Masato Yamanaka

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Relic abundance of dark matter is investigated in the framework of universal extra dimension models with right-handed neutrinos. These models are free from the serious Kaluza-Klein (KK) graviton problem that the original universal extra dimension model has. The first KK particle of the right-handed neutrino is a candidate for dark matter in this framework,(More)
Modification of standard big-bang nucleosynthesis is considered in the minimal supersymmetric standard model to resolve the excessive theoretical prediction of the abundance of primordial lithium 7. We focus on the stau as a next-lightest superparticle, which is long lived due to its small mass difference with the lightest superparticle. It provides a(More)
Universal extra dimension (UED) models with right-handed neutrinos are studied. The introduction of the neutrinos makes us possible not only to describe Dirac neutrino masses but also to solve the cosmological problem called the KK graviton problem. This problem is essentially caused by the late time decay of a KK photon into a KK graviton and a photon, and(More)
We calculate the production rates of the second Kaluza-Klein (KK) photon γ(2) and Z boson Z(2) at the LHC including all significant processes in the minimal universal extra dimension model. For discrimination of the minimal universal extra dimension model from other TeV scale models in the hadron collider experiment, γ(2) and Z(2) play a crucial role. In(More)
Relic abundance of dark matter is investigated in the framework of universal extra dimension models with right-handed neutrinos. These models are free from the serious KaluzaKlein (KK) graviton problem that the original universal extra dimension model possesses. The first KK particle of the right-handed neutrino is a candidate for dark matter in this(More)
Toshifumi Jittoh, Kazunori Kohri, 3 Masafumi Koike, Joe Sato, Takashi Shimomura, 5 and Masato Yamanaka Department of Physics, Saitama University, Shimo-okubo, Sakura-ku, Saitama, 338-8570, Japan Physics Department, Lancaster University LA1 4YB, UK Department of Physics, Tohoku University, Sendai 980-8578, Japan Departament de F ísica Teòrica and IFIC,(More)
We propose a new process of μ- e- → e- e- in a muonic atom for a quest of charged lepton flavor violation. The Coulomb attraction from the nucleus in a heavy muonic atom leads to significant enhancement in its rate, compared to μ+ e- → e+ e-. The upper limit of the branching ratio is estimated to be of the orders of O(10(-17)-10(-18)) for the photonic and(More)