Theoretical study of multistep direct reaction mechanism in preequilibrium nuclear reaction processes

预平衡核反应过程多步直接反应机理的理论研究

• 批准号: 07640416
• 负责人: WATANABE Yukinobu
• 金额: $ 1.28万
• 依托单位: KYUSHU 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 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07640416/
• 关键词: Preequilibrium nuclear reaction; Multistep direct reaction; Semi-classical distorted wave approximation; SCDW model; Intermediate energy; Proton-induced reaction; Wigner transform; Nuclear in-medium effect; 半古典的歪曲波モデル; ウィグナー変換; 交換項; 並列SCDW計算コード

We have proposed a new semi-quantal model to describe the multistep direct (MSD) reaction processes in preequilibrium nuclear reactions, which is called the semi-classical distorted wave model : it is referred to as the SCDW model. The purpose of this work is to investigate the MSD mechanism in the preequilibrium particle emission of nucleon-induced reactions in the intermediate energy region.First of all, we have developed a way of calculating the MSD cross sections with the Quasi-Random Number Monte Carlo method, and succeeded in the SCDW calculations for the leading three MSD steps. The code was applied to proton-induced reactions on medium-heavy nuclei (i.e., ^<58>Ni and ^<90>Zr) for incident energies of several tens of MeV to 200 MeV.The result showed good agreement with the experimental data without any adjustable parameters, except at very forward and backward angles. We found that the underestimation seen at large angles is due to the momentum distribution of target nucleons given by the local Femi-gas model. To improve this situation, we have developed a new approach in which the Wigner transform of one-body density matrix is incorporated in the SCDW model. The discrepancy was indicated to be removed by using more realistic single-particle wave functions in the harmonic oscillator or Woods-Saxson ponetial, instead of the local Fermi-gas model.In addition, we have found that the SCDW model is applicable to analyzes of (p, nx) reactions by taking into account the Q value correctly. Moreover, the result of SCDW calculations with in-medium NN cross sections showed that the in-medium effect is not much apreciable in the MSD process for incident energies up to 200 MeV.Finally, we have attempted to extend the SCDW model so that the matrix elements of sffective interaction is directly calculated, and investigated the off-shell effect on the MSD cross sections. As a result, we have not found a strong off-shell effect in the MSD reaction process continuum.

我们提出了一个新的半定量模型，以描述预元核反应中的多步直接（MSD）反应过程，该反应称为半经典失真波模型：它称为SCDW模型。这项工作的目的是研究中间能区域中核子诱导反应的粒子颗粒发射中的MSD机制。首先，我们开发了一种用quasi-random数量蒙特卡洛方法来计算MSD横截面的方法，并在SCDW计算中取得了成功的三个MSD步骤。该代码适用于质子诱导的中等重核（即， ^<58> ni和 ^<90> Zr）上的质子诱导的反应，用于几十MEV至200 MeV的入射能的入射能。结果显示出与实验数据的良好一致性，没有任何可调节的参数，除非在非常向前和向后的角度。我们发现，低估的低估是由于局部FEMI-GAS模型给出的靶核的动量分布所致。为了改善这种情况，我们开发了一种新方法，其中SCDW模型中纳入了一体密度矩阵的Wigner变换。表示差异可以通过在谐波振荡器或伍兹 - 萨克森重音中使用更逼真的单粒子波函数来消除，而不是本地的费米 - 气体模型。此外，我们发现SCDW模型适用于（P，nx）反应的分析Q值正确。此外，使用中等内部横截面的SCDW计算的结果表明，在MSD过程中，中等效应的效应不可超过200 meV。我们试图扩展SCDW模型，以便直接计算SFFETECTION相互作用的矩阵元素对MSD交叉效应，并对MSD进行了不合时宜的效应。结果，我们在MSD反应过程连续体中没有发现强大的外壳效应。

项目成果

M. Kawai, Y. Watanabe, H. Shinohara: "Semiclassical distorted wave model for multi-step direct process in (p, p'x) and (p, nx) reactions" acta physica slovaca. 45. 693-704 (1995)

M. Kawai、Y. Watanabe、H. Shinohara：“(p, px) 和 (p, nx) 反应中多步直接过程的半经典扭曲波模型”《物理学报》。

Y.Watanabe,H.Shinohara,M,Higashi,and M,Kawai: "Semi-Classical Distorted wave Model Analysis of(p,p'x)and(p,nx)Reactions at Intermediate Enegies" JAERI-Conf 96-008(日本原子力研究所). 266-271 (1996)

Y. Watanabe、H. Shinohara、M、Higashi 和 M、Kawai：“中间能量反应 (p,px) 和 (p,nx) 的半​​经典扭曲波模型分析” JAERI-Conf 96-008 （日本原子能研究所）266-271（1996）。

M.Kawai, et al.: "Semi-Classical Distorted Wave Model for Multi-step Direct Process in(p,p'x)and (p,nx)Reactions" acta physica slovaca(Proc.of Int.Symp.on Pre-Equilibrium Reactions). 45. 693-704 (1995)

M.Kawai 等人：“(p,px) 和 (p,nx) 反应中多步直接过程的半经典畸变波模型” 物理学报 (Proc.of Int.Symp.on Pre)

Y.Watanabe: ""Application of the Feshbach-Kerman-Koonin model to (p, p) reactions at low incident enargies"" acta physica slovaca. Vol.45. 749-756 (1995)

Y.Watanabe：“Feshbach-Kerman-Koonin 模型在低入射能量 (p, p) 反应中的应用”《acta physical slovaca》。