Kazuhiro Tobe

Physics at a future Neutrino Factory and super-beam facility

The conclusions of the Physics Working Group of the International Scoping Study of a future Neutrino Factory and super-beam facility (the ISS) are presented. The ISS was carried out by the international community between NuFact05, (the 7th International Workshop on Neutrino Factories and Super-beams, Laboratori Nazionali di Frascati, Rome, 21–26 June 2005) and NuFact06 (Ivine, CA, 24–30 August 2006). The physics case for an extensive experimental programme to understand the properties of the neutrino is presented and the role of high-precision measurements of neutrino oscillations within this programme is discussed in detail. The performance of second-generation super-beam experiments, beta-beam facilities and the Neutrino Factory are evaluated and a quantitative comparison of the discovery potential of the three classes of facility is presented. High-precision studies of the properties of the muon are complementary to the study of neutrino oscillations. The Neutrino Factory has the potential to provide extremely intense muon beams and the physics potential of such beams is discussed in the final section of the report.The conclusions of the Physics Working Group of the International Scoping Study of a future Neutrino Factory and super-beam facility (the ISS) are presented. The ISS was carried out by the international community between NuFact05, (the 7th International Workshop on Neutrino Factories and Superbeams, Laboratori Nazionali di Frascati, Rome, June 21-26, 2005) and NuFact06 (Irvine, California, 2430 August 2006). The physics case for an extensive experimental programme to understand the properties of the neutrino is presented and the role of high-precision measurements of neutrino oscillations within this programme is discussed in detail. The performance of second generation super-beam experiments, beta-beam facilities, and the Neutrino Factory are evaluated and a quantitative comparison of the discovery potential of the three classes of facility is presented. High-precision studies of the properties of the muon are complementary to the study of neutrino oscillations. The Neutrino Factory has the potential to provide extremely intense muon beams and the physics potential of such beams is discussed in the final section of the report. The ISS Physics Working Group Editors: S.F. King1, K. Long2, Y. Nagashima3, B.L. Roberts4, and O. Yasuda5.

Lepton-Flavor Violation in the Supersymmetric Standard Model with Seesaw-Induced Neutrino Masses

Abstract We examine the lepton-flavor violation caused by a Yukawa coupling matrix y ν , ij for right-handed neutrinos in the supersymmetric standard model. We stress that decay rates for τ → μγ and μ → eγ are largely enhanced in a parameter region where left-right mixing terms in the slepton mass matrix are substantially large. Especially, these decay rates may reach the range to be accessible to near future experiments even if the SO(10)-like boundary condition on y ν , ij is used. We also discuss how the rates behave if one changes the ansatz on the Yukawa coupling matrix for the right-handed neutrinos.

Phenomenology of a littlest Higgs model with T parity: Including effects of T-odd fermions

We study the collider phenomenology of a littlest Higgs model with T parity. We first stress the important role of the T-odd SU(2)-doublet fermions (introduced to make the model T-parity invariant) in high energy scattering processes, such as qq? ?WH+WH- where WH± are the T-odd partners of W bosons. Because the mass of the T-odd SU(2)-doublet fermions cannot be too heavy to be consistent with low energy data, they can be copiously produced at the CERN Large Hadron Collider (LHC). Therefore, we study the collider phenomenology of the model with emphasis on the contributions of the T-odd fermion to the production of the heavy T-parity partners (either bosons or fermions) of the usual particles at the LHC. The production cross sections and the decay branching ratios of the new heavy particles are classified and various experimental signatures are discussed.

Higgs boson production and decay in little Higgs models with T-parity

Abstract We study Higgs boson production and decay in a certain class of little Higgs models with T-parity in which some T-parity partners of the Standard Model (SM) fermions gain their masses through Yukawa-type couplings. We find that the Higgs boson production cross section of a 120 GeV Higgs boson at the CERN LHC via gg fusion process at one-loop level could be reduced by about 45%, 35% and 20%, as compared to its SM prediction, for a relatively low new particle mass scale f = 600 , 700 and 1000 GeV, respectively. On the other hand, the weak boson fusion cross section is close to the SM value. Furthermore, the Higgs boson decay branching ratio into di-photon mode can be enhanced by about 35% in small Higgs mass region in certain case, for the total decay width of Higgs boson in the little Higgs model is always smaller than that in the SM.

Suppression of proton decay in the missing-partner model for supersymmetric SU(5) GUT

Abstract We construct a missing-partner model for supersymmetric SU(5) GUT assuming the Peccei-Quinn symmetry, in which the SU(5) gauge coupling constant remains in the perturbative regime below the gravitational scale ∼ 2.4 × 1018 GeV. The Peccei-Quinn symmetry suppresses the dangerous dimension-five operators for the nucleon decay much below the limit from the present proton-decay experiments. We also stress that due to this suppression mechanism our model can accommodate even the large tan βH (∼ 60) scenario which has been recently suggested to explain the observed value of the m b m τ ratio.

Light minimal supersymmetric standard model Higgs boson scenario and its test at hadron colliders.

We show that in the Minimal Supersymmetric Standard Model, the possibility for the lightest CP-even Higgs boson to be lighter than

Exact event rates of lepton flavor violating processes in supersymmetric SU(5) model [Phys. Lett. B 391 (1997) 341]

Z

Virtual effects of light gauginos and higgsinos : A precision electroweak analysis of split supersymmetry

boson (as low as about 60 GeV) is, contrary to the usual belief, not yet excluded by LEP2 data or any other existing experimental data. The characteristic of the light Higgs boson scenario (LHS) is that the

Survey of Higgs interpretations of the diboson excesses

ZZh

Testing the littlest Higgs model with T parity at the CERN Large Hadron Collider

coupling and the decay branching ratio