Nucleon resonance in electromagnetic reaction at GeV region

GeV 区域电磁反应中的核共振

• 批准号: 07640405
• 负责人: SATO Toru
• 金额: $ 0.77万
• 依托单位: Osaka University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07640405/
• 关键词: Electron Scattering; Bavyon Resonance; Meson photoproduction; Delta Resonance

We have studied the structure of uncleon resonance using the electromagnetic probe around GeV region. Nucleon resonances can be studied using meson-nucleon scattering and meson-photoproduction processes. These resonances stay in the meson-nucleon continuum. Therefore the theoretical analysis including the coupling of resonance to the continuum and also the non-resonant processes is essentially important to determine the resonance properties.In this project we focus on the electromagnetic structure of DELTA<@D233@>D2. In order to have a consistent treatment of meson nucleon system in terms of hadronic degrees of freedom, we used a method of unitary transformation, which was developed to study meson exchange current in nuclei. Using the unitary transformation method, we constructed effective hamiltonian for pion-nucleon scattering and pion-photoproduction including non-resonant processes. This model was shown to give a good description of the pion-nucleon scattering around the DELTA regi … More on. We studied the recent polarization data of pion photoproduction by LEGS.This quantity is known to be sensitive to the E2/M1 ratio of DELTA electromagnetic decay. As a results, we found non-resonance processes play important role in the electromagnetic decay of delta. Our value of M1 amplitude was found to be consistent with the prediction of constituent quark model, while the previous analyzes using multipole amplitude reported about 50% larger value. The difference is due to the contribution of the non-resonant process, which was not clearly separated in those analyzes. Finally our result of E2/M1 ratio is E2/M1 = (0.0(]SY.+-。[)1.3) %. This new value of E2/M1 gives an important information on the structure of delta in particular D-wave component of delta.Currently we are extending our project into the higher energy region including eta production. Around the threshold of eta production, N^<**> (1535) dominates the amplitude. Therefore we expect a new insight on the N^<**> structure from this project. Less

我们用GeV区附近的电磁探头研究了单子共振的结构。核子共振可以用介子-核子散射和介子-光产生过程来研究。这些共振保持在介子-核子连续体中。因此，包括共振与连续介质的耦合以及非共振过程在内的理论分析对于确定共振性质至关重要。在本项目中，我们主要研究Delta&lt；@D233@&gt；D2的电磁结构。为了用强子自由度统一处理介子核子系统，我们使用了一种研究核内介子交换电流的么正变换方法。利用么正变换方法，我们构造了包含非共振过程的介子-核子散射和介子-光产生的有效哈密顿量。这个模型很好地描述了…附近的介子-核子散射还有更多。我们研究了最近用LEGS产生的π介子的偏振数据，这个量对Delta电磁衰变的E_2/M_1比值很敏感。结果发现，非共振过程在三角洲的电磁衰变中起着重要作用。我们的M1振幅值与成分夸克模型的预测值是一致的，而以前使用多极振幅值的分析报告的值要大50%左右。这种差异是由于非共振过程的贡献，在这些分析中没有明确地分开。最后，我们得到的E_2/M_1比值为E_2/M_1=(0.0(]Sy.+-)。[)1.3)%。这个新的E2/M1值提供了关于三角洲结构的重要信息，特别是三角洲的D波成分。目前，我们正在将我们的项目扩展到包括ETA生产在内的更高能量领域。在ETA产生的阈值附近，N^&lt；**&gt；(1535)占主导地位。因此，我们期待从这个项目中对N^&lt；**&gt；结构有一个新的见解。较少

项目成果

Toru Sato: "Meson-exchange model for π N scattering and δN → πN reaction" Physical Review C. 54・5. 2660-2684 (1996)

佐藤彻：“π N 散射和 δN → πN 反应的介子交换模型”《物理评论》C. 54・5（1996）。

M.Wakamatsu: "Extended Nambu-Jona-Lasinio Model and Hidden Local Symmetry of Low Energy QCD" Phys.Rev.D54. 6459-6474 (1996)

M.Wakamatsu：“扩展的 Nambu-Jona-Lasinio 模型和低能量 QCD 的隐藏局部对称性”Phys.Rev.D54。

Masashi Wakamatsu: "Tracing the Origin of the g_A Problem in the Skyrme Model" Progress of Theoretical Physics. 95・1. 143-173 (1996)

若松正史：《Skyrme 模型中 g_A 问题的起源》《理论物理学进展》95・1（1996）。

T.Sato: "Meson-Exchange Model for piN Scattering and gammaN * piN Reaction" Phys.Rev.C54. 2660-2684 (1996)

T.Sato：“piN 散射和 gammaN * piN 反应的介子交换模型”Phys.Rev.C54。

M.Wakamatsu: "Tracing the Origin of the g_A Problem in the Skyrme Model" Prog.Theor.Phys.95. 143-173 (1996)

M.Wakamatsu：“追踪 Skyrme 模型中 g_A 问题的起源”Prog.Theor.Phys.95。