arXiv subjects

Hyung Do Kim

Publications and source records attributed to Hyung Do Kim.

At least 37 records · Page 2Linked to original sources

arXiv2010

Light Higgs Scenario in BMSSM and LEP Precision Data

In this Letter we consider very light Higgs fields in BMSSM(Beyond MSSM). The spectrum below TeV scale is the same as the MSSM but the Higgs potential is modified and is well described in terms of effective dimension five and six operators. A correction from the BMSSM operators allows us to consider new parameter space of Higgs sector which is not allowed in the MSSM. It can be regarded as a constrained version of general 2 Higgs doublet model (2HDM) as long as Higgs sector is concerned. We focus on the possibility that CP odd Higgs (A) mass is about 7 or 8 GeV and charged Higgs mass is comparable to W mass. At the same time one of the CP even Higgs (h) is light enough such that h and A production at the Z pole is kinematically allowed. The tension between forward backward asymmetry of bottom quark Ab_FB measured at LEP and the Standard Model prediction can be ameliorated if bottom quark pair produced from light CP even Higgs is taken into account.

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arXiv2009

Higgs Phenomenology of Scalar Sequestering

The light Higgs mass in the MSSM is highly constrained and is predicted to be close to M_Z which causes a tension between the LEP II Higgs mass bound 114 GeV and the natural electroweak symmetry breaking in the MSSM. The usual way to increase the light CP even Higgs mass was to increase the quartic coupling of the up type Higgs. We point out that the light Higgs mass can be increased by reducing the off-diagonal term in the mass matrix when tan beta is moderate, which is about 5 to 10. As a result no mixing and/or a Higgs mixing angle of the opposite sign arises and the branching ratio of Higgs decay is drastically changed. This is possible in scalar sequestering scenario in which mu parameter can be large independently of the electroweak symmetry breaking. We also discuss the same effect in the BMSSM.

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arXiv2008

Gaugino mass in AdS space

We study supersymmetric QED in AdS4 with massless matter. At 1-loop the ultra-violet regulator of the theory generates a contribution to the gaugino mass that is naively inconsistent with unbroken supersymmetry. We show that this effect, known in flat space as anomaly mediated supersymmetry breaking, is required to cancel an infra-red contribution arising from the boundary conditions in AdS space, which necessarily break chiral symmetry. We also discuss an analogous UV/IR cancellation that is independent of supersymmetry.

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arXiv2007

Natural mu and Bmu in gauge mediation

We propose a natural solution to the mu problem in gauge mediation. It relies on the logarithmic dependence of the effective Kahler potential on the messenger threshold superfield X. Thus, mu and Bmu naturally arise at one and two loops, respectively. Moreover B has the same phase as the gaugino mass and the supersymmetric CP problem is solved as well.

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arXiv2007

Mixed Bino-Wino-Higgsino Dark Matter in Gauge Messenger Models

Almost degenerate bino and wino masses at the weak scale is one of unique features of gauge messenger models. The lightest neutralino is a mixture of bino, wino and higgsino and can produce the correct amount of the dark matter density if it is the lightest supersymmetric particle. Furthermore, as a result of squeezed spectrum of superpartners which is typical for gauge messenger models, various co-annihilation and resonance regions overlap and very often the correct amount of the neutralino relic density is generated as an interplay of several processes. This feature makes the explanation of the observed amount of the dark matter density much less sensitive to fundamental parameters. We calculate the neutralino relic density assuming thermal history and present both spin independent and spin dependent cross sections for the direct detection. We also discuss phenomenological constraints from b to s gamma and muon g-2 and compare results of gauge messenger models to well known results of the mSUGRA scenario.

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arXiv2006

Gauge Messenger Models

We consider gauge messenger models in which X and Y gauge bosons and gauginos are messengers of supersymmetry breaking. In simple gauge messenger models, all the soft parameters except mu and Bmu are calculated in terms of a single scale parameter M_SUSY which is proportional to F/M_GUT. Unique prediction on dark matter in gauge messenger models is discussed. (Based on hep-ph/0601036 and hep-ph/0607169)

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arXiv2006

Mediation of Supersymmetry Breaking in Gauge Messenger Models

We study gauge mediation of supersymmetry breaking in SU(5) supersymmetric grand unified theory with gauge fields as messengers. The generated soft supersymmetry breaking parameters lead to close to maximal mixing scenario for the Higgs mass and highly reduce the fine tuning of electroweak symmetry breaking. All gaugino, squark and slepton masses are determined by one parameter -- the supersymmetry breaking scale. The characteristic features are: negative and non-universal squark and slepton masses squared at the unification scale, non-universal gaugino masses, and sizable soft-trilinear couplings. In this scenario, all soft supersymmetry breaking parameters at the unification scale can be smaller than 400 GeV and all the superpartners can be lighter than 400 GeV and still satisfy all the limits from direct searches for superpartners and also the limit on the Higgs mass. The lightest supersymmetric particle is gravitino or a sizable mixture of bino, wino and higgsino. We also consider a possible contributions from additional messengers in vector-like representations, and a contribution from gravity mediation, which is estimated to be comparable.

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arXiv2006

Radiatively Generated Maximal Mixing Scenario for the Higgs Mass and the Least Fine Tuned Minimal Supersymmetric Standard Model

We argue that given the experimental constraints on the Higgs mass the least fine tuned parameter space of minimal supersymmetric standard model is with negative stop masses squared at the grand unification scale. While stop mass squared is typically driven to positive values at the weak scale, the contribution to the Higgs mass squared parameter from the running can be arbitrarily small, which reduces fine tuning of electroweak symmetry breaking. At the same time the stop mixing is necessarily enhanced and the maximal mixing scenario for the Higgs mass can be generated radiatively even when starting with negligible mixing at the unification scale. This highly alleviates constraints on possible models for supersymmetry breaking in which fine tuning is absent.

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arXiv2005

Hiding An Extra Dimension

We propose a new geometry and/or topology of a single extra dimension whose Kaluza-Klein excitations do appear at much higher scale than the inverse of the length/volume. For a single extra dimenion with volume $Nπρ$ which is made of N intervals with size $πρ$ attached at one point, Kaluza-Klein excitations can appear at $1/ρ$ rather than $1/Nρ$ which can hide the signal of the extra dimenion sufficiently for large N. The geometry considered here can be thought of a world volume theory of self intersecting branes or an effective description of complicated higher dimensional geometry such as Calabi-Yau with genus or multi-throat configurations. This opens a wide new domain of possible compactifications which deserves a serious investigation.

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arXiv2005

Quark and Lepton Masses in 5D SO(10)

We construct a five dimensional supersymmetric SO(10)$\times$D$_3$ grand unified model with an $S^1/(Z_2 \times Z^\prime_2)$ orbifold as the extra dimension. The orbifold breaks half of the supersymmetry and breaks the SO(10) gauge symmetry down to ${\rm SU(4)}_C \times {\rm SU(2)}_L \times {\rm SU(2)}_R$. The Higgs mechanism is used to break the remaining gauge symmetry the rest of the way to the Standard Model. We place matter fields variously in the bulk and on the orbifold fixed points and the resulting massless fields are mixtures between these brane and bulk fields. A chiral adjoint field in the bulk gets a U(1)$_X$ vacuum expectation value, resulting in an $X$-dependent localization of the bulk matter fields and the Standard Model Higgs field. This Higgs field localization allows us to simultaneously explain the hierarchies $m_u < m_d$ and $m_t \gg m_b$. The model uses 11 parameters to fit the 13 independent low energy observables of the quark and charged lepton Yukawa matrices. The model predicts the values of two quark mass combinations, $\f{m_u}{m_c}$ and $m_d m_s m_b$, each of which are predicted to be approximately $1 σ$ above their experimental values. The remaining observables are successfully fit at the 5% level.

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arXiv2005

Electroweak Symmetry Breaking from SUSY Breaking with Bosonic See-Saw Mechanism

We introduce the idea of bosonic see-saw mechanism in analogy with the see-saw mechanism. Bosonic see-saw is a new symmetry breaking mechanism and we apply it to explain electroweak symmetry breaking as an inevitable consequence of supersymmetry breaking. The breaking of electroweak symmetry occurs at tree level once supersymmetry is broken. Absence of color/charge breaking in this model is related to doublet-triplet splitting in grand unified theory. An extension of MSSM with a weak triplet shows very interesting results especially when mu =0. It provides the most natural understanding of why we have only electroweak symmetry breaking rather than having color/charge breaking. In the limit mu=0, the model predicts very light chargino mass, 104 GeV while Higgs is heavy, 130 GeV.

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arXiv2004

A New Mechanism For Baryogenesis Living Through Electroweak Era

We present a new mechanism for baryogenesis by introducing a heavy vector-like SU(2)_W singlet quark(s) with Q_{em}=2/3 quark U or Q_{em}=-1/3 quark D. The lifetime of the heavy quark is assumed to be in the range 2 \times 10^{-11}s < t < 1s. Being SU(2)_W singlet, it survives the electroweak phase transition era. It mixes with SU(2)_W doublet quarks with tiny mixing angles to satisfy the FCNC constraints, where a simple Z_2 symmetry is suggested for realizing this scheme. The heavy quark asymmetry is generated in analogy with the old GUT scenario.

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arXiv2004

Quark Mass Textures and sin 2 beta

Recent precise measurements of sin 2 beta from the B-factories (BABAR and BELLE) and a better known strange quark mass from lattice QCD make precision tests of predictive texture models possible. The models tested include those hierarchical N-zero textures classified by Ramond, Roberts and Ross, as well as any other hierarchical matrix Ansatz with non-zero 12 = 21 and vanishing 11 and 13 elements. We calculate the maximally allowed value for sin 2 beta in these models and show that all the aforementioned models with vanishing 11 and 13 elements are ruled out at the 3 sigma level. While at present sin 2 beta and |Vub/Vcb| are equally good for testing N-zero texture models, in the near future the former will surpass the latter in constraining power.

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arXiv2003

Neutrinos in 5D SO(10) Unification

We study neutrino physics in a 5D supersymmetric SO(10) GUT. We analyze several different choices for realizing the See-Saw mechanism. We find that the "natural" scale for the Majorana mass of right-handed neutrinos depends critically on whether the right-handed neutrinos are located in the bulk or localized on a brane. In the former case, the effective Majorana mass is "naturally" of order the compactification scale, about 10^{14} GeV. Note, this is the value necessary for obtaining a light tau neutrino mass approximately 10^{-2} eV which, within the context of hierarchical neutrino masses, is the right order of magnitude to explain atmospheric neutrino oscillations. On the other-hand when the right-handed neutrino is localized on the brane, the effective Majorana mass is typically larger than the compactification scale. Nevertheless with small parameters of order 1/10 - 1/30, an effective Majorana mass of order 10^{14} GeV can be accommodated. We also discuss the constraints on model building resulting from the different scenarios for locating the right-handed neutrinos.

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arXiv2003

Unification in 5D SO(10)

Gauge unification in a five dimensional supersymmetric SO(10) model compactified on an orbifold $S^1/(Z_2 \times Z_2^{\prime})$ is studied. One orbifolding reduces N=2 supersymmetry to N=1, and the other breaks SO(10) to the Pati-Salam gauge group $\ps$. Further breaking to the standard model gauge group is made through the Higgs mechanism on one of the branes. The differences of the three gauge couplings run logarithmically even in five dimensions and we can keep the predictability for unification as in four dimensional gauge theories. We obtain an excellent prediction for gauge coupling unification with a cutoff scale $M_* \sim 3 \times 10^{17}$ GeV and a compactification scale $M_c \sim 1.5 \times 10^{14}$ GeV. Finally, although proton decay due to dimension 5 operators may be completely eliminated, the proton decay rate in these models is sensitive to the placement of matter multiplets in the 5th dimension, as well as to the unknown physics above the cutoff scale.

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arXiv2002

Radius-dependent gauge unification in AdS5

We examine the relation of the 4-dimensional low energy coupling of bulk gauge boson in a slice of AdS5 to the 5-dimensional fundamental couplings as a function of the orbifold radius R. This allows us to address the gauge coupling unification in AdS5 by means of the radius running as well as the conventional momentum running. We then compute the radius dependence of 1-loop low energy couplings in generic AdS5 theory with 4-dimensional supersymmetry, and discuss the low energy predictions when the 5-dimensional couplings are assumed to be unified.

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arXiv2002

Gauge coupling renormalization in orbifold field theories

We investigate the gauge coupling renormalization in orbifold field theories preserving 4-dimensional N=1 supersymmetry in the framework of 4-dimensional effective supergravity. As a concrete example, we consider the 5-dimensional Super-Yang-Mills theory on a slice of AdS_5. In our approach, one-loop gauge couplings can be determined by the loop-induced axion couplings and the tree level properties of 4-dimensional effective supergravity which are much easier to be computed.

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arXiv2002

Running of Gauge Couplings in AdS5 via Deconstruction

Running of gauge couplings on a slice of AdS5 is examined using the deconstruction set-up. Logarithmic running instead of (linear) power law is justified when the cutoff is lower than the curvature scale. Most of interesting features in warped gauge theory including the localization of Kaluza-Klein modes, the widening of higher Kaluza-Klein spectrum spacing are well captured within the framework of the deconstruction.

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