Kwang Sik Jeong

Phenomenology of mixed modulus-anomaly mediation in fluxed string compactifications and brane models

In some string compactifications, for instance the recently proposed KKLT set-up, light moduli are stabilized by nonperturbative effects at supersymmetric AdS vacuum which is lifted to a dS vacuum by supersymmetry breaking uplifting potential. In such models, soft supersymmetry breaking terms are determined by a specific mixed modulus-anomaly mediation in which the two mediations typically give comparable contributions to soft parameters. Similar pattern of soft terms can arise also in brane models to stabilize the radion by nonperturbative effects. We examine some phenomenological consequences of this mixed modulus-anomaly mediation, including the pattern of low energy sparticle spectrum and the possibility of electroweak symmetry breaking. It is noted that adding the anomaly-mediated contributions at MGUT amounts to replacing the messenger scale of the modulus mediation by a mirage messenger scale (m3/2/MPl)?/2MGUT where ? = m3/2/[M0ln (MPl/m3/2)] for M0 denoting the modulus-mediated contribution to the gaugino mass at MGUT. The minimal KKLT set-up predicts ? = 1. As a consequence, for ? = (1), the model can lead to a highly distinctive pattern of sparticle masses at TeV scale, particularly when ? = 2.

Little SUSY hierarchy in mixed modulus-anomaly mediation

Abstract Motivated by the KKLT string compactification involving a supersymmetry-breaking uplifting potential, we examine 4D effective supergravity with a generic form of uplifting potential, focusing on the possibility that the resulting mixed modulus-anomaly mediated soft terms realize the little hierarchy between the Higgs boson masses m H and the sparticle masses m SUSY . It is noted that for some type of uplifting potential, the anomaly-mediated contribution to m H 2 at M GUT can cancel the subsequent renormalization group evolution of m H 2 down to TeV scale, thereby the model can naturally realize the little hierarchy m H 2 ∼ m SUSY 2 / 8 π 2 which is desirable for the lightest Higgs boson mass to satisfy the experimental bound. In such models, the other Higgs mass parameters μ and B can have the desirable size μ ∼ B ∼ m H without severe fine-tuning of parameters, although the gravitino is much heavier than the Higgs boson. Those models for the little hierarchy avoid naturally the dangerous SUSY flavor and CP violations, and predict nearly degenerate low energy gaugino masses, pure Higgsino LSP, and also a specific relation between the stop and gaugino masses.

Supersymmetry breaking and moduli stabilization with anomalous U(1) gauge symmetry

We examine the effects of anomalous U(1)A gauge symmetry on soft supersymmetry breaking terms while incorporating the stabilization of the modulus-axion multiplet responsible for the Green-Schwarz (GS) anomaly cancellation mechanism. In case of the KKLT stabilization of the GS modulus, soft terms are determined by the GS modulus mediation, the anomaly mediation and the U(1)A mediation which are generically comparable to each other, thereby yielding the mirage mediation pattern of superparticle masses at low energy scale. Independently of the mechanism of moduli stabilization and supersymmetry breaking, the U(1)A D-term potential can not be an uplifting potential for de Sitter vacuum when the gravitino mass is smaller than the Planck scale by many orders of magnitude. We also discuss some features of the supersymmetry breaking by red-shifted anti-brane which is a key element of the KKLT moduli stabilization.

The 7 keV axion dark matter and the X-ray line signal

Abstract We propose a scenario where the saxion dominates the energy density of the Universe and reheats the standard model sector via the dilatonic coupling, while its axionic partner contributes to dark matter decaying into photons via the same operator in supersymmetry. Interestingly, for the axion mass m a ≃ 7 keV and the decay constant f a ≃ 10 14 – 15 GeV , the recently discovered X-ray line at 3.5 keV in the XMM Newton X-ray observatory data can be explained. We discuss various cosmological aspects of the 7 keV axion dark matter such as the production of axion dark matter, the saxion decay process, hot dark matter and isocurvature constraints on the axion dark matter, and the possible baryogenesis scenarios.

TeV scale mirage mediation and natural little supersymmetric hierarchy

TeV scale mirage mediation has been proposed as a supersymmetry-breaking scheme reducing the fine-tuning for electroweak symmetry breaking in the minimal supersymmetric extension of the standard model. We discuss a moduli stabilization setup for TeV scale mirage mediation which allows an extradimensional interpretation for the origin of supersymmetry breaking and naturally gives a weak-scale size of the Higgs

7 keV sterile neutrino dark matter from split flavor mechanism

B

Higgs mixing and diphoton rate enhancement in NMSSM models

parameter. The setup utilizes the holomorphic gauge kinetic functions depending on both the heavy dilaton and the light volume modulus whose axion partners are assumed to be periodic fields. We also examine the low-energy phenomenology of TeV scale mirage mediation, particularly the constraints from electroweak symmetry breaking and flavor changing neutral current processes.

String theoretic QCD axion with stabilized saxion and the pattern of supersymmetry breaking

Abstract The recently discovered X-ray line at about 3.5 keV can be explained by sterile neutrino dark matter with mass, m s ≃ 7 keV , and the mixing, sin 2 2 θ ∼ 10 − 10 . Such sterile neutrino is more long-lived than estimated based on the seesaw formula, which strongly suggests an extra flavor structure in the seesaw sector. We show that one can explain both the small mass and the longevity based on the split flavor mechanism where the breaking of flavor symmetry is tied to the breaking of the B − L symmetry. In a supersymmetric case we find that the 7 keV sterile neutrino implies the gravitino mass about 100 TeV .

Singlet-doublet Higgs mixing and its implications on the Higgs mass in the PQ-NMSSM

A bstractWe study the implications of the LHC Higgs signals on the Higgs mixing in the next-to-minimal supersymmetric standard model (NMSSM). The Higgs couplings can depart from their values in the standard model (SM) due to mixing effects. However the Higgs signal rate in the WW and ZZ channels can remain close to the SM values, as observed at the LHC, even if the SM-like Higgs boson with a mass near 125 GeV has a large singlet component. This allows to get a sizable enhancement in the Higgs to diphoton rate through the charged-higgsino loop contribution, as well as a sizable reduction of the Higgs to

Electroweak symmetry breaking in supersymmetric gauge-Higgs unification models

b\overline{b}