Diffraction at an elliptical cylinder with a strongly prolate cross section

The problem of diffraction of a high-frequency plane wave by an infinite cylinder, whose cross section is a strongly prolate ellipse, was considered. The field asymptotics in the boundary layer near the surface were obtained. These asymptotics contain a parameter that characterizes the degree of ellipse elongation, which is equal to the ratio of the transverse wave size squared to the longitudinal size. The approximation accuracy and the applicability domain of the asymptotic formulas were investigated by comparing them to the numerical data obtained in the pdetool environment of the MatLab package.     

Reaction cross section measurements of the neutron-rich isotopes8,9,11Li at 80 MeV/nucleon

Total interaction cross sections have been measured for⁸Li on C and Pb targets, for⁹Li on C, Al, Cu, Sn and Pb targets as well as for¹¹Li on C, Sn and Pb targets. For each beam, we also used a plastic scintillator as target. The measurements with the scintillator targets are used to extract reduced nuclear radii of the lithium isotopes. These radii are then used for the calculation of the nuclear part of the total cross section for the other targets. The total electromagnetic-dissociation (EMD) cross sections have been deduced and are compared to different models. A strong target-charge-dependent EMD cross section is measured for¹¹Li reaching 2.96 _–0.82 ^+0.84 b for the Pb target. In the⁹Li case, a large EMD cross section for high-Z targets has been observed which amounts to 0.75 ± 0.45 b for the Pb target. The EMD cross sections of both,⁹Li and¹¹Li, may be understood by the giantdipole-resonance model.This work forms part of the PhD Thesis of B. Blank     

Determination of the cross section of the pion and nucleon interaction with iron nuclei in the energy range 0.5–5.0 TeV

Direct measurements of the total cross sections of the cosmic ray pion, proton and neutron inelastic interaction with iron nuclei in the energy range 0.5–5.0 TeV are performed. The σ_πⁱⁿ, σ_pⁱⁿ and σ_nⁱⁿ dependences on energy are determined. The results are compared with the data obtained from accelerators as well as with multiple scattering theory conclusions.     

Calculation of the cross section of helium ionization by an electron impact with the formation of a helium ion in an excited state

The total cross sections of He and He⁺ ionization by an electron impact are calculated in the first Born approximation. Calculations of the matrix elements are carried out by the Fock-Dirac multiconfiguration relativistic method using an intermediate type of coupling with orthogonal functions of the initial and final states. A single-electron wave function of the continuous spectrum for an Auger electron is obtained using the Fock-Dirac single-configuration method. The results of the calculations performed with orthogonal and nonorthogonal wave functions of the initial and final states are compared. The ionization cross sections are calculated for cases in which a knock-on electron of the continuous spectrum is described by both the orthogonal and nonorthogonal wave functions with respect to the wave functions of the core electrons.     

Simulation study of neutrino nucleus cross section measurement in a segmented detector at a spallation neutron source

Knowledge of ν_e-Fe/Pb differential cross sections for ν_e energy below several tens of MeV scale is believed to be crucial in understanding supernova physics. In a segmented detector at a spallation neutron source, ν_e energy reconstructed from the electron range measurement is strongly affected because both multiple scattering and electromagnetic showers occur along the electron passage in target materials. In order to estimate these effects, a simulation study has been performed with a cube block model assuming perfect tracking precision. The energy spectrum distortion is observed to be proportional to the atomic number of the target material. Feasibility of unfolding the distorted ν_e energy spectrum is studied for both Fe and Pb. An evaluation of the statistical accuracy attainable is therefore provided for a segmented detector.     

Upper limit on the cross section for elastic neutralino-nucleon scattering in a neutrino experiment at the Baksan Underground Scintillator Telescope

The results of a neutrino experiment that involved 24.12 yr of live time of observation of muons from the lower Earth’s hemisphere with the aid of the Baksan Underground Scintillator Telescope are presented. In the problem of searches for a signal from the annihilation of dark matter in the Sun, an upper limit on the cross section for the elastic scattering of a weakly interacting massive particle (WIMP) on a nucleon was obtained at a 90% confidence level from an analysis of data accumulated within 21.15 yr of live time of observation. A neutralino in a nonminimal supersymmetric theory was considered for a WIMP. The best limit at the Baksan Underground Scintillator Telescope on the cross section for spin-dependent neutralino interactionwith a proton corresponds to 3×10^?4 pb for the neutralino mass of 210 GeV/c ². This limit is three orders of magnitude more stringent than similar limits obtained in experiments that detected directly WIMP scattering on target nuclei.     

Isospin effect of the in-medium nucleon-nucleon cross section in excited nuclear reactions

Using relativistic mean field theory, the neutron and the proton density distribution of 56Ni nuclei could be obtained in the ground state and the excited state. Based on the framework of the quantum molecular dynamics model, the 56Ni nuclei have been simulated in ground state and in the neutron or proton excited state. We then used the three different states of 56Ni to collide with the 56Ni in the ground state. To discuss the evolution of the nuclear stopping in different reactions, two kinds of different excited nuclear reactions were studied at different reaction energies and at different impact parameters. Studies have shown that the nuclear stopping of an excited nuclear reaction is sensitive to the isospin-dependent in-medium nucleon-nucleon cross section, compared with the response value of the ground state nuclear reaction. So, it is better for the excited nuclei to extract the isospin dependence of nucleon-nucleon cross section information.     

Isospin effect of the in-medium nucleon-nucleon cross section in excited nuclear reactions

Using relativistic mean field theory, the neutron and the proton density distribution of ⁵⁶Ni nuclei could be obtained in the ground state and the excited state. Based on the framework of the quantum molecular dynamics model, the ⁵⁶Ni nuclei have been simulated in ground state and in the neutron or proton excited state. We then used the three different states of ⁵⁶Ni to collide with the ⁵⁶Ni in the ground state. To discuss the evolution of the nuclear stopping in different reactions, two kinds of different excited nuclear reactions were studied at different reaction energies and at different impact parameters. Studies have shown that the nuclear stopping of an excited nuclear reaction is sensitive to the isospin-dependent in-medium nucleon-nucleon cross section, compared with the response value of the ground state nuclear reaction. So, it is better for the excited nuclei to extract the isospin dependence of nucleon-nucleon cross section information.     

铝原子激发态近阈限光电离截面测量

本文利用激光烧蚀、激光泵浦-探测、共振增强多光子电离和飞行时间质谱相结合的实验技术,根据离子产额和电离激光能量的关系,获取铝原子激发态的光电离截面;并研究了光电离截面与电离富余能的依赖关系.电离富余能0-2.98 eV内光电离截面值范围为15.6±1.7 Mb-2.3±0.9 Mb,激发态的寿命为17.6±1.8,16.9±1.7ns.在光电离截面的测量中,总的均方根误差上限约为17%.     

铝原子激发态近阈限光电离截面测量

本文利用激光烧蚀、激光泵浦-探测、共振增强多光子电离和飞行时间质谱相结合的实验技术,根据离子产额和电离激光能量的关系,获取铝原子激发态的光电离截面;并研究了光电离截面与电离富余能的依赖关系.电离富余能0-2.98 e V内光电离截面值范围为15.6±1.7 Mb-2.3±0.9 Mb,激发态的寿命为17.6±1.8,16.9±1.7 ns.在光电离截面的测量中,总的均方根误差上限约为17%.     

Double Chooz project: Status of a reactor experiment aimed at searches for neutrino oscillations

Double Chooz is an experiment that is devoted to searches for reactor-antineutrino oscillations at the CHOOZ nuclear power plant. This project is aimed at measuring the unknown mixing angle θ ₁₃. It is assumed that the value of θ ₁₃ will be extracted from an analysis of the distortion of the antineutrino spectra obtained in relative measurements at two distances from the nuclear reactors by means of two identical detectors. The method makes it possible to minimize systematic errors of the experiment and to improve the sensitivity to the sought parameter. To date, the most stringent constraint on the parameter θ ₁₃ was obtained from the CHOOZ experiment in 1995–1997 [sin²(2θ ₁₃) < 0.19, with the difference of the squares of the neutrino masses being Δm ₁₃ ² = 2.5 × 10^?3 eV²].     

Total reaction cross section from the interaction of 4He ions with 28Si at 10–30 MeV

New results have been obtained for the energy dependence of the total reaction cross section σ _R of ⁴He on ²⁸Si in the energy range E _α ≤ 30 meV.     

He-CO相互作用势及散射截面的理论研究

利用改进的MS势模型拟合出了He-CO体系一种形式简单的各向异性相互作用势,应用拟合的势能,采用全量子力学的密耦方法计算了基态氦原子和CO分子碰撞的散射截面,分析并总结了散射截面的变化规律。计算结果表明拟合势能不但表达形式简洁,而且较好的描述了He-CO系统相互作用的特征。为进一步研究He与CO微观碰撞机理有一定的参考价值。     

He-CO相互作用势及散射截面的理论研究

利用改进的MS势模型拟合出了He-CO体系一种形式简单的各向异性相互作用势,应用拟合的势能,采用全量子力学的密耦方法计算了基态氦原子和CO分子碰撞的散射截面,分析并总结了散射截面的变化规律。计算结果表明拟合势能不但表达形式简洁,而且较好的描述了He-CO系统相互作用的特征。为进一步研究He与CO微观碰撞机理有一定的参考价值。     

An interaction of nucleons at an energy between 1014 and 1015 eV/nucleon

A jet (0+14) with primary energy {3.3 _{– 2.2} ^{+ 5.3} }. 10¹⁴ eV/nucl. was observed in the I-stack. An interaction with very small multiplicity (n _s =3or 4)found in the axis of the jet is probably caused by another nucleon from the -primary. 10 particles of the narrow cone have opening angles of some 10^–4 radians, 4 particles in the diffuse cone are emitted at angles of a few 10^–2 radians. A pronounced anisotropy exists in the C. M. system. The coefficient of inelasticity 0.1was calculated directly extrapolating the measured energies of secondaries. The interpretation of the whole event is in good agreement with Heisenberg's theory of multiple production of particles.