Natsumi Nagata

Gluon contribution to dark matter direct detection

In this article we have calculated the spin-independent cross section of nucleon-dark matter scattering process at loop level, which is relevant to dark matter direct detection. Paying particular attention to the scattering of gluon with dark matter, which contributes as leading order in the perturbation, we have systematically evaluated loop diagrams with tracking the characteristic loop momentum which dominates in the loops. Here loop diagrams whose typical loop momentum scales are the masses of quarks and other heavier particles are separately presented. Then, we have properly taken into account each contribution to give the cross section. We assume that the dark matter is pure bino or wino in the supersymmetric models. The application to other models is straightforward.

Direct detection of electroweak-interacting dark matter

Assuming that the lightest neutral component in an SU(2)L gauge multiplet is the main ingredient of dark matter in the universe, we calculate the elastic scattering cross section of the dark matter with nucleon, which is an important quantity for the direct detection experiments. When the dark matter is a real scalar or a Majorana fermion which has only electroweak gauge interactions, the scattering with quarks and gluon are induced through one- and two-loop quantum processes, respectively, and both of them give rise to comparable contributions to the elastic scattering cross section. We evaluate all of the contributions at the leading order and find that there is an accidental cancellation among them. As a result, the spin-independent cross section is found to be

Direct Search of Dark Matter in High-Scale Supersymmetry

\mathcal{O}\left( {{{10}^{ - \left( {46 - 48} \right)}}} \right)

Decoupling can revive minimal supersymmetric SU(5)

cm2, which is far below the current experimental bounds.

Dark matter and gauge coupling unification in nonsupersymmetric SO(10) grand unified models

We study direct detection of dark matter in a supersymmetric model where most supersymmetric particles have very high-scale masses beyond the weak scale. In the scenario, a Wino-like or a Higgsino-like neutralino is a good candidate for the dark matter in the Universe. The neutralino scatters off nuclei by a Higgs boson exchange diagram and also electroweak loop diagrams. It is found that the elastic-scattering cross section with nuclei is enhanced or suppressed due to constructive or deconstructive interference among the diagrams. Such a cross section is within the reach of future experiment in some parameter region.

Interpretations of the ATLAS Diboson Resonances

A bstractWe revisit proton decay via the color-triplet Higgs multiplets in the minimal supersymmetric grand unified model with heavy sfermions. Although the model has been believed to be excluded due to the too short lifetime of proton, we have found that it is possible to evade the experimental constraints on the proton decay rate if the supersymmetric particles have masses much heavier than the electroweak scale. With such heavy sfermions, the 126 GeV Higgs boson is naturally explained, while they do not spoil the gauge coupling unification and the existence of dark matter candidates. Since the resultant proton lifetime lies in the regions which may be reached in the future experiments, proton decay searches may give us a chance to verify the scenario as well as the supersymmetric grand unified models.

A complete calculation for direct detection of Wino dark matter

Unlike minimal SU(5), SO(10) provides a straightforward path towards gauge coupling unication

Higgsino Dark Matter in High-Scale Supersymmetry

The ATLAS collaboration has reported excesses in searches for resonant diboson production decaying into hadronic final states. This deviation from the Standard Model prediction may be a signature of an extra bosonic particle having a mass of around 2 TeV with a fairly narrow width, which implies the presence of a new perturbative theory at the TeV scale. In this paper, we study interpretations of the signal and its implication to physics beyond the Standard Model. We find that the resonance could be regarded as a leptophobic vector particle, which could explain a part of the observed excesses without conflict with the present constraints from other direct searches for heavy vector bosons at the LHC as well as the electroweak precision measurements.

QCD effects on direct detection of wino dark matter

Abstract In the anomaly-mediated supersymmetry (SUSY) breaking scenario, neutral gaugino of SU ( 2 ) L multiplet, Wino, can be the lightest SUSY particle and become a candidate for dark matter. We calculated scattering cross section of Wino dark matter with nucleon, which is responsible for direct detection of the dark matter, on the assumption that the SUSY particles and the heavier Higgs bosons have masses of the order of the gravitino mass in the SUSY standard model. In such a case, the Wino–nucleon coupling is generated by loop processes. We have included two-loop contribution to Wino–gluon interaction in the calculation, since it is one of the leading contributions to the Wino–nucleon coupling. It was found that the spin-independent scattering cross section with proton is 10 − ( 46 – 48 ) cm 2 . While it is almost independent of the Wino mass, the result is quite sensitive to the Higgs boson mass due to the accidental cancellation.

Reevaluation of Neutron Electric Dipole Moment with QCD Sum Rules

A bstractWe study a supersymmetric (SUSY) Standard Model in which a Higgsino is light enough to be dark matter, while the other SUSY particles are much heavier than the weak scale. We carefully treat the effects of heavy SUSY particles to the Higgsino nature, especially taking into account the renormalization effects due to the large hierarchy between the Higgsino and the SUSY breaking scales. Inelastic scattering of the Higgsino dark matter with a nucleus is studied, and the constraints on the scattering by the direct detection experiments are discussed. This gives an upper limit on the new physics scale. Bounds on the dark matter-nucleon elastic scattering, the electric dipole moments, and direct production of Higgsinos, on the other hand, give a lower limit. We show the current status on the limits and discuss the future prospects.