Browsing by Autor "S. Ogio"

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A small air-shower array at Mount Chacaltaya
(Elsevier BV, 1996) F. Kakimoto; S. Ogio; Y. Shirasaki; N. Gironda; T. Kaneko; H. Yoshii; Toshihiko Baba; K. Nishi; N. Tajima; Y. Yamada
Chemical composition of primary cosmic rays with energies from 1015 to 1016.5 eV
(Elsevier BV, 2001) Y. Shirasaki; F. Kakimoto; S. Ogio; N. Gironda; M. Takeda; T. Kaneko; H. Yoshii; Toshihiko Baba; Sakae Sano; K. Nishi
Searches for Ultra–High‐Energy Gamma Rays from SN 1987A and Centaurus X‐3
(IOP Publishing, 1996) H. Yoshii; T. Baba; T. Kaneko; K. Suga; F. Kakimoto; S. Ogio; Y. Shirasaki; N. Gironda; M. Teshima; Y. Toyoda
Searches for gamma rays above 100 TeV from SN 1987A and above 50 TeV from Cen X-3 were carried out with an air shower array at Mount Chacaltaya over a period of 3 years. The array, which consists of 13 4 m2 and 28 1 m2 scintillation detectors, was located on a slope of about 30 facing southward to e ectively observe air showers coming from the directions of these sources. In the analysis, a selection by shower age parameter was applied to reduce the background due to showers initiated by protons or nuclei.
Solar neutron events in association with large solar flares in November 2003
(Elsevier BV, 2005) K. Watanabe; Y. Muraki; Y. Matsubara; Kazuaki Murakami; T. Sako; P. Miranda; R. Ticona; A. Velarde; F. Kakimoto; S. Ogio
The cosmic ray primary composition at the knee region from lateral distributions of atmospheric C˘erenkov photons in extensive air showers
(Elsevier BV, 2008) H. Tokuno; F. Kakimoto; S. Ogio; Daiki Harada; Yuta Kurashina; Y. Tsunesada; N. Tajima; Y. Matsubara; A. Morizawa; O. Burgoa
The Energy Spectrum and the Chemical Composition of Primary Cosmic Rays with Energies from 10<sup>14</sup>to 10<sup>16</sup>eV
(IOP Publishing, 2004) S. Ogio; F. Kakimoto; Yuta Kurashina; O. Burgoa; Daiki Harada; H. Tokuno; H. Yoshii; A. Morizawa; E. Gotoh; H. Nakatani
We have measured extensive air showers with primary energies above 6 TeV at Mount Chacaltaya in Bolivia. The data were collected by an air shower array called the Minimum Air Shower (MAS) array starting in 2000 March. We applied an equi-intensity analysis method to the extensive air showers extended over the region of their maximum development. We varied the mixture of protons and iron in our simulations and compared these to the data to determine the mixing ratio of protons as a function of the primary energy. Using this, we derived the primary energy spectrum from 1014 to 5 × 1016 eV. Consequently, we conclude that the power-law index of the spectrum changes gradually around 1015.5 eV and that the obtained proton ratio decreases with increasing energy. We directly measured the longitudinal development of air showers generated by primaries with energies around the knee. We found that the average mass number of primary cosmic rays shows a steady increase with energy above 1014.5 eV and that the dominant component around the knee is not protons.