Author
Y. Yamamoto
Bio: Y. Yamamoto is an academic researcher from Konan University. The author has contributed to research in topics: Air shower & Cosmic ray. The author has an hindex of 24, co-authored 132 publications receiving 2413 citations.
Topics: Air shower, Cosmic ray, Medicine, Gamma ray, Telescope
Papers published on a yearly basis
Papers
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Hirosaki University1, Saitama University2, Chinese Academy of Sciences3, Yokohama National University4, Hebei Normal University5, Tibet University6, Shandong University7, Southwest Jiaotong University8, Yunnan University9, Kanagawa University10, Utsunomiya University11, University of Tokyo12, Konan University13, Shibaura Institute of Technology14, Shinshu University15, Tsinghua University16, Waseda University17, National Institute of Informatics18, College of Industrial Technology19, Shonan Institute of Technology20
TL;DR: Two-dimensional high-precision anisotropy measurement for energies from a few to several hundred teraelectronvolts (TeV) is presented, using the large data sample of the Tibet Air Shower Arrays, revealing finer details of the known anisotropies.
Abstract: The intensity of Galactic cosmic rays is nearly isotropic because of the influence of magnetic fields in the Milky Way. Here, we present two-dimensional high-precision anisotropy measurement for energies from a few to several hundred teraelectronvolts (TeV), using the large data sample of the Tibet Air Shower Arrays. Besides revealing finer details of the known anisotropies, a new component of Galactic cosmic ray anisotropy in sidereal time is uncovered around the Cygnus region direction. For cosmic-ray energies up to a few hundred TeV, all components of anisotropies fade away, showing a corotation of Galactic cosmic rays with the local Galactic magnetic environment. These results have broad implications for a comprehensive understanding of cosmic rays, supernovae, magnetic fields, and heliospheric and Galactic dynamic environments.
259 citations
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Hirosaki University1, Chinese Academy of Sciences2, Yokohama National University3, Hebei Normal University4, Tibet University5, Shandong University6, Southwest Jiaotong University7, Yunnan University8, Kanagawa University9, Utsunomiya University10, University of Tokyo11, Konan University12, Waseda University13, Shinshu University14, Tsinghua University15, Saitama University16, National Institute of Informatics17, College of Industrial Technology18, Max Planck Society19, Shonan Institute of Technology20
TL;DR: In this paper, the authors presented an updated all-particle energy spectrum of primary cosmic rays in a wide range from 10 14 to 10 17 eVusing 5:5 ; 10 7 events collected from 2000 November through 2004 October by the Tibet-III air-shower array located 4300 m in altitude.
Abstract: We present an updated all-particle energy spectrum of primary cosmic rays in a wide range from 10 14 to 10 17 eVusing 5:5 ; 10 7 events collected from 2000 November through 2004 October by the Tibet-III air-shower array located 4300 m abovesealevel(anatmosphericdepthof 606gcm � 2 ).Thesizespectrumexhibitsasharpkneeatacorrespondingprimary energy around 4 PeV. This work uses increased statistics and new simulation calculations for the analysis. We discuss our extensive Monte Carlo calculations and the model dependencies involved in thefinal result, assuming interaction models QGSJET01c and SIBYLL2.1, and heavy dominant (HD) and proton dominant (PD) primary composition models. Pure protonandpureironprimarymodelsarealsoexaminedasextremecases.A detector simulationwasalsoperformedtoimproveouraccuracyindeterminingthesizeof theairshowersandtheenergyof theprimaryparticle.Weconfirmedthatthe all-particle energy spectra obtained under various plausible model parameters are not significantly different from each other, which was the expected result given the characteristics of the experiment at high altitude, where the air showers of the primary energy around the knee reach near-maximum development, with their features dominated by electromagnetic components,leadingtoaweakdependenceontheinteractionmodel or theprimarymass.Thisisthehighest statistical and the best systematics-controlled measurement covering the widest energy range around the knee energy region.
194 citations
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TL;DR: In this article, five emulsion chambers were analyzed with two different dilution factors exposed to the 50-, 100-, and 300-GeV electron beams at Fermi National Accelerator Laboratory.
Abstract: Five emulsion chambers were analyzed with two different dilution factors exposed to the 50-, 100-, and 300-GeV electron beams at Fermi National Accelerator Laboratory. The longitudinal development and lateral distribution of the number of shower tracks within a certain radius (\ensuremath{\le} 100 \ensuremath{\mu} m) both roughly agree with the theoretical transition and lateral curves by Nishimura and Kidd connected by a spacing factor equal to the dilution factor. The error of the cascade energy measurement by the conventional way, using the transition curves within a radius 50 \ensuremath{\mu} m, is 18-28% for 50-100 GeV and 13-14% for 300 GeV. Track length within a cylinder of the same radius gives less ambiguity than the above method, when the track length is summed up till the depth is greater than 1.4 times the depth of the maximum number of shower tracks within a radius 50 \ensuremath{\mu} m. Other results with details are also described.
189 citations
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TL;DR: In this article, the authors evaluate the exposure during nadir observations with JEM-EUSO, the Extreme Universe Space Observatory, on-board the Japanese Experiment Module of the International Space Station.
148 citations
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Hirosaki University1, Saitama University2, Chinese Academy of Sciences3, Tibet University4, Shandong University5, Southwest Jiaotong University6, Yunnan University7, Kanagawa University8, Utsunomiya University9, University of Tokyo10, Konan University11, Shibaura Institute of Technology12, Yokohama National University13, Shinshu University14, Shonan Institute of Technology15
TL;DR: In this paper, the sidereal anisotropy of cosmic ray intensity in the multi-TeV region observed with the Tibet-III air shower array during the period from 1999 through 2003 was analyzed.
Abstract: We present the large-scale sidereal anisotropy of Galactic cosmic-ray intensity in the multi-TeV region observed with the Tibet-III air shower array during the period from 1999 through 2003. The sidereal daily variation of cosmic rays observed in this experiment shows an excess of relative intensity around 4-7 hr local sidereal time as well as a deficit around 12 hr local sidereal time. While the amplitude of the excess is not significant when averaged over all declinations, the excess in individual declination bands becomes larger and clearer as the viewing direction moves toward the south. The maximum phase of the excess intensity changes from ~7 hr at the Northern Hemisphere to ~4 hr at the equatorial region. We also show that both the amplitude and the phase of the first harmonic vector of the daily variation are remarkably independent of primary energy in the multi-TeV region. This is the first result determining the energy and declination dependences of the full 24 hr profiles of the sidereal daily variation in the multi-TeV region with a single air shower experiment.
120 citations
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1,327 citations
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TL;DR: In this article, the interplay between these observations and theoretical models of the prompt gamma-ray burst and its afterglow is reviewed, and a model of the burst's origin and mechanism is proposed.
Abstract: Gamma-ray bursts are the most luminous explosions in the Universe, and their origin and mechanism are the focus of intense research and debate. More than three decades after their discovery, and after pioneering breakthroughs from space and ground experiments, their study is entering a new phase with the recently launched Swift satellite. The interplay between these observations and theoretical models of the prompt gamma-ray burst and its afterglow is reviewed.
1,294 citations
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TL;DR: A survey of the theory and experimental tests for the propagation of cosmic rays in the Galaxy up to energies of 10 15 eV is given in this article, followed by an exposition of basic principles.
Abstract: We survey the theory and experimental tests for the propagation of cosmic rays in the Galaxy up to energies of 10 15 eV. A guide to the previous reviews and essential literature is given, followed by an exposition of basic principles. The basic ideas of cosmic-ray propagation are described, and the physical origin of its processes is explained. The various techniques for computing the observational consequences of the theory are described and contrasted. These include analytical and numerical techniques. We present the comparison of models with data, including direct and indirect—especially γ-ray—observations, and indicate what we can learn about cosmic-ray propagation. Some important topics, including electron and antiparticle propagation, are chosen for discussion.
1,072 citations
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TL;DR: PAMELA data challenge the current paradigm of cosmic-ray acceleration in supernova remnants followed by diffusive propagation in the Galaxy and find that the spectral shapes of these two species are different and cannot be described well by a single power law.
Abstract: Protons and helium nuclei are the most abundant components of the cosmic radiation Precise measurements of their fluxes are needed to understand the acceleration and subsequent propagation of cosmic rays in our Galaxy We report precision measurements of the proton and helium spectra in the rigidity range 1 gigavolt to 12 teravolts performed by the satellite-borne experiment PAMELA (payload for antimatter matter exploration and light-nuclei astrophysics) We find that the spectral shapes of these two species are different and cannot be described well by a single power law These data challenge the current paradigm of cosmic-ray acceleration in supernova remnants followed by diffusive propagation in the Galaxy More complex processes of acceleration and propagation of cosmic rays are required to explain the spectral structures observed in our data
900 citations
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TL;DR: In this paper, the authors discuss the possible mechanisms for the generation of cosmological magnetic fields, discuss their evolution in an expanding universe filled with the cosmic plasma and provide a critical review of the literature on the subject.
Abstract: We review the possible mechanisms for the generation of cosmological magnetic fields, discuss their evolution in an expanding Universe filled with the cosmic plasma and provide a critical review of the literature on the subject. We put special emphasis on the prospects for observational tests of the proposed cosmological magnetogenesis scenarios using radio and gamma-ray astronomy and ultra-high-energy cosmic rays. We argue that primordial magnetic fields are observationally testable. They lead to magnetic fields in the intergalactic medium with magnetic field strength and correlation length in a well defined range. We also state the unsolved questions in this fascinating open problem of cosmology and propose future observations to address them.
662 citations