arXiv subjects

Jihn E. Kim

Publications and source records attributed to Jihn E. Kim.

At least 91 records · Page 5Linked to original sources

arXiv2013

General self-tuning solutions and no-go theorem

We consider brane world models with one extra dimension. In the bulk there is in addition to gravity a three form gauge potential or equivalently a scalar (by generalisation of electric magnetic duality). We find classical solutions for which the 4d effective cosmological constant is adjusted by choice of integration constants. No go theorems for such self-tuning mechanism are circumvented by unorthodox Lagrangians for the three form respectively the scalar. It is argued that the corresponding effective 4d theory always includes tachyonic Kaluza-Klein excitations or ghosts. Known no go theorems are extended to a general class of models with unorthodox Lagrangians.

hep-th↗

arXiv2012

Axino mass

I will talk on my recent works. Axino, related to the SUSY transformation of axion, can mix with Goldstino in principle. In this short talk, I would like to explain what is the axino mass and its plausible mass range. The axino mass is known to have a hierarchical mass structure depending on accidental symmetries. With only one axino, if G_A=0 where G=K+ 2ln|W|, we obtain axino mass= gravitino mass. For G_A nonzero, the axino mass depends on the details of the Kaehler potential. I also comment on the usefulness of a new parametrization of the CKM matrix.

hep-ph↗

arXiv2012

Effective SUSY modified after LHC run

Some supersymmetric models after the recent LHC reports are discussed. Especially, the light Higgs boson around 125GeV is attempted to be accommodated. An extra Z' from GUTs, and the scalar and pseudoscalar Higgs bosons in supersymmetric extension of the standard model are also discussed.

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arXiv2012

Inverted effective SUSY with combined Z' and gravity mediation, and muon anomalous magnetic moment

Effective supersymmetry(SUSY) where stop is the lightest squark may run into a two-loop tachyonic problem in some Z' mediation models. In addition, a large A term or/and a large stop mass are needed to have about a 126 GeV Higgs boson with three families of quarks and leptons. Thus, we suggest an inverted effective SUSY(IeffSUSY) where stop mass is larger compared to those of the first two families. In this case, it is possible to have a significant correction to the anomalous magnetic moment of muon. A three family IeffSUSY in a Z' mediation scenario is explicitly studied with the Z' quantum number related to B-L. Here, we adopt both the Z' mediation and gravity mediation where the Z' mediation is the dominant one for stop, while the gravity mediation is the dominant one for the muonic leptons and Higgs multiplets. We present a numerical study based on a specific anomaly free model, and show the existence of the parameter region where all the phenomenological conditions are satisfied.

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arXiv2012

Singlet superfield extension of the minimal supersymmetric standard model with Peccei-Quinn symmetry and a light pseudoscalar Higgs boson at the LHC

Motivated by the mu-problem and the axion solution to the strong CP-problem, we extend the MSSM with one more chiral singlet field $X_e$. The underlying PQ-symmetry allows only one more term $X_e H_u H_d$ in the superpotential. The spectrum of the Higgs system includes a light pseudoscalar $a_X$ (in addition to the standard CP-even Higgs boson), predominantly decaying to two photons: $a_X \to γγ$. Both Higgs bosons might be in the range accessible to current LHC experiments.

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arXiv2012

Mixing of axino and goldstino, and axino mass

Axino, related to the SUSY transformation of axion, can mix with goldstino in principle. This case is realized when some superfields carrying nonvanishing Peccei-Quinn charges develop both scalar VEVs and F-terms. In this case, we present a proper definition of axion and axino. With this definition, we present the QCD axino mass in the most general framework, including non-minimal Kähler potential. The axino mass is known to have a hierarchical mass structure depending on accidental symmetries. With only one axino, if $G_A=0$ where $G=K+\ln|W|^2$, we obtain $m_{\tilde a}=m_{3/2}$. For $G_A\ne 0$, the axino mass depends on the details of the Kähler potential. In the gauge mediation scenario, the gaugino mass is the dominant axino mass parameter. Therefore, we can take the theoretical QCD axino mass as a free parameter in the study of its cosmological effects, ranging from eV to multi-TeV scales, without a present knowledge on its ultraviolet completion.

hep-ph↗

arXiv2012

Axino Cold Dark Matter Revisited

Axino arises in supersymmetric versions of axion models and is a natural candidate for cold or warm dark matter. Here we revisit axino dark matter produced thermally and non-thermally in light of recent developments. First we discuss the definition of axino relative to low energy axion one for several KSVZ and DFSZ models of the axion. Then we review and refine the computation of the dominant QCD production in order to avoid unphysical cross-sections and, depending on the model, to include production via SU(2) and U(1) interactions and Yukawa couplings.

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arXiv2012

Z' from SU(6)$\times$SU(2)_h GUT, Wjj anomaly and Higgs boson mass bound

A general electroweak scale $Z'$ is applied in a supersymmetric SU(6)$\timesSU(2)_h$ grand unification model, to have a $\Z_6$ for the hexality. We briefly show that there cannot exist any baryonic U(1)$'_B$ in any subgroup of E$_6$. Any effect that requires sizable $Z'$ couplings to quarks like the reported Wjj anomaly of CDF, if observed, implies a substantial $Z'$ coupling to leptons or Higgs doublets. The kinetic mixing considered in a supersymmetric model from E$_6$ is restricted by the gauge coupling unification and neutrino mixing. The mass of $Z'$ is strongly constrained by the electroweak $ρ_0$ parameter. We conclude that $Z'$ mass much above 10 TeV is favored by considering the neutrino mixing and proton decay constraint in supersymmetric models. In this sense, the CDF $Wjj$ anomaly cannot be fitted to any electroweak model descending from E$_6$. Furthermore, if $Z'$ is found at several hundred GeV, any grand unification group embedded in E$_6$ such as SU(6)$\times$SU(2), SO(10), SU(5)$\times$U(1), SU(5), SU(4)$\times$SU(4), and SU(3)$^3$, needs fine-tuned gauge couplings. We also discuss the U(1)$'$ effect on the tree level mass of the lightest MSSM Higgs boson.

hep-ph↗

arXiv2012

A simple expression of the Jarlskog determinant

Making the whole determinant of the CKM matrix V real, the imaginary part of any one term of the determinant of V (e. g. |Im V_{31}V_{22}V_{13}|) is the Jarlskog determinant J. We also point out that the maximality of the weak CP violation is a physical statement

hep-ph↗

arXiv2011

The CKM matrix with maximal CP violation from Z(12) symmetry

The recent accurate determination of the CKM parameters including the maximal CP phase 90 degrees enables us to write down the up-type and down-type quark mass matrices to a high degree of accuracy. The lightest element(the uu element) of the quark mass texture (not the mass eigenvalue) has a power lambda**6 where lambda=sin(Cabibbo angle). The CP phase of 360 degrees divided by an integer hints a discrete symmetry. Since lambda**6 is the highest power among the quark mass matrix elements, we present as an example a possibility that the maximal CP phase 90 degrees is obtainable from a supersymmetric Z(12) discrete symmetry model.

hep-ph↗

arXiv2011

Gauge mediation to effective SUSY through U(1)s with a dynamical SUSY breaking, and string compactification

We investigate the possibility of U(1)' mediation, leading to an effective SUSY where the first two family sfermions are above 100 TeV but the third family sfermions and the Higgs doublets are in the TeV region(or the light stop case). The U(1)' gaugino, Zprimino, needs not to be at a TeV scale, but needs to be somewhat lighter than the messenger scale. We consider two cases, one the mediation is only through U(1)' and the other through U(1)' and the electroweak hypercharge U(1)_Y. In the SUSY field theory framework, we calculate the superpartner mass spectra for these two cases. We also point out that the particle species needed for these mechanisms are already obtained from a Z(12-I) orbifold compactification.

hep-ph↗

arXiv2011

Parametrization of PMNS matrix based on dodeca-symmetry

The dodeca symmetry is designed to obtain the Cabibbo angle $θ_C^{\rm CKM}$ approximately $15^{\rm o}$ and the (11) element of $\Vp$ as $\cos 30^{\rm o}$, leading to $θ_1^{\rm PMNS}+θ_C^{\rm CKM}\simeq 45^{\rm o}$. This leading order dodeca symmetric $\Vp$ is corrected by small parameters, especially as an expansion in terms of a small parameter $β$. Neglecting two Majorana phases, the expression of $\Vp$ contains four parameters: a small $β$, and three $\Od(1)$ parameters $A,B,$ and $δ$. From the neutrino oscillation data, we present two parametrizations and estimate their $β$'s.

hep-ph↗

arXiv2011

An exact CKM matrix related to the approximate Wolfenstein form

Noting the hierarchy between three mixing angles, $θ_{2,3}={\cal O}(θ_1^2)$, we present an exact form of the quark mixing matrix, replacing Wolfenstein's approximate form. In addition, we suggest to rotate the unitarity triangle, using the weak CP phase convention where the phase is located at the (31) element $\sinθ_1\sinθ_2 e^{iδ}$ while the (13) element $\sinθ_1\sinθ_3$ is real. For the $(ab)$ unitarity triangle, the base line (x-axis) is defined from the product of the first row elements, $V_{1a}V^*_{1b}$, and the angle between two sides at the origin is defined to be the phase $δ$. This is a useful definition since every Jarlskog triangle has the angle $δ$ at the origin, defined directly from the unitarity condition. It is argued that $δ$ represents the barometer of the weak CP violation, which can be used to relate it to possible Yukawa textures.

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arXiv2011

Supersymmetric three family chiral SU(6) grand unification model from F-theory

We obtain a supersymmetric three family chiral SU(6) grand unification model with the global family symmetry SU(3)[family] from F-theory. This model has nice features such as all the fermion masses are reasonably generated and there results only one pair of Higgs doublets, realizing the doublet-triplet splitting from the family symmetry SU(3)[family]. The proton hexality is realized toward the proton stability problem. There is a room to fit the three gauge couplings using the F-theory flux idea and we obtain the proton lifetime in the 10^{36-37} yr region.

hep-ph↗

arXiv2011

Quark and lepton mixing angles with a dodeca-symmetry

The discrete symmetry D_12 at the electroweak scale is used to fix the quark and lepton mixing angles. At the leading order, the Cabbibo angle theta_C is 15^o, and the PMNS matrix is of a bi-dodeca-mixing form giving the Solar-neutrino angle theta_sol=30^o. Thus, there results the relation theta_sol+theta_C ~ 45^o. Out of discrete vacua, a certain vacuum is chosen for this assignment to be consistent with the dodeca-symmetry. A shift of theta_C from 15^o to 13.14^o might arise from a small breaking of the dodeca-symmetry. The spontaneous breaking leading to the required electroweak vacuum is made possible by introducing an additional parity in an effective field approach or by realizing the electroweak dodeca-symmetry explicitly at a high energy scale. At the vacuum we chose Arg.Det.M_q is nonzero, and hence a solution of the strong CP problem invites a very light axion at a high energy scale. We also comment how the next level corrections can fit the mixing angles to the observed values.

hep-ph↗

arXiv2011

The D0 same-charge dimuon asymmetry and possibile new CP violation sources in the $B_s-\bar{B}_s$ system

Recently, the D0 collaboration reported a large CP violation in the same-sign dimuon charge asymmetry which has the $3.2 σ$ deviation from the value estimated in the Standard Model. In this paper, several new physics models are considered: the MSSM, two Higgs doublet model, the recent dodeca model, and a new $Z'$ model. Generally, it is hard to achieve such a large CP violation consistently with other experimental constraints. We find that a scheme with extra non-anomalous U(1)$'$ gauge symmetry is barely consistent. In general, the extra $Z'$ gauge boson induces the flavor changing neutral current interactions at tree level, which is the basic reason allowing a large new physics CP violation. To preserve the U(1)$'$ symmetry at high energy, SU(2)$_L$ singlet exotic heavy quarks of mass above 1 TeV and the Standard Model gauge singlet scalars are introduced.

hep-ph↗

arXiv2010

Self-tuning of the cosmological constant

Here, I discuss the cosmological constant (CC) problems, in particular paying attention to the vanishing cosmological constant. There are three cosmological constant problems in particle physics. Hawking's idea of calculating the probability amplitude for our Universe is peaked at CC = 0 which I try to obtain after the initial inflationary period using a self-tuning model. I review what has been discussed on the Hawking type calculation, and present a (probably) correct way to calculate the amplitude, and show that the Kim-Kyae-Lee self-tuning model allows a finite range of parameters for the CC = 0 to have a singularly large probability, approached from the AdS side.

hep-th↗

arXiv2010

Constraining WIMP magnetic moment from CDMS II experiment

We consider a degenerate or a nearly degenerate dark matter sector where a sizable magnetic moment of an almost Dirac type neutral dark matter candidate N is anticipated. Then, due to soft photon exchange, the cross-section in direct detection of N can be enhanced at low Q^2 region. We discuss the implication of this type of models in view of the recent CDMS II report.

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