Ken Ichi Okumura

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.

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

New constraints on SUSY flavour mixing in light of recent measurements at the Tevatron

B

Neutralino dark matter in mirage mediation

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.

Sparticle masses in deflected mirage mediation

Abstract We discuss the implications, for general flavour mixing, of the recent results regarding the new allowed range for mixing in the B s meson system, as well as the new improved bounds on BR ( B ¯ s → μ + μ − ) . Constraints on right handed insertions, in particular, improve considerably in the large tan β regime where the contributions to B s mixing are dominated by double Higgs penguins. Similarly, the allowed regions of parameter space when varying multiple insertions also decrease significantly.

Axionic Mirage Mediation

We study the phenomenology of neutralino dark matter (DM) in a mirage mediation scenario of supersymmetry breaking which results from the moduli stabilization in some string/brane models. Depending upon the model parameters, especially the anomaly to modulus mediation ratio determined by the moduli stabilization mechanism, the nature of the lightest supersymmetric particle (LSP) changes from bino-like neutralino to Higgsino-like neutralino via a bino–Higgsino mixing region. For the bino-like LSP, the standard thermal production mechanism can give the right amount of relic DM density through the stop/stau–neutralino coannihilation or the pseudoscalar Higgs resonance process. We also examine the prospect of direct and indirect DM detection in various parameter regions of mirage mediation. Neutralino DM in the galactic halo might be detected by near future direct detection experiments in the case of the bino–Higgsino mixed LSP. The gamma ray flux from the galactic centre might be detectable also if the DM density profile takes a cuspy shape.

Flavor and CP conserving moduli mediated SUSY breaking in flux compactification

We discuss the sparticle mass patterns that can be realized in deflected mirage mediation scenario of supersymmetry breaking, in which the moduli, anomaly, and gauge mediations all contribute to the MSSM soft parameters. Analytic expression of low energy soft parameters and also the sfermion mass sum rules are derived, which can be used to interpret the experimentally measured sparticle masses within the framework of the most general mixed moduli-gauge-anomaly mediation. Phenomenological aspects of some specific examples are also discussed.

Current and future limits on general flavour violation in b ! s transitions in minimal supersymmetry

In this talk, we propose a model of mirage mediation, in which Peccei‐Quinn symmetry is incorporated. In this axionic mirage mediation, it is shown that the Peccei‐Quinn symmetry breaking scale is dynamically determined around 1010 GeV to 1012 GeV due to the supersymmetry breaking effects. The problems in the original mirage mediation such as the μ‐problem and the moduli problem can be solved simultaneouly. Furthermore, in our model the axino, which is the superpartner of the axion, is the lightest sparticle.

TeV scale mirage mediation in NMSSM

In certain class of flux compactification, moduli mediated supersymmetry (SUSY) breaking preserves flavor and CP at leading order in the perturbative expansion controlled by the vacuum expectation value of the messenger modulus. Nevertheless there still might be dangerous flavor or CP violation induced by higher order Kahler potential. We examine the constraints on such SUSY breaking scheme imposed by low energy flavor and/or CP violating observables. It is found that all phenomenological constraints can be satisfied even for generic form of higher order Kahler potential and sparticle spectra in the sub-TeV range, under plausible assumptions on the size of higher order correction and flavor mixing angles. This implies for instance that mirage mediation scheme of SUSY breaking, which involves such modulus mediation together with an anomaly mediation of comparable size, and also the modulus-dominated mediation realized in flux compactification can be free from the SUSY flavor and CP problems, while giving gaugino and sfermion masses in the sub-TeV range.