Bumseok Kyae

130 GeV Fermi gamma-ray line from dark matter decay

Abstract 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 ( ϕ ˜ DM → γ γ ) by the dimension 6 operator suppressed with the mass of the grand unification scale ( ∼ 10 16 GeV ), L ⊃ | ϕ ˜ DM | 2 F μ ν F μ ν / M GUT 2 , in which the scalar dark matter ϕ ˜ DM develops a TeV scale vacuum expectation value. We propose a viable model explaining the 130 GeV gamma-ray line.

Light dark matter for Fermi-LAT and CDMS observations

Abstract Light fermionic/scalar dark matter (DM) ( m DM ≈ 8 GeV ) neutral under the standard model can be responsible for the CDMS and CoGeNT signals, and the Fermi-LAT gamma-ray excesses. In order to explain them in a relatively simple framework, we have explored various DM annihilation and scattering processes, discussing important phenomenological constraints coming from particle physics. Assuming that the two independent observations have a common DM origin and the processes arise through a common mediator, DM should annihilate into tau/anti-tau lepton pairs through an s -channel, and scatter with nuclei through a t -channel process. To avoid the p -wave suppression, a new Higgs-like scalar field with a mass of O ( 1 ) TeV is necessary as a common mediator of both the processes. We propose a supersymmetric model realizing the scenario.

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.

Weak Mixing Angle and Proton Stability in F-theory GUT

Abstract 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 gauge group SU ( 5 ) × U ( 1 ) X is embedded in SO ( 10 ) and E 8 . To prohibit the dimension 4 and 5 proton decay processes, the structure group associated with monodromy should be SU ( 3 ) ⊥ or smaller. Extra heavy vector-like pairs of { 5 − 2 , 5 ¯ 2 } except only one pair of Higgs should be 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 θ W 0 = 3 8 at the GUT scale, the fluxes are turned on only on the flavor branes.

Perspective on completing natural inflation

We present a perspective on the inflation paths in

Primordial gravitational wave of BICEP2 from dynamical double hybrid inflation

2-, 3-, \cdots, N-

Vector-like leptons and extra gauge symmetry for the natural Higgs boson

flation models based on the ultraviolet completion in heterotic string theory, where a number of grand unification scale axions are used. The number of non-Abelian gauge groups for a natural inflation is restricted in string compactification, and we argue that the most plausible completion of natural inflation from a theory perspective is the 2-- and 3--flation.

U(1)

Abstract BICEP2 has observed a primordial gravitational wave corresponding to the tensor-to-scalar ratio of 0.16. It seems to require a super-Planckian inflationary model. In this paper, we propose a double hybrid inflation model, where the inflaton potential dynamically changes with the evolution of the inflaton fields. During the first phase of inflation over 7 e-folds, the power spectrum can be almost constant by a large linear term in the hybrid potential, which is responsible also for the large tensor-to-scalar ratio. In the second phase of 50 e-folds, the dominant potential becomes dynamically changed to the logarithmic form as in the ordinary supersymmetric hybrid inflation, which is performed by the second inflaton field. In this model, the sub-Planckian field values ( ∼ 0.9 M P ) can still yield the correct cosmic observations with the sufficient e-folds.

_{B_1+B_2-2L_1}

A bstractFor raising the radiative Higgs mass without a serious fine-tuning in the Higgs sector, we introduce vector-like lepton doublets and neutral singlets {L, Lc; N, Nc}, and consider their order one Yukawa coupling to the Higgs W ⊃ yNLhuNc. The 125 GeV Higgs mass can be naturally explained with the stop mass squared of ~ (500 GeV)2 and even without the A-term contributions. It is possible because of the quartic power of yN in the radiative Higgs mass correction, and much less stringent mass bounds on extra leptonic matter. In order to avoid blowup of yN at higher energy scales, a non-Abelian gauge extension of the MSSM is attempted, under which {L, Lc; N, Nc} are charged, while all the ordinary MSSM superfields remain neutral. We discuss the gauge coupling unification. This mechanism can be applied also for enhancing h0 → γγ with W ⊃ yELchuE, if the charged lepton singlets {E, Ec} are also introduced.

mediation for the natural SUSY and the anomalous muon g-2

Abstract We propose a U ( 1 ) ′ mediated supersymmetry (SUSY) breaking, in which U ( 1 ) ′ is identified with U ( 1 ) B 1 + B 2 − 2 L 1 . The U ( 1 ) B 1 + B 2 − 2 L 1 gauge symmetry, which is anomaly-free with the field contents of the minimal supersymmetric standard model, assigns ± 1 / 3 charges to the first and second generations of the quarks, and ∓2 to the first generation of the leptons. As a result, the first two generations of squarks acquire masses of about 7 TeV, and the first generation of the sleptons do those of 40 TeV, respectively, in the presence of one or three pairs of extra vector-like matter { 5 , 5 ¯ } . Non-observation on extra colored particles below 1 TeV at the large hadron collider, and also the flavor violations such as μ − → e − γ are explained. By virtue of such a gauge symmetry, proton stability can be protected. The other squarks and sleptons as well as the gauginos can obtain masses of order 10 2 − 3 GeV through the conventional gravity or gauge mediated SUSY breaking mechanism. The relative light smuon/sneutrino and the neutralino/chargino could be responsible for the ( g − 2 ) μ deviated from the standard model prediction. The stop mass of ∼ 500 GeV relieves the fine-tuning problem in the Higgs sector. Two-loop effects by the relatively heavy sfermions can protect the smallness of the stop mass from the radiative correction by the heavy gluino ( ≳ 1 TeV ). Extra vector-like matter can enhance the radiative corrections to the Higgs mass up to 126 GeV, and induce the desired mixing among the chiral fermions after U ( 1 ) B 1 + B 2 − 2 L 1 breaking.