110 citations · 427 across the 11 of their papers we have counts for
10 papers
Revisiting Bino-Slepton Coannihilation Dark Matter in Light of Recent Experimental Results
Koichi Hamaguchi, Atsuya Niki, Kwok Hei To
Despite being a simple and well-motivated thermal relic scenario, coannihilation dark matter (DM) has remained largely unexplored experimentally due to the difficulty of probing it…
Decaying gravitino dark matter and an upper bound on the gluino mass
Koichi Hamaguchi, Fuminobu Takahashi, T. T. Yanagida
We show that, if decaying gravitino dark matter is responsible for the PAMELA and ATIC/PPB-BETS anomalies in the cosmic-ray electron and positron fluxes, both a reheating temperatu…
Cosmic Ray Positron and Electron Excess from Hidden-Fermion Dark Matter Decays
Koichi Hamaguchi, Satoshi Shirai, T. T. Yanagida
The anomalies observed in recent cosmic ray experiments seem to strongly constrain the nature of the dark matter. In this letter, we investigate a possibility of the fermionic dark…
Decaying Dark Matter Baryons in a Composite Messenger Model
Koichi Hamaguchi, Eita Nakamura, Satoshi Shirai +1
A baryonic bound state with a mass of O(100) TeV, which is composed of strongly interacting messenger quarks in the low scale gauge mediation, can naturally be the cold dark matter…
Strongly Interacting Gauge Mediation at the LHC
Koichi Hamaguchi, Eita Nakamura, Satoshi Shirai +1
Strongly interacting gauge mediation (SIGM) of supersymmetry breaking is very attractive, since it naturally predicts a light gravitino of mass $\lsim{\cal O}(10)$ eV, which causes…
Supersymmetric seesaw model for the (1+3)-scheme of neutrino masses
F. Borzumati, K. Hamaguchi, T. Yanagida
A four-neutrino spectrum with a sterile neutrino without significant involvement in the atmospheric and solar neutrino oscillation experiments has been recently advocated as the co…
Cosmological Gravitino Problem in Gauge-Mediated Supersymmetry Breaking Models
T. Asaka, K. Hamaguchi, Koshiro Suzuki
We investigate the cosmological gravitino problem in gauge-mediated supersymmetry breaking models, where the gravitino becomes in general the lightest supersymmetric particle (LSP)…
Long-Lived Superheavy Particles in Dynamical Supersymmetry-Breaking Models in Supergravity
K. Hamaguchi, K. -I. Izawa, Yasunori Nomura +1
Superheavy particles of masses with lifetimes are very interesting, since their decays may account for the ultra-high en…
Long Lived Superheavy Dark Matter with Discrete Gauge Symmetries
K. Hamaguchi, Yasunori Nomura, T. Yanagida
The recently observed ultra-high energy (UHE) cosmic rays beyond the Greisen-Zatsepin-Kuzmin bound can be explained by the decays of some superheavy particles forming a part of…
Superheavy Dark Matter with Discrete Gauge Symmetries
K. Hamaguchi, Yasunori Nomura, T. Yanagida
We show that there are discrete gauge symmetries protect naturally heavy X particles from decaying into the ordinary light particles in the supersymmetric standard model. This make…