension five proton decay operators. The suitable fermion mass hierarchy can be reproduced by higher…