Hitoshi Murayama

Hitoshi MurayamaHitoshi Murayama

Hitoshi Murayama has worked on a wide range of subjects, including phenomenology of particle collider experiments, neutrino physics, dark matter models, baryogenesis, inflation, models of physics beyond the standard model, dynamics of supersymmetric field theories, topological field theory.

Popular Talk

  • Mystery of Anti-matter (Video). Talk at Physics is for Kids BBQ at Aspen Center for Physics aired by Grass Roots TV. See The Incredibles, Simpsons, and Einstein all in the same talk.
  • E=mc2. 2005 Buhl Lecture at Carnegie Mellon University, April 21, 2005. This famous equation, part of the theory of relativity set forth by Einstein in April 1905, changed our understanding of nature at the most fundamental level. "c" is the speed of light. It is the ultimate speed in the universe; nothing can go faster. "m" stands for mass. For centuries after Newton it was believed that mass is absolute. But this equation of Einstein revealed that mass is yet another form of energy, "E", that can change to other forms -- kinetic, gravitational, chemical, thermal, nuclear -- and back again to mass. An electron and an anti-electron annihilate into pure energy; in turn, energy can create matter and anti-matter. The fascinating story of energy and mass is still evolving a century since Einstein as we understand more of where they come from, how they shape the universe, and the missing pieces of the universe: Dark Matter and Dark Energy.
  • Watch a similar talk aired on UCTV (Video)


Research Accomplishments

  • He discovered anomaly mediation of supersymmetry breaking with Gian Giudice, Markus Luty, and Riccardo Rattazzi, with more than 500 citations to date. It is a subtle quantum mechanical effects of supergravity that eluded researchers for twenty years before this work. It has become one of the standard mechanisms of mediating supersymmetry breaking from the hidden sector with a remarkable "UV insensitivity" that solves the flavor problem in supersymmetry.
  • He proposed that the superpartner of right-handed neutrino is an attractive candidate for the inflaton with Hiroshi Suzuki, Tsutomu Yanagida, and Jun'ichi Yokoyama. It naturally creates the baryon asymmetry of the universe, together with dark matter. It predicts the tensor mode fluctuation detectable in the near future.
  • He invented a mechanism of electroweak symmetry breaking that does not rely on the Higgs mechanism using boundary conditions in extra dimensions with Csaba Csaki, Christophe Grojean, Luigi Pilo, and John Terning. It overcomes the usual unitarity constraint in the WW scattering by an infinite tower of spin one states, without any elementary spin zero bosons.
  • He initiated precision study of supersymmetry at colliders with Toshifumi Tsukamoto, Keisuke Fujii, Mashiro Yamaguchi, and Yasuhiro Okada. The technique outlined in this work can potentially uncover grand unification or supersymmetry breaking mechanism at 1016 GeV or beyond. He has been a strong advocate for International Linear Collider.
  • He showed rather tight cosmological limits on light gravitino predicted in models of gauge mediated supersymmetry breking with Takeo Moroi and Masahiro Yamaguchi.
  • He proposed a potential solution to the cosmic coincidence problem, why we seem to live at a special moment in the evolution of the universe when dark matter, dark energy, and radiation components of the universe have energy densities rather close to each other, with Nima Arkani-Hamed, Lawrence Hall, and Chris Kolda.
  • He has pointed out that traditional parameterization of neutrino oscillation data actually missed a half of the parameter space, which he dubbed "the dark side", with his students Alexander Friedland and André de Gouvêa.
  • He exposed the impact of underground proton decay search experiments on various scenarios of physics at unification and Planck scales, with Junji Hisano, Tsutomu Yanagida, David B. Kaplan, Aaron Pierce, Daniel Larson, Roni Harnik, and Marc Thormeier.
  • He is a member of the KamLAND experiment that has discovered "oscillation" of neutrinos coming from nuclear power plants.

Current Research Projects

  • Map out strategies to discriminate among many new physics scenarios at future collider experiments, by obtaining information on spin of new particles in a fully model independent fashion.
  • Work out complementarity between indirect dark matter detection experiments using gamma-rays and neutrinos, as well as direct detection exeperiments and colliders.
  • Demonstrate that the impact of hidden sector particles in his recent simplified mechanism of gauge mediation can be discerned at future colliders.
  • Discuss strategies on proving seesaw mechanism of neutrino mass as well as its relevance to the matter anti-matter asymmetry of the universe based on culmination of accelerator, astrophysical, laboratory, and underground experiments.