arXiv subjects

Kyu Jung Bae

Publications and source records attributed to Kyu Jung Bae.

49 records · Page 3Linked to original sources

arXiv2013

Implications of mixed axion/neutralino dark matter for the Cosmic Frontier: a Snowmass whitepaper

If one simultaneously invokes the SUSY solution to the gauge hierarchy problem and the PQ solution to the strong CP problem, then one might expect mixed axion/neutralino dark matter (DM), i.e. two dark matter particles. In this case, dark matter production involves oscillation production of axions, thermal and non-thermal neutralino production and thermal and non-thermal production of axinos and saxions. The latter particles may feed additional neutralinos into the cosmic soup, or dilute all relics via additional entropy production, or feed dark radiation into the cosmos. Depending on the SUSY and PQ model, the PQ scale can easily exist from 10^9-10^{16} GeV. Axions may lie well beyond the range currently being probed by experiment. In the case of relic WIMPs, theoretical predictions must be rescaled for the possibility that WIMPs only comprise a fraction of the local DM abundance.

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arXiv2013

Dark Radiation Constraints on Mixed Axion/Neutralino Dark Matter

Recent analyses of WMAP9 data show that dark radiation-- parametrized by the apparent number of additional neutrinos ΔN_{eff} contributing to the cosmic expansion-- is consistent with the Standard Model and bounded from above by about ΔN_{eff} ~< 0.5 at 95% CL. We consider the mixed axion/neutralino cold dark matter scenario which arises in R-parity conserving supersymmetric (SUSY) models wherein the strong CP problem is solved by hadronic axions with a concommitant axion(a)/saxion(s)/axino(\ta) supermultiplet. Our new results include improved calculations of thermal axion and saxion production and include effects of saxion decay to axinos and axions. We show that the above bound on ΔN_{eff} is easily satisfied if saxions are mainly thermally produced and m_{LSP} < m_{\ta} \lesssim m_s. However, if the dominant mechanism of saxion production is through coherent oscillations, the WMAP9 data provides a strong bound on saxion production followed by saxion decays to axions. Furthermore we show that scenarios with mixed neutralino/axion dark matter are highly constrained by combined WMAP9, BBN and Xe-100 constraints. In particular, supersymmetric models with a standard overabundance of neutralino dark matter are excluded for all values of the Peccei-Quinn breaking scale. Next generation WIMP direct detection experiments may be able to discover or exclude mixed axion-neutralino CDM scenarios where $s\to aa$ is the dominant saxion decay mode.

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arXiv2012

Peccei-Quinn NMSSM in the light of 125 GeV Higgs

We study the phenomenology of the Peccei-Quinn invariant extension of the next-to-minimal supersymmetric standard model (NMSSM) in view of the recent discovery of a 125 GeV Higgs boson. The minimal model having no quadratic and cubic terms of the NMSSM singlet field predicts a light singlino-like lightest supersymmetric particle (LSP). The model is strongly constrained by the Higgs invisible decay and the dark matter characteristic of the LSP, while some constraints can be relaxed by assuming that the saxion, the CP-even companion of the axion in the Peccei-Quinn sector, causes a late-time entropy production diluting the thermal LSP density. The collider signal of the model contains multi-jet and $h/W/Z$ plus missing energy, which can be discovered in the early stage of the 14 TeV LHC running.

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arXiv2012

125 GeV Higgs as a pseudo-Goldstone boson in supersymmetry with vector-like matters

We propose a possibility of the 125 GeV Higgs being a pseudo-Goldstone boson in supersymmetry with extra vector-like fermions. Higgs mass is obtained from loops of top quark and vector-like fermions from the global symmetry breaking scale f at around TeV. The mu, Bmu/mu \sim f are generated from the dynamics of global symmetry breaking and the Higgs quartic coupling vanishes at f as tan beta \simeq 1. The relation of msoft \sim $4πM_Z$ with f \sim mu \sim m_soft \sim TeV is obtained and large mu does not cause a fine tuning for the electroweak symmetry breaking. The Higgs to di-photon rate can be enhanced from the loop of uncolored vector-like matters. The stability problem of Higgs potential with vector-like fermions can be nicely cured by the UV completion with the Goldstone picture.

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arXiv2012

Cosmology of the DFSZ axino

We study the cosmological impact of the supersymmetric DFSZ axion model. Extending recent works, we first provide a comprehensive analysis of thermal production of the DFSZ axino considering all the possible scattering, decay and inverse decay processes depending on various mass parameters and the reheat temperature. Although it is hard for the DFSZ axino to be in thermal equilibrium, its coupling is still large enough to generate huge axino population which can turn into overabundant neutralino density. We examine the neutralino parameter space to identify the dark matter property depending on the Peccei-Quinn scale. As the Peccei-Quinn scale becomes higher resulting in longer axino lifetime, the neutralino dark matter appears in a lighter Higgsino-like LSP region or a more restricted Bino-like LSP region allowing a resonant annihilation through a CP-odd Higgs boson to meet stronger reannihilation.

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arXiv2011

Effective interactions of axion supermultiplet and thermal production of axino dark matter

We discuss the effective interactions of axion supermultiplet, which might be important for analyzing the cosmological aspect of supersymmetric axion model. Related to axino cosmology, it is stressed that three seemingly similar but basically different quantities, the Wilsonian axino-gluino-gluon coupling, the 1PI axino-gluino-gluon amplitude, and the PQ anomaly coefficient, should be carefully distinguished from each other for correct analysis of the thermal production of axinos in the early Universe. It is then noticed that the 1PI axino-gluino-gluon amplitude at energy scale p in the range M_Φ< p < v_{PQ} is suppressed by (M_Φ^2)/(p^2) in addition to the well-known suppression by p/(16π^2 v_{PQ}), where M_Φis the mass of the heaviest PQ-charged and gauge-charged matter supermultiplet in the model, which can be well below the PQ scale v_{PQ}. As a result, axino production at temperature T>M_Φis dominated by the production by matter supermultiplet, not by the production by gauge supermultiplet. Still the axino production rate is greatly reduced if M_Φ<< v_{PQ}, which would make the subsequent cosmology significantly altered. This would be most notable in the supersymmetric DFSZ model in which M_Φcorresponds to the Higgsino mass which is around the weak scale, however a similar reduction is possible in the KSVZ model also. We evaluate the relic axino density for both the DFSZ and KSVZ models while including the axino production in the processes involving the heaviest PQ-charged and gauge-charged matter supermultiplet.

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arXiv2010

Light neutralino dark matter with a very light Higgs for CoGeNT and DAMA/LIBRA data

Recently, the CoGeNT collaboration reported the WIMP candidate signal events exceeding the known backgrounds where the light WIMP with large cross section is supported. Motivated by this issue, we analyze a light neutralino dark matter scenario with a very light CP-even Higgs mediation in the elastic scattering process, which provides the mass and direct detection cross section to explain the CoGeNT result. To be compatible with the result of LEP experiments, the light CP-even Higgs is favored to be in 9 to 10 GeV. Such a scenario can be realized in the "Beyond the MSSM" context. The relic abundance consistent with the WMAP result can be obtained when twice of neutralino mass is close to the light Higgs mass via the resonance enhancement of the annihilation cross section. As a result, the neutralino mass is predicted to be at around 5 to 6 GeV.

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arXiv2010

Wrong-Higgs Interactions without Flavor Problems and their Effects on Physical Observables

We consider the wrong-Higgs interactions such as type-III two Higgs doublet models. Generally, such interactions cause flavor problems. However, if new Yukawa interactions have the same flavor structure as that of the standard model(SM), we do not have any flavor problems. In this work we propose a microscopic model for the wrong-Higgs interactions aligned with SM ones in the context of supersymmetry(SUSY) and show their phenomenological implications. Low energy contraints from muon g-2 and rare B decays can be relieved and it can be viable to have low mass superparticle spectra with light dark matter which is preferred by recent experiments such as DAMA/LIBRA, CDMS-II and CoGeNT. We also briefly discuss modification of Higgs decay in colliders.

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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

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].

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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.

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arXiv2008

Update of axion CDM energy density

We improve the estimate of the axion CDM energy density by considering the new values of current quark masses, the QCD phase transition effect and a possible anharmonic effect.

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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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