Motoi Endo

Bottom-up approach to moduli dynamics in heavy gravitino scenario: Superpotential, soft terms, and sparticle mass spectrum

The physics of moduli fields is examined in the scenario where the gravitino is relatively heavy with mass of order 10 TeV, which is favored in view of the severe gravitino problem. The form of the moduli superpotential is shown to be determined, if one imposes a phenomenological requirement that no physical

Cosmic string from D-term inflation and curvaton

CP

New constraint on squark flavor mixing from 199Hg electric dipole moment

phase arise in gaugino masses from conformal anomaly mediation. This bottom-up approach allows only two types of superpotential, each of which can have its origins in a fundamental underlying theory such as superstring. One superpotential is the sum of an exponential and a constant, which is identical to that obtained by Kachru et al. (KKLT), and the other is the racetrack superpotential with two exponentials. The general form of soft supersymmetry-breaking masses is derived, and the pattern of the superparticle mass spectrum in the minimal supersymmetric standard model is discussed with the KKLT-type superpotential. It is shown that the moduli mediation and the anomaly mediation make comparable contributions to the soft masses. At the weak scale, the gaugino masses are rather degenerate compared to the minimal supergravity, which bring characteristic features on the superparticle masses. In particular, the lightest neutralino, which often constitutes the lightest superparticle and thus a dark matter candidate, is a considerable admixture of gauginos and Higgsinos. We also find a small mass hierarchy among the moduli, gravitino, and superpartners of the standard-model fields. Cosmological implications of the scenario are briefly described.

Recent measurements of CP asymmetries of B→ϕK0 and B→η′KS at B-factories suggest new CP violation in left-handed squark mixing

Abstract We study effects of the cosmic string in the D -term inflation model on the cosmic microwave background (CMB) anisotropy. In the D -term inflation model, gauged cosmic string is usually formed, which may significantly affect the CMB anisotropy. We see that its study imposes important constraint. In order to realize the minimal model of D -term inflation, we see that the coupling constant λ in the superpotential generating the inflaton potential should be significantly small, λ ≲ O (10 −4 –10 −5 ). We also discuss that a consistent scenario of the D -term inflation with λ ∼1 can be constructed by adopting the curvaton mechanism where the cosmic density fluctuations are generated by a primordial fluctuation of a late-decaying scalar field other than the inflaton.

Large supersymmetric contribution to CP asymmetry of Bd → ΦKS from left-handed squark mixing

Abstract A new constraint is obtained on the CP-violating flavor mixing between the left-handed top scalar quark ( t L ) and charm scalar quark ( c L ) , by considering a chargino loop contribution to chromo-electric dipole moment of strange quark, which is limited by the electric dipole moment of the 199Hg atom. It is found that the flavor mixing should be suppressed to the level of O (0.1) for the CP phase of order unity, when tanβ is relatively large and sparticle masses lie in a few hundred GeV range. Although it is much stronger than the known constraint from the chargino loop contribution to b→sγ, the moderate constraint we obtain here is argued to leave room for sizable supersymmetric contribution to the CP asymmetry in Bd0→φKs.

Muon magnetic dipole moment and Higgs mass in supersymmetric SU(5) models

Abstract Recent results on the mixing-induced CP asymmetries of B → ϕ K 0 and B → η ′ K S measured at B-factories appear to indicate discrepancies from the Standard Model expectation. Explanation of this possible anomaly is given in the context of supersymmetric extension of the Standard Model. It is shown that the present data, if the average of two experiments is taken, implies additional CP violation appearing in the generation mixing of left-handed squarks rather than that of right-handed ones. This explanation is argued to disfavor many mediation mechanisms of supersymmetry breaking, including minimal supergravity, because renormalization group effects via Yukawa interaction are unlikely to generate the desired mass mixing.

Recent Muon g−2 result in deflected anomaly-mediated supersymmetry breaking

Abstract Supersymmetric contribution to the CP asymmetry of B d → φK S is re-examined. It is emphasized that our analysis takes into account the recently found constraint from the mercury electric dipole moment, in addition to the well-known constraint from the branching ratio of b → sγ . We show that, despite these constraints, the CP asymmetry can considerably deviate from the Standard Model prediction, if the CP-odd flavor mixing comes from left-handed squarks. Alignment mechanism of sfermion masses and mixing may imprint the required flavor mixing at high energy scale.

Phenomenology of Minimal Supergravity with Vanishing A and B Soft Supersymmetry-Breaking Parameters

Abstract We study the muon magnetic dipole moment and the Higgs mass in the framework of the supersymmetric SU(5) models. In this analysis, all the relevant parameters in the Lagrangian are taken to be free; in particular, assumption of the universal scalar mass is not adopted. Negative search for the Higgs boson at the LEPxa0II experiment sets an important constraint on the supersymmetric contribution to the muon magnetic dipole moment aμ(SUSY). It is shown that, for a fixed value of the lightest Higgs mass, the maximum possible value of aμ(SUSY) becomes significantly larger in the general SU(5) case compared to the case of the universal scalar mass (i.e., the case of the so-called “CMSSM”). We also point out that, if we take relatively large value of the trilinear scalar couplings, the constraint from the Higgs mass is drastically relaxed. In this case, aμ(SUSY) can be as large as ∼50×10−10 even for small value of tanβ (say, for tanβ=5).

Raising Sfermion Masses by Adding Extra Matter Fields

Abstract We study the deflected anomaly-mediated supersymmetry breaking (AMSB) scenario in the light of the recent result of the Muon g−2 from Brookhaven E821 experiment. The E821 result suggests the deviation from the SM prediction, though there remain unsettled uncertainties. We find that the supersymmetric contribution to the Muon g−2 can be O (10 −9 ) , large enough to fill the deviation, with other experimental constraints satisfied. In particular, the Higgs mass and b→sγ put severe constraints on the model and large tanβ is favored to enhance the Muon g−2.

Radiative CP Phases in Supergravity Theories

Abstract The ansatz of vanishing A and B parameters eliminates CP-violating complex phases in soft supersymmetry-breaking parameters of the minimal supersymmetric standard model, and thus provides a simple solution to the supersymmetry CP problem. Phenomenological implications of this ansatz are investigated in the framework of minimal supergravity. We show that electroweak symmetry breakdown occurs, predicting relatively large tan β . The ansatz survives the Higgs mass bound as well as the b → sγ constraint if the universal gaugino mass is larger than 300xa0GeV. We also find that the supersymmetric contribution to the anomalous magnetic moment of muon lies in an experimentally interesting region of order 10 −9 in a large portion of the parameter space.