A Study of Nucleon Structure based on the Chiral Quark Soliton Model

基于手性夸克孤子模型的核子结构研究

• 批准号: 03640271
• 负责人: WAKAMATSU Masashi
• 金额: $ 0.13万
• 依托单位: Osaka University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1991
• 资助国家: 日本
• 起止时间: 1991 至 1992
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-03640271/
• 关键词: effective theory of QCD; model of baryons; fopological soliton; spontaneous breaking of chiral symmetry; Nambu-Goldstone boson; nonperturbative field theory; Dirac sea; spin contents of the proton; 南部・ゴールドストーンボソン; 南部・ゴ-ルドスト-ンボソン

The chiral quark soliton model (CQSM) is undoubtedly the simplest model of baryons, which incorporates the basic feature of the low energy QCD, i. e. the chiral symmetry and its spontaneous breaking. A main motivation of our study of this model is to understand the underlying dynamical meaning of the Skyrme model in which the nucleon (a fermion) is constructed from the pion fields (bosons). Taking care of the interesting correspondence between the classical pion field configuration in the Skyrme model and the mean-field potential for quarks in the CQSM, we have succeeded to clarify the microscopic foundation of the Skyrme model. This hoewever does not mean that these two models are completely equivalent. We have rather shown that, for a reasonable choice of the model parameters, the CQSM is more realistic than the Skyrme model in many respects. From the practical viewpoint, one of the most prominant features of the CQSM is that it enables us to solve the nucleon bound state problem with full inclusion of the Dirac-sea quark degrees of freedom in addition to the N_c valence quarks in it. We have found that the qq sea inside the nucleon is isospin asymmetric in completely consistent with the recent NMC analysis of the nucleon structure functions. According to our nonperturbative analysis, this isospin asymmetry of the qq sea inside the nucleon is an inevitable consequence of the spontaneous chiral symmetry breaking, combined with the flavor asymmetry certainly existing in the valence quark numbers in the nucleon. This then breaks down the widespread dogma of the perturbative QCD that the qq sea in the nucleon carries no flavor quantum numbers.

手性夸克孤子模型（CQSM）无疑是最简单的重子模型，它融合了低能QCD的基本特征，即。 e.手性对称性及其自发破缺。我们研究该模型的一个主要动机是了解 Skyrme 模型的潜在动力学意义，其中核子（费米子）是由介子场（玻色子）构建的。考虑到 Skyrme 模型中的经典介子场结构与 CQSM 中夸克的平均场势之间有趣的对应关系，我们成功地阐明了 Skyrme 模型的微观基础。但这并不意味着这两个模型完全等效。我们已经证明，对于模型参数的合理选择，CQSM 在很多方面都比 Skyrme 模型更现实。从实用的角度来看，CQSM最突出的特点之一是它使我们能够在解决核子束缚态问题时除了N_c价夸克之外还完全包含狄拉克-海夸克的自由度。我们发现核子内部的qq海是同位旋不对称的，这与最近NMC对核子结构函数的分析完全一致。根据我们的非微扰分析，核子内部 qq 海的同位旋不对称性是自发手性对称性破缺的必然结果，再加上核子中价夸克数中肯定存在的风味不对称性。这打破了微扰 QCD 的普遍教条，即核子中的 qq 海不携带风味量子数。

项目成果

佐藤 透: "Applicafion of Semi-Classical Method to the Polarizafion Problem of Hypernuclei" Z. Phys. A. (1993)

Toru Sato：“半经典方法在超核极化问题中的应用”Z. Phys A. (1993)

佐藤 透: "π NN Ststem and the Method of Unitary Transformation" FewーBody Systems. (1992)

Toru Sato：“π NN Ststem 和酉变换方法”少体系统 (1992)。

若松 正志: "Comparative Anclysis of the πN Sigma Term in Two Effective Theories" Physics Letters B. (1993)

Masashi Wakamatsu：“两种有效理论中 πN Sigma 项的比较分析”Physics Letters B. (1993)

M. Wakamatsu: "Is the qq Sea in the Nucleon Isospin Symmetric?" Phys. Rev. D44. 2631-2634 (1991)

M. Wakamatsu：“核子同位旋中的 qq 海是对称的吗？”

若松 正志: "How DiracーSea Quarks affect the Neutron Charge Distribution" Physics Letter B. 269. 394-400 (1991)

Masashi Wakamatsu：“狄拉克-海夸克如何影响中子电荷分布”《物理快报》B. 269. 394-400 (1991)