Proton Elastic Scattering from 14Be and Halo Effects

The elastic scattering ofp-14Be system at Elab = 200 MeV is evaluated within the relativistic impulse approximation. We discuss the effects of the halo neutrons on the three observables of the elastic scattering system,such as differential cross section dσ/dΩ, analyzing power Ay and spin rotation Q. The results of the three observables of the elastic scattering of p-14Be system are compared with those of p-12C and p-16O systems at the same energy as Elab = 200 MeV. We have found that in the small angular region the Ay and Q, as well as dσ/dΩ, are quite sensitive to the nucleon density distributions on the surface of the target nucleus and offer some unique behaviors of halo nuclei.     

入射质子的能量对质子与晕核弹性散射观测量的影响

用相对论脉冲近似(RIA)对不同的中能质子(200MeV, 400MeV和800MeV)与¹⁴Be, ¹⁶O和¹²C的弹性散射进行了研究, 讨论了不同的入射能量对3种观测量, 即微分散射截面、分析本领和自旋转动函数的影响. 研究发现在小散射角的区域晕中子对观察量的影响趋势保持一致, 不随入射质子能量的改变而改变.     

小角度范围内弱束缚核17F弹性散射微分截面的奇异行为

在兰州放射性束流线(RIBLL)上完成了¹⁷F/¹⁷O+²⁰⁸Pb的弹性散射微分截面角分布测量. 分析了¹⁷F/¹⁷O弹性散射产物微分截面的对数(ln(dσ/dθ))随散射角平方(θ²)的依赖关系. 结果表明, 在所测量的角度范围内(6°—20°), ¹⁷O的这一依赖关系可以用一条直线很好地拟合, 而¹⁷F的这一依赖关系需要两条不同斜率的直线才能拟合. ¹⁷F数据拟合中的这种斜率改变可能起因于¹⁷F的奇异结构. 对其他实验组数据的分析支持以上的结论, 即在一定的角度范围内, 弱束缚核与稳定核相比, 弹性散射产物微分截面的对数与散射角平方的依赖关系有明显的差异, 这可以作为深入研究“晕核”和“皮核”的一个新探针.     

K-Nucleus Elastic Scattering and Momentum-Dependent Optical Potentials

The K-nucleus differential elastic scattering cross section for 12C and 40 Ca at pκ = 800 Me V/c is calculated with three momentum-dependent optical potential models,which are density-dependent,relativistic mean field,and hybrid model,respectively.It is found that the forms of momentum-dependent optical potential models proposed by us are reasonable and gain success in the calculations and the momentum-dependent hybrid model is the best model for the K- nucleus elastic scattering.     

快中子在Li核上的弹性散射微分截面

用伴随粒子飞行时间法测量了14.7MeV中子在⁶Li和⁷Li核上的弹性散射截面,并用蒙特卡罗方法对中子在样品中的通量衰减、多次散射作了修正.本文工作与他人工作以及理论数据作了比较.给出了截面的勒让德系数;截面实验点总误差在10%到15%之间,其中统计误差为1%-5%.     

High Energy Proton-Proton Elastic Scattering in the Pomeron Exchange Model

We study high energy proton-proton elastic scattering in the framework of Pomeron exchange model. The cross section of the process are calculated without any free parameters. Our finding is that Pomeron exchange theory gives perfect fits to total cross section at the energy of√s higher than 10 GeV and to differential cross section at the momentum transfer [t] less than 1.5 GeV2. For total cross section at lower energy √s ＜ 10 GeV and differential cross section at larger momentum transfer region of |t| ＞ 1.5 GeV2, the Pomeron exchange theory needs to be improved.     

晕核6He(25 MeV/u)在9Be上的弹性散射研究

分析了北京大学核物理实验小组在日本RIKEN实验室完成的25 MeV/u 6He和9Be的弹性散射实验数据，得到了弹性散射微分截面角分布. 利用双折叠模型，并通过拟合弹性散射微分截面得到了此弹靶体系在此能量下的弹性散射光学势. We analyzed the 6He elastic scattering from 9Be target at 25 MeV/u. A Center of Beam (CB) method was used to calibrate the particle tracking detectors and set the reference system of the detection system. The double folding model approach was used to calculate the real part of the optical model potential. The preliminary optical model potential parameters were extracted by fitting the experimental differential elastic scattering cross sections.     

High Energy Proton-Proton Elastic Scattering in the Pomeron Exchange Model

We study high energy proton-proton elastic scattering in the framework of Pomeron exchange model. The cross section of the process are calculated without any free parameters. Our finding is that Pomeron exchange theory gives perfect fits to total cross section at the energy of √(s) higher than 10 GeV and to differential cross section at the momentum transfer |t| less than 1.5 GeV². For total cross section at lower energy √(s)<10 GeV and differential cross section at larger momentum transfer region of |t|>1.5 GeV², the Pomeron exchange theory needs to be improved.     

用电子散射研究丰质子核的质子晕结构

理论和实验结果都表明¹⁷F的第一激发态有质子晕存在.用相对论平均场理论和Eikonal近似研究了质子晕核¹⁷F的第一激发态的电子弹性散射过程. 计算了¹⁷F的第一激发态的电荷形状因子,并与¹⁶O和¹⁹F的结果进行了对比和讨论.结果显示质子晕的存在会使中等转移动量的电荷形状因子产生明显的变化,并且使低转移动量的电荷形状因子趋于降低.这说明电子散射对质子晕的存在是非常敏感的,表明可以用电子散射对奇特核的质子晕结构进行更精细的研究.     

Dirac Optical Potential of p-14Be and Pronounced “Long-Tail“ Shape

The Dirac optical potential for p-14Be elastic scattering is evaluated by the relativistic impulse approximation. Each of the real part and the imaginary part of the potential shows a pronounced “long tail“ for the proton elastic scattering from halo nucleus 14Be compared with the potentials for proton scattering from its adjacent nuclei 12C and 16O, which do not have halo structures. This kind of “long tail“ phenomenon suggests another signature for halo nuclei.     

Dirac Optical Potential of p-^14Be and Pronounced “Long-Tail” Shape

The Dirac optical potential for p-^14 Be elastic scattering is evaluated by the relativistic impulse approximation. Each of the real part and the imaginary part of the potential shows a pronounced “long tail” for the proton elastic scattering from halo nucleus ^14Be compared with the potentials for proton scattering from its adjacent nuclei ^12C and ^16O, which do not have halo structures.This kind of “long tail” phenomenon suggests another signature for halo nuclei.     

基于壳模型单体密度矩阵的折叠模型质子弹性散射分析

利用折叠模型计算得到折叠势实部并结合Koning和Delaroche光学势的虚部, 计算分析了质子与^30—40S的弹性散射数据. 通过引入Woods-Saxon势下核壳模型单体密度矩阵, 消除了折叠模型计算中常用的定域近似. 分析比较了定域近似对折叠势以及弹性散射截面计算的影响. 计算结果与折叠模型以及JLM模型计算结果进行了比较.     

Total Nuclear Reaction Cross Section Induced by Halo Nuclei and Stable Nuclei

We develop a method for calculation of the total reaction cross sections induced by the halo nuclei and stable. nuclei. This approach is based on the Glauber theory, which is valid for nuclear reactions at high energies. It is extended for nuclear reactions at low energies and intermediate energies by including both the quantum correction and Coulomb correction under the assumption of the effective nuclear density distribution. The calculated results of the total reaction cross section induced by stable nuclei agree well with 30 experimental data within 10 percent accuracy. The comparison between the numerical results and 20 experimental data for the total nuclear reaction cross section induced by the neutron halo nuclei and the proton halo nuclei indicates a satisfactory agreement after considering the halo structure of these nuclei, which implies quite different mean fields for the nuclear reactions induced by halo nuclei and stable nuclei. The halo nucleon distributions and the root-mean-square radii of these nuclei can be extracted from the above comparison based on the improved Glauber model, which indicates clearly the halo structures of these nuclei. Especially,it is clear to see that the medium correction of the nucleon-nucleon collision has little effect on the total reaction cross sections induced by the halo nuclei due to the very weak binding and the very extended density distribution.     

Total Nuclear Reaction Cross Section Induced by Halo Nuclei and Stable Nuclei

We develop a method for calculation of the total reaction cross sections induced by the halo nuclei and stable nuclei. This approach is based on the Glauber theory, which is valid for nuclear reactions at high energies. It is extended for nuclear reactions at low energies and intermediate energies by including both the quantum correction and Coulomb correction under the assumption of the effective nuclear density distribution. The calculated results of the total reaction cross section induced by stable nuclei agree well with 30 experimental data within 10 percent accuracy.The comparison between the numerical results and 20 experimental data for the total nuclear reaction cross section induced by the neutron halo nuclei and the proton halo nuclei indicates a satisfactory agreement after considering the halo structure of these nuclei, which implies quite digerent mean fields for the nuclear reactions induced by halo nuclei and stable nuclei. The halo nucleon distributions and the root-mean-square radii of these nuclei can be extracted from the above comparison based on the improved Glauber model, which indicates clearly the halo structures of these nuclei. Especially,it is clear to see that the medium correction of the nucleon-nucleon collision has little effect on the total reaction cross sections, induced by the halo nuclei due to the very weak binding and the very extended density distribution.     

推广的Glauber理论及其在晕核散射中的应用

介绍了推广到晕核散射的Glauber理论,并用其研究晕核¹⁴Be的散射问题.弹核的密度分布分别采用谐振子密度分布和相对论平均场理论计算得到具有两个晕中子结构的密度分布,对晕核模型的多重积分采用蒙特卡洛数值积分方法.计算了不同能量下¹⁴Be,¹²Be与靶核¹²C散射的反应截面,并与实验结果进行比较,¹⁴Be的两个中子采用具有晕中子密度分布的理论计算与实验符合较好,而采用不具有晕中子密度分布的结果与实验值相差较大.     

丰质子核反应中轻带电粒子发射的同位旋效应

采用同位旋相关的Boltzmann—Langevin方程计算了核素^12-15N和^17-20Ne反应中轻带电粒子发射的同位旋效应。^12-15N与^28Si靶的反应结果显示轻带电粒子的产生截面有明显的同位旋效应,^12N的轻带电粒子产生截面突然增大,与实验得出的结论相同,由此检验了所采用的计算方法的可行性。同时还计算了^17-20Ne与^9Be靶的反应,发现^17Ne的轻带电粒子产生截面也是突然增大,并且其质子分布有较大的弥散,据此认为^17Ne可能具有晕结构。 Within the Boltzmann-Langevin equation, the isospin effects on the production cross sections of light charged particles （LCP） in the reaction of proton rich nuclei were studied. We have calculated the LCP productio n cross sections of the reaction ^12-15N ＋ ^28Si at 55 MeV/u and ^17-20Ne ＋ ^9Be at 60 MeV/u. The LCP production cross sections of ^12N increase abnormally in comparison with those of ^13-15N. The result accorded with experimental one. It also happened to ^17-20Ne. It suggests that ^17Ne is probably a proton halo nucleus.     

Elastic scattering of sodium and cesium atoms at ultracold temperatures

The elastic scattering properties in a mixture of sodium and cesium atoms are investigated at cold and ultracold temperatures. Based on the accurate interatomic potential for the NaCs mixture, the interspecies s-wave scattering lengths, the effective ranges and the p-wave scattering lengths are calculated by the quantal method and the semiclassical method, respectively. The s-wave scattering lengths are 512.7a₀ for the singlet state and 33.4a₀ for the triplet state. In addition, the spin-change and elastic cross sections are also calculated, and the g-wave shape resonance is found in the total elastic cross sections.     

17F和18Ne与质子的弹性散射角分布

采用逆运动学方法对放射性核束¹⁷F和¹⁸Ne与质子进行弹性散射实验,得到了实验测量微分截面.用较准确描述放射性核素性质的CH89参数化的光学势为初始光学势,用扭曲波玻恩近似的理论计算程序DWUCK4和自动参数搜索程序ABOD对实验数据进行光学势参数理论拟合,得到了与实验数据相符合的光学势参数.将得到的光学势参数进行分析,得到了17F和18Ne实势相互作用均方根半径分别为3.239fm和3.317fm.     

Experimental Study on Light Scattering of High Concentration Suspension

To understand the optical properties of living tissue in the NIR range, it appeared informative to investigate the scattering properties of high concentration particle suspension. We measured the angular light scattering of aqueous suspension of 3.5 μmφ polystyrene particles contained in a 60 μm thick cuvette up to 50% volume concentration at 805 nm wavelength using a goniophotometer. We found that the discrepancy between the measurement and the Monte Carlo simulation becomes larger with increased concentration, which is attributable to the phase function change as well as the scattering coefficient change.     

计算中低能量电子与水分子弹性散射微分截面

运用耦合通道光学势方法计算了在中低能量下的电子与水分子碰撞弹性散射微分截面,其中靶的极化效应被包含在一个从头算的等价局域势中.随后将计算结果与实验值和其它理论计算结果进行了比较.结果显示这种计算方法对于电子与极化分子体系碰撞是非常适用的.