On high-energy elastic scattering of protons by nuclei

The two coupled channel formalism for high energy elastic scattering [1] is extended to include spin and isospin effects. For a spin and isospin zero nucleus these manifest themselves by additional spin-orbit terms in the potentials. Explicit formulas for these potentials are obtained in terms of the fully spin and isospin dependent nucleon-nucleon scattering amplitude, the ground state nuclear form factor and the state dependent correlation functions. The coupling potential except for a small term arising from double spin and isospin flip process involving nuclear excitation depends only upon the pair correlations.Numerical calculations are performed for the elastic scattering of 1 GeV protons incident on ⁴He. Various phenomenological dynamical two-body correlations as well as correlations generated from the Reid soft-core and Tabakin potentials in an approximate Brueckner-Hartree-Fock calculation are considered. The angular distribution beyond its first diffraction minimum as well as the polarization in the same angular range are shown to be sensitive to these correlations. However, the present accuracy of the experimental data and the lack of knowledge of the nucleon-nucleon scattering amplitude prevent any definitive conclusion about their nature.     

Structure of light neutron-rich nuclei and mechanism of elastic proton scattering

Differential cross sections for elastic p ⁶He, p ⁸Li, and p ⁹Li scattering at two energies of 70 and 700 MeV per nucleon were calculated within the Glauber theory of multiple diffractive scattering. Threeparticle wave functions (α-n-n for ⁶He, α-t-n for ⁸Li, and ⁷Li-n-n for ⁹Li) were used for realistic potentials of intercluster interactions. The sensitivity of elastic scattering to proton-nucleus interaction and to the structure of nuclei was explored. In particular, the dependence of the differential cross section on the contribution of higher order collisions, on scattering on the core and peripheral nucleons, and on the contribution of small wave-function components and their asymptotic behavior was determined. A comparison with available experimental data and with the results of calculations within different formalisms was performed.     

Vacuum polarization effects in elastic scattering of protons by nuclei

Sensitivity of spin observables in elastic proton scattering by nuclei to the vacuum polarization correction δϱ_VAC is explored. The Dirac optical potential is calculated from a complete set of Lorentz invariant amplitudes, Dirac-Hartree densities and the existing estimate of δϱ_VAC based on quantum hadrodynamics.     

6Li与核弹性散射的微观光学势

从基本的Dirac-Brueckner-Hartree-Fock微观理论出发,得到同时包含实部和虚部的核子-核散射的微观光学势,并利用折叠模型直接获得了核一核散射参数无关的整体微观光学势.考虑到核.核散射去弹过程高级项的贡献和6Li的碎裂效应,在微观光学势的实部和虚部中引入了修正因子NR,N1.系统研究了入射粒子6Li与靶核12C,28Si,40Ca,58Ni,90Zr和208Pb散射的微观光学势,计算中虚部增强因子取N1≈3.0,而实部修正因子NR对于给定的碰撞系统几乎是一个常数.理论很好地再现了所有被研究靶核和入射能量的弹性散射实验数据.参数无关的微观理论对核.核散射,尤其是对不稳定核.核系统反应的描述是有价值的.     

Microscopic analysis of antiproton-nucleus elastic scattering

Elastic antiproton-nucleus scattering is analysed with a microscopic optical model potential obtained by convoluting an effective interaction with target densities. Local, energy- and density-dependent complex effective interactions are constructed from reaction matrices generated with the Dover-Richard and Paris potentials. Effects of nuclear medium correction on the final results are examined. Comparison is made between the calculated results and the experimental data from LEAR which include the first polarization data as well as differential cross sections.     

Optical-model analysis of Li elastic scattering

The elastic scattering cross sections of 28 MeV ⁶Li ions from the nuclei ¹¹B, ¹²C and ¹³C were analyzed using the optical model. The analysis has been extended to other ⁶Li elastic scattering data on ¹⁶O (29.8 MeV) and on ¹²C (24.5 and 30.6 MeV) previously measured elsewhere. The fits obtained with the usual six-parameter Woods-Saxon potential are good. Parameter ambiguities were studied and the results of the analysis were compared with the predictions of the folding model.     

Elastic scattering of high-energy protons from nuclei

The elastic scattering of high-energy protons from zero-spin nuclei is considered within the framework of Glauber theory. The sensitivity of the cross sections to the nuclear structure and to the proton-nucleon amplitude is studied. Results of calculations demonstrating the investigated effects are presented for the case of 1 GeV proton scattering from ⁴He, ¹⁶O and ⁵⁸Ni.     

Multichannel nuclear reactions involving light neutron-rich nuclei: Microscopic approach

The influence of the Pauli exclusion principle on the relative motion of light neutron-rich nuclei in their collision is investigated within the microscopicmethod using as an example ¹¹Be + n and ¹⁰Be + ² n nuclear reactions, as well as ³ n + n and ² n + ² n reactions. Antisymmetrization effects related to the kinetic and potential energy of the relative motion of colliding nuclei are analyzed. The influence of the Pauli exclusion principle on the kinetic energy of the relative motion of the ¹¹Be nucleus and a neutron is shown to result in their attraction. The same phenomenon is observed for the case of the ³ n + n cluster system. The strength of such attraction is high enough to ensure the existence of a bound state in the ¹²Be nucleus and a low-energy resonance in the tetraneutron. The conclusion is drawn that, for a resonance state in the ⁴ n system to exist, the value of the oscillator length must be large enough. It is shown also that increasing the oscillator length results in depression of the cluster-cluster potential. The text was submitted by the authors in English.     

Analysis of elastic and inelastic hadron scattering on 6,7Li nuclei within diffraction theory

Within Glauber-Sitenko multiple-scattering theory, the differential cross sections for elastic and inelastic proton, positive-pion, and positive-kaon scattering on ^6,7Li nuclei are calculated at incident-hadron energies ranging between 0.143 and 1.0 GeV. The ⁶Li and ⁷Li wave functions are taken in, respectively, the α2N and the αt clustermodel. The resulting cross sections are investigated as functions of the scattered-particle energy, parameters of the model wave functions, and various scattering multiplicities. It is concluded that a partial filling of the diffraction minimum in the cross section is due to the D-wave contribution to the wave function for the ⁶Li target nucleus.     

The elastic scattering of protons by deuterium

Proton-deuteron elastic scattering was investigated with a gas target. Excitation curves were taken at 45.28°, 90.26°, and 118.92° c.m. for lab proton energies from 4.5 to 11.5 MeV. Angular distribution were taken at 4.45, 5.45, 6.50, 7.46, 8.47, 9.47, 10.47 and 11.47 MeV from 30° to 140° c.m. Differential cross sections were measured with an absolute error of less than ±3%. The scattering data were compared with predictions derived from the scattering amplitudes of Aaron, Amado and Yam ¹⁰). No evidence for the existence of ³He excited states was found in this energy range.     

Influence of the Mott-Schwinger interaction on the elastic scattering of protons

It is demonstrated that the Mott-Schwinger interaction must be taken into account when analyses of polarisation measurements in proton scattering at energies below the Coulomb barrier are to be performed with high accuracy. A treatment of the effect is worked out in perturbation theory, and the reliability of the method is demonstrated. It is shown how the resulting badly converging series for the “Mott-Schwinger amplitude” can conveniently be summed by means of Padé-approximation. Numerical results are presented for several representative cases.     

Elastic scattering of 1-GeV protons by nuclei

The calculated elastic scattering of 1.04-GeV protons by ²⁰⁸Pb, ⁵⁸Ni, and ⁴⁰Ca is compared with experiment. The effects of the spin-orbit potential, Pauli and short-range correlations, variations in the ratio of the real to the imaginary part of the nucleon-nucleon scattering amplitude at 0° are found to have similar effects. Further experiments are required before these effects can be disentangled. Changes of the neutron density compared to the proton density can be distinguished. The proton polarization by elastic scattering by ²⁰⁸Pb and ⁴⁰Ca is calculated omitting the effects of correlations.     

Parity-violating asymmetry in elastic electron scattering on nuclei: Partial-wave analysis

Elastic scattering of longitudinally polarized electrons on heavy nuclei is known to be a promising method for studying neutral parity violating, weak interactions. With the aim of investigating the effect of Coulomb distortion on the calculated asymmetry we develop a complete partial-wave analysis for the Dirac equation in the presence of a parity-odd potential in addition to the Coulomb potential. We apply our analysis to a set of selected nuclei with spin zero. The physical features of the resulting asymmetries are discussed and a comparison to the Born approximation is made.     

Optical-model analysis of the elastic scattering of 100 MeV protons from Mg and Si

Elastic scattering differential cross sections for the interaction of 100 MeV protons with ²⁴Mg and ²⁸Si have been measured using a high-resolution Ge(Li) spectrometer to resolve the inelastic scattering contribution to the elastic peak. The results have been analysed using the conventional optical model, and the experimental differential cross sections and total reaction cross section are excellently reproduced. The results agree with previous analyses of the elastic scattering of 100 MeV protons on 1p shell nuclei in that no set of geometric parameters can provide a quantitative fit to both nuclei. It is observed, however, that the fluctuations of the optical-model parameters for optimum fits are decreased over the fluctuations observed for the 1p shell nuclei. The present results combined with previous optical-model analyses on ²⁴Mg and ²⁸Si at 50 MeV and 40 MeV respectively, are found to be consistent with an energy dependence of dV/dE ≈ −0.3 for the depth of the real central potential in agreement with other, more extensive, investigations of the energy dependence for protons elastically scattered from ¹⁶O and ⁴⁰Ca.     

Fourier analysis of elastic light scattering spectrum of epithelial cell nuclei

<正>A new method for simultaneously determining the size and refractive index of epithelial cell nuclei is presented.The function of the modified elastic light scattering spectrum is regarded as a function of wave number factor,Q=2λ~(-1)sin(θ/2).The modified spectrum has a constant oscillation period with its frequency proportional to the average diameter of cell nuclei.To the same average diameter,the different relative refractive indexes of epithelial cell nuclei only induce the horizontal shift of the spectra.Both the oscillation frequency and the horizontal shift are quantified by the fast Fourier transform on the modified spectra.The average diameter can be figured out through the peak frequency divided by the value of the refractive index of the surrounding medium.The phase angle of the peak frequency has an approximate linear relationship with the relative refractive index of epithelial cell nuclei.     

Neutron elastic scattering on T = 0 nuclei

Neutron elastic scattering on Si, S and Ca has been measured at 11, 20 and 26 MeV using the Ohio University 11 MeV Tandem Van de Graaff. A time-of-flight technique was used and the angular distributions covered an angular range from 15° through 155°. The measured cross sections were corrected for dead time, source anisotropy, detector efficiency, finite geometry, neutron flux attenuation and multiple scattering. Individual as well as global fits to the data using an optical-model search code are presented. The comparison of the optical-model analysis to the neutron and proton elastic scattering data in the case of ⁴⁰Ca, allows an empirical determination of the Coulomb correction term which may be parametrized as $\text{0.46 Z/A}\text{1}\text{3}$. It is also shown that the elastic scattering and inelastic scattering to the first 2⁺ states in ²⁸Si and ³²S may be fitted using the same optical-model parameters obtained for ⁴⁰Ca using the coupled-channel formalism.     

Microscopic description of low-energy neutron scattering by nuclei

The Bloch and Gillet shell-model formalism extended to continuum states is applied to lowenergy neutron scattering by nuclei. It is shown that complete antisymmetrization leads in the r-representation to corrective terms which yield important corrections to the scattering lengths. Calculations are performed within a model restricted configuration space for the target nuclei ¹²C, ¹³C, ¹⁶O, ¹⁷O and ⁴⁰Ca. We predict values for the spin-dependent scattering amplitude for ¹³C and ¹⁷O. The antisymmetrization problem in the case of a large configuration mixing is studied for the ¹⁹F target nucleus. The resonant effects of the compound nucleus are then very important and the results become very sensitive to the configuration space and the interaction parameters.