Chou-Yang model and predictions for high-energy pion-deuteron scattering

Using fits to the available data on the pion and deuteron electromagnetic form factors and the Chou-Yang model, the computed values of differential cross-sections for high-energy pion-deuteron elastic scattering agree reasonably well with the available experimental data. Whereas only a shoulder is expected to appear up to energies of several hundreds of GeV, a dip and a secondary maximum are predicted to be conspicuous only forP _lab≫400 GeV/C. The position of the dip starts at a much lower value, |t _d| ≅ 0.5–0.6 GeV², as compared to the corresponding position in thepp scattering. The positions of the first dip are plotted against total cross-section which can be verified by future high-energy experiments. Limitations of the model predictions for ultrahigh energies are pointed out.     

Convergent polynomial expansion,energy dependence of slope parameters,scaling hypothesis and predictions forπ ± p andK + p scattering

A phenomenological representation for differential cross-section recently proposed using Mandelstam analyticity and convergent polynomial expansion (CPE) which has been found to be successful in describing scaling of the differential cross-section-ratio data for several elastic diffractive and inelastic nondiffractive processes is used to analyse the energy dependence of the slope-parameter data at high energies, extrapolate the slope parameter and predict the differential cross-section ratio as a function of |t| at higher energies forπ ^± pndK ⁺ p scattering. Following the method of Hansen and Krisch it is found that, in spite of the existence of rather widely varying data points for nearbys values, a more systematic trend in the energy dependence of the slope parameter emerges when a statistical average of the existing high-energy data is used. Extrapolating the fits to the average data ontos → ∞ provides strong evidence in favour of a model-independent result that asymptotically theπ ^± p slopes may be equal. There is also a strong indication to the effect that each of these two slopes may be equal to theK ⁺ p slope fors → ∞. Using the scaling curves generated by the existing data on differential cross-section ratio and extrapolated values of the slope parameter, the differential cross-section ratio for each of the three processes is predicted as a function of |t| for higher energies.     

激光-电子康普顿散射物理特性研究

对激光-电子康普顿散射物理特性即能量特性和微分截面角分布进行了仔细的研究.计算结果显示出光子能量和微分截面角分布的简单结构.康普顿散射X射线光源具有散射光子的能量易调节、方向性好等特点.在入射电子束能量很高时,X射线近乎单向出射.光源色散度较大,但实验上可以获得色散（带宽）小的X射线.对于各种波长的激光,在很宽的电子束能量范围（1 MeV—10 GeV）内,散射X射线光子的总截面和前向发射圆锥内（半圆锥角1/γ,其中γ=E/m₀ 关键词： 康普顿散射 能量特性 微分截面 角分布     

Incoherent X-radiation produced by relativistic electrons in crystals

Differential and integral features of incoherent X-radiation, induced by relativistic electrons in crystals, are studied for observation angles θ_γ several times greater than γ^-1, where γ is the projectile Lorentz factor. The existence of sharp maxima and a minimum of the five-folded incoherent differential cross-section as a function of the final electron angles, and a dip minimum when the cross-section is taken as a function of the photon energies, is demonstrated. At near backward observation angles the three-folded cross-section shows a maximum in the region of several keV photon energies. The obtained results allow us to optimize the conditions for coincidence experiments, minimizing the incoherent contribution to the total radiation yield, and helping to analyse results of finite-size detector experiments with crystal targets. Received: 2 July 2001 / Accepted: 26 November 2001     

Modifications in high energy higher order Born approximation

A systematic study is made to find out the differential scattering cross-section in the case of electron-atom collisions. The first and the second Born terms ofO(1/k _i ) are calculated in the framework of Yates high energy higher order Born approximation. The second Born term ofO(1/k _i ² ) is calculated using the second order Wallace term, the third term is calculated using the Glauber-eikonal series of Yates. The method is applied to the elastic scattering of electrons by atomic hydrogen in the energy range 100–400 eV and by helium for energies 200 eV and 400 eV. Comparison is made with other theoretical results and the experimental data.     

Neutron scattering by anharmonic crystals and the effect of sublattice displacements

A theory has been given for the scattering of neutrons by anharmonic crystals, for which terms of the typeV ⁽³⁾ (k _1j1; —k _1j1;o _j) which contribute to the sublattice displacements are not neglected. Using the standard perturbation theory in the interaction picture or Green’s function method, an expression has been derived for the differential scattering cross-section which brings in the shift and the width of the phonons in one-phonon energy exchange processes. It is shown that the sublattice displacements will modify the phase factor arising from the scattering by any atom in the unit cell, and the Debye-Waller factor also gets altered both by the sublattice displacements as well as by higher order terms arising from anharmonicity. It is shown that the differential scattering cross-section contains a term linearly depending on the third order anharmonicity coefficientV ⁽³⁾ (k _1j1;k _2j2;k _3j3) and neutron scattering by crystals should provide a useful method for evaluating the third order anharmonicity coefficients.     

Convergent polynomial expansion,scaling of differential cross-section and computation of scaling functions for elastic diffraction scattering processes

Existing data on the differential cross-section ratio at high energies for pp, p, π^±p andK ^±p scatering have been fitted by the proposed convergent polynomial expansion to determine the unknown coefficients in the scaling function. It is found that the data are very well represented within and somewhat outside the peak regions by only four or five terms in the proposed series in terms of Laguerre polynomials.     

Zeros of the helicity amplitudes of Σ+-p elastic scattering

Optimally exploiting the analytic structure of the helicity amplitudes of Σ⁺-p scattering we locate their zeros by making a fit to the differential cross-section curves at 40, 100 and 150 MeV energies. Minute changes in the positions of the zeros produced detectable noises in the fit. It was observed that quite reliable predictions for the phase shifts can also be obtained from this analysis.     

Elastic pp scattering in the cern sps energy region

The pronounced dip-bump structure with a sharp minimum at |t| = 1.5 (GeV/c)², recently observed in elastic $\text{p}$p scattering at P_L = 50 GeV/c at the CERN SPS, is explained by the quark multiple scattering model with a realistic wavefunction for the proton and the antiproton. It is predicted that a second dip will appear around |t| = 7 (GeV/c)² at P_L = 50 GeV/ c and at higher energies.     

Elastic scattering of e∓ by Na atoms

ABSTRACT

The differential, integrated elastic, momentum transfer, viscosity and total cross-sections along with Sherman function for the elastic scattering of electrons and positrons by sodium atoms have been calculated within the framework of complex projectile–atom optical potential model at the impact energies 0.1 ≤ E_i ≤ 10⁴ eV for both the projectiles. The relativistic Dirac partial wave techniques, with accurate analytical charge densities, are used to obtain the scattering amplitudes. The present results produce satisfactory agreement with the experimental measurements and other theoretical calculations available in the literature.     

Absolute double differential ionization cross-section for electron impact: He

Summary A complete set of absolute double differential cross-section (DDCS) for electron impact ionization of helium has been measured at an incident energyE ₀=500 eV. The angular distributions of the ejected and scattered electrons between 40 and 435.5 eV have been measured over the angular range of (10÷145)^o. This work supplements the mapping of DDCS for ejected electron energies close to (E ₀−IP)/2 (IP is the He 1s ionization energy), a region where the experimental data are fragmentary. The possibility of representing the full Bethe surface with a simple functional form is investigated. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Vibrational and rotational excitation effects of the N(2D) + D2(X1Σg +) → ND(X3Σ+) + D(2S) reaction

The effects of the rovibrational excitation of reactants in the N(²D) + D₂(X¹Σ_g⁺) → ND(X³Σ⁺) + D(²S) reaction are calculated in a collision energy range from the threshold to 1.0 eV using the time-dependent wave packet approach and a second-order split operator. The reaction probability, integral cross-section, differential cross-section and rate constant of the title reaction are calculated. The integral cross-section and rate constant of the initial states v = 0, j = 0, 1, are in good agreement with experimental data available in the literature. The rotational excitation of the D₂ molecule has little effect on reaction probability, integral cross-section and the rate constant, but it increased the sideways and forward scattering signals. The vibrational excitation of the D₂ molecule reduced the threshold and broke up the forward–backward symmetry of the differential cross-section; it also increased the forward scattering signals. This may be because the vibrational excitation of the D₂ molecule reduced the lifetime of the intermediate complex.     

A Numerical Calculation for Electron Impact Excitation of Copper

The scattering of electrons by atomic copper has been studied using Born approximation and the concept of the generalized oscillator strength (GOS). Differential and total cross-sections for the excitation of the 3d¹⁰ 4p² P state are calculated at incident energies of 100 eV and are compared with other available experimental and theoretical data. The agreement between our calculation for the differential cross-section and the available experimental results is fairly good at the forward angles, while the agreement at large angles is poor. The calculated total cross-sections are compared with the experimental data and those predicted by several theories. It is found that our calculation for the total cross-sections are in a good agreement with the close coupling calculation of Msezane and Henry (1986a, Physical Review A 33, 1631) for incident energies greater than 20 eV. The integrated cross-section measurements of Ismail and Teubner (1995, Journal of Physics B: Atomic, Molecular and Optical Physics 28, 4164) are in good agreement with the present calculation.     

Total scattering cross-section and extraction of low energy parameters of Σ±p scattering

The lowest momentum at which the total scattering cross-section data are available for Σ⁺ p and Σ⁻ p scattering is 145 MeV/c and 142.5 MeV/c respectively. Thus extracting low energy parameters amounts to extrapolating the data to still lower energies. Using the analytic structure of foward scattering amplitude to advantage a parameterization of theσ _T is presented which is hoped to be more reliable and stable for deriving results through extrapolation. The scattering lengths and effective ranges for the Σ⁺ p and Σ⁻ p are also estimated.     

Optical potential analysis of proton elastic scattering from <Superscript>12</Superscript>C based on the <Emphasis Type="Italic">α</Emphasis>-particle model

Based on an α-particle model of ¹²C, an optical potential for intermediate-energy proton- ¹²C scattering is presented in the framework of the KMT theory. The parameterized proton- ⁴He amplitude, the required basic input for constructing the optical potential, is obtained by fitting the proton- ⁴He scattering data. The differential cross-sections and analyzing powers of the proton- ¹²C elastic scattering at incident energies ranging from 0.2 to 1.0GeV have been calculated by using the obtained optical potential. The main features of the measured angular distributions of the cross-section and the analyzing power can be satisfactorily described. The proton- ¹²C total cross-sections have also been calculated, and the results are in good agreement with the experimental data at energies below 0.6GeV but underestimate the data about 6% at higher energies.     

Scattering of electrons with formyl radical

A detailed theoretical study is carried out for electron interactions with formyl radical (HCO) with incident energies ranging from 0.01 to 5000 eV. This wide range of energy has allowed us to investigate a variety of processes and report data on vertical electronic excitation energies, dissociative electron attachment (DEA) and total cross-section along with scattering rate coefficients. We observed Ramsaur–Townsend minimum at 0.59 and 0.74 eV using DZP and cc-pDVZ basis sets, respectively. HCO has large number of low-lying excited states and the present study finds an overall good agreement with earlier reported data. In order to compute total cross-section, we have employed ab initio R-matrix method (0.01 to ～ 20 eV) and the spherical complex optical potential method (～ 10 to 5000 eV) employing static-exchange plus polarisation potential. The R-matrix calculations are performed using a close coupling method with the aid of 21 target states, 1191 configuration state functions and 195 channels. The DEA cross-sections of fragmentation of H^?, excitation cross- sections and scattering rate coefficients are reported for the first time. Total cross section presented here will provide a reference data set over an extensive impact energy range.     

Correlation of resonance scattering and superconductivity in PbxSn1−xTe solid solutions doped with In

The Hall coefficient and resistivity were measured on a series of samples of Pb_xSn_1−xTe with 0x0.45 and 5 at% of InTe as a dopant. All samples show p-type conductivity with hole concentration in the range from 10¹⁹ to 10²¹ cm⁻³ at 77 K. A slight decrease of Hall mobility and corresponding increase in the scattering cross-section of holes by impurity atoms was observed with an extremum at x=0.25. All samples exhibit a transition to a superconducting state with the critical temperatures ranging from 0.3 to 3.0 K. The maximum of dH_c2/dT (where H_c2 is the second critical field) correlates with the fall in mobility (or rise in the scattering cross-section of holes), which shows that the resonance scattering mechanism is playing an important role in the enhancement of superconducting properties of these solid solution materials.     

| m | Partial wave treatment for two-dimensional Coulomb-scattering and Regge pole

The symmetry and |m| partial-wave analysis for two-dimensional (2D) Coulomb-scattering is investigated. As a function of energyE, the |m| partial-wave scattering amplitudef _|m|(θ) is analytically continuated to the, negativeE (complexk) plane, and it is found that the bound state energy eigenvalues (E<0) are just located at the poles off _|m|(θ) on the positive imaginaryk axis as is expected. In addition, as a function of |m|,f _|m|(θ) is analytically continuated to the complex |m| plane, the bound state energy eigenvalues are just located at the poles off _|m|(θ) on the positive real |m| axis.