| Project/Area Number |
15340205
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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 | 一般 |
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| Research Field |
Particle/Nuclear/Cosmic ray/Astro physics
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| Research Institution | Kyoto Sangyo University |
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Principal Investigator |
OKADA Kenji Kyoto Sangyo University, Faculty of Science, Professor, 理学部, 教授 (90093385)
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| Co-Investigator(Kenkyū-buntansha) |
TAKEUTCHI Fujio Kyoto Sangyo University, Faculty of Science, Professor, 理学部, 教授 (40121537)
YOSHIMURA Yoshio Kyoto Sangyo University, KEK, emeritus professor, 高エネルギー加速器研究機構, 名誉教授 (50013397)
CHIBA Masami Tokyo Metropolitan Univ., Graduate school of Science and Engineering, Research Associate, 大学院理工学研究科, 助教 (60128577)
小林 正明 高エネルギー加速器研究機構, 素粒子原子核研究所, 名誉教授 (40013388)
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| Project Period (FY) |
2003 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥6,800,000 (Direct Cost: ¥6,800,000)
Fiscal Year 2006: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2005: ¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 2004: ¥3,200,000 (Direct Cost: ¥3,200,000)
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| Keywords | DIRAC Experiment / π^+π^-atom / QCD / Chiral perturbation / pion scattering length / πK atom / scintillating fiber hodoscope / topological trigger device / 実験核物理 / S-波散乱長 / ππ原子 / ダイバーホドスコープ / ハドロニック原子 / 中間子原子 / PSPM / π^+π^-原子寿命 / DIRAC experiment / pion scattering length / SCIFI hodoscope / シンチレーティングファイバー / トポロジカルトリガー / ππ散乱長 |
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| Research Abstract |
The DIRAC experiment (PS212) aims to measure the lifetime of π+π^- atoms using 24GeV proton beam provided by the CERN PS. The precise measurement of the lifetime enables to determine an s-wave pion-pion scattering length in a model independent way. The ππ scattering length has been calculated by means of Chiral perturbation theory with a precision of 5% at the starting stage of the DIRAC experiment. Now the precision of the calculation is better than 2.5%. The results are based on the assumption of a spontaneous chiral symmetry breaking due to a strong quark condensation. Therefore, a precise comparison of the theoretical value with the experimental one provides an opportunity to verify the current understanding of chiral symmetry breaking in QCD and to check the magnitude of the quark condensation.
We analyzed 30% of the collected data and deduced the lifetime as τ = [2.91+0.49-0.62] X 10^<-15> s. This lifetime corresponds to the scattering length |a0・a2| = 0.264+0.033・0.020m_π^<-1>. The errors are mostly due to statistics.
In this DIRAC experiment, Japan group has developed a topological trigger device consisting of scintillating-fiber hodoscopes(SFD), peak-sensing circuits(PSC), ADC/TDC hybrid read-out circuits(F1) and trigger logic circuits(TLC). They can select out online a real π^+π^- pair due to a dissociation of π^+π^- atom from a huge amount of background events. As the second stage of the DIRAC experiment we measure a lifetime of πK-atoms. For the πK measurements more than ten time intense beam than the π^+π^- measurement is required. We developed new high resolution scintillating fiber hodoscopes(HRH) consisting of 480 column made of 280μm fine fibers and 30 multi-anode photo multipliers with 16 channels. We found that the HRH has an excellent spatial resolution of 75μm and a time resolution of 0.56ns in rms.
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