Keisuke Harigaya

Publications (10)0 Total impact

• Article: A Simple Solution to the Polonyi Problem in Gravity Mediation

  Keisuke Harigaya, Masahiro Ibe, Kai Schmitz, Tsutomu T. Yanagida
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  ABSTRACT: The Polonyi field is a necessary ingredient in any viable scenario of gravity mediated supersymmetry breaking. However, it is known that the presence of the Polonyi field leads to several serious cosmological problems, which are collectively referred to as the Polonyi problem. We show that the Polonyi problem can be solved if the Polonyi field couples to a pseudo modulus in the superpotential and this pseudo modulus has a large field expectation value during inflation. To illustrate our idea, we construct an explicit model which can be readily connected to scenarios of gravity mediation. The generation of the mass parameters contained in our model by strong gauge dynamics is also commented on.
  01/2013;
• Article: Model Independent Analysis of Interactions between Dark Matter and Various Quarks

  Biplob Bhattacherjee, Debajyoti Choudhury, Keisuke Harigaya, Shigeki Matsumoto, Mihoko M. Nojiri
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  ABSTRACT: Present and future expected limits on interactions between dark matter and various quarks are thoroughly investigated in a model-independent way. In particular, the constraints on the interactions from the Large Hadron Collider (LHC) experiment are carefully considered with focusing on mono jet + missing transverse energy, mono b-jet + missing transverse energy, and top quark(s) + missing transverse energy channels. Model-independent upper limits (expected limits) on the cross section times acceptance for non-standard model events are derived at 7 TeV (8 or 14 TeV) running of the LHC experiment. With assuming that the dark matter is a singlet real scalar or a singlet Majorana fermion, we also put constraints on several operators describing its interactions with up, down, strange, charm, bottom and top quarks. These constraints are compared to those obtained by cosmological and astrophysical observations of the dark matter.
  12/2012;
• Article: Chaotic Inflation with a Fractional Power-Law Potential in Strongly Coupled Gauge Theories

  Keisuke Harigaya, Masahiro Ibe, Kai Schmitz, Tsutomu T. Yanagida
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  ABSTRACT: Models of chaotic inflation with a fractional power-law potential are not only viable but also testable in the foreseeable future. We show that such models can be realized in simple strongly coupled supersymmetric gauge theories. In these models, the energy scale during inflation is dynamically generated by the dimensional transmutation due to the strong gauge dynamics. Therefore, such models not only explain the origin of the fractional power in the inflationary potential but also provide a reason why the energy scale of inflation is much smaller than the Planck scale.
  11/2012;
• Article: Non-Gaussianity from Attractor Curvaton

  Keisuke Harigaya, Masahiro Ibe, Masahiro Kawasaki, Tsutomu T. Yanagida
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  ABSTRACT: We propose a curvaton model in which the initial condition of the curvaton oscillation is determined by its attractor behavior during inflation. Assuming a chaotic inflation model, we find that the initial condition determined by the attractor behavior is appropriate to generate a sizable non-Gaussianity contribution to the curvature perturbation, which will be tested in the foreseeable future. Implications on the thermal history of the universe and on particle physics models are also discussed.
  11/2012;
• Article: High Scale SUSY Breaking From Topological Inflation

  Keisuke Harigaya, Masahiro Kawasaki, Tsutomu T. Yanagida
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  ABSTRACT: The recently observed mass ~ 125 GeV for the Higgs boson suggests a high-energy scale SUSY breaking, above O(10) TeV. It is, however, very puzzling why nature chooses such a high energy scale for the SUSY breaking, if the SUSY is a solution to the hierarchy problem. We show that the pure gravity mediation provides us with a possible solution to this puzzle if the topological inflation is the last inflation in the early universe. We briefly discuss a chaotic inflation model in which a similar solution can be obtained.
  11/2012;
• Article: Seesaw mechanism with Occam’s razor

  Keisuke Harigaya, Masahiro Ibe, Tsutomu T. Yanagida
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  ABSTRACT: We discuss the seesaw mechanism which includes the minimum number of parameters for successful leptogenesis and three neutrino oscillations in the spirit of Occam’s razor. We show that models with two right-handed neutrinos with two texture zeros supported by Occam’s razor cannot fit the observed neutrino parameters consistently for the normal light neutrino mass hierarchy. For the inverted light neutrino mass hierarchy, on the other hand, we find that the models can fit the observed neutrino parameters consistently. Besides, we show that the model predicts the maximal Dirac CP-phase of the neutrino mixing matrix in the measurable range in the foreseeable future for the inverted neutrino mass hierarchy. We also show that the predicted effective Majorana neutrino mass responsible for the neutrinoless double beta decay is around 50 meV which is also within reach of future experiments.
  Phys. Rev. D. 07/2012; 86(1).
• Article: Seesaw Mechanism with Occam's Razor

  Keisuke Harigaya, Masahiro Ibe, Tsutomu T. Yanagida
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  ABSTRACT: We discuss the seesaw mechanism which includes the minimum number of parameters for successful leptogenesis and three neutrino oscillations in the spirit of Occam's razor. We show that models with two right-handed neutrinos with two texture zeros supported by Occam's razor cannot fit the observed neutrino parameters consistently for the normal light neutrino mass hierarchy. For the inverted light neutrino mass hierarchy, on the other hand, we find that the models can fit the observed neutrino parameters consistently. Besides, we show that the model predicts the maximal Dirac CP-phase of the neutrino mixing matrix in the measurable range in the foreseeable future for the inverted neutrino mass hierarchy. We also show that the predicted effective Majorana neutrino mass responsible for the neutrinoless double beta decay is around 50 meV which is also within reach of future experiments.
  05/2012;
• Article: Search for the Top Partner at the LHC using Multi-b-Jet Channels

  Keisuke Harigaya, Shigeki Matsumoto, Mihoko M. Nojiri, Kohsaku Tobioka
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  ABSTRACT: Vector-like quarks are introduced in various new physics models beyond the standard model (SM) at the TeV scale. We especially consider the case that the quark is singlet (triplet) under the SU(2)$_L$ (SU(3)$_c$) gauge group and couples only to the third generation quarks of the SM. The vector-like quark of this kind is often called a top partner. The top partoner $t_p$ decays into $bW, tZ$ and $th$. In the ATLAS and CMS collaborations, the top partner has been searched in the final states of $bW$ and $tZ$, while the search based on the decay mode $t_p\to th$ has not been started yet. However, the decay into $th$ is important since it is significantly enhanced if some strong dynamics exists in the TeV scale. In the presence of a light higgs boson, the decay mode $t_p\to th$ followed by $h\to b\bar{b}$ produces three bottom quarks. We study the sensitivity for the top partner using multi-b-jet events at the 8 TeV run of the LHC experiment. The multi-b-jet eventss turn out to play a complementary role to the existing $t_p\rightarrow bW$ and $tZ$ searches by the ATLAS and CMS collaborations.
  04/2012;
• Source

  Available from: ArXiv

  Article: Testing Little Higgs Mechanism at Future Colliders

  Keisuke Harigaya, Shigeki Matsumoto, Mihoko M. Nojiri, Kohsaku Tobioka
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  ABSTRACT: In the framework of the little higgs scenario, coupling constants of several interactions are related to each other to guarantee the stability of the higgs boson mass at one-loop level. This relation is called the little higgs mechanism. We discuss how accurately the relation can be tested at future e+e- colliders, with especially focusing on the top sector of the scenario using a method of effective lagrangian. In order to test the mechanism at the top sector, it is important to measure the Yukawa coupling of the top partner. We consider higgs associated production and threshold production of the top partner, and find that the mechanism can be tested precisely using the associate production when the center of mass energy is large enough. The threshold production also allows us to test it even if the center mass energy is not so large.
  09/2011;
• Source

  Available from: ArXiv

  Article: LHC Test of CDF $Wjj$ anomaly

  Keisuke Harigaya, Ryosuke Sato, Satoshi Shirai
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  ABSTRACT: We discuss a test of the CDF dijet anomaly at the LHC. The recent observed dijet mass peak at the CDF is well fitted by a new particle with a mass of around 150 GeV, which decays into two jets. In this paper, we focus on only $Wjj$ signal to avoid model dependence, and comprehensively study the LHC discovery/exclusion reach. We found almost all the models are inconsistent with the result of the LHC, unless only valence quarks contribute the new process. We also discuss further prospects of the LHC search for this anomaly.
  07/2011;