100—300MeV~3He(π~-,n)~2H反应的微观描述

本文将G.E.Brown等研究π-核散射的Isobar模型推广应用到中能(π,N)反应的描述上,用唯象近似方法处理多体效应,探讨了非静态修正、核子关联波函数以及出射核子扭曲效应对反应微分截面的影响,计算了100-300MeV~3He(π~-,n)~2H反应角分布,所得结果与实验基本一致。     

重离子碰撞中多重散射机制的研究

我们试图在刚性炮弹近似下,用Glauber方法研究高能核-核碰撞过程。本文具体处理了137GeV的α粒子和¹²C的弹性散射,认为α-¹²C的散射是由α粒子与靶核¹²C内的核子-核子多重散射过程。我们没有引入任何可调参数。计算的微分截面与实验结果进行了比较,符合是满意的,从而支持了多重散射的机制。     

高能重离子单举反应动量分布的研究

本文在核子-核子弹性散射的基础上研究了高能重离子碰撞。利用Glauber近似导出了高能重离子单举反应炮弹碎片动量分布的表示式。根据实验上的动量分布,推出炮弹核内不同预碎片间的动量分布,其结果是:结合得愈紧的预碎片其相对于剩余部分的动量分布就愈窄,换言之,它们之间的相对距离就愈大。     

100—300MeV3He(π－,n)2H反应的微观描述

本文将G.E.Brown等研究π^－核散射的Isobar模型推广应用到中能(π,N)反应的描述上,用唯象近似方法处理多体效应, 探讨了非表态修正、核子关联波函数以及出射核子扭曲效应对反应微分截面的影响, 计算了100—300MeV³He(π^－,n)²H反应角分布, 所得结果与实验基本一致.     

能量损失效应引起的核Drell-Yan微分截面比的压低

核环境中夸克的能量损失可以通过高能核Drell-Yan过程的核依赖进行测量. 利用文献中给出的夸克能量损失公式和从轻子－原子核深度非弹性散射实验数 据得到的束缚核子中的部分子分布函数, 计算了FNAL E772 800GeV的质子打击不同原子核的Drell-Yan过程截面比, 发现考虑能量损失的计算结果与FNAL E772实验数据符合甚好. 建议在利用核Drell-Yan过程实验数据抽取束缚核子内部分子分布函数时应该考虑能量损失效应.     

华德等式和电子深度非弹散射

本文用[1]中方法继续对电子深度非弹散射过程进行讨论.文中给出结构函数中的不可约图的一般表达式,用华德等式将它们与核子电流矩阵元的核、核子的 B-S 方程的核联系起来.文中在不考虑封闭的层子线圈图的贡献和核子方程中的积分核作位势假定的情况下,给出结构函数的表达式和计算方法,用核子方程解出的波函数和方程的积分核可将结构函数算出来.     

基于色散光学模型的40Ca核子散射数据计算

对钙同位素核数据的研究具有重要的理论价值和应用前景,其中⁴⁰Ca作为天然钙最主要的同位素,是一种重要的材料核素.本文采用色散光学模型对球形核⁴⁰Ca的核子弹性散射数据进行计算.通过考虑色散光学模型势中实部势的非定域性以及虚部势的壳间隙结构,实现了对⁴⁰Ca相关核子散射数据的良好描述,其中包括中子总截面、核子弹性散射角分布以及分析本领.此外,本文计算了色散光学模型势的实部体积分,其随能量的变化图像在费米能附近出现了明显的色散峰结构.     

高能核核碰撞透明性的研究

用多重散射理论研究了高能核核碰撞的透明性.本文的理论很好地说明了实验结果.表明高能核核碰撞主要是核子核子的两体相互作用过程.     

高能强子弹性散射和原子核的短程关联

本文在Glauber近似下,用Jastrow关联的波函数研究了原子核中短程关联对高能强子弹性散射的影响。为此,采用了Jastrow波函数的行列式的形式。对260MeV的π^--¹²C的弹性散射进行了计算,并与实验结果作了比较,结果表明:短程关联对微分截面的影响是很重要的。     

Glauber方法和高能下核-核非弹性散射

在Glauber多次散射的框架下, 给出了高能下核-核非弹性散射振幅的严格表示式. 以1.37GeVα在C¹²上的非弹性散射为例, 用硬球近似和严格方法分别计算了C¹²的α⁺和3^－态的微分截面, 在以这两种方法计算所得的微分截面之间, 存在着一定的差异, 在这一算例中, 这些差异反映了不同方法的物理图象.     

Inelastic interactions of fast nucleons with nuclei and fission of nuclei

The cross section for the fission of actinide nuclei that is induced by fast neutrons is considered as a fraction of the cross section for inelastic nucleon interaction with nuclei. In turn, inelastic nucleon interaction with a nucleus is treated as scattering on intranuclear nucleons. It is shown that this interaction model describes satisfactorily the cross section for the inelastic interaction of 60- to 2200-MeV nucleons for a broad set of nuclei and that the energy dependence of the cross section for the fission of actinide nuclei that is induced by 400- to 1000–MeV protons replicates the energy dependence of the cross section for inelastic interactions with respective nuclei. From the model used, it follows that the cross sections for proton-nucleus interactions exceed cross sections for respective neutron-nucleus interactions in the energy range extending up to 550 MeV; at higher energies neutron cross sections are larger than proton cross sections.     

The effective interaction for unbound nucleons and the optical potential

The effective interaction for an unbound nucleon in a complex nucleus is studied with particular emphasis upon the relationship of the unbound state interaction with the interaction for bound states. A successful unified treatment of unbound and bound states is given, and the unbound state effective interaction is related to the standard “optical model”. The attractive force for an unbound nucleon is shown to be of an exchange type and is best represented by a non-local, energy-independent potential which can be calculated, at least for not too high incident nucleon energy, from the attractive interaction between bound nucleons in a nucleus. We relate the unbound state potential to the bound state effective force as calculated by Negele using Hartree-Fock theory.

A non-local potential used by Elton, Webb, and Barrett in a successful analysis of electron scattering is shown, with minor modification, to work remarkably well in an analysis of elastic scattering of protons. Excellent agreement with experiment is obtained for the differential cross section and the polarization of protons with an incident energy up to 60 MeV scattered from ⁴⁰Ca, ⁵⁸Ni, ¹²⁰Sn and ²⁰⁸Pb. The real potential parameters are shown to be independent of the incident energy and physically reasonable; the imaginary potential parameters agree with expectations from Fermi gas and collective models. Bound state energy levels are also calculated with no readjustment of the real potential parameters in order to check the consistency of the interaction with the bound states, and the results are in good agreement with Negele.

The interaction of Skyrme as modified by Vautherin and Brink is also used in an analysis of elastic proton scattering. Good results are obtained for the differential cross section and the polarization for 20 MeV protons scattered from ⁵⁸Ni. At higher incident proton energy, and for larger nuclei, the results are poorer.     

A microscopic description of inelastic 12C scattering from 208Pb

Heavy-ion inelastic scattering is described microscopically by using an effective nucleon-nucleon interaction and RPA hole-particle wave functions. The relative cross sections for different multipoles can be sensitive to the range of the interaction. The strength is determined by fitting elastic scattering. The model is used to analyze 98 MeV ¹²C ions exciting ²⁰⁸Pb. The range required is shorter than that for the bare interaction between nucleons. Collective model fits are also presented for comparison.     

Elastic and inelastic scattering of protons from Li between 25 and 45 MeV

The elastic and inelastic scattering of protons from ⁶Li has been studied at incident energies of 25.9, 29.9, 35.0, 40.1 and 45.4 MeV. The 2.18 MeV (3⁺, T = 0) first excited state of ⁶Li was found to be strongly excited, but the 3.56 MeV (0⁺, T = 1) second excited state was quite weakly excited. Angular distributions for excitation of the 2.18 MeV level were measured at all five energies, while angular distributions for excitation of the 3.56 MeV level were extracted only at 25.9 and 45.4 MeV. To test the applicability of the optical model for the scattering of protons from such a light nucleus the elastic scattering angular distributions have been analyzed using the eleven-parameter search code SEEK. Available polarization angular distributions were included in the analysis. Reasonable fits to the data have been obtained with an average geometry potential. Theoretical estimates of the real part of the optical potential and the inelastic scattering differential cross sections have been made using the microscopic model for proton-nucleus scattering. Both phenomenological and realistic forces have been considered and the necessary nuclear transition densities have been extracted from experimental elastic and inelastic electron scattering data. An estimate of a possible spin-spin term in the optical potential has also been made.     

Phenomenological local potential analysis of π+ scattering

π⁺-nucleus scattering cross section are calculated by solving a Schrödinger equation reduced from the Klein-Gordon equation. Local potentials are assumed, and phenomenological potential parameters are searched energy dependently for π⁺ scattering from ¹²C, ⁴⁰Ca, and ²⁰⁸Pb to reproduce not only differential elastic cross sections but also inelastic and total and reaction cross sections at 800 MeV/c pion laboratory momentum. The collective model is used to calculate the angular distributions of differential inelastic cross sections for pions leading to the lowest 2⁺ and 3^? states of ¹²C. The deformation parameters and lengths are extracted and compared to the corresponding ones from other works. Local potentials well describe the scattering of pions from nuclei.     

Elastic and inelastic scattering of 178 MeV protons from 58Ni and 60Ni

The elastic and inelastic scattering of 178 MeV protons from ⁵⁸Ni and ⁶⁰Ni has been studied. Angular distributions were measured for the differential cross sections for elastic scattering as well as inelastic scattering from excited states below about 5 MeV, all with natural parity. For the elastic and for the inelastic scattering from the first excited state (2⁺ in both nuclei, the angular distributions for the polarization were also measured. The measurements extend out to c.m. angles of about 60°, corresponding to a momentum transfer of about 600 MeV/c.The elastic and inelastic scattering data were compared to the results of coupled-channel calculations in the vibrational model using a deformed spin-orbit interaction of the full Thomas form. Good agreement was found in general showing that the main features of the experimental results are well described in this model.     

The contribution of nuclear inelastic excitation to the optical potential for heavy ions

Using the plane-wave approximation we derive analytical expressions for both the real and imaginary parts of the polarization potential arising from nuclear inelastic scattering. These potentials and the resulting elastic and inelastic cross sections are compared with exact coupledchannel calculations for ¹³C on ⁴⁰Ca at 68 MeV. The agreement, for the most part, is good. We also briefly discuss the numerical non-local potentials for this system and the imaginary polarization potential for ¹⁶O on ²⁰⁸Pb at 104 MeV.     

Effect of the shell structure of nuclei on p 15C and p 15N scattering within diffraction theory

The differential cross sections for elastic proton scattering on ¹⁵C and ¹⁵N nuclei at energies of 150 and 800 MeV were calculated within the diffraction theory of Glauber multiple scattering. Shellmodel wave functions were used in these calculations, and particular attention was given to analyzing the sensitivity of the calculated features to distinctions between the shell structure of the ¹⁵C nucleus and the shell structure of the ¹⁵N nucleus. The calculations were performed in the approximation of double scattering. The multiple-scattering operator was written in a form that permits taking into account collisions with nucleons belonging to different shells. It is shown that the difference in structure between the two nuclei in question leads to substantial distinctions between the differential cross sections for scattering at an energy of 800 MeV and scattering angles larger than 25°.     

A microscopic model analysis of the 90Zr(p,n) IAS transition

Direct reaction (p, n) data to the isobaric analogue of the ground state of ⁹⁰Zr is analysed within a DWA using a complex effective two-nucleon transition interaction, the real part of which has been used in many previous inelastic scattering analyses. Using collective model form factors in the ansatz for the imaginary part of the transition interaction and allowing for virtual resonance excitation, the differential cross sections from the scattering of 18.5–45 MeV protons are well reproduced. The parameters of the required complex interaction have a smooth energy variation similar to that required by a microscopic model analysis of proton inelastic scattering to collective states in nuclei.