The University of Tokyo · Physics and Astronomy
Professor Hitoshi Murayama's research lab focuses on theoretical particle physics and cosmology, exploring physics beyond the Standard Model through minimal and phenomenologically viable extensions. Key research directions include baryogenesis, leptogenesis, dark matter, and inflationary cosmology, with a strong emphasis on connecting fundamental particle physics with cosmological observations. The lab develops models that unify dark energy, dark matter, neutrino masses, and baryon asymmetry within a minimal framework, often using supersymmetry and supergravity to address these puzzles. Recent work centers on right-handed sneutrino-driven chaotic inflation and the role of supersymmetric particles in generating the observed matter-antimatter asymmetry.
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We construct the new Minimal Standard Model that incorporates the new discoveries of physics beyond the Minimal Standard Model (MSM): dark energy, non-baryonic dark matter, neutrino masses, as well as baryon asymmetry and cosmic inflation, adopting the principle of minimal particle content and the most general renormalizable Lagrangian. We base the model purely on empirical facts rather than aesthetics. We need only six new degrees of freedom beyond the MSM. It is free from excessive flavor-chan
We make explicit the statement that the minimal supersymmetric (SUSY) SU(5) model has been excluded by the SuperKamiokande search for the process $\stackrel{\ensuremath{\rightarrow}}{p}{K}^{+}\overline{\ensuremath{\nu}}.$ This exclusion is made by first placing limits on the colored Higgs triplet mass, by forcing the gauge couplings to unify. We also show that taking the superpartners of the first two generations to be very heavy in order to avoid flavor changing neutral currents, the so-called
We present a model of chaotic inflation driven by the superpartner of the right-handed neutrino (N${\mathrm{\ifmmode \tilde{}\else \~{}\fi{}}}_{\mathit{R}}$). This model gives the correct magnitude of the density perturbation observed by the Cosmic Background Explorer satellite with a right-handed neutrino mass \ensuremath{\simeq}${10}^{13}$ GeV, which is also preferred by the Mikheyev-Smirnov-Wolfenstein solution to the solar neutrino problem. The reheating process is the dacay of the coherentl
We propose a K\"ahler potential in supergravity which successfully accommodates chaotic inflation. This model can have a large gravitino mass without giving a large mass to squarks and sleptons, and thus is free from both the gravitino problem and entropy crisis. In this model baryogenesis takes places naturally, identifying the inflaton with a right-handed sneutrino with its mass M\ensuremath{\simeq}${10}^{13}$ GeV, which is consistent with the COBE data and the Mikheyev-Smirnov-Wolfenstein sol
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