2007 Fiscal Year Final Research Report Summary
Development of high-energy particle astrophysics in Tibet
| Project/Area Number |
17403004
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 海外学術 |
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| Research Field |
Particle/Nuclear/Cosmic ray/Astro physics
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| Research Institution | Kanagawa University |
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Principal Investigator |
YUDA Toshinori Kanagawa University, Faculty of Engineering, Professor (60092368)
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| Co-Investigator(Kenkyū-buntansha) |
TAKITA Masato Univ. of Tokyo, ICRR, Associate Professor (20202161)
OHNISHI Munehiro Univ. of Tokyo, ICRR, Assistant Professor (10260514)
HOTTA Naoki Utsunomiya Univ., Faculty of Education, Professor (60157039)
YAMAMOTO Yoshiaki Konan Univ., 理工学部, Associate Professor (70068112)
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| Project Period (FY) |
2005 – 2007
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| Keywords | Tibet / air-shower array / high energy gamma-ray / high-energy cosmic-ray / knee region / sun shadow / International Collaboration / China |
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| Research Abstract |
The present air-shower array at Yangbajing in Tibet was completed in the late fall of 2003 and has then been successively operating to date. The array(Tibet-III) consists of about 800 scintillation counters, which are deployed at a grid of 7.5m spacing covering the area of 37000m^2. The trigger rate of air-shower events is set to about 1.7kHz and the arrival direction of each event can be estimated with an inaccuracy of less than 0.9 degrees in the energy region over 3 TeV. The main objectives are to search for high-energy gamma rays from active celestial objects and to study very high energy Galactic cosmic rays. These observations are very important to clarify the origin of cosmic rays and their acceleration mechanism.
The main results obtained until now are as follows.
1) The energy spectrum of all-particle cosmic rays has been observed in the wide energy range from 10^<14> to 10^<17> eV with a sharp knee at the energy around 4x1015 eV.
2) The energy spectra of primary protons and heli
… More
ums are for the first time observed in the knee energy region.
3) High energy gamma rays above about 3 TeV have been successfully observed from the Crab Nebula and active galactic nuclei such as Mrk421 and Mrk501. A long-term correlation between RV gamma-ray s and X-ray flares from XMM Newton satellite was observed to provide information about electron acceleration at the source.
4) An energy dependence of the large-scale anisotropy of the Galactic cosmic rays has been for the first time observed and also significant anisotropy of multi-TeV cosmic rays is observed in the direction of Cygnus region.
5) A variation of the sun shadow during the solar activity cycles was successively monitored with the air shower array, and we succeeded to get new information about the solar magnetic field.
Last year we constructed a 100m^2 water-Cherenkov-type muon detector in the underground of the Tibet air shower array. The total area of muon detectors will be expanded up to about 10000m^2 in the very near future. This instrument with a wide field of view then becomes the most sensitive? gamma-ray detector at energies above several times 10 TeV in the world. It is expected that this experiment enables us to provide very important results on the acceleration of high energy cosmic rays, which is still unresolved. Less
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