arXiv subjects

Bumseok Kyae

Publications and source records attributed to Bumseok Kyae.

At least 37 records · Page 2Linked to original sources

arXiv2013

Hidden-sector-assisted 125 GeV Higgs boson

In order to significantly raise the mass of the supersymmetry Higgs boson, we consider a radiative correction to it by heavy (\sim 1 TeV) hidden sector fields, which communicate with the Higgs through relatively heavy "messengers" (300-500 GeV). The messenger fields (S, \bar{S}) are coupled to the Higgs ("y_HSH_uH_d," y_H\lesssim 0.7) and also to hidden sector fields with a Yukawa coupling of order unity. The hidden sector fields are assumed to be large representations of a hidden gauge group, and so their scalar partner masses can be heavier than other typical soft scalars in the visible sector. Even with a relatively small y_H (\sim 0.2) or tanβ\sim 10 but without top-stop's considerable contributions, the radiative correction by such hidden sector fields can be enhanced enough to yield the 125 GeV Higgs mass.

hep-ph↗

arXiv2013

Singlet Extension of the MSSM for 125 GeV Higgs Mass with the Least Tuning

In order to raise the Higgs mass up to 125 GeV and relieve the fine-tuning associated with the heavy s-top mass in the minimal supersymmetric standard model (MSSM), we propose a new singlet extension of the MSSM. In this scenario, the additional Higgs mass is radiatively generated also in a hidden sector, and the effect is tansmitted to the Higgs through a messenger field. The Higgs mass can be efficiently increased by the parameters of the superpotential as in the extra matter scenario, but free from the constraints on extra colored matter fields by the LHC experiments. As a result, the tuning problem can be remarkably mitigated by taking low enough messenger mass (\sim 300 GeV) and mass parameter scales (\sim 500 GeV).

hep-ph↗

arXiv2013

130 GeV Fermi gamma-ray line from dark matter decay

The 130 GeV gamma-ray line based on tentative analyses on the Fermi-LAT data is hard to be understood with dark matter annihilation in the conventional framework of the MSSM. We point out that it can be nicely explained with two body decay of a scalar dark matter ($\tildeϕ_{\rm DM}\rightarrowγγ$) by the dimension 6 operator suppressed with the mass of the grand unification scale ($\sim 10^{16}$ GeV), ${\cal L}\supset|\tildeϕ_{\rm DM}|^2F_{μν}F^{μν}/M_{\rm GUT}^2$, in which the scalar dark matter $\tildeϕ_{\rm DM}$ develops a TeV scale vacuum expectation value. We propose a viable model explaining the 130 GeV gamma-ray line.

hep-ph↗

arXiv2012

Spectral Index and Non-Gaussianity in Supersymmetric Hybrid Inflation

We consider a supersymmetric hybrid inflation model with two inflaton fields. The superpotential during inflation is dominated by W=(κS+κ' S')M^2, where S, S' are inflatons carrying the same U(1)_R charge, κ, κ' are dimensionless couplings, and M (\sim 10^{15-16} GeV) is a dimensionful parameter associated with a symmetry breaking scale. One light mass eigenstate drives inflation, while the other heavier mass eigenstate is stuck to the origin. The smallness of the lighter inflaton mass for the scalar spectral index n_s\approx 0.96, which is the center value of WMAP7, can be controlled by the ratio κ'/κthrough the supergravity corrections. We also discuss the possibility of the two field inflation and large non-Gaussianity in this setup.

hep-ph↗

arXiv2012

Primordial curvature perturbation during and at the end of multi-field inflation

We study the generation of the primordial curvature perturbation in multi-field inflation. Considering both the evolution of the perturbation during inflation and the effects generated at the end of inflation, we present a general formula for the curvature perturbation. We provide the analytic expressions of the power spectrum, spectral tilt and non-Gaussianity for the separable potentials of two inflaton scalars, and apply them to some specific models.

astro-ph.CO↗

arXiv2011

Natural Hybrid Inflation Model with Large Non-Gaussianity

We propose an inflationary model ("natural hybrid model"), which combines the supersymmetric hybrid model and the natural inflation model to achieve the spectral index of 0.96, and the axion decay constant smaller than the Planck scale, f<< M_P. By introducing both U(1)_R and a shift symmetry and employing the minimal Kahler potential, the eta-problem can be still avoided. The two inflaton fields in this model can admit large non-Gaussianity.

astro-ph.CO↗

arXiv2011

Weak Mixing Angle and Proton Stability in F-theory GUT

It is pointed out that a class of flipped SU(5) models based on F-theory naturally explains the gauge coupling unification. It is because the group SU(5) x U(1)_X is embedded in SO(10) and E_8. To prohibit the dimension 4 and 5 proton decay processes, the structure group should be SU(3) or smaller. Extra heavy vector-like pairs of {5_{-2},5*_2} except only one pair of Higgs should be also disallowed, because they could induce the unwanted dimension 5 proton decays. We construct a simple global F-theory model considering these points. To maintain sin^2 theta_W^0 = 3/8 at the GUT scale, the fluxes are turned-on only on the flavor branes.

hep-th↗

arXiv2010

PAMELA's cosmic positron from decaying LSP in SO(10) SUSY GUT

We propose two viable scenarios explaining the recent observations on cosmic positron excess. In both scenarios, the present relic density in the Universe is assumed to be still supported by thermally produced WIMP or LSP (χ). One of the scenarios is based on two dark matter (DM) components (χ,X) scenario, and the other is on SO(10) SUSY GUT. In the two DM components scenario, extremely small amount of non-thermally produced meta-stable DM component [O(10^{-10}) < n_X /n_χ] explains the cosmic positron excess. In the SO(10) model, extremely small R-parity violation for LSP decay to e^\pm is naturally achieved with a non-zero VEV of the superpartner of one right-handed neutrino (\tildeν^c) and a global symmetry.

hep-ph↗

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.

hep-ph↗

arXiv2009

Decaying LSP in SO(10) GUT and PAMELA's Cosmic Positron

We suppose that the lightest supersymmetric particle (LSP) in the minimal supersymmetric standard model (MSSM) is the dark matter. The bino-like LSP can decay through the SO(10) gauge interactions, if one right-handed (RH) neutrino (ν^c_1) is lighter than the LSP and its superpartner (\tildeν^c_1) develops a vacuum expectation value (VEV), raising extremely small R-parity violation naturally. The leptonic decay modes can be dominant, if the VEV scale of {\bf 16}_H is a few orders of magnitude lower than the VEV of {\bf 45}_H (\approx 10^{16} GeV), and if a slepton (\tilde{e}^c_1) is relatively lighter than squarks. The desired decay rate of the LSP, Γ_χ \sim 10^{-26} sec.^{-1} to explain PAMELA data can be naturally achieved, because the gaugino mediating the LSP decay is superheavy. From PAMELA data, the SU(3)_c x SU(2)_L x SU(2)_R x U(1)_{B-L} breaking scale (or the {\bf 16}_H VEV scale) can be determined. A global symmetry is necessary to suppress the Yukawa couplings between one RH (s)neutrino and the MSSM fields. Even if one RH neutrino is quite light, the seesaw mechanism providing the extremely light three physical neutrinos and their oscillations is still at work.

hep-ph↗

arXiv2009

PAMELA/ATIC anomaly from the meta-stable extra dark matter component and the leptophilic Yukawa interaction

We present a supersymmetric model with two dark matter (DM) components explaining the galactic positron excess observed by PAMELA/HEAT and ATIC/PPB-BETS: One is the conventional (bino-like) lightest supersymmetric particle (LSP) χ, and the other is a TeV scale meta-stable neutral singlet N_D, which is a Dirac fermion (N,N^c). In this model, N_D decays dominantly into χe^+e^- through an R parity preserving dimension 6 operator with the life time τ_N\sim 10^{26} sec. We introduce a pair of vector-like superheavy SU(2) lepton doublets (L,L^c) and lepton singlets (E,E^c). The dimension 6 operator leading to the N_D decay is generated from the leptophilic Yukawa interactions by W\supset Ne^cE+Lh_dE^c+m_{3/2}l_1L^c with the dimensionless couplings of order unity, and the gauge interaction by {\cal L}\supset \sqrt{2} g'\tilde{e}^{c*}e^cχ+ h.c. The superheavy masses of the vector-like leptons (M_L, M_E\sim 10^{16} GeV) are responsible for the longevity of N_D. The low energy field spectrum in this model is just the MSSM fields and N_D. Even for the case that the portion of N_D is much smaller than that of χin the total DM density [{\cal O}(10^{-10}) \lesssim n_{N_D}/n_χ], the observed positron excess can be explained by adopting relatively lighter masses of the vector-like leptons (10^{13} GeV \lesssim M_{L,E} \lesssim 10^{16} GeV). The smallness of the electron mass is also explained. This model is easily embedded in the flipped SU(5) grand unification, which is a leptophilic unified theory.

hep-ph↗

arXiv2009

PAMELA/ATIC Anomaly from Exotic Mediated Dark Matter Decay

We discuss dark matter decay mediated by exotically charged particles ("exotics") in a supersymmetric model with two dark matter (DM) components: One is the (bino-like) lightest supersymmetric particle (LSP) χ, and the other is a newly introduced meta-stable neutral singlet $N$. $N$ decays to χe^+e^- via a dimension 6 operator induced by a penguin-type one loop diagram with the life time of 10^{26} sec., explaining energetic cosmic e^\pm excess observed recently by PAMELA and ATIC/PPB-BETS. The superheavy masses of exotics (\sim 10^{15-16} GeV) are responsible for the longevity of $N$. The superpartner of $N$ develops the vacuum expectation value (VEV) of order TeV so that the DM $N$ achieves the desired mass of 2 TeV. By the VEV, the U(1)_R symmetry is broken to the discrete Z_2 symmetry, which is identified with the matter parity in the minimal supersymmetric standard model (MSSM). Since we have the two DM components, even extremely small amount of $N$ [O(10^{-10}) < (n_N/n_χ)] could account for the observed positron flux with relatively light exotics' masses [10^{12} GeV < M_{exo.} < 10^{16} GeV].

hep-ph↗

arXiv2009

SU(5)_{flip} x SU(5)' from Z_{12-I}

Based on the Z_{12-I} orbifold compactification of the heterotic string theory, we construct a flipped-SU(5) model with three families of the standard model matter and ingredients for dynamical supersymmetry breaking. The doublet-triplet splittings in the Higgs representations 5_{-2} and \bar{5}_{2} are achieved by the couplings 10_{1}10_{1}5_{-2} and \bar{10}_{-1}\bar{10}_{-1}\bar{5}_{2}, where 10_{1} and \bar{10}_{-1} develop GUT scale vacuum expectation values, breaking the flipped-SU(5) down to the standard model gauge group. In this model, all the exotic states are decoupled from the low energy physics, and sin^2θ_W^0=3/8. Above the compactification scale, the flipped-SU(5) gauge symmetry is enhanced to the SO(10) gauge symmetry by including the Kaluza-Klein (KK) modes. The hidden sector gauge group is SU(5)'. The threshold correction by the KK modes allow a very wide range for the hidden sector confining scale (10^{11} GeV -- 10^{16} GeV). One family of hidden matter (\bar{10}' and 5') gives rise to dynamical supersymmetry breaking.

hep-ph↗

arXiv2009

The minimal two DM components with SUSY

We present the dark matter extension of the minimal supersymmetric standard model by one more two component stable fermion N toward explaining the recent rising high energy positron spectrum of the PAMELA data. The needed coupling can arise in the flipped-SU(5) GUT.

hep-ph↗

arXiv2009

White dwarf axions, PAMELA data, and flipped-SU(5)

Recently, there are two hints arising from physics beyond the standard model. One is a possible energy loss mechanism due to emission of very weakly interacting light particles from white dwarf stars, with a coupling strength ~ 0.7x10^{-13}, and another is the high energy positrons observed by the PAMELA satellite experiment. We construct a supersymmetric flipped-SU(5) model, SU(5)xU(1)_X with appropriate additional symmetries, [U(1)_H]_{gauge}x[U(1)_RxU(1)_Γ]_{global}xZ_2, such that these are explained by a very light electrophilic axion of mass 0.5 meV from the spontaneously broken U(1)_Γand two component cold dark matters from Z_2 parity. We show that in the flipped-SU(5) there exists a basic mechanism for allowing excess positrons through the charged SU(2) singlet leptons, but not allowing anti-proton excess due to the absence of the SU(2) singlet quarks. We show the discovery potential of the charged SU(2) singlet E at the LHC experiments by observing the electron and positron spectrum. With these symmetries, we also comment on the mass hierarchy between the top and bottom quarks.

hep-ph↗

arXiv2009

Two dark matter components in N_{DM}MSSM and dark matter extension of the minimal supersymmetric standard model and the high energy positron spectrum in PAMELA/HEAT data

We present the dark matter (DM) extension (by N) of the minimal supersymmetric standard model to give the recent trend of the high energy positron spectrum of the PAMELA/HEAT experiments. If the trend survives by future experiments, the MSSM needs to be extended. Here, we minimally extend the MSSM with one more DM component N together with a heavy lepton E, and introduce the coupling e_R E_R^c N_R. This coupling naturally appears in the flipped SU(5) GUT models. This N_{DM}MSSM contains the discrete symmetry Z_6, and for some parameter ranges there result two DM components. For the MSSM fields, the conventional R-parity, which is a subgroup of Z_6, is preserved. We also present the needed parameter ranges of these additional particles.

hep-ph↗

arXiv2008

Orbifold SUSY GUT from the Heterotic String

From the string partition function, we discuss the mass-shell and GSO projection conditions valid for Kaluza-Klein (KK) as well as massless states in the heterotic string theory compactified on a nonprime orbifold. Based on the obtained conditions we construct a 4D string standard model, which is embedded in a 6D SUSY GUT by including KK states above the compactification scale. We discuss the stringy threshold corrections to gauge couplings, including the Wilson line effects.

hep-ph↗

arXiv2008

Kaluza-Klein masses in nonprime orbifolds: Z(12-I) compactification and threshold correction

Analyzing the one-loop partition function, we discuss possible Kaluza-Klein (KK) states in the orbifold compactification of the heterotic string theory, toward the application to the threshold correction. The KK massive states associated with (relatively) large extra dimensions can arise only in non-prime orbifolds. The GSO projection condition by a shift vector $V^I$ is somewhat relaxed above the compactification scale 1/R. We also present the other condition on Wilson line $W$, $P\cdot W={\rm integer}$. With the knowledge of the partition function, we obtain the threshold corrections to gauge couplings, which include the Wilson line effects. We point out the differences in string and field theoretic orbifolds.

hep-th↗