arXiv subjects

Otto C. W. Kong

Publications and source records attributed to Otto C. W. Kong.

88 records · Page 5Linked to original sources

arXiv1999

Neutrino Oscillations and Flavor Structure of Supersymmetry without R-Parity

Focusing on a simple three neutrino oscillation scenario motivated by the recent Super-Kamiokande result, we discuss both tree-level and 1-loop contributions to neutrino masses in supersymmetry without R-parity, aiming at discerning the flavor structure issues of the theory. The single-VEV parametrization framework, which allows the first consistent treatment of the bilinear and trilinear R-parity violating terms, and hence the tree and 1-loop contributions, without any assumption on the nature of R-parity violation. Though the very small neutrino masses implies stringent suppressions of the relevant R-parity violating couplings, we show that there is still room for understanding the suppressions as a simple consequence of the general flavor hierarchy.

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arXiv1998

Could the $τ$ be substantially different from $e$ and $μ$ in the supersymmetric standard model?

R-parity stands as an ad hoc assumption in the most popular version of the supersymmetric standard model. More than fifteen years' studies of R-parity violations have been restricted to various limiting scenarios. We illustrate how the single-VEV parametrization provides a workable framework to analyze the phenomenology of the complete theory of supersymmetry without R-parity. In our comprehensive study of various aspects of the resulting leptonic phenomenology at tree-level, we find that the physical $τ$ lepton could actually bear substantial gaugino and higgsino components, making it very different from the $e$ and the $μ$.

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arXiv1998

Gauge Mediated Supersymmetry Breaking and Spontaneous CP Violation as a Solution to the Strong CP Problem

The origin of CP violation is a major mystery, especially in relation to the strong CP problem. CP being a spontaneously broken symmetry could provide an elegant solution. However, such models have difficulty making themselves compatible with low-energy supersymmetry, which is popularly accepted as the solution to the hierarchy problem. We demonstrate that a certain class of low scale supersymmetric ``Nelson-Barr'' type models can solve the strong and supersymmetric CP problems while at the same time generating sufficient weak CP violation in the $K^{0}-\bar{K}^{0}$ system. Gauge-mediated supersymmetry breaking is used to provide the needed squark mass degeneracies and $A$-term proportionalities; though that proves to be still insufficient for a generic Nelson-Barr model. The workable model we consider here, essentially a supersymmetric version of the aspon model, has the Nelson-Barr mass texture enforced by a U(1) gauge symmetry, broken at the TeV scale. The resulting model is predictive with rich phenomenology soon to be available. Feasibility of the model considered is established by a detailed renormalization group studies.

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arXiv1998

Two-Higgs-Doublet-Models and Radiative CP Violation

We discuss the feasibility of spontaneous CP violation being induced by radiative corrections in 2HDM's. Specifically, we analyze the cases of gaugino/higgsino effect on MSSM, and a new model with an extra exotic quark doublet. The new model, while demonstrating well the Georgi-Pais theorem, is also expected to be phenomenlogically interesting.

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arXiv1998

Standard-Model-like Chiral Spectra and the Origin of the Families

We outline our approach to understand the family structure through the idea of a SM-like chiral fermion spectrum, one that is derivable from anomaly cancellation conditions in the same way as the one family SM, under an extended symmetry, which after breaking to the SM symmetry yields the three families as the residual chiral content. An example of a relatively simple scalar sector which gives an acceptable symmetry breaking pattern and naturally hierarchical quark mass matrices is also discussed for a successful $SU(4)_A\otimes SU(3)_C\otimes SU(2)_L\otimes U(1)_X$ model. This is a summary of a seminar given at the 37th IUKT winter school, for the proceedings.

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arXiv1998

A Solution to the Strong CP Problem with Gauge-Mediated Supersymmetry Breaking

We demonstrate that a certain class of low scale supersymmetric ``Nelson-Barr'' type models can solve the strong and supersymmetric CP problems while at the same time generating sufficient weak CP violation in the $K^{0}-\bar{K}^{0}$ system. In order to prevent one-loop corrections to $\barθ$ which violate bounds coming from the neutron electric dipole moment (EDM), one needs a scheme for the soft supersymmetry breaking parameters which can naturally give sufficient squark degeneracies and proportionality of trilinear soft supersymmetry-breaking parameters to Yukawa couplings. We show that a gauge-mediated supersymmetry breaking sector can provide the needed degeneracy and proportionality, though that proves to be a problem for generic Nelson-Barr models. The workable model we consider here has the Nelson-Barr mass texture enforced by a gauge symmetry; one also expects a new U(1) gauge superfield with mass in the TeV range. The resulting model is predictive. We predict a measureable neutron EDM and the existence of extra vector-like quark superfields which can be discovered at the LHC. Because the $3\times 3$ Cabbibo-Kobayashi-Maskawa matrix is approximately real, the model also predicts a flat unitarity triangle and the absence of substantial CP violation in the $B$ system at future $B$ factories. We discuss the general issues pertaining to the construction of such a workable model and how they lead to the successful strategy. A detailed renormalization group study is then used to establish the feasibility of the model considered.

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arXiv1998

A Simple Phenomenological Parametrization of Supersymmetry without R-Parity

We present a parametrization of the supersymmetric standard model without R-parity that permits efficient phenomenological analyses of the full model without a priori assumptions. Under the parametrization, which is characterized by a single vacuum expectation value for the scalar components of the Y=-1/2 superfields, the expressions for tree-level mass matrices are quite simple. They do not involve the trilinear R-parity violating couplings; however, the bilinear μ_i terms do enter and cannot be set to zero without additional assumptions. We set up a framework for doing phenomenology and show some illustrative results for fermion mass matrices and related bounds on parameters. We find in particular that large values of tan(beta) can suppress R-parity violating effects, substantially weakening experimental constraints.

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arXiv1997

On Radiative CP Violation in (Supersymmetric) Two Higgs Doublet Models

We discuss the feasibility of spontaneous CP violation being induced by radiative corrections in 2HDM's, emphasizing on a consistent treatment at 1-loop level. Specifically, we analyze the cases of gaugino/higgsino effect on MSSM, and a new model proposed here with an extra, exotic, quark doublet. The latter model is phenomenologically interesting. One conclusion is that some fine tuning is in general needed for the scenario to work. The case for the new model requires a tree level mass mixing between the two Higgses, which fits in the standard SUSY picture. The fine tuning requires is then very moderate in magnitude and in a way natural.

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arXiv1997

Strong CP and Low-energy Supersymmetry

A spontaneously-broken CP provides an alternative to the KM mechanism for CP violation with the advantage that the strong CP problem is solved. We consider, for such a model with a new gauged U(1), the incorporation of low-energy supersymmetry and find the constraints on alignment and squark degeneracy. The conclusion is that although the $\barθ$ constraints are much less severe than in other generic schemes with supersymmetry breaking and spontaneous CP violation, one restriction remains stronger than needed in the MSSM for suppression of FCNC.

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arXiv1997

Quarks, Squarks and Textures

By studying symmetric mass textures for the up and down quark sectors, and expanding in a small parameter $λ\sim sinθ_C$, bounds are set on entries commonly assumed to vanish. Consequences of a 2 + 1 family structure which can result from horizontal symmetry are examined. Generalizing to squarks, we study suppression of Flavor Changing Neutral Currents by mass degeneracy and/or small mixing angles.

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arXiv1996

A New Approach to the Family Structure

In this letter, we introduce a new approach to formulate the family structure of the standard model. Trying to mimic the highly contrained representation structure of the standard model while extending the symmetry, we propose a $SU(4)\otimes SU(3)\otimes SU(2)\otimes U(1)$ symmetry with a SM-like chiral spectra basically "derived" from the gauge anomaly constraints. Embedding the SM leads to $SU(4)_A\otimes SU(3)_C\otimes SU(2)_L\otimes U(1)_X$ models, which upon the $SU(4)_A\otimes U(1)_X \longrightarrow U(1)_Y$ symmetry breaking, gives the three families naturally as a result. A specific model obtained from the approach is illustrated. The model, or others from our approach, holds promise of a very interesting phenomenology. We sketch some of the results here. An interesting possiblity of supersymmetrizing the model with the EW-Higgses already in the spectrum is noted. A comparison with other approaches is also discussed.

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arXiv1996

The Three Families from $SU(4)_A\otimes SU(3)_C\otimes SU(2)_L\otimes U(1)_X$ SM-like Chiral Models

We give a detailed description of the model construction procedures about our new approach to the family structure of the standard model. SM-like chiral fermion spectra, largely "derivable" from the gauge anomaly constraints, are formulated in a $SU(N)\otimes SU(3)\otimes SU(2)\otimes U(1)$ symmetry framework as an extension of the SM symmetry. The $N=4$ case gives naturally three families as a result, with $U(1)_Y$ nontrivially embedded into the $SU(4)_A\otimes U(1)_X$. Such a spectrum has extra vector-like quarks and leptons. We illustrate how an acceptable symmetry breaking pattern can be obtained through a relatively simple scalar sector which gives naturally hierarchical quark mass matrices. Compatibility with various FCNC constraints and some interesting aspects of the possible phenomenological features are discussed, from a non-model specific perspective. The question of incorporating supersymmetry without putting in the Higgses as extra supermultiplet is also addressed.

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arXiv1996

Horizontal Symmetry for Quark and Squark Masses in Supersymmetric SU(5)

Recent interest in horizontal symmetry model building has been driven mainly by the large top mass and hence strong hierarchy in quark masses, and the possibility of appropriately constrained soft squark mass matrices, in place of an assumed universality condition, for satisfying the relevant FCNC constraints. Here we present the first successful SUSY-$SU(5)$ model that has such a feature. The horizontal symmetry is a gauged $(Q_{12} \times U(1))_H$ ($\subset (SU(2) \times U(1))_H$). All nonrenormalizable terms compatible with the symmetry are allowed in the mass matrix constructions. Charged lepton masses can also be accommodated.

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arXiv1995

Dicyclic Horizontal Symmetry and Supersymmetric Grand Unification

It is shown how to use as horizontal symmetry the dicyclic group $Q_6 \subset SU(2)$ in a supersymmetric unification $SU(5)\otimes SU(5)\otimes SU(2)$ where one $SU(5)$ acts on the first and second families, in a horizontal doublet, and the other acts on the third. This can lead to acceptable quark masses and mixings, with an economic choice of matter supermultiplets, and charged lepton masses can be accommodated.

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arXiv1995

Quark Mass Textures Within a Finite Non-Abelian Dicyclic Group

Using as a flavor symmetry a finite nonabelian dicyclic $Q_{2N}$ group, we show how to derive quark mass matrices with two arrangements of symmetric texture zeros which are phenomenologically viable. Three other such acceptable textures in the recent literature are unattainable in this approach and hence disfavored. We assume massive vector-like fermions and Higgs singlets transforming as judiciously-chosen $Q_{2N}$ doublets and use the tree-level mass generation mechanism of Froggatt and Nielsen.

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arXiv1995

The Light, the Heavy and the Superheavy --- a Nonabelian Flavor Symmetry for the Full Hierarchy

We give a preliminary report of a new quark mass matrix model basing on a $SU(5)\otimes SU(5)\otimes Q_{12}$ symmetry embedding into a fully gauged $SU(5)\otimes SU(5)\otimes SU(2)$.~\cite{fk} The two $SU(5)$'s contain the standard SUSY $SU(5)$ as a diagonal subgroup, while the $Q_{12}$ or $SU(2)$ is horizontal. Starting by assuming a judiciously-chosen set of chiral supermultiplets, and a pattern of spontaneous symmetry breaking, we obtain the low-energy chiral fermions together with a spectrum of superheavy fermions at two different scales. The latter mediate Froggatt-Nielsen tree graphs that give rise to a phenomenologically viable effective quark mass matrix texture. The model is the first example of a nontrivial combination of supersymmetry without R-parity, gauged nonabelian horizontal symmetry and unification/anti-unification. It is expected to have some very interesting features in SUSY-GUT phenomenology.

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