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

这项研究旨在通过提取自旋和规则(池田和规则)的猝灭值来定量地探索原子核中的夸克自由度。为此，我们需要得到精确的β^B(GT)值，这可以通过在中间能量下的(n，p)反应来实现。我们已经在大阪大学核物理研究中心建造了(n，p)设施。测量了300 MeV下^&lt；90&gt；Zr(n，p)反应截面和分析功率的精确角分布。将多极分解分析应用于^&lt；90&gt；Zr(n，p)数据，得到了激发能为70 MeV.4的可靠的σ(ΔL=0分布。σ(ΔL=0)用于获取B(β^GT)值。将连续谱中的B(β^GT)值积分到适当的激发能后，得到总的B(β^GT)强度为S(β^)=3.0±0.4 5。利用以前得到的S(β^-)值，根据自旋求和规则(池田求和规则)，可以得到猝灭值为：Q=[S(β^-)-S(β^)]/3(N-Z)=0.83±0.06.6。这个Q值导致朗道-米格达尔(Lm)参数g‘_&lt；NΔ&gt；=0.28-0.35。g’‘&lt；NΔ&gt；的小表明Δ空穴态的贡献很小。这意味着原子核中的夸克自由度相当小。首次从实验中得到了目前的g‘_Δ&gt；值。该项目顺利完成，成果丰硕。

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.