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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 …


  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 …