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A group of researchers including scientists from Nagoya University, the J-PARC Center, Tokyo Institute of Technology, Osaka University, Kyushu University, and Japan Atomic Energy Agency study the angular distribution of gamma-rays emitted from a neutron capture reaction with polarized neutrons. This is the basis of CP-violation research experiments using nuclear reactions. In particle physics CP-violation is one of the origins of the matter universe; however, only tiny violations have thus far been observed. Unknown CP-violating processes are sought through various …


Assistant Professor Takeshi Kobayashi of the Kobayashi-Maskawa Institute for the Origin of Particles and the Universe (KMI), Nagoya University, proposes that an elementary particle called the axion could have been the origin of the cosmic structure of our universe. Astrophysical studies in the past decades have established that the cosmic structure, including galaxies and galaxy clusters, arises from tiny fluctuations in the energy density when the universe was young; however the origin of this primordial density fluctuation still remains one …


A group of researchers including scientists from the RIKEN Nishina Center for Accelerator-Based Science, University of Tokyo, Nagoya University, and the Japan Atomic Energy Agency (JAEA) used the spin-polarized Relativistic Heavy Ion Collider at Brookhaven National Laboratory in the United States to show that in polarized proton-proton collisions, the neutral pions in the very forward area of collisions—where direct interactions involving quarks and gluons are not applicable—still have a large degree of left-right asymmetry. This finding suggests that the previous …


Scientists from the international XENON collaboration, an international experimental group including the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), University of Tokyo; the Institute for Cosmic Ray Research (ICRR), University of Tokyo; the Institute for Space-Earth Environmental Research (ISEE), Nagoya University; the Kobayashi-Maskawa Institute for the Origin of Particles and the Universe (KMI), Nagoya University; and the Graduate School of Science, Kobe University, announced today that data from their XENON1T, the world’s most sensitive dark …


Prototype Schwarzschild–Couder Telescope (pSCT, see Fig. 1), one of prototype telescopes developed for the Cherenkov Telescope Array (CTA) project, observed the Crab Nebula and successfully detected very-high-energy gamma rays from the object with a statistical significance of 8.3σ (Figs. 2–4). The viability of two new technologies used in pSCT, the Schwarzschild–Couder optical system with a large field of view of 8 degrees and a small camera pixel size of 6 mm realized by using silicone photomultipliers (SiPMs), have been proved …


  The Belle II experiment—an international collaboration of physicists searching for signs of undiscovered particles—has published the experiment’s first results in a paper selected as an Editors’ Suggestion in Physical Review Letters. The results offer physicists new clues in their hunt for dark matter, a substance believed to make up some 85% of the universe. The Belle II experiment, which operates at the SuperKEKB electron-positron collider in Tsukuba, Japan, searched for a hypothetical new particle called the Z’ that may …


Novel mechanism to avoid theoretical bound on kaon rare decays Researchers try to revisit a theoretical bound, which is based on symmetries, between the charged and neutral kaon rare decays into the pion and neutrinos. Last September, KOTO experiment searching for neutral kaon rare decay reported events with an unexpected rate, which is much bigger than the standard model predictions. So far, KOTO experiment has not claimed that these events are the rare kaon decay signals. On the other hand, …


  A research group including Associate Professor Kazuhiro Nakazawa, of the Kobayashi-Maskawa Institute for the Origin of Particles and the Universe (KMI), Nagoya University, detected a downward burst of gamma rays during lightning discharge with scintillation detectors at the Kashiwazaki-Kariwa Nuclear Power Station at sea level in Japan. This research was published in Physical Review Letters on August 7, 2019.   Although lightning is a familiar natural phenomenon, thunderclouds still hold many mysteries. Terrestrial gamma ray flashes (TGFs), which are …


A research group including Associate Professor Kazuhiro Nakazawa, KMI, Nagoya University has observed high-energy radiation phenomena coming from thunder-clouds, and found a prolonged steady emission resulted in a short burst of radiation associated with a lightning discharge. The evolution of the phenomena strongly suggests the initial long emission is related with the triggering of the lightning. The research group was performing ground-based gamma-ray observation campaign aiming at winter thunder-clouds in Hokuriku-region. In the work, they observed a minute-long radiation from …


“Neutron is a massive and chargeless particle, which can be used for various precision measurements”, Associate Professor Masaaki Kitaguchi of KMI says. “We have successfully developed a new type of position sensitive detector with extremely-high resolution of 11 nm. It can be a strong tool for experiments with neutrons.” Nuclear emulsion is used for various experiments for particle physics with muons and neutrinos, which is also applied to imaging through a pyramid today. Nagoya University team is continuing to develop …

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