Butsuri
Online ISSN : 2423-8872
Print ISSN : 0029-0181
ISSN-L : 0029-0181
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Showing 1-23 articles out of 23 articles from the selected issue
Preface
Contents
Interdisciplinary
  • Kazunori Akiyama, Masanori Nakamura, Yosuke Mizuno, Mareki Honma
    2020 Volume 75 Issue 1 Pages 4-9
    Published: January 05, 2020
    Released: July 13, 2020
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    On April 10, 2019, the Event Horizon Telescope (EHT) collaboration has revealed the first-ever images of a black hole shadow. This exciting news immediately ran around the world. The EHT links ground-based radio telescopes around the globe to form an Earth-sized computational telescope with an unprecedented high angular resolution using very long baseline interferometry (VLBI) at millimeter wavelengths. The first images they successfully obtained are the visual evidence of a supermassive black hole (SMBH) at the center of a giant elliptical galaxy M87. The final images reveal an asymmetric ring morphology of the central compact radio source with a diameter of 42±3 μas. This strongly suggests that we see gravitationally lensed emission from plasma located very close to the SMBH event horizon. From the measured ring size, we derived a SMBH mass of (6.5±0.7)×109M⦿. The image provides solid evidence for the presence of a BH at the center of M87 and supports the longstanding hypothesis that a SMBH powers an active galactic nucleus. Moreover, it demonstrates that VLBI at millimeter/submillimeter wavelengths offers a powerful method to explore gravity in its most extreme limit and at a previously inaccessible mass scale. An existence of the black hole in the universe, Albert Einstein first predicted it over a century ago with his general theory of relativity, has been finally confirmed by the EHT collaboration. In this volume, we will overview the project, and introduce data processing and imaging. Then, we describe the comparison with the theory and the interpretation of observations to conclude the physics behind. Future direction of the EHT is also briefly outlined.

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Researches
  • Masahiko Iwasaki, Fuminori Sakuma, Takumi Yamaga
    Type: Researches
    2020 Volume 75 Issue 1 Pages 10-15
    Published: January 05, 2020
    Released: July 13, 2020
    JOURNALS RESTRICTED ACCESS

    We observed a nucleus consist of a K- meson and two protons, “K-pp”, at the J-PARC. The binding energy is as large as ~50 MeV, which is about 10 times larger than the standard nuclear binding energy, and the width is ~100 MeV. The momentum transfer analysis is indicating that the size of “K-pp” could be as small as ~0.5 fm. The results will provide new insights on the origin of hadron mass and the physics at the very high density matter, such as a core of neutron stars.

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  • Yuta Takahashi, Shigeki Hirose, Yutaro Sato, Katsuro Nakamura
    Type: Researches
    2020 Volume 75 Issue 1 Pages 16-21
    Published: January 05, 2020
    Released: July 13, 2020
    JOURNALS RESTRICTED ACCESS

    Interactions of elementary particles are a key to understand the origin of our universe. Recently the BaBar, Belle and LHCb experiments have reported an anomaly in B meson decays, which may be a hint of lepton flavor universality violation induced by leptoquarks with a mass of O(1) TeV. In response, the ATLAS and CMS experiments have accelerated their direct searches for the leptoquarks with 13 TeV pp collisions at the Large Hadron Collider. These experiments have been driving new physics searches with different approaches. The B-anomaly may be resolved in the next few years as a discovery of new physics, which can change our current understanding of elementary particles dramatically.

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  • Takatsugu Ishikawa, Jirohta Kasagi
    Type: Researches
    2020 Volume 75 Issue 1 Pages 22-27
    Published: January 05, 2020
    Released: July 13, 2020
    JOURNALS RESTRICTED ACCESS

    The total and differential cross sections for the γd→π0π0d reaction has been measured at the Research Center for Electron Photon Science (ELPH), Tohoku University, for the first time. The total cross section as a function of the γd center-of-mass energy shows resonance-like behavior peaked at approximately 2.47 and 2.63 GeV. In π0d invariant-mass distributions, a clear peak is observed at 2.14±0.01 GeV with a width of 0.09±0.01 GeV. The measured angular distribution of deuteron emission is rather flat, suggesting a sequential process γdRIS→π0RIV→π00d) with isoscalar (I=0) and isovector (I=1) dibaryon states RIS and RIV, respectively. Dibaryons seem to be selectively produced in coherent double neutral-meson photoproduction reactions. We try to search for other dibaryons and investigate properties of them looking at this kind of reactions. Using the virtual photon γ* in electron inelastic scattering instead of the real photon γ, information on the size of isoscalar dibaryon states would be obtained.

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  • Ryuhei Harada
    Type: Researches
    2020 Volume 75 Issue 1 Pages 28-33
    Published: January 05, 2020
    Released: July 13, 2020
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    Rare events relevant to the biological functions are induced in long-time scales. Generally, it is difficult to identify the rare events of biomolecules due to the limitation of current accessible time scales of normal MD simulations. To identify the rare events efficiently, we have developed several rare event sampling methods based on distributed computing. In the present paper, we review one of our rare event sampling methods called outlier flooding method (OFLOOD) and introduce its applications to mini-proteins in order to elucidate their folding pathways.

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  • Ken H. Nagai, Hiroshi Ito, Takuma Sugi
    Type: Researches
    2020 Volume 75 Issue 1 Pages 34-39
    Published: January 05, 2020
    Released: July 13, 2020
    JOURNALS RESTRICTED ACCESS

    Our study of collective motion of nematodes is introduced. To investigate the dependence of the collective motion on various parameters, we used Caenorhabditis elegans, which can be observed under diverse conditions and whose many types of motility mutants are known. When worms were highly concentrated, they formed a dynamically fluctuating network structure on a glass substrate, a plastic substrate, and agar surface. We constructed a minimal multi-particle model considering the characteristics of motility of isolated worms and the two-body interaction of worms. With a large number of particles, a dynamical network corresponding to that of worms was formed. The dependence of the collective motion on various parameters was well reproduced by the model.

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