Study of quark degrees of freedom in nuclei by precise measurement of Gamow-Teller spin sum rule value

精确测量伽莫夫-泰勒自旋和规则值研究原子核夸克自由度

基本信息

批准号：
10304018
负责人：
SAKAI Hideyuki
金额：
$ 24.05万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10304018/
关键词：
Gamow-Teller transition Ikeda spin sum rule quark degrees of freedom (n,p) reaction mono-chromatic neutron beam クォーク自由度 (n,p)反応ガモフテラーベータ崩壊単色中性子源

项目摘要

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) parameterg'_<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.

这项研究旨在通过提取旋转总规则的淬火值（IKEDA SUM规则）来定量探索核中的夸克自由度。为此，我们需要获得可以通过中间能量（n，p）反应来实现的精度β^+ b（gt）值。这项研究是按照以下方式进行的。1。我们已经在大阪大学核物理研究中心建造了（N，P）设施。2。横截面和分析能力的精确角度分布已在300 meV.3处测量 ^<90> Zr（n，p）反应。多极分解分析（MDA）已应用于 ^<90> Zr（n，p）数据，可靠的σ（ΔL= 0）分布提取至令人兴奋的能量为70 meV.4。 σ（Δl= 0）用于获得B（β^+ GT）值。在连续体中将B（β^+ gt）值整合到适当的兴奋能量之后，总B（β^+ GT）强度以S（β^+）= 3.0±0.4.5获得。通过使用先前获得的s（β^ - ）值，可以根据自旋和规则（IKEDA和规则）的淬灭值得出：q = [s（β^ - ） - s（β^+）]/3（n -z）= 0.83±0.06.6。该Q值导致Landau-Migdal（LM）参数G'_<nδ> = 0.28-0.35。g'_<nδ>的小度表明δ孔状态贡献的较小。这意味着核中的夸克自由度很小。当前的G'_<nδ>是从实验中首次获得的。该项目的完成非常顺利，结果成果。