2005 Fiscal Year Final Research Report Summary
Proton quasifree scattering at 1 GeV and medium effects in nuclear field
| Project/Area Number |
15340080
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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 | Kyushu University |
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Principal Investigator |
NORO Tetsuo Kyushu University, Department of Physics, Professor, 大学院理学研究院, 教授 (30164750)
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| Co-Investigator(Kenkyū-buntansha) |
SAGARA Kenshi Kyushu University, Department of Physics, Professor, 大学院理学研究院, 教授 (00128026)
SAKAGUCHI Harutaka Kyoto University, Department of Physics, Ass.Prof., 大学院理学研究科, 助教授 (30025465)
HATANAKA Kichiji Osaka University, Res.Center for Nucl.Phys., Professor, 核物理研究センター, 教授 (50144530)
WAKASA Tomotsugu Kyushu University, Department of Physics, Ass.Prof., 大学院理学研究院, 助教授 (10311771)
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| Project Period (FY) |
2003 – 2005
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| Keywords | Proton quasifree scattering / medium effects / polarization / relativistic effect |
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| Research Abstract |
This program was mainly performed as an international collaboration experiment held at Petersburg Nuclear Physics Institute in Russia by using the 1 GeV synchrocyclotron. Experiments at 400 MeV proton beam by using the cyclotron complex at Research Center for Nuclear Physics, Osaka University, and a collaboration work with Prof. Hillhouse, University of Schtellenbosch in South Africa, are also important parts of this program. Prof. Hillhouse stayed at Fukuoka for two to four months in 2004 and 2005, respectively. The purpose of this program was to investigate Dirac relativistic effects, which is one of possible nuclear medium effects in the hadronic level..
The experiments in Russia were performed twice and the proton quasifree scattering off a 160 target, which is a p-shell nucleus, and a 40Ca target, an sd closed-shell nucleus. In the former case, only the differential cross section were measured for a reason in the preparation of detector system, while both of the cross section and induced polarization were measured in the latter case.
It is a long staying problem that the analyzing power (Ay) for proton quasifree scattering is significantly reduced from the values estimated by using the nucleon-nucleon interaction in free space, but we firstly compare the reduction rate in a wide incident-energy region quantitatively. The result shows that the reduction rate is similar for both of 1 GeV and 400 MeV energies, from which we can conclude that the reduction is not caused by mixture of some complicated processes as two-step processes. From an experimental result with many kinds of target nuclei, it is also found that this reduction shows a monotone function of the Q-value of the reaction. From the theoretical side, it is found that only 50% of this reduction is explained as a Dirac relativistic effect. This may suggest existence of some additional medium effect, such as meson-mass modifications.
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