Quark cluster model and the R-matrix theory treatment of NN scattering

A microscopic quark cluster model has been developed for six-quark states consisting of two s³ quark clusters. The consequences of channel nonorthogonality and existence of Pauliforbidden states are investigated explicitly by solving the eigenvalue problem of the resonating group method (RGM) kernel. Since the RGM kernels needed are all available, the form of the six-quark states given in this paper is very suited to detailed RGM calculations. A rigorous treatment based on the R-matrix theory has been carried out to obtain NN phase shifts. The spin-spin term of the quark-quark interaction favors states of higher color-spin symmetry. This explains the larger change caused by the hidden color states in the ³S₁ phase shifts than in the ¹S₀ phase shifts. Phase shifts calculated with inclusion of the delta and hidden color states are still too repulsive. It is pointed out that there arises a subtle problem in adding the one-boson exchange potential by hand to the RGM equation.     

Electron scattering from levels in 208Pb with excitation energies up to 6.2 MeV and spins up to J = 10

Spectra of electrons scattered inelastically from ²⁰⁸Pb have been measured in the region of excitation energies up to 6.2 MeV. The measured form factors are indicative for spins of the excited states up to J = 10.     

Relativistic optical model on the basis of the Moscow potential and lower phase shifts for nucleon-nucleon scattering at laboratory energies of up to 3 GeV

Data of a partial-wave analysis of nucleon-nucleon scattering at energies of up to E _lab = 3 GeV (lower partial waves) and the properties of the deuteron are described within the relativistic optical model based on deep attractive quasipotentials involving forbidden states (as exemplified by the Moscow potential). Partial-wave potentials are derived by the inverse-scattering-problem method based on the Marchenko equation by using present-day data from the partial-wave analysis of nucleon-nucleon scattering at energies of up to 3 GeV. Channel coupling is taken into account. The imaginary parts of the potentials are deduced from the phase equation of the variable-phase approach. The general situation around the manifestation of quark effects in nucleon-nucleon interaction is discussed.     

Elastic scattering based on energy-dependent relativistic Love-Franey model at energies between 20 and 800 MeV

In order to investigate the elastic scattering,we fit scattering observables of the weighted fits (WF16)with the relativistic Love-Franey (RLF) model.The masses,cutoff parameters,and initial coupling strengths of RLF are assumed to be independent of energy.Because the energy boundary between low energy and high energy is around 200 Me V,the masses,cutoff parameters,and initial coupling strengths of RLF are obtained by fitting scattering observables of WF16 at an incident energy of 200 MeV.With t...     

πp phase shifts from 88 to 310 MeV

Phase shift solutions are presented at pion kinetic energies from 88 to 292 MeV where new measurements of the differential elastic cross section are available, and at 310 MeV. The resulting phase shifts are fitted to effective-range formulae. The resonant P₃₃ phase shift is allowed to take different values for π⁺p and π^?p scattering. There are differences in mass and width between these charge states of the resonance of M⁰ ? M⁺⁺ = 1.4 ± 0.4 MeV/c² and Γ⁰ ? Γ⁺⁺ = 10.3 ± 1.3 MeV/c². The difference in width can be accounted for largely but not entirely by the Coulomb barrier, the channel π^?p → γn, and the difference in phase space between π^?p → π⁰n and π⁺p → π⁺p.     

Prompt neutron multiplicity distribution for 235U(n,f) at incident energies up to 20 MeV

For the n+<'235>U fission reaction, the total excitation energy partition of the fission fragments, the average neutron kinetic energy <ε>(A) and the total average energies E<,γ>(A) removed by γ rays as a function of fission fragment mass are given at incident energies up to 20 MeV. The prompt neutron multiplicity as a function of the fragment mass, ν(A), for neutron-induced fission of <'235>U at different incident neutron energies is calculated. The calculated results are checked with the total average prompt neutron multiplicities ν and compared with the experimental and evaluated data. Some prompt neutron and γ emission mechanisms are discussed.     

Simple method for obtaining electron scattering phase shifts from energies of an atom in a cavity

We present a simple method for obtaining elastic scattering phase shifts and cross sections from precise ab initio many-body perturbation theory energies of atoms in variable cavities. This method does not require calculations of wave functions of continuum states, can be generalized to many atoms and ions, and is extremely convenient because existing codes developed for energy calculations can be used without modification. The high precision of the method and close agreement with experiment are illustrated on examples of e-Ar and e-Kr scattering. Correlations as well as relativistic corrections are systematically considered.     

Eighth-order methods for elastic scattering phase shifts

Two new hybrid eighth-algebraic-order two-step methods with phase lag of order 12 and 14 are developed for computing elastic scattering phase shifts of the one-dimensional Schrödinger equation. Based on these new methods we obtain a new variable-step procedure for the numerical integration of the Schrödinger equation. Numerical results obtained for the integration of the phase shift problem for the well-known case of the Lennard-Jones potential show that these new methods are better than other finite-difference methods.     

Differential cross section,analyzing power and phase shifts for p-3He elastic scattering below 1.0 MeV

Differential cross sections and analyzing powers for the elastic scattering of polarized protons by unpolarized ³He nuclei have been measured at eight energies between 0.3 MeV and 1.0 MeV for scattering angles θ_c.m. = 52.4°–173.3°. The cross-section values were normalized to the Rutherford cross section for proton-krypton scattering. The analyzing powers have been measured with a statistical accuracy of about 0.001. The phase-shift analysis based on these data included all phases for orbital angular momenta l ≦ 1 and the channel-spin mixing parameter for the P waves. An energy parametrization of the phase shifts by an effective-range approximation allowed a simultaneous utilization of all data.     

Elastic scattering of γ-rays from lead for energies from 0.145 to 1.33 MeV

Differential cross sections for elastic scattering of 889 and 1120 keV γ-rays from lead have been measured at angles ranging from 30° to 150°. These results and previously measured differential cross sections at 145, 279, 412, 662 and 1332 keV are compared with theoretical predictions taking into account Rayleigh scattering, nuclear Thomson scattering, and Delbrück scattering. The Rayleigh amplitudes of the K-shell were obtained from the theory of Brown et al., the amplitudes of the other shells from form factors calculated from relativistic HFS wave functions. Discrepancies are found at 145, 889, 1120 and 1332 keV while the experimental data at 279, 412 and 662 keV are in good agreement with the theory. A discussion of possible explanations and consequences is presented.     

On the T-matrix formula for multichannel coulomb scattering

It is pointed out that in scattering theory for Coulomb like forces the conventional expression for the off-energy-shell T-matrix does not lead to the correct on-energy-shell T-matrix. An alternative expression giving the correct on-energy shell limit is discussed.     

Fast calculation technique for scattering in T-matrix method

In scattering calculations using the T-matrix method, the calculation of the T-matrix involves multiplication and inversion of matrices. These two types of matrix operations are time-consuming, especially for the matrices with large size. Petrov et al. [D. Petrov, Y. Shkuratov, G. Videen, Opt. Lett. 32 (2007) 1168] proposed an optimized matrix inversion technique, which suggests the inversion of two matrices, each of which contains half the number of rows. This technique reduces time-consumption significantly. On the basis of this approach, we propose another fast calculation technique for scattering in the T-matrix method, which obtains the scattered fields through carrying out only the operations between matrices and the incident field coefficient. Numerical results show that this technique can decrease time-consumption by more than half that of the optimized matrix inversion technique by Petrov et al.     

T-matrix method formulation applied to the study of flexural waves scattering from a through obstacle in a plate

Elastic wave scattering in a flat thin plate hosting a through obstacle of arbitrary closed form is examined using a numerical technique based on the T-matrix approach, which is applied to describe of flexural waves in plates. The limiting cases of a hole and a rigid obstacle are considered. The vibrations of the plate are described by the Kirchhoff model. The far field backscattered amplitude as a function of wave frequency for inclusions of elliptic, triangular and square form with rounded corners is analysed numerically. Comparison of present results for circular obstacles with the analytical solutions obtained by other authors show excellent agreement.     

Neutron-neutron scattering length from the 2H(n,np)n reaction at bombarding energies up to 27 MeV

The n-n interaction has been investigated in a kinematically complete experiment with high statistical accuracy via the ²H(n, np)n reaction at bombarding energies up to 27 MeV, extending previous measurements to higher energies and to a different geometry. The analysis with exact three-body calculations yields ann = ?16.9 ± 0.6 fm.     

Low energy scattering data and phase shifts

We point out that at any given low energyσ _tot and a ratio of integrated scattering data likeF/B can, in principle, be used unambiguously to finds-andp-wave phase shifts. Thus efforts to obtain other low energy data like elastic dσ/dΩ andP/E are unnecessary. It is also indicated that the mere knowledge whetherF/B is greater than or less than unity enables us to draw important conclusions about the nature of the interaction in thep-state without performing detailed calculations. Thus a strong case is made out for obtaining much more preciseF/B data than are presently available. The discussion refers mainly to low energy ∧p scattering data.     

200MeV以下质子-核散射的相对论微观描述

应用Dirac Brückner-Hartree-Fock方法, 采用新的G矩阵分解方式研究了核子在核介质中的同位旋相关的相对论微观光学势，采用定域密度近似得到有限核的相对论微观光学 势.讨论了有限核的相对论微观光学势及其Schrdinger等价势与入射质子能量的关系，计 算了200MeV以下质子入射40⁴⁰Ca和208²⁰⁸Pb核的弹性散射角分布 和分析本领，得到了与实验相一致的结果，并将这种方法推广用于不稳定核的研究.通过对C a同位素的计算可以看出，在相 关键词： 相对论微观光学势 Dirac Brückner-Hartree-Fock 不对称核物质 定域密度近似