Renormalizable SUSY SO Research Articles

Conditions for suppressing dimension-five proton decay in renormalizable SUSY SO(10) GUT

The SUSY SO(10) GUT is in severe tension with the experimental bounds on proton partial lifetimes because proton decay mediated by colored Higgsinos (dimension-five proton decay) is too rapid. In this paper, we pursue the possibility that a texture of the Yukawa coupling matrices in a renormalizable SUSY SO(10) GUT model suppresses dimension-five proton decay. We focus on a general renormalizable SUSY SO(10) GUT model which contains 10 + 126 + overline{textbf{126}} + 120 representation fields and where the Yukawa coupling matrices of the 16 matter fields with the 10, overline{textbf{126}} , 120 fields, Y10, Y126, Y120, provide the quark and lepton Yukawa couplings and Majorana mass of the singlet neutrinos. We find that if components in certain flavor bases, {left({Y}_{10}right)}_{u_R{d}_R} , {left({Y}_{126}right)}_{u_R{d}_R} , {left({Y}_{10}right)}_{u_R{s}_R} , {left({Y}_{126}right)}_{u_R{s}_R} , {left({Y}_{10}right)}_{u_L{d}_L} , {left({Y}_{126}right)}_{u_L{d}_L} , {left({Y}_{10}right)}_{u_L{s}_L} , {left({Y}_{126}right)}_{u_L{s}_L} , {left({Y}_{10}right)}_{u_L{u}_L} , {left({Y}_{126}right)}_{u_L{u}_L} , are all on the order of the up quark Yukawa coupling, dimension-five proton decay can be suppressed while the Yukawa coupling matrices still reproduce the realistic quark and lepton masses and flavor mixings. We numerically obtain specific Yukawa coupling matrices satisfying the above conditions, calculate proton partial lifetimes from them and evaluate how dimension-five proton decay is suppressed when these conditions are met.

Peccei-Quinn symmetry and nucleon decay in renormalizable SUSY SO(10)

We suggest simple ways of implementing Peccei-Quinn (PQ) symmetry to solve the strong CP problem in renormalizable SUSY SO(10) models with a minimal Yukawa sector. Realistic fermion mass generation requires that a second pair of Higgs doublets survive down to the PQ scale. We show how unification of gauge couplings can be achieved in this context. Higgsino mediated proton decay rate is strongly suppressed by a factor of (MPQ/MGUT)2, which enables all SUSY particles to have masses of order TeV. With TeV scale SUSY spectrum, pto overline{v}{K}^{+} decay rate is expected to be in the observable range. Lepton flavor violating processes μ → eγ decay and μ − e conversion in nuclei, induced by the Dirac neutrino Yukawa couplings, are found to be within reach of forthcoming experiments.

Goldstone modes in renormalizable supersymmetric SO(10) model

We solve the Goldstone modes in the renormalizable SUSY SO(10) model with general couplings. The Goldstones are expressed by the Vacuum Expectation Values and the Clebsch–Gordan coefficients of relevant symmetries without explicit dependence on the parameters of the model.

Examining a renormalizable supersymmetric SO(10) model

We examine a renormalizable SUSY SO(10) model without fine-tuning. We show how to construct MSSM doublets and to predict proton decay. We find that in the minimal set of Yukawa couplings the model is consistent with the experiments, while including 120_H to fit the data there are inconsistencies.

Spontaneous CP violation in SUSY [formula omitted

A scenario is suggested for spontaneous CP violation in non-SUSY and SUSY SO ( 10 ) . The idea is to have a scalar potential which generates spontaneously a phase, at the high scale, in the VEV that gives a mass to the RH neutrinos. As a possible realization the case of the minimal renormalizable SUSY SO ( 10 ) is discussed in detail and one finds that a phase is induced in the CKM matrix. It is also pointed out that, in these models, the scales of Baryogenesis, Seesaw, Spontaneous CP violation and Spontaneous U ( 1 ) PQ breaking are all of the same order of magnitude.

A renormalizable SO(10) GUT scenario with spontaneous CP violation

We consider fermion masses and mixings in a renormalizable SUSY SO(10) GUT with Yukawa couplings of scalar fields in the representation \(\mathbf{10}\oplus\mathbf{120}\oplus\overline{\mathbf{126}}\). We investigate a scenario defined by the following assumptions. (i) We have a single large scale in the theory, the GUT scale. (ii) The small neutrino masses are generated by the type I seesaw mechanism with negligible type II contributions. (iii) We assume a suitable form of spontaneous CP breaking that induces hermitian mass matrices for all fermion mass terms of the Dirac type. Our assumptions define an 18-parameter scenario for the fermion mass matrices for 18 experimentally known observables. Performing a numerical analysis, we find excellent fits to all observables in the case of both the normal and inverted neutrino mass spectrum.

Fermion masses and mixings inSO(10)models and the neutrino challenge to supersymmetric grand unified theories

We present a detailed study of the quark and lepton mass spectra in a SO(10) framework with one 10_H and one \bar{126}_H Higgs representations in the Yukawa sector. We consider in full generality the interplay between type-I and type-II seesaws for neutrino masses. We first perform a \chi^2 fit of fermion masses independent on the detailed structure of the GUT Higgs potential and determine the regions in the parameter space that are preferred by the fermion mass sum rules. We then apply our study to the case of the minimal renormalizable SUSY SO(10) GUT with one 10_H, one \bar{126}_H, one 126_H, and one 210_H Higgs representations. By requiring that proton decay bounds are fulfilled we identify a very limited area in the parameter space where all fermion data are consistently reproduced. We find that in all cases gauge coupling unification in the supersymmetric scenario is severely affected by the presence of lighter than GUT (albeit B-L conserving) states. We then conclusively show that the minimal supersymmetric SO(10) scenario here considered is not consistent with data. The fit of neutrino masses with type-I and type-II seesaws within a renormalizable SO(10) framework strongly suggests a non-SUSY scenario for gauge unification.

CPviolation in a minimal renormalizable supersymmetricSO(10)model and beyond

We investigate the role of CP phases within the renormalizable SUSY SO(10) GUT with one 10_H, one 126bar_H one 126_H and one 210_H Higgs representations and type II seesaw dominating the neutrino mass matrix. This framework is non trivially predictive in the fermionic sector and connects in a natural way the GUT unification of b and tau Yukawa couplings with the bi-large mixing scenario for neutrinos. On the other hand, existing numerical analysis claim that consistency with quark and charged lepton data prevents the minimal setup from reproducing the observed CP violation via the Cabibbo-Kobayashi-Maskawa (CKM) matrix. We re-examine the issue and find by inspection of the fermion mass sum rules and a detailed numerical scan that, even though the CKM phase takes preferentially values in the second quadrant, the agreement of the minimal model with the data is actually obtained in a non negligible fraction of the parameter space. We then consider a recently proposed renormalizable extension of the minimal model, obtained by adding one chiral 120-dimensional Higgs supermultiplet. We show that within such a setup the CKM phase falls naturally in the observed range. We emphazise the robust predictivity of both models here considered for neutrino parameters that are in the reach of ongoing and future experiments.

Proton decay in a minimal SUSY SO(10) model for neutrino mixings

A minimal renormalizable SUSY SO(10) model with B–L symmetry broken by 126 Higgs field has recently been shown to predict all neutrino mixings and the ratio Δm2⊙/Δm2A in agreement with observations. Unlike models where B–L is broken by 16 Higgs, this model guarantees automatic R-parity conservation and hence a stable dark matter as well as the absence of dim=4 baryon violating operator without any additional symmetry assumptions. In this paper, we discuss the predictions of the model for proton decay induced at the GUT scale. We scan over the parameter space of the model allowed by neutrino data and find upper bounds on the partial lifetime for the modes τ(n→π0ν̄)=2τ(p→π+ν̄)⩽(5.7−13)×1032 yrs and τ(n→K0ν̄)⩽2.97×1033 yrs for the average squark mass of a TeV and wino mass of 200 GeV, when the parameters satisfy the present lower limits on τ(p→K+ν̄) mode. These results can be used to test the model.

Gauge mediated proton decay in a renormalizable SUSY SO(10) with realistic mass matrices

Proton decay via d=5 operators is excluded by now not only in the framework of SUSY SU(5) but also its extensions like SUSY SO(10) are on the verge of being inconsistent with d=5 decays. It is reasonable therefore to suppress, e.g. by a symmetry, the d=5 operators and to consider gauge boson induced d=6 decays. This is suggested in several recent papers in the framework of models with a lighter $ M_X$. We discuss here explicitly the fermionic sector of such a renormalizable SUSY SO(10) with realistic mass matrices. We find that the recently ``observed'' large leptonic mixing leads to an enhancement of the nucleon decay channels involving $\mu$'s and in particular the $\mu^+\pi^o$, $\mu^+\pi^-$ modes.