– Theory –
Theoretical Elementary Particle Physics Laboratory [E Lab]
Junji HISANO, Masaharu TANABASHI (Professor)
Masaki SHIGEMORI (Designated Professor (G30))
Masashi HAYAKAWA, Nobuhiro MAEKAWA, Tadakatsu SAKAI, Kazuhiro TOBE (Associate Professor)
Yuki SATO (Research Assistant Professor)
Through research on elementary particle phenomena over a wide energy range from 1 GeV to 1019 GeV, we are developing new particle theory models which go beyond the present Standard Model. We also investigate the dynamics of field theories as a framework describing properties of elementary particles. Current topics include dynamical symmetry breaking models (composite Higgs models), supersymmetric/extra-dimensional theories and related elementary particle phenomena, grand unified theory, superstring theory, ultra-high precision calculation of QED, and lattice gauge theory. In addition, we are studying mathematical aspects of field theories.
Quark-Hadron Theory Group [H Lab]
Masayasu HARADA (Professor)
Chiho NONAKA, (Associate Professor)
We aim to theoretically understand diverse phenomena of quarks/gluons and their many-body systems, or hadrons, in the fundamental theory of strong interaction, QCD. Research subjects include hadron properties and phase transition phenomena in QCD at high temperatures and high densities, phenomenology of heavy-ion collision experiments, and hadron structure. With an eye to experiments as well as theoretical aspects, we are developing new theories in an effective theory framework, phenomenological models, and fundamental aspects of QCD using lattice QCD, as well as novel analytical approaches based on these theories.
Gravity and Particle Cosmology Group [QG Lab]
Shin’ichi NOJIRI (Professor)
Yasusada NAMBU (Associate Professor)
YOO Chulmoon (Lecturer)
In our laboratory, we are investigating gravitational physics including higher dimensional theories like superstring. We try to solve the problems of the inflation epoch in the early universe, and accelerating expansion of the present universe, and the phenomena under the strong gravity as in the black hole. We aim to find any constraint and/or any clue for the understanding of the nature of the gravity theory from the cosmological observations etc. We are mainly working in the following themes of recent researches.
Dark energy: Now it is believed that there should be something unknown, whose density should be about 70% of the critical density, in the present universe. We call this substance as “dark energy”. The dark energy is generating the accelerating expansion of the universe. We are now investigating, various models of the dark energy and we aim to obtain any clue of the theory coming from higher dimensions, like superstring theory, and we are considering how we could verify this kind of theory by the experiments and/or observations.
Space-time and quantum theory: Various phenomena in physics occurs in the container called “space-time”, whose shape is deformed by the gravity. It is believed that the quantum theory of the gravity could be obtained by summing up the shapes of the space-time. By using the formulation where the summation is obtained by discretizing the space-time into a set of simplices as in Figure, we try to clarify the nature of the gravity as a quantum theory.
Other topics: We are also studying the primordial fluctuations via quantum effects by considering the quantum entanglement. Black hole physics, like the Hawking radiation by using the fluid, the high energy phenomena, which could be generated by an extremely large black hole in the nucleus of active galaxies, etc., are also investigated.
Theoretical Plasma Physics Laboratory [P Lab]
Tomo-Hiko WATANABE (Professor)
Shinya MAEYAMA (Lecturer)
Plasmas in laboratories and space involve a variety of nonlinear phenomena in the non-equilibrium states. Turbulence and shocks are the typical examples. We are theoretically studying the nonlinear plasma physics by utilizing numerical methods and high performance computing. Current research topics cover kinetic plasma turbulence and transport, shock formation and particle acceleration in space, self-excitation of auroras etc. We are also developing numerical methods for fluid and kinetic plasma simulations as well as nonlinear plasma theories.
Cosmology Group [C Lab]
Naoshi SUGIYAMA (Professor)
Kiyotomo ICHIKI (Associate Professor)
Hiroyuki TASHIRO (Research Associate Professor)
Atsushi NISHIZAWA (Research Lecturer)
Shu-ichiro YOKOYAMA (Assistant Professor)
Daichi KASHINO (Research Assistant Professor)
We are theoretically studying the origin and evolution of structures in the universe. We are mostly working on the field of Observational Cosmology. With recent breakthroughs in space observation techniques, unexpected features of the universe have been successively revealed. This situation highlights the role of theoretical research toward understanding phenomena in the universe. In our laboratory, we strive to theoretically understand the hierarchy of the universe from celestial bodies such as stars and galaxies to the universe itself, through physics and multifaceted approaches, including analytic theory, numerical simulation, and theoretical analysis of observational data.
Laboratory of Theoretical Astronomy & Astrophysics [TA Lab]
Shu-ichiro INUTSUKA (Professor)
Tsuyoshi INOUE (Associate Professor)
Hiroshi KOBAYASHI (Assistant Professor)
We investigate the origins of astrophysical objects in the universe. Although our current focus is mainly on the formation of stars and planets, we are also investigating various astrophysical processes such as cosmic ray acceleration, gas accretion and energy dissipation around compact objects, etc. using analytical and numerical methods for Newtonian or relativistic (magneto-)hydrodynamics and kinematics.
Laboratory of Galaxy Evolution [Ω Lab]
Tsutomu T. TAKEUCHI (Associate Professor)
A galaxy is a large agglomeration of stars, gas, and dark matter, and is a fundamental unit on the cosmological scale. Galaxies appear to be very different in various wavelengths or energy regions, hence multiwavelength observations are fundamentally important. In the context of cosmic evolution over the last 13.7 billion years, we are examining the formation and evolution of galaxies, with an emphasis of their star formation activities. As a multi-wavelength approach, we study galaxy evolution from two standpoints: data analysis from ground-based instruments, space telescopes, and astronomical satellites, and modeling of the emission from galaxies which reproduce observations.
We have also just started to explore the physics of the very early Universe with radio data taken with ground based and space facilities by applying our knowledge and experience on galaxy evolution.
Science of Complexity Theory Laboratory [ΣT Lab]
Hitoshi SAKAGAMI (Visiting Professor)
We investigate complexity as it appears in high energy-density physics and, in particular, in laser plasmas, via computer simulations. Current research topics include particle acceleration by short pulse lasers, which is expected to have medial applications. We are also interested in the generation of highly-energetic electrons by ultra-high intensity lasers, since this is one of the crucial issues in fast ignition of laser fusion. Another topic under investigation is the inevitable hydrodynamic instability in implosion of laser fusion. In order to carry out these studies, we are developing new techniques for high-performance computing and highly accurate simulations. These techniques will allow unparalleled level of insight into a variety of scientific problems.
The interaction between an ultra-high intensity laser and overdense plasma for fast ignition research.
– Experiment –
Fundamental Particle Physics Laboratory [F Lab]
Mitsuhiro NAKAMURA (Professor)
Toshiyuki NAKANO (Lecturer)
Osamu SATO (Assistant Professor)
Tsutomu FUKUDA, Hiroki ROKUJYO (Research Assistant Professor)
Identifying dark matter, which remains a mystery, is the ultimate challenge in elementary particle physics. Neutrino mass, if it exists, may partly solve this mystery. Although observations of cosmic rays and solar neutrinos suggest neutrino oscillation, neutrinos resulting from an oscillation have yet to be captured. However, nuclear emulsion technology as along with an international collaboration with research groups in Europe has enabled the OPERA experiment, which aims to capture emerging tau-neutrinos. This nuclear emulsion technology focuses on a very powerful method of searching for supersymmetric particles, or WIMPs, and a project using this technology is in the planning stages. The nuclear emulsion technology, which our laboratory has been developing for more than thirty years, is employed not only in elementary particle research,
but is also finding applications in the research of hadrons containing charm quarks and γ-ray astronomy as well as the diagnosis of the interior of reinforced columns and blast furnaces, which X-rays cannot penetrate.
High Energy Physics Laboratory [N Lab]
Toru IIJIMA (Professor)
Makoto TOMOTO (Research Professor)
Kenji INAMI (Associate Professor)
Yasuyuki HORII (Lecturer)
We use frontier high-energy particle accelerators to study elementary particles, which constitute matter, and their interactions. In the B-factory experiment, we use an electron-positron collider with the world’s highest luminosity, and study the violation of particle-antiparticle symmetry (CP violation) in B-meson decays and searching for tau-lepton decays induced by new physics beyond the standard model. In Europe, the LHC experiment, which is a proton-proton collision experiment with the world’s highest energy, has been launched. In this experiment, we try to discover the Higgs particle, which is predicted by theory to explain the origin of mass, and also new particles beyond the standard model.
Furthermore, we are actively conducting research and development on the TOP counter and aerogel RICH, which are particle detectors originating from our own ideas.
Laboratory of Particle Properties [Φ Lab]
Hirohiko SHIMIZU (Professor)
Masaaki KITAGUCHI (Associate Professor)
Katsuya HIROTA, Hideki KORI (Research Associate Professor)
Takuya OKUDAIRA (Assistant Professor)
We study the properties of elementary particles and physics laws behind them through precision measurements.
We start our researches with the slow neutrons: the chargeless massive particle with the lifetime as long as 15 minutes.
We apply advanced neutron optics to control the instantaneously most intense slow neutrons in the energy range of 100 neV to 1 eV from the spallation neutron source of the J-PARC (Japan Proton Accelerator Research Complex) to overcome the present experimental limitations to discover new physics in the breaking of discrete symmetries, short-range gravity, etc.
Laboratory of Cosmic-Ray Imaging [μ Lab]
Kunihiro MORISHIMA(Associate Professor)
Nobuko KITAGAWA(Research Assistant Professor)
Radio Astronomy Laboratory [A Lab]
Yoichi TAMURA, Kengo TACHIHARA (Associate Professor)
Hiroaki YAMAMOTO (Assistant Professor)
Understanding how stars, galaxies and supermassive black holes formed and have been evolved across the Hubble time is one of the biggest challenges in modern astrophysics. We are trying to address those big questions by exploiting millimeter/submillimeter-wave observations of interstellar gas and dust---origins of every astronomical objects---in the Milky Way, nearby and high redshift galaxies. We use not only NANTEN2, a 4-m radio telescope that we are operating in Chile, to study molecular clouds in the Milky Way and the Magellanic Clouds, but ASTE and ALMA to unveil forming galaxies in the remote Universe. We also develop instruments for these existing and future radio telescopes which allow for cutting-edge sciences.
Space Astronomy Laboratory (Infrared Astronomy Group) [UIR Lab]
Hidehiro KANEDA (Professor)
Taro MATSUO (Associate Professor)
Kumiko MORIHANA (Lecturer)
Takuma KOKUSHO (Assistant Professor)
The main purpose of our research is to understand the properties of interstellar dust and gas under various environments in our Galaxy and nearby galaxies through near- to far-infrared observations using satellites and balloons. We have developed a far-infrared imaging spectrometer for AKARI, the first Japanese infrared astronomical satellite, which was launched in February 2006. We are analyzing AKARI data extensively to pursue the above scientific researches. We are also developing cryogenic optics and far-infrared detectors for future space missions such as SPICA. We are deeply involved in the JAXA-led project of SPICA, which will be the 2nd Japanese infrared astronomical satellite to be launched in 2017.
Space Astronomy Laboratory (High-energy Astronomy Group) [Uxg Lab]
Seiji KAWAMURA (Professor)
Kazuhiro NAKAZAWA (Associate Professor)
Kazunori ISHIBASHI, Ikuyuki MITSUISHI(Lecturer)
By observing the universe with high-energy photons (X-rays) or even gravitational waves (GW), we can investigate the high-energy phenomena in the universe. We are developing new GW detection schemes such as space antenna, DECIGO, for low-frequency GWs from the inflation period in the early universe. We are also developing next generation X-ray mirrors, its multilayer reflectors, and high-throughput thermal shields, and observing energetic objects, such as clusters of galaxies and super massive black holes. We are the member of X-ray observatories to be launched soon, such as XRISM for spectroscopy and IXPE for X-ray polarimetry and proposing more. Observational research on the misterious MeV gamma-rays of thunder-cloud are also on-going.
Science of Complexity Experiment Laboratory [ΣE Lab]
Kenichi NAGAOKA (Visiting Professor)
A remarkable characteristic of plasma as a nonlinear medium is the “self-organization” of spatiotemporal structures through the interplay of instability and nonlinearity. This phenomenon is widely observed in space, solar atmosphere, ionosphere and in laboratory devices. In our research group, linear and nonlinear phenomena in plasmas are experimentally studied by exploring a variety of laboratory plasmas.
Our experiments are mainly performed at the Large Helical Device and “HYPER-I” at the National Institute for Fusion Science.