265 research outputs found

    Gravitino Production in the Early Universe and Its Implications to Particle Cosmology

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    Effects of the unstable gravitino on the big-bang nucleosynthesis (BBN) and its implications to particle cosmology are discussed. If the gravitino mass is smaller than \sim 20 TeV, lifetime of the gravitino becomes longer than \sim 1sec and its decay may spoil the success of the standard BBN. In order to avoid such a problem, upper bound on the reheating temperature after the inflation is obtained, which may be as low as \sim 10^{5-6} GeV. For a successful baryogenesis with such low reheating temeprature, a consistent scenario based on the large cutoff supergravity (LCSUGRA) hypothesis of supersymmetry breaking, where the gravitino and sfermion become as heavy as \sim O(1-10 TeV), is proposed. In the LCSUGRA, non-thermal leptogenesis can produce large enough baryon asymmetry. We also see that, in the LCSUGRA scenario, relic density of the lightest superparticle becomes consistent with the WMAP value of the dark matter density in the parameter region required for the successful non-thermal leptogenesis. In this case, the dark matter density may be reconstructed with the future e^+e^- linear collider.Comment: Talk given at PASCOS05, Gyeongju, Korea (June 2005). 13 pages, 5 figure

    Effects of the right-handed neutrinos on \Delta S = 2 and \Delta B = 2 processes in supersymmetric SU(5) model

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    We discuss an extra source of CP and flavor violations in supersymmetric SU(5) grand unified model with the right-handed neutrinos. In such a model, the right-handed down-type squarks \tilde{d}_R interact with the right-handed neutrinos above the GUT scale, and the renormalization group effect can generate sizable off-diagonal elements in the mass matrix of \tilde{d}_R. Because of new Yukawa phases which exist in the SU(5) model, these off-diagonal elements have, in general, large CP violating phases. The renormalization group induced off-diagonal elements affect the K and B decays. In particular, in this model, supersymmetric contribution to the \epsilon_K parameter can be as large as the currently measured experimental value, and hence the effect might be seen as an anomaly in the on-going test of the Cabibbo-Kobayashi-Maskawa triangle.Comment: 13 pages, 3 figures, typo correcte

    SUSY CP Problem in Gauge Mediation Model

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    SUSY CP problem in the gauge mediation supersymmetry breaking model is reconsidered. We pay particular attention to two sources of CP violating phases whose effects were not seriously studied before; one is the effect of the breaking of the GUT relation among the gaugino masses due to the field esponsible for the GUT symmetry breaking, and the other is the supergravity effect on the supersymmetry breaking parameters, in particular, on the bi-linear supersymmetry breaking Higgs mass term. We show that both of them can induce too large electric dipole moments of electron, neutron, and so on, to be consistent with the experimental bounds.Comment: 15 pages, 3 figures, corrected typos, The version to appear in PL

    Early Decay of Peccei-Quinn Fermion and the IceCube Neutrino Events

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    IceCube observed high-energy neutrino flux in the energy region from TeV to PeV. The decay of a massive long-lived particle in the early universe can be the origin of the IceCube neutrino events, which we call an "early decay scenario." In this paper, we construct a particle physics model that contains such a massive long-lived particle based on the Peccei-Quinn model. We calculate the present neutrino flux, taking account of realistic initial energy distributions of particles produced by the decay of the massive long-lived particle. We show that the early decay scenario naturally fits into the Peccei-Quinn model, and that the neutrino flux observed by IceCube can be explained in such a framework. We also see that, based on that model, a consistent cosmological history that explains the abundance of the massive long-lived particle is realized.Comment: 20 pages, 2 figures; v2: references added; v3: version accepted for publication in PL
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