Browsing by Author "Kikuchi, Tatsuru"

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    D-term contributions to the mixed modulus-anomaly mediated supersymmetry breaking
    (Elsevier, 2006-10-12) Fukuyama, Takeshi; Kikuchi, Tatsuru; Okada, Nobuchika; Ritsumeikan University; High Energy Accelerator Research Organization (KEK); Graduate University for Advanced Studies - Japan; University of Alabama Tuscaloosa
    We investigate effects of D-term contributions to the mixed modulus-anomaly mediated supersymmetry breaking scenario. In the original scenario, the tachyonic slepton problem in the pure anomaly mediated supersymmetry breaking is cured by modulus contributions. We generalize the scenario so as to include contributions from the D-terms of U(1)(gamma) and the gauged U(1)(B-L) which is motivated in a grand unified theory based on a higher rank gauge group such as SO(10). As a consequence of additional D-term contributions to scalar masses, we obtain various soft supersymmetry breaking mass spectra, which are different from those obtained in the conventional mixed modulus-anomaly mediated supersymmetry breaking. Especially, we find that the lightest superpartner (LSP) neutralinos can be various types, such as higgsino-like, wino-like and bino-like degenerating with the next LSP sfertmons. (c) 2006 Elsevier B.V. All rights reserved.
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    Unparticle dark matter
    (Elsevier, 2008-07-24) Kikuchi, Tatsuru; Okada, Nobuchika; High Energy Accelerator Research Organization (KEK); Graduate University for Advanced Studies - Japan; University of Alabama Tuscaloosa
    Once a parity is introduced in unparticle physics, under which unparticle provided in a hidden conformal sector is odd while all Standard Model particles are even, unparticle can be a suitable candidate for the cold dark matter (CDM) in the present universe through its coupling to the Standard Model Higgs doublet. We find that for Higgs boson mass in the range, 114.4 GeV less than or similar to m(h) less than or similar to 250 GeV, the relic abundance of unparticle with mass 50 GeV less than or similar to m(u) less than or similar to 80 GeV can be consistent with the currently observed CDM density. In this scenario, Higgs boson with Mass m(h) less than or similar to 160 GeV dominantly decays into a pair of unparticles and such an invisible Higgs boson may be discovered in future collider experiments. (C) 2008 Elsevier B.V. All rights reserved.
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    Unparticle physics and Higgs phenomenology
    (Elsevier, 2008-04-03) Kikuchi, Tatsuru; Okada, Nobuchika; High Energy Accelerator Research Organization (KEK); University System of Maryland; University of Maryland College Park; University of Alabama Tuscaloosa
    Recently, conceptually new physics beyond the Standard Model has been proposed, where a hidden conformal sector provides "unparticle" which couples to the Standard Model sector through higher dimensional operators in low energy effective theory. Among several possibilities, we focus on operators involving unparticle, the Higgs doublet and the gauge bosons. Once the Higgs doublet develops the vacuum expectation value, the conformal symmetry is broken and as a result, the mixing between unparticle and Higgs boson emerges. We find that this mixing can cause sizable shifts for the couplings between Higgs boson and a pair of gluons and photons, because these couplings exist only at the loop level in the Standard Model. These Higgs couplings are the most important ones for the Higgs boson search at the CERN Large Hadron Collider, and the unparticle physics effects may be observed together with the discovery of Higgs boson. (C) 2008 Elsevier B.V. All rights reserved.
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    Unparticle physics at the photon collider
    (American Physical Society, 2008-05-19) Kikuchi, Tatsuru; Okada, Nobuchika; Takeuchi, Michihisa; High Energy Accelerator Research Organization (KEK); Graduate University for Advanced Studies - Japan; Kyoto University; University of Alabama Tuscaloosa
    Recently, a conceptually new physics beyond the standard model (SM), unparticle, has been proposed, where a hidden conformal sector is coupled to the SM sector through higher dimensional operators. In this setup, we investigate unparticle physics at the photon collider, in particular, unparticle effects on the gamma gamma ->gamma gamma process. Since this process occurs at loop level in the SM, the unparticle effects can be significant even if the cutoff scale is very high. In fact, we find that the unparticle effects cause sizable deviations from the SM results. The scaling dimension of the unparticle d(u) reflects the dependence of the cross section on the final state photon invariant mass, so that precision measurements of this dependence may reveal the scaling dimension of the unparticle.