1990 Fiscal Year Final Research Report Summary
Observation of Cosmic-Ray Antiprotons by Emulsion Chamber
| Project/Area Number |
63540227
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
核・宇宙線・素粒子
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| Research Institution | Kanagawa University |
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Principal Investigator |
TATEYAMA Nobuhito Kanagawa University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (30102239)
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| Co-Investigator(Kenkyū-buntansha) |
TORII Shoji Kanagawa University, Faculty of Engineering, Assistant, 工学部, 助手 (90167536)
SHIRAI Tatuya Kanagawa University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (20102238)
TAIRA Toshio Kanagawa University, Faculty of Engineering, Professor, 工学部, 教授 (10101320)
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| Project Period (FY) |
1988 – 1989
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| Keywords | Cosmicray antiproton / Antiproton / Nuclear emulsion experiment / 荷電粒子飛跡解析 / 画像自動解析 |
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| Research Abstract |
The observation of the low-energy antiprotons would have profound implications for cosmology and propagation of the cosmic rays. Especially in the energy range less than 300 Mev, production of secondary antiproton is suppressed in a gaeactic space by the kinematical limit and the abundance of antiproton present us the key to the problem. The experimental results of antiproton-proton ratio (P/P) for energies less than 1 GeV have been already reported by several authors and the upper limit of P/P is 2.8X10^<-5>. However, those are inconsistent with each other and present us problems to current cosmological models, closed galaxy model and leaky-box model and other models. Our experiment to search for antiprotons in this energy region has been carried out with the emulsion stack flown by the balloon from Prince Albert, Saskatchewan, Canada in August 1987. Cut-off energy is 170 MeV. The exposure by the flight achieved about 22.5 hours at an altitude of 37 km.
Detection of antiproton
The incid
… More
ent cosmic ray particles make 'stars' in the emulsion stack. Among them, the antiproton stop in the emulsion shows the characteristic pattern ; 'bend' just before the vertex point. The data of branching ratios for pp annihilation at rest shows that over ninety percent of annihilation produce more than 2 charged pions. So we define the antiproton candidate that shows the 'bend' near the vertex with more than 2 charged particles. When we make an microscope examination, there are two processes to get the antiproton candidate among many charged tracks and background. At first, we scan a emulsion by microscope with automatic image processing and select the charged tracks from background. In this process, 12 pictures, obtained by changing a focus under 250 magnifications, are processed by background reduction and are reconstructed to one image with charged tracks. The second, this imageis reprocessed with Hough-transformation and the antiproton candidates selected by its pattern.
result
(1) We developed the advanced image processing technique to scan charged particles in emulsion and reconstructed tracks.
(2) The total volume of emulsion in which we have scanned is 1.18 cm3. We have number distribution of secondary particles and the number distribution of secondary particles in 'bend' events. We have not obtained antiproton candidate.
We get result the behavior of primary cosmic ray particles in the stack by simulation. We can expect the p/p ratio in the energy region between 170 Mev and 300 Mev to 2.6X10^<-5> by the comparison with simulation. Less
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[Publications] T. Tira, T. Shirai, N. Tateyama, S. Torii, J. Nishimura, M. Fujii, T. Kobayashi, H. Aizu, Y. Komori, S. Tasaka, A. Nishio: ""Observation of cosmic-ray antiprotons by emulsion stack"" Proceedings of 21ST Internatonal cosmic ray conference. VoL. 3.281-283 (1990)
Description
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