A Theoretical Study of Hadronic Interactions and the Structure of the Nucleon

强子相互作用和核子结构的理论研究

• 批准号: 0070368
• 负责人: John Londergan
• 金额: $ 22.2万
• 依托单位: Indiana University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-07-01 至 2003-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0070368&HistoricalAwards=false
• 关键词: Theoretical; Study; Hadronic; Interactions; Structure

0070368Londergan There are two major topics to be studied in this proposal. The first deals with the quark sub-structure of protons and neutrons, and related baryons. We are studying the validity of charge symmetry, which states that up quarks in the proton and down quarks in theneutron should behave in identical ways. This approximate symmetry is very well preserved in nuclear physics, but we showed that previous experiments appeared to require significant deviations fromcharge symmetry at the quark level. A re-analysis of the experimental data suggests that charge symmetry is valid to a high degree of precision in high energy physics. We also propose to investigate the process by which quarks produced at high energies ``fragment'' into baryons. We want to see whether these processes depend on the type, or ``flavor,'' of quark which produces the baryon. We are developing a model for this process, and looking at the production of Lambda hyperons. The simplest model for the Lambda particle consists of an up, down and strange quark. It is customary to assume that up, down and strange quarks contribute equally to the fragmentation leading to a Lambda particle. Our preliminary investigations suggest significant differences from this simple ``flavor symmetric'' model. We can explain in simple qualitative terms why this model should be wrong, and we predict where large flavor symmetry violation should occur. We also propose to investigate bound state and scattering properties for particles in two dimensional systems. We are particularly interested in systems whose transverse dimensions are of the same order as the particle wavelength. In these cases, binding and scattering are dominated by wave effects. We have recently published a book on this subject ("Binding and Scattering in Two-Dimensional Systems", Londergan, Carini and Murdock, Springer-Verlag, 1999). We have shown that our work is relevant to the properties of electrons in quantum wires, confined electromagnetic modes in waveguides, and confined and propagating states in optical systems called ``photonic crystals.'' In this proposal we will focus on the properties of ``defect states,'' which are found when one starts with a finite periodic system, and then changes the properties of one or more of the cells producing the periodic system. The principal investigator is Director of the Indiana University Nuclear Theory Center.

0070368 Londergan本提案中有两个主要议题需要研究。 第一部分讨论质子和中子的夸克子结构，以及相关的重子。 我们正在研究电荷对称性的有效性，它指出质子中的上夸克和中子中的下夸克应该以相同的方式行为。 这种近似对称性在核物理中保存得很好，但我们表明，以前的实验似乎需要在夸克水平上显著偏离电荷对称性。 对实验数据的重新分析表明，电荷对称性在高能物理中具有很高的精确度。 我们还打算研究夸克在高能下“碎裂”成重子的过程。 我们想知道这些过程是否取决于产生重子的夸克的类型或“味道”。 我们正在为这一过程开发一个模型，并研究Lambda超子的产生。 最简单的λ粒子模型由上夸克、下夸克和奇异夸克组成。 通常认为上夸克、下夸克和奇夸克对导致λ粒子的碎裂的贡献是相等的。 我们的初步调查表明，与这种简单的“风味分析”模型有显着差异。 我们可以用简单的定性术语解释为什么这个模型是错误的，我们预测哪里应该发生大的味道对称性破坏。 我们还提出了研究二维系统中粒子的束缚态和散射性质。 我们特别感兴趣的系统，其横向尺寸是相同的数量级的粒子波长。 在这些情况下，结合和散射由波效应主导。 我们最近出版了一本关于这个主题的书（“二维系统中的结合和散射”，Londergan，卡里尼和默多克，Springer-Verlag，1999）。 我们已经表明，我们的工作是相关的量子线中的电子，在波导中的限制电磁模式，并在光学系统中被称为光子晶体的限制和传播状态的属性。在这个提议中，我们将集中讨论“缺陷态”的性质，当我们从一个有限的周期系统开始，然后改变产生周期系统的一个或多个单元的性质时，就会发现缺陷态。 首席研究员是印第安纳州大学核理论中心主任。