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Study of Nuclear Isovector Spin Response Functions by Quasi-elastic Scattering

核等矢量自旋响应函数的准弹性散射研究

基本信息

批准号：
12640294
负责人：
ICHIMURA Munetake
金额：
$ 1.22万
依托单位：
Hosei University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12640294/
关键词：
Spin-isospin modes Response function Quasi-elastic scattering Continuum RPA DWIA Two step process Landau-Migdal parameter (p,n) reaction スピン応答関数 (p, n)反応ガモフ・テラー遷移ランダウ・ミグダル・パラメータパイオン凝縮偏極移行係数 DWIA 連続RPA ランダウミグダルパラメータ有効

项目摘要

We developed a theoretical framework to analyse the spin observables of the charge exchange quasi-elastic scattering, which gives us information of the isovector spin response functions. The framework consists of three aspects: (1) Nuclear response functions are calculated by the continuum random phase approximation, which takes into account the radial dependent effective mass and the spreading widths of the particles and the holes, and include the Δ isobar; (2) One-step process of the reaction is calculated by the distorted wave impulse approximation; and (3) the two-step processes are estimated by the plane wave approximation. In the calculition of the one- and two-step processes, the above mentiond response functions are used.Using this theoretical framework we analysed ^<12>C, ^<40>Ca(p^^→, n^^→) reactions at 350 and 500MeV at various angles. The spin-longitudinal response functions were well reproduced, and consistent with long predicted enhancement. This is the first evidence of a precusor phenomenon of the pion condensation. We evaluated the Landau-Migdal parameters to reproduce the data. We found that the often used universality ansatz does not hold, and the obtained values are consitent with those obtaied from the Gamov-Teller transition strength distribution. Reproduction of the transverse response functions was much improved but not yet satisfactory.

我们建立了一个理论框架来分析电荷交换准弹性散射的自旋观测值，从而得到了等矢量自旋响应函数的信息。该框架包括三个方面：(1)核响应函数采用考虑径向相关有效质量、粒子和空穴扩散宽度的连续体随机相位近似计算，并包括Δ等压线；(2)采用畸变波脉冲近似计算反应的一步过程；(3)用平面波近似估计两步过程。在一步和两步过程的计算中，使用上述响应函数。利用这一理论框架，我们分析了350和500MeV不同角度下的^<12>C, ^<40>Ca（p^^→，n^^→）反应。自旋-纵向响应函数得到了很好的再现，与长期预测的增强一致。这是π介子凝聚前兆现象的第一个证据。我们评估了Landau-Migdal参数以重现数据。我们发现常用的普适性分析不成立，所得值与伽莫夫-泰勒跃迁强度分布的结果一致。横向响应函数的再现得到了很大的改进，但仍不能令人满意。