Elastic scattering from the multiperipheral model

Elastic scattering in the Multiperipheral Model (MPM) is examined by use of a new method for simplifying unitary calculations - multiparticle impact parameter. The t dependence of elastic scattering in the MPM is related to the average transverse momentum of produced particles, the average multiplicities (observables), phase variation with transverse momentum, and clustering (not observables, in general). It is shown that MPM's are inconsistent with the combination of elastic and multiparticle data, unless either the cluster size or the phases have rather strong energy dependence.     

Fermionic and bosonic scattering phases on a topological kink

A general approach to the scattering of fundamental fermions and bosons on a topological kink excitation is considered. An asymptotic LSZ-analysis for secondary quantized Heisenberg fields and kink motion is developed and some new results for the phases of one-particle matrix elements for the elastic scattering on the kink are derived.     

Phase-shift analysis of spin-correlation coefficients in p-d scattering: A solution to the 2S defect

A phase-shift analysis of combined cross-section and spin-correlation data has been performed for the elastic scattering of protons by deuterons. Reliable doublet phases have been extracted and compared with extensive Faddeev-type calculations using different rank-one separable interactions. The effect of P-wave N-N forces is discussed and intrinsic strengths and range are deduced.     

Elastic scattering of an electron by the negative lithium ion

In the framework of the many-body theory, the differential and total cross sections of elastic scattering of slow electrons by the negative lithium ion Li⁻ are obtained. Calculations are performed both in the Hartree-Fock single-particle approximation and with regard to many-electron correlations, which take into account the dynamic polarization of the core. Features observed in the behavior of the phases and cross sections for p and d partial waves are associated with resonance scattering of electron waves. Considering the dynamic polarization of the core by an incident electron heightens the diffraction character of the scattering. The real process is compared with particle scattering in models with a repulsive potential.     

Hulthén potential models for <Emphasis Type="BoldItalic">α−α</Emphasis> and <Emphasis Type="BoldItalic">α−</Emphasis>He<Superscript><Emphasis Type="BoldItalic">3</Emphasis></Superscript> elastic scattering

Simple Hulthén-type potential models are proposed to treat the α?α and \(\alpha {-} \text {He}^{3}\) elastic scattering. The merit of our approach is examined by computing elastic scattering phases through the judicious use of the phase function method. Reasonable agreements in scattering phase shifts are obtained with the standard data.     

Determination of the scattering amplitude from the differential cross-section and unitarity

When the differential cross-section for spin-zero elastic scattering is given, the elastic unitarity condition constitutes a nonlinear integral equation for the phase of the scattering amplitude. Existence and uniquences theorems for solutions of the equation were obtained by Newton and Martin. Some improvements of the Newton-Martin results on uniqueness and iterative construction of solutions are obtained. Certain details of rigour in the applications of Schauder's theorem by Newton and by Martin are supplied. The case of inelastic spin-zero scattering is treated by adding a term to the unitarity condition to account for absorption. It is shown that in the inelastic region one may have infinitely many different scattering amplitudes with a given differential cross-section. This result is potentially important in phase-shift analysis, since it means that there is a continuum ambiguity in the determination of phases and elasticities from scattering data.Work supported in part by the National Science Foundation and a NATO Research Grant.     

Mass spectrum and elastic scattering in the massive SU(2)f Schwinger model on the lattice

We calculate numerically scattering phases for elastic meson-meson scattering processes in the strongly coupled massive Schwinger model with an SU(2) flavor symmetry. These calculations are based on Lüscher's method in which finite size effects in two-particle energies are exploited. The results from Monte Carlo simulations with staggered fermions for the lightest meson (“pion”) are in good agreement with the analytical strong-coupling prediction. Furthermore, the mass spectrum of low-lying mesonic states is investigated numerically. We find a surprisingly rich spectrum in the mass region [m_π, 4m_π].     

Quantum theory of atom-surface scattering: Incommensurate and fluid adsorbates

The problem of atomic scattering from adsorbate-covered surfaces, treated earlier for the case of commensurate overlayers, is considered again in the eikonal approximation for incommensurate lattice phases and for fluid phases. Stochastic methods are employed and for a specific model (hard bosses on a plane) it is shown how the statistical and geometric problems can be separately solved. In order to explain the meaning of the coherent and incoherent scattering contributions a time-dependent theory is introduced and it is shown that the incoherent “elastic” scattering is in fact weakly inelastic and (for classical diffusion with diffusion coefficient D) has an energy width of the order ?DQ², where Q is the parallel momentum transfer. The problem of the decay of substrate diffraction intensities when the coverage of random impurities is increased is also discussed.     

The amplitude phase pattern of strong interactions at 45 GeV/c

The amplitude phase pattern, previously exhibited for a variety of strong interaction processes at energies ranging from barely over 100 MeV to several GeV, is shown to manifest itself also at 40–45 GeV/c for pion-nucleon elastic and charge exchange scattering. In this phase pattern the relative phases of the planar transverse optimal amplitudes are multiples of 90 degrees.     

Elastic scattering of low-energy electrons by a uranium atom: Reliability of theoretical predictions of based on a model description

We used the method of phase functions to solve the radial relativistic Dirac equation and nonrelativistic Schroedinger equation. With these solutions, we investigated the elastic scattering of slow electrons by a uranium atom, and obtained numerical values for the total cross section and elastic scattering phases. In order to check the correctness of the results found from the method of phase functions, in all cases we also solved the Dirac and Schroedinger equations by direct numerical integration. Several types of polarization and exchange potentials were used to simulate the scattering process. We conclude that the strong dependence of the cross section for elastic scattering of an electron by uranium on the shape of the effective potential of the latter at small kinetic energies (E _k<5 eV) makes it impossible to predict the presence or absence of a Ramsauer effect reliably. Zh. éksp. Teor. Fiz. 111, 1214–1228 (April 1997)     

Ambiguity on the imaginary potentials in the Dirac formalism for the elastic and the inelastic scattering of nucleons

The Dirac formalism for the elastic scattering of nucleons has been extended to a coupled channel formalism taking into account collective excited states. Calculations for the scattering of 500 MeV protons on ⁴⁰Ca shows large second-order effects on the elastic scattering. The imaginary scalar potential and the imaginary vector potential can be varied widely without giving so large effects on the elastic scattering. This large ambiguity is not limited to this case.     

Theory of incommensurate magnetic correlations across the insulator-superconductor transition of underdoped La2-xSrxCuO4

The main feature in the elastic neutron scattering of La2-xSrxCuO4 is the existence of incommensurate peaks with positions that jump from 45 degrees to 0 degrees at 5% doping. We show that the spiral state of the t-t(')-t(')-J model with realistic parameters describes these data perfectly. We explain why in the insulator the peak is at 45 degrees while it switches to 0 degrees precisely at the insulator-metal transition. The calculated positions of the peaks are in agreement with the data in both phases.     

Influence of the matrix on boron detection by auger electron spectroscopy (AES)

The difficulties of boron detection by AES in catalysts containing low concentrations of boron can be partially associated with elastic scattering of Auger electrons. In the present work, the Monte Carlo approach is used to estimate the effects of Auger electron collisions in different matrices. Elastic scattering events are described within the partial wave expansion method. The scattering centres are approximated by the Thomas-Fermi-Dirac potentials. It is found that elastic collisions decrease the boron KLL Auger electron signal by up to 10%. In addition, the sampling depth of AES is strongly decreased. This decrease reaches 35% for medium atomic number elements. The values of parameters correcting for elastic scattering effects are determined for boron embedded in 14 elements. An attempt is also made to interpolate the correcting parameters for matrices not considered in the present work.     

Multiperipheralism and elastic scattering

Elastic scattering is calculated via unitarity, using a variety of multiperipheral models. Although special attention is paid to the effect of spinning cluster production, interference terms and phases, the forward elastic slopes thus calculated are still not consistent with experiment. An alternative type of dynamics is suggested.     

On the re-summation of enhanced pomeron diagrams

Dominant contributions of enhanced pomeron diagrams to elastic hadron–hadron scattering amplitude are re-summed to all orders. The formalism is applied to calculate total hadronic cross sections and elastic scattering slopes. An agreement with earlier results is obtained.     

水下目标弹性声散射信号分离

水下目标弹性声散射与其他声散射成分在时域和频域上均存在混叠, 现有信号处理方法受分辨力限制无法在混叠状态下识别目标弹性声散射特征. 针对这个问题, 提出了一种目标弹性声散射信号分离方法. 以目标回波亮点模型为基础, 分析了线性调频信号入射时目标声散射成分的信号特性, 提出了一种目标声散射成分向单频信号的映射方法, 并理论推导出了目标声散射结构与映射结果之间的线性对应关系, 实现了通过窄带滤波分离出目标弹性声散射成分. 仿真与消声水池实验数据处理结果表明, 该方法基本可以完全分离出目标回波信号中的弹性声散射成分, 分离出的弹性声散射具有与理论一致的信号特征, 验证了该分离方法的有效性.     

Model differential cross section of elastic scattering of electrons by atoms in the Monte Carlo simulation of the passage of electrons in a substance

A new model differential cross section is proposed for describing elastic scattering of electrons in simulating the passage of electrons through a substance by the Monte Carlo method. This differential cross section correctly describes the first and second transport scattering cross sections, but is characterized by the total elastic scattering cross section much smaller than the actual value of the total elastic scattering cross section. The application of this differential cross section makes it possible to considerably reduce the number of elastic collisions in the Monte Carlo simulation of passage of electrons in a substance and to model the passage of high-energy electrons using the individual collision model.