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

• 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

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.

本文通过提取自旋和规则（Ikeda和规则）的猝灭值，对原子核中的夸克自由度进行了定量研究。为此，我们需要获得精确的β^+ B（GT）值，这可以通过中能（n，p）反应来实现。我们在大坂大学核物理研究中心建造了（n，p）装置。测量<90>了300 MeV ~+ Zr（n，p）反应截面和分析本领的精确角分布。多极分解分析（MDA）已被应用到^<90>Zr（n，p）数据和可靠的σ（ΔL = 0）分布提取到70 MeV的激发能量。σ（ΔL = 0）用于获得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。通过使用先前获得的S（β^-）值，根据自旋求和规则（Ikeda求和规则）可以导出猝灭值为：Q = [S（β^-）- S（β^+）]/3（N-Z）= 0.83 ±0.06.6。该Q值导致Landau-Migdal（LM）参数g '_&lt;NΔ&gt; = 0.28- 0.35。g'_&lt;NΔ&gt;的小表明Δ空穴态贡献的小。这意味着原子核中夸克的自由度相当小。首次从实验中得到了目前的g '_&lt;NΔ&gt;值。该项目已顺利完成，成果丰硕。

项目成果

H. Sakai: "Gamow-Teller strength and quenching: probed by recent precise (p, n) and (n, p) measurements at 300 MeV"Nucl. Phys.. A690. 66c-77c (2001)

H. Sakai：“Gamow-Teller 强度和淬火：通过最近在 300 MeV 下的精确 (p, n) 和 (n, p) 测量进行探测”Nucl。

H. Sakai et al.: "Gamow-Teller strength in the continuum and quenching problem"Nucl. Phys.. A649. 251c-259c (1999)

H. Sakai 等人：“连续介质中的 Gamow-Teller 强度和淬火问题”Nucl。

H.Sakai et al.: "Gamow-Teller strength in the continuum." Nucl.Phys.printing.

H.Sakai 等人：“连续体中的伽莫夫泰勒强度。”

H. Sakai and M. Ichimura: "New face of spin-isospin nuclear responses"Journal of the Physical Society of Japan. Vol. 70, No. 7. 492-501 (2001)

H. Sakai 和 M. Ichimura：“自旋-同位旋核反应的新面貌”日本物理学会杂志。

T.Wakasa, et al.,: "Polarization transfer and spin response functions in quasi-elastc (p^^→, n^^→) neactions at 34b MeV" Phys.Rev.C. printing.

T. Wakasa 等人：“34b MeV 准弹性 (p^^→, n^^→) 反应中的偏振传递和自旋响应函数” Phys.Rev.C。