[PDF] Pion Double Charge Exchange Scattering Above The Delta Resonance eBook

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Page : 15 pages
File Size : 20,5 MB
Release : 1990
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Data are presented on pion-nucleus double-charge-exchange scattering at energies between 300 and 500 MeV, the highest energies measured so far, together with a review of results at lower energies. The small-angle excitation functions disagree with predictions based on a six-quark cluster model and on an optical model consistent with single-charge-exchange scattering at these energies, but they are consistent with a distorted-wave calculation. Data on f--2-shell nuclei are in partial agreement with a two-amplitude model which is successful at lower energies. In order to achieve good understanding of this process at these energies, more work, both experimental and theoretical, is needed. 16 refs., 6 figs.

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Page : pages
File Size : 43,50 MB
Release : 1983
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The .delta.33 resonance is strongly excited in pion-nucleon scattering, but there is clearly only a limited amount of information that can be learned in scattering the pion from an isolated nucleon. One learns that there is a resonance of mass 1232 MeV, width 115 MeV, and, if one is willing to introduce a dynamical model, something about the off-shell extension of the amplitude. One stands to learn much more from pion-nucleus scattering because in this case the .delta.33 resonance has an opportunity to scatter from nucleons, and how this occurs is not well understood. What do we know about the .delta.-N interaction for pion-nucleus scattering. The isobar-hole model was invented to deal directly with the .delta.33-nucleus dynamics, and a phenomenological determination of the isobar shell-model potential was attempted. The unknown dynamics deltaU/sub .delta./ is contained in a central isoscalar spreading potential of strength W0 and a spin orbit potential deltaU0 = W0rho + spin-orbit. The real part of W0rho is measured relative to the nucleon-nucleus potential. From a more theoretical point of view, one would like to be able to calculate deltaU/sub .delta./, including its isospin dependence, from an underlying dynamical model which is formulated in terms of the basic effective meson-baryon couplings. Some salient properties of these couplings can be determined from models of quark-bag structure, which raises the exciting possibility of learning about these fundamental issues from pion scattering. Attempts at Los Alamos to build a theoretical framework to deal with these and other issues are described. (WHK).

Author : William R Gibbs
Publisher : World Scientific
Page : 622 pages
File Size : 34,50 MB
Release : 1990-09-24
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ISBN : 9814611875

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What do you associate with chemistry? Explosions, innovative materials, plastics, pollution? The public's confused and contradictory conception of chemistry as basic science, industrial producer and polluter contributes to what we present in this book as chemistry's image as an impure science. Historically, chemistry has always been viewed as impure both in terms of its academic status and its role in transforming modern society. While exploring the history of this science we argue for a characteristic philosophical approach that distinguishes chemistry from physics. This reflection leads us to a philosophical stance that we characterise as operational realism. In this new expanded edition we delve deeper into the questions of properties and potentials that are so important for this philosophy that is based on the manipulation of matter rather than the construction of theories./a

Author : M J Vicente-vacas
Publisher : World Scientific
Page : 730 pages
File Size : 27,8 MB
Release : 1992-03-27
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ISBN : 9814555916

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The proceedings reflect the recent experimental and theoretical progress in pion nuclear physics in topics like pionic atoms, pion absorption, charge exchange, (π, 2π), and others involving pions in nuclei using different probes, as electron photons or heavy ions. Related topics on chiral symmetry, low energy πN and (γ, π⁰) and quark degrees of freedom are also addressed.

Author : Carl Carlson
Publisher : World Scientific
Page : 787 pages
File Size : 22,10 MB
Release : 1997-02-21
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ISBN : 981454664X

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This book is devoted to phenomena that are of interest to both particle and nuclear physicists. The topics include nucleon structure (including spin structure), electron, neutrino, and hadron scattering from nucleons and nuclei, strange matter, the standard model, theory of nucleons and nuclei from both the QCD and nucleon-meson viewpoints, new experimental techniques, and new facilities.