Small-angle scattering and diffraction

The direct measurement of magnetic fields by magnetometers, originally made of the Earth's magnetic field, has been now extended to solar planets by numerous satellite missions. Magnetic effects have been observed in the solar neighborhood and even near some comets, such as the Giotto mission to comet Halley. However, observations of magnetic fields in cosmic objects require remote sensing methods.     

Antishadow scattering and diffraction dissociation

Zeitschrift für Physik C Particles and Fields - We consider diffractive dissociation processes at high energies in the framework of chiral quark model with unitarization via generalized...     

The diffraction pattern of pp elastic scattering and the composite structure of the proton

The consequences of the quark-glue structure of hadrons for pp elastic scattering are examined in a simple model where the glue is taken to be the active constituent in normal (low p_T) hadronic collisions. Earlier work based on the study of pp inelastic diffraction led to the conclusion that the glue-glue elastic amplitude t_g is approximately Gaussian in the glue-glue impact parameter b_g, with maximum opacity at b_g = 0. A slight refinement of this approximation, in which t_g is almost maximally opaque over a small b_g interval and is Gaussian at larger b_g, is now shown to account for the remarkable diffraction structure observed in pp elastic scattering at ISR energies. A very simple form is obtained for the form factor describing the impact parameter distribution of the glue inside a proton relative to the proton itself.     

Vacuum decay by inverse scattering

We discuss the decay of false vacua which originate from quantum mechanical effects. In particular we examine the $\text{1}\text{N}$ expansion of the O(N) λφ⁴ model. This model has an effective potential which is complex for large values of the field. In a previous paper we showed that this effective potential could not be used to calculate the decay rate directly. In the present work we show that the vacuum can decay via poles in the effective action which are evident when it is written in terms of scattering variables.     

Coherent diffraction imaging through shift-invariant scattering

Optical Review - In this paper, we present a method for single-shot phase imaging with a wide field of view based on coherent diffraction imaging. Coherent diffraction imaging can be implemented by...     

Neutron diffraction and inelastic scattering from adsorbed molecules

Neutron scattering measurements on the structure and dynamics of adsorbed phases at the gas solid interface have proliferated in the last five years and this paper reports some recently obtained results for the systems methane-graphite and ammonia-graphite, which show BET type I and type III isotherms respectively. These systems clearly illustrate the differences in both structure and dynamics to be expected in other examples where either wetting of the surface or non-wetting behaviour occurs upon adsorption. Evidence for phase transitions in both types of system coming from diffraction is reported, and this is substantiated by measurements using inelastic scattering to follow the molecular dynamics. The neutron inelastic scattering from molecules adsorbed on platinum black and in zeolites reveals some of the virtues of neutron inelastic scattering for the study of chemisorbed species. Finally, some preliminary experiments on neutron small angle scattering at the solid liquid interface in polystyrene latex-water sols are reported.     

Study of the atomic structure and dynamics of Cu-Fe nanocomposites by X-ray diffraction and inelastic neutron scattering

The atomic structure and the dynamics of Cu_{1 ? x} Fe _x samples (x = 0.15, 0.5, and 0.85) obtained by melt spinning from the elements that are immiscible under standard conditions has been investigated. The change in the physical properties of the system obtained in this way is due to the formation of nanocrystallites.     

Acoustical diffraction tomographic imaging under non-weak scattering

Under the assumption of weak scattering,the acousticaldiffraction tomographic imaging of an object can be reconstructed byusing the Born (or Rytov) approximation method.When the weak scat-tering assumption within the medium is not satisfied the multipleultrasound scattering must be taken into account.In this case,the reconstruction results under the first-order Born approximation will beseriously distorted.In this paper we introduce an"intermediate objectfunction"into the wave equation and take iterative modification in spacedomain and spatial frequancy domain based on Born approximation.Inthis way,the distorted image will be improved step by step.In order toexamine the method as mentioned above,we have just tried to makecomputerized simulations.The initial result shows that the quality of theimage reconstructed from the object under non-weak scattering may beimproved significantly.     

An analysis of diffraction in deep-inelastic scattering

We propose a simple parametrization for the deep-inelastic diffractive cross section. It contains the contribution of production to both the longitudinal and the transverse diffractive structure functions, and of the production of final states from transverse photons. We start from the hard region and perform a suitable extrapolation into the soft region. We test our model on the 1994 ZEUS and H1 data, and confront it with the H1 conjecture of a singular gluon distribution. Received: 30 June 1998 / Revised version: 3 September 1998 / Pulished online: 3 December 1998     

Note on shadowing and diffraction in deep-inelastic lepton scattering

We discuss the close relation between shadowing in deep-inelastic lepton-nucleus scattering and diffractive photo- and leptoproduction of hadrons from free nucleons. We show that the magnitude of nuclear shadowing at small Bjorken-x, as measured by the E665 and NMC collaborations, is directly related to HERA data on the amount of diffraction in the scattering from free nucleons. Received: 16 October 1998     

Studying the metal structure of anticorrosive cladding for the nuclear-reactor vessels by neutron diffraction and small-angle neutron scattering

The results of neutron studies of the metal nanostructure of anticorrosive cladding for vessels of WWER -1000 nuclear reactors under different conditions of additional tempering are presented. In the anticorrosive-cladding material, small structural components (inhomogeneities) with a correlation radius of 2–3 nm are observed which form fractal structures with a scale of more than 100 nm. It is shown that at different annealing temperature, these small objects create new structures at crystal boundaries in the form of defect surfaces with the fractal dimension D _s = 2.4–2.6. In samples of anticorrosive cladding, nonmagnetic austenitic γ-phase iron (γ-Fe) and magnetic δ-ferrite (α-Fe) are observed. The alloy is found to be magnetically hard.     

Elastic scattering of hadrons outside the diffraction cone

The model-independent solution of the s-channel unitarity condition for the imaginary part of the hadronic elastic scattering amplitude outside the diffraction peak allows to make conclusions about the shape of the differential cross sections in this region. The eigensolution of the homogeneous linear integral equation and the iterative solutions of the inhomogeneous equation with different assumptions about the behavior of the overlap function and the real part of the amplitude are presented. The properties of the overlap function and of the ratio of the real-to-imaginary part of the amplitude are discussed. In particular, it is explicitly shown that the ratio changes its sign at a definite value of the transferred momentum. Some comments concerning the present day experimental results about the behavior of the differential cross section of elastic scattering outside the diffraction cone are given.     

衍射散射式颗粒粒度测量法的研究新进展

介绍了衍射散射式颗粒粒度测量法的基本光路结构和理论模型,讨论了决定其性能优劣的重要指标--测量下限,对影响测量下限向小粒径范围延伸的参数进行了分析.继而介绍了近年来国内外主要粒度仪品牌在光学结构和散射理论模型方面所做的改进,阐述了它们的工作原理和性能特点.最后对衍射散射式颗粒粒度测量法的发展前景做出了展望,从修正理论模...     

Effect of the shell structure of nuclei on p 15C and p 15N scattering within diffraction theory

The differential cross sections for elastic proton scattering on ¹⁵C and ¹⁵N nuclei at energies of 150 and 800 MeV were calculated within the diffraction theory of Glauber multiple scattering. Shellmodel wave functions were used in these calculations, and particular attention was given to analyzing the sensitivity of the calculated features to distinctions between the shell structure of the ¹⁵C nucleus and the shell structure of the ¹⁵N nucleus. The calculations were performed in the approximation of double scattering. The multiple-scattering operator was written in a form that permits taking into account collisions with nucleons belonging to different shells. It is shown that the difference in structure between the two nuclei in question leads to substantial distinctions between the differential cross sections for scattering at an energy of 800 MeV and scattering angles larger than 25°.     

Vacuum structure in quantum gravity

The physical interpretation of the Eguchi-Hanson (EH) instanton solution is suggested. This solution describes the tunneling transition which connects vacua with opposite orientations. The diagonal vacuum states are symmetric and antisymmetric superpositions of states with a given orientation. The EH instantons lead to appearance of the induced Einstein term and of the large induced cosmological term in the effective action of the conformal gravity theory.     

A model for the high energypp and¯pp diffraction scattering

The high energy elasticpp and¯pp scattering is studied within the framework of a specific model for the diffractive background. The double Pomeron exchange as well as secondary trajectory contributions are properly taken into account. The total cross section, the phase of the forward amplitude and the angular distribution are computed and compared with the existing experimental data.