Koichi Hamaguchi

Supersymmetric standard model from the heterotic string.

We present a [FORMULA: SEE TEXT] orbifold compactification of the E8xE8 heterotic string which leads to the (supersymmetric) standard model gauge group and matter content. The quarks and leptons appear as three 16-plets of SO(10), whereas the Higgs fields do not form complete SO(10) multiplets. The model has large vacuum degeneracy. For generic vacua, no exotic states appear at low energies and the model is consistent with gauge coupling unification. The top quark Yukawa coupling arises from gauge interactions and is of the order of the gauge couplings, whereas the other Yukawa couplings are suppressed.

LEPTOGENESIS IN INFLATON DECAY

Abstract We study a leptogenesis via decays of heavy Majorana neutrinos produced non-thermally in inflaton decays. We find that this scenario is fully consistent with existing supersymmetric inflation models such as for topological or for hybrid inflation and the Froggatt-Nielsen mechanism generating hierarchies in quark and lepton mass matrices. The reheating temperature T R of inflation may be taken as low as T R ≃10 8 GeV to avoid the cosmological gravitino problem.

Leptogenesis in inflationary universe

We investigate leptogenesis via decays of heavy Majorana neutrinos which are produced nonthermally in inflaton decays. We make a comprehensive study on leptogenesis assuming various supersymmetric (SUSY) models for hybrid, new, and topological inflations. For an estimation of the lepton asymmetry we adopt the Froggatt-Nielsen mechanism for mass matrices of quarks and leptons. We find that all of these models are successful in producing enough lepton asymmetry to explain the baryon number in the present universe. Here we impose low reheating temperatures such as

Leptogenesis from (tilde)N-dominated early universe

{T}_{R}\ensuremath{\lesssim}{10}^{8}\mathrm{GeV}

Supergravity at colliders

in order to suppress the abundance of gravitinos so they do not conflict with big-bang nucleosynthesis. Furthermore, we find that leptogenesis works very well even with

Study of late decaying charged particles at future colliders

{T}_{R}\ensuremath{\simeq}{10}^{6}\mathrm{GeV}

Leptogenesis with almost degenerate majorana neutrinos

in the SUSY hybrid or new inflation model. It is known that such a reheating temperature is low enough to suppress the abundance of gravitinos of mass

Cosmological gravitino problem in gauge-mediated supersymmetry breaking models

{m}_{3/2}\ensuremath{\simeq}100\mathrm{GeV}

Higgsino and wino dark matter from Q-ball decay in Affleck–Dine baryogenesis

\char21{}1 TeV. Thus, leptogenesis is fully consistent with big-bang nucleosynthesis in a wide region of the gravitino mass.

Higgs Mass and Muon Anomalous Magnetic Moment in Supersymmetric Models with Vector-Like Matters

We investigate in detail leptogenesis by the decay of a coherent right-handed sneutrino