Browsing by Autor "H. Yoshii"

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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
Arrival directions of large air showers, low-mu showers and old-age low-mu air showers observed at St. Chacaltaya
(NASA Headquarters, 1985) T. Kaneko; K. Hagiwara; H. Yoshii; N. Martinić; L. Siles; P. Miranda; F. Kakimoto; Toru Obara; N. Inoue; K. Suga
Arrival directions of air showers with primary energies in the range 10 to the 16.5 power eV to 10 to the 18th power eV show the first harmonic in right ascension (RA) with amplitude of 2.7 + or - 1.0% and phase of 13-16h. However, the second harmonic in RA slightly seen for showers in the range 10 to the 18th power eV to 10 to the 19th power eV disappeared by accumulation of observed showers. The distribution of arrival directions of low-mu air showers with primary energies around 10 to the 15th power eV observed at Chacaltaya from 1962 to 1967 is referred to, relating to the above-mentioned first harmonic. Also presented in this paper are arrival directions of old-age low-mu air showers observed at Chacaltaya from 1962 to 1967, for recent interest in gamma-ray air showers.
Búsqueda de gamma ray burst en el monte Chacaltaya. Experimento INCA
(1998) Renán Cabrera; O. Saavedra; S. Vernetto; H. Yoshii; Takeo Kaneko; F. Kakimoto; K. Nishi; S.D Bartelemy; G.S Fishman
Búsqueda de gamma ray bursts en el monte de Chacaltaya: Experimento INCA
(1998) Renán Cabrera; A. Velarde; D. Urzagasti; O. Saavedra; G. Navarra; S Verneto; H. Yoshii; Takeo Kaneko; F. Kakimoto; K. Nishi
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
Energetic delayed hadrons in large air showers observed at 5200m above sea level
(1985) T. Kaneko; K. Hagiwara; H. Yoshii; N. Martinić; L. Siles; P. Miranda; F. Kakimoto; I. Tsuchimoto; N. Inoue; K. Suga
Energetic delayed hadrons in air showers with electron sizes in the range 10 to the 6th power to 10 to the 9th power were studied by observing the delayed bursts produced in the shield of nine square meter scintillation detectors in the Chacaltaya air-shower array. The frequency of such delayed burst is presented as a function of electron size, core distance and sec theta.
Search for GeV GRBs at Chacaltaya
(1998) A. Castellina; P. L. Ghia; C. Morello; G. Trinchero; P. Vallania; S. Vernetto; G. Navarra; O. Saavedra; H. Yoshii; T. Kaneko
In this paper we present the results of a search for GeV Gamma Ray Bursts made by the INCA experiment during the first 9 months of operation. INCA, an air shower array located at Mount Chacaltaya (Bolivia) at 5200 m a.s.l., has been searching for GRBs since December 1996. Up to August, 1997, 34 GRBs detected by BATSE occurred in the field of view of the experiment. For any burst, the counting rate of the array in the 2 hours interval around the burst trigger time has been studied. No significant excess has been observed. Assuming for the bursts a power low energy spectrum extending up to 1 TeV with a slope α=−2 and a duration of 10 s, the obtained 1 GeV-1 TeV energy fluence upper limits range from 7.9 10−5 erg cm−2 to 3.5 10−3 erg cm−2 depending on the event zenith angles.
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.
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.