2001 Fiscal Year Final Research Report Summary
Study of quark degrees of freedom in nuclei by precise measurement of Gamow-Teller spin sum rule value
| Project/Area Number |
10304018
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
素粒子・核・宇宙線
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| Research Institution | The University of Tokyo |
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Principal Investigator |
SAKAI Hideyuki Graduate School of Science, The University of Tokyo, Professor, 大学院・理学系研究科, 教授 (90030030)
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| Co-Investigator(Kenkyū-buntansha) |
HATANAKA Kichiji Osaka University, RCNP, Professor, 核物理研究センター, 教授 (50144530)
AOI Nori Graduate School of Science, The University of Tokyo, Research Associate, 大学院・理学系研究科, 助手 (00311647)
TAMII Atsushi Graduate School of Science, The University of Tokyo, Research Associate, 大学院・理学系研究科, 助手 (20302804)
WAKASA Tomotsugu Osaka University, RCNP, Research Associate, 核物理研究センター, 助手 (10311771)
OKAMURA Hiroyuki Saitama University, Faculty of Science, Associate Professor, 理学部, 助教授 (10221144)
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| Project Period (FY) |
1998 – 2001
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| Keywords | Gamow-Teller transition / Ikeda spin sum rule / quark degrees of freedom / (n,p) reaction / mono-chromatic neutron beam |
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| Research Abstract |
This research is intended to explore quantitatively the quark degrees of freedom in nuclei by extracting a quenching value of spin sum rule (Ikeda sum rule). For that we need to obtain the precise β^+ B(GT) value which can be accomplished through the (n,p) reaction at intermediate energy.
This research was carried out in the following way.
1. We have constructed the (n,p) facility at the Research Center for Nuclear Physics at Osaka University.
2. The precise angular distributions for the cross sections and analyzing powers have been measured for ^<90>Zr(n,p) reaction at 300 MeV.
3. The multipole decomposition analysis (MDA) has been applied to the ^<90>Zr(n,p) data and the reliable σ(ΔL = 0) distribution is extracted up to an excitation energy of 70 MeV.
4. The σ(ΔL = 0) is used to get the B(β^+ GT) value. After integrating the B(β^+ GT) values in the continuum up to an appropriate excitation energy, the total B(β^+ GT) strength is obtained as S(β^+)=3.0 ± 0.4.
5. By using the previously obtained S(β^-) value, the quenching value in terms of the spin sum rule (Ikeda sum rule) can be derived as:
Q = [S(β^-) - S(β^+)]/3(N - Z) = 0.83 ±0.06.
6. This Q value leads to the Landau-Migdal (LM) parameter
g'_<NΔ> = 0.28-0.35.
The smallness of g'_<NΔ> indicates the smallness of the Δ-hole state contribution. This implies that the quark degrees of freedom in nuclei is rather small. Present g'_<NΔ> value is obtained for the first time from the experiment. This project has been completed very smoothly with fruitful results.
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