High-energy fixed-angle elastic scattering

The leading behavior of high-energy, fixed-angle, hadron-hadron scattering is obtained in a model in which on-mass-shell colored quarks exchange colored gluons. The resultant differential cross sections are compared with the data, indicating that such a mechanism does not dominate the physical scattering process.     

Analyticity and quark-gluon structure of hadron total cross sections

The amplitudes of hadron-hadron forward elastic scattering at high energies are investigated on the basis of analyticity and crossing symmetry. A universal uniformizing variable for them is proposed, and the formulas for crossing-even and crossing-odd amplitudes are derived. The same parameters in these formulas determine the real and imaginary (total cross sections) parts of the amplitudes. The analysis of the parameters determined from experimental data clearly points to the quark-gluon structure of hadron total cross sections. The total cross sections for hyperon-proton scattering are predicted. They are consistent with experimental data and, in particular, with the new SELEX-collaboration measurement σ_tot(Σ^?p).     

Differential cross sections of proton compton scattering at photon laboratory energies between 700 and 1000 MeV

Differential cross sections of proton Compton scattering have been measured at the Bonn 2.5 GeV synchrotron. 78 data points are presented as angular distributions at photon lab energies of 700, 750, 800, 850, 900, and 950MeV. The c.m. scattering angle ranges from 40°–130°, corresponding to a variation of the four momentum transfer squared betweent=?0.10 tot=?0.96 GeV² at 700 and 950 MeV, respectively. Two additional differential cross sections have been measured at 1000MeV, 35.6° and 47.4°. The angular distributions show forward peaks whose extrapolations to 0° are consistent with calculated forward cross sections taken from literature. The small angle data (|t| ?0.2 GeV²) together with the calculated cross sections at 0° are also consistent with the assumption of a slope parameterB of 5 GeV^?2. For the first time a rerise of the angular distributions towards backward angles has been observed. It becomes less steep with increasing energy. The most interesting feature of the angular distributions is a sharp structure which appears betweent=?0.55 GeV² at 700MeV andt=?0.72 GeV² at 950 MeV. Such a rapid varation of the differential cross section witht has never been ovserved in elastic hadron-hadron scattering or photoproduction processes. It indicates the existence of a dynamical mechanism which could be a peculiarity of Compton scattering.     

Spin effects in high energy hadron-hadron scattering

The spin-flip amplitudes of the meson-nucleon and nucleon-nucleon scattering are calculated in the framework of the dynamic model taking into account the interactions at large distances. The consideration of the strong form factors at the corresponding vertex and prea-symptotic contributions allowed us to describe correctly the differential cross sections and spin effects of hadron-hadron scattering at high energies. On this basis predictions at high and superhigh energies are made.     

Angular distributions of scattered excited muonic hydrogen atoms

Coulomb deexcitation differential cross sections of excited muonic hydrogen in collisions with the hydrogen atom are studied for the first time. In the fully quantum-mechanical close-coupling approach, both the differential cross sections for the nl → n′l′ transitions and l-averaged differential cross sections have been calculated for the initial exotic atom states with n = 2–6 at kinetic energies of E _cm = 0.01–15 eV and for scattering angles of ϑ_cm = 0°–180°. The vacuum polarization shifts of the ns states are taken into account. The differential cross sections of the elastic and Stark scattering obtained in the same approach are also presented. The main features of the calculated differential cross sections are discussed, and a strong anisotropy of Coulomb deexcitation cross sections is predicted. The text was submitted by the authors in English.     

ELASTIC SCATTERING OF FAST NEUTRONS FROM Fe,Cu AND Pb

Using time of flight technique the elastic differential cross sections were measured for neutrons from natural Fe, Cu, and Pb in the energy range 1.10 to 1.40 MeV.The effect of neutron attenuation and multiple scattering in the sample is corrected by extrapolation of the experimental results. The correction of scattering angles due to the finite source-sample-detector geometry is also considered. The measured elastic differential cross sections are expressed by Legendre polynomial expansions, from which the total cross sections are obtained.The Optical-Model Calculations are carried out which show a reasonable consistency with the measured values.     

1.30-2.21MeV质子在硅上的160°散射截面测量

采用薄靶对能量 1.30 - 2 .2 1MeV质子在纯度为 99.99%硅上的非卢瑟福弹性背散射截面(16 0°背散射角 )进行了测量 .质子束由 2× 1.7MV串列加速器提供 ,测量仪器采用金硅面垒探测能谱仪 .实验中最低能区进入卢瑟福弹性散射能区 ,测量结果与以前发表的结果进行了比较 .所测量数据可供从事背散射分析技术的有关人员参考 . The elastic backscattering cross sections of H + from silicon for a wide energy range are very useful parameters in the proton backscattering analysis for investigating silicon content and distribution profiles in the films. It is necessary to measure the scattering cross sections with good accuracy at a large scattering angle for the applications of proton backscattering analysis. The present paper reports our measured results of differential elastic backscattering cross sections of 1.30-2.21 MeV...     

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.     

Reggeon, Pomeron and Glueball, Odderon-Hadron-Hadron Interaction at High Energies - From Regge Theory to Quantum Chromodynamics

Based on analysis of scattering matrix S, and its properties such as analyticity, unitarity, Lorentz invariance, and crossing symmetry relation, the Regge theory was proposed to describe hadron-hadron scattering at high energies before the advent of QCD, and correspondingly a Reggeon concept was born as a mediator of strongly interaction. This theory serves as a successful approach and has explained a great number of experimental data successfully, which proves that the Regge theory can be regarded as a basic theory of hadron interaction at high energies and its validity in many applications. However, as new experimental data come out, we have some difficulties in explaining the data. The new experimental total cross section violates the predictions of Regge theory, which shows that Regge formalism is limited in its applications to high energy data. To understand new experimental measurements, a new exchange theory was consequently born and its mediator is called Pomeron, which has vacuum quantum numbers. The new theory named as Pomeron exchange theory which reproduces the new experimental data of diffractive processes successfully. There are two exchange mediators： Reggeon and Pomeron. Reggeon exchange theory can only produce data at the relatively lower energy region, while Pomeron exchange theory fits the data only at higher-energy region, separately. In order to explain the data in the whole energy region, we propose a Reggeon-Pomeron model to describe high-energy hadron- hadron scattering and other diffractive processes. Although the Reggeon-Pomeron model is successful in describing high-energy hadron-hadron interaction in the whole energy region, it is a phenomenological model. After the advent of QCD, people try to reveal the mystery of the phenomenological theory from QCD since hadron-hadron processes is a strong interaction, which is believed to be described by QCD. According to this point of view, we study the QCD nature of Reggeon and Pomeron. We claim that the Reggeon exchange is an exchange of mult     

Elastic and inelastic scattering of 58Ni +90,94Zr

Pure elastic and inelastic scattering cross sections have been measured for the systems ⁵⁸Ni +^90,94Zr at energies near the Coulomb barrier where not only quasi-elastic and fusion but also deep-inelastic process come into play. Coupled channels calculations including both projectile and target inelastic excitations can successfully explain the elastic and inelastic scattering angular distributions with an energy-independent semi-empirical bare potential. The calculation reproduces also the sum of the total quasi-elastic, fusion and deep-inelastic cross sections. Received: 14 September 1998 / Revised version: 21 October 1998     

Total cross sections,real part of the amplitude,and slope of diffraction cones of the pp and ¯pp forward scattering

In the framework of the model described in [6], analytic expressions are obtained for the ratio of the real part of the forward scattering amplitude to its imaginary part, and for the total cross sections and the slopes of diffraction cones for hadron-hadron and hadron-antihadron interactions. A comparison with the existing experimental data for pp and pp interaction shows that that the computed values of parameters of the elastic scattering are in good qualitative and fair quantitative agreement with their observed values in a wide range of energies s = 5 to 546 GeV.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 65–70, May, 1990.     

Absolute electron scattering cross sections for the CF2 radical

Using a crossed electron-molecular beam experiment, featuring a skimmed nozzle beam with pyrolytic radical production, absolute elastic cross sections for electron scattering from the CF2 molecule have been measured. A new technique for placing measured cross sections on an absolute scale is used for molecular beams produced as skimmed supersonic jets. Absolute differential cross sections for CF2 are reported for incident electron energies of 30-50 eV and over an angular range of 20-135 deg. Integral cross sections are subsequently derived from those data. The present data are compared to new theoretical predictions for the differential and integral scattering cross sections, as calculated with the Schwinger multichannel variational method using the static-exchange and static-exchange plus polarization approximations.     

Differential, elastic integral and moment transfer cross sections for electron scattering from N2 at intermediate- and high-energies

A complex optical model potential modified by incorporating the concept of bonded atom, with the overlapping effect of electron clouds between two atoms in a molecule taken into consideration, is firstly employed to calculate the differential cross sections, elastic integral cross sections, and moment transfer cross sections for electron scattering from molecular nitrogen over the energy range 300—1000eV by using additivity rule model at Hartree—Fock level. The bonded-atom concept is used in the study of the complex optical model potential composed of static, exchange, correlation polarization and absorption contributions. The calculated quantitative molecular differential cross sections, elastic integral cross sections, and moment transfer cross sections are compared with the experimental and theoretical ones wherever available, and they are found to be in good agreement with each other. It is shown that the additivity rule model together with the complex optical model potential modified by incorporating the concept of bonded atom is completely suitable for the calculations of differential cross section, elastic integral cross section and moment transfer cross section over the intermediate- and high-energy ranges.     

Low energy elastic differential electron scattering from H2O

Normalized differential cross sections for elastic (rotationally averaged) electron scattering from gaseous water (H2O) are obtained using the relative flow method against helium with a thin aperture collimating source of gas instead of a tube. This method obviates the use of gas kinetic molecular diameters for helium or water. Our measurements are found to be largely in quantitative disagreement with past differential elastic electron scattering measurements and suggest that present recommended electron scattering total cross sections for water be revised.     

强子物质中的介子-介子散射(英文)

建立了一个夸克交换模型和提出了一个夸克-反夸克湮灭模型来研究介子-介子散射。从量子色动力学我们得到一个依赖于温度的夸克作用势。从微扰量子色动力学推导对应于夸克-反夸克湮灭和产生的跃迁势。模型给出基态介子质量的实验值,并且在玻恩近似下能说明真空中阈能附近的π-π弹性散射相移的实验值。从S矩阵元出发,推导散射的跃迁振幅和截面公式。计算出涉及π,ρ,K,K*的反应的非极化截面。发现这些截面具有强烈的温度依赖性。We have established a quark-interchange model and have proposed a quark-antiquark annihilation model to study meson-meson scattering. From QCD we obtain a temperature-dependent quark potential. The transition potential corresponding to quark-antiquark annihilation and creation is derived in perturbative QCD. The experimental ground-state meson masses are reproduced and the experimental data of elastic phase shifts for ππ scattering near the threshold energy in vacuum can be accounted for in the Born approximation. Starting from S-matrix element, we derive the transition amplitude and the cross section for the scattering. Unpolarised cross sections for reactions involving π, ρ, K and K* are calculated. Remarkable temperature dependence of the cross sections is found.     

Elastic scattering of electrons by europium and ytterbium atoms

The method of relativistic optical potential is applied to studying elastic scattering of electrons by europium and ytterbium atoms in a wide range of collision energies up to 2 keV. The angular dependences of the scattering differential cross sections and the energy dependences of the scattering integral (total, elastic, momentum transfer, and viscosity) cross sections are calculated in both spin-polarized and spin-unpolarized approximations. It is shown that the spin-polarized approximation should be used to calculate the scattering cross sections at energies below 10 eV for a europium atom. The low-energy scattering of an electron by a europium atom is characterized by P-, D-, and F-wave shape resonances. For an ytterbium atom, the calculated cross sections are in good agreement with available experimental data and with those obtained by calculation in terms of the relativistic convergent close-coupling method.     

重离子弹性散射中的角分散研究

简要评述了重离子弹性散射角分散研究的内容、 方法及物理意义。通过前角区重离子弹性散射产物微分截面的角分布测量,作出角分散图ln(dσ/dθ)\|θ2。 分析经典偏转函数, 从而在实验上确定了反应系统的核虹角。 在低能、 重靶的重离子反应系统中, 核虹角远小于擦边角。 晕核及弱束缚核比稳定核具有更小的核虹角和更大的核相互作用范围。 经典偏转函数的计算有助于提供一套光学势参数, 以便于拟合弹性散射产物的微分截面。 In terms of the angular dispersion plot of ln(dσ/dθ) versus θ2, which can be obtained from the angular distribution of the elastic scattering differential cross sections in heavy ion collisions, systematic analysis on the angular dispersions is made by using classical deflection function for the available experimental data on the target of 208Pb. Our systematic analyses bring about some important results. Firstly, there is an angular dispersion turning angle at forward angular range beyond the grazing angle. Secondly, the nuclear rainbow angle for such reaction systems can be determined by measuring differential cross sections of elastic scattering at forward angular range and analyzing the angular dispersion. Thirdly, analysis of angular dispersion may provide a way to determine a set of optical potential parameters by means of fitting the experimental data of elastic scattering differential cross sections. Finally, for the halo nuclei as the projectiles, there is an exotic behaviour, i. e., smaller angular dispersion turning angle.     

Collisions of halo nuclei within a dynamical eikonal approximation

The dynamical eikonal approximation unifies the semiclassical time-dependent and eikonal methods. It allows calculating differential cross sections for elastic scattering and breakup in a quantal way by taking into account interference effects. Good agreement is obtained with experiment for 11Be breakup on 208Pb. Dynamical effects are weak for elastic scattering.     

中子与52Cr反应截面的理论分析

根据中子与天然核Cr及其同位素反应的总截面,去弹性散射截面和弹性散射角分布的实验数据,获得了入射中子能量从1MeV—250MeV的一组普适中子与Cr及其同位素反应的光学模型势参数.应用光学模型,扭曲波玻恩近似理论,宽度涨落修正的Hauser-Feshbach理论,和预平衡反应的激子模型,计算和分析了中子与⁵²Cr反应的所有截面、角分布、能谱和双微分截面.理论计算与实验数据进行了分析比较.