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Title: Pion double charge exchange in a composite-meson model

Abstract

The pion double charge exchange amplitude is evaluated in a composite-meson model based on the four-quark interaction. The model assumes that the mesons are two-quark systems and can interact with each other only through quark loops. To evaluate the meson exchange current contribution, the form factors of the two-pion decay modes of the {rho},{sigma}, and f{sub 0} mesons have been used in the calculations. The contribution of the four-quark box diagram has been taken into account as well as a contact diagram. The contributions of the {rho},{sigma}, and f{sub 0} mesons increase the forward scattering cross section, which depends weakly on the energy.

Authors:
;  [1]
  1. New York City College of Technology, City University of New York, 300 Jay Street, Brooklyn, New York 11201 (United States)
Publication Date:
OSTI Identifier:
20990971
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 1; Other Information: DOI: 10.1103/PhysRevC.75.015203; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; BOSON-EXCHANGE MODELS; CHARGE EXCHANGE; D S MESONS; FEYNMAN DIAGRAM; FORM FACTORS; HADRONIC PARTICLE DECAY; NUCLEAR MODELS; PION-NUCLEON INTERACTIONS; PIONS; QUARKS; RHO-770 MESONS

Citation Formats

Kezerashvili, R. Ya., and Boyko, V. S. Pion double charge exchange in a composite-meson model. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.015203.
Kezerashvili, R. Ya., & Boyko, V. S. Pion double charge exchange in a composite-meson model. United States. doi:10.1103/PHYSREVC.75.015203.
Kezerashvili, R. Ya., and Boyko, V. S. Mon . "Pion double charge exchange in a composite-meson model". United States. doi:10.1103/PHYSREVC.75.015203.
@article{osti_20990971,
title = {Pion double charge exchange in a composite-meson model},
author = {Kezerashvili, R. Ya. and Boyko, V. S.},
abstractNote = {The pion double charge exchange amplitude is evaluated in a composite-meson model based on the four-quark interaction. The model assumes that the mesons are two-quark systems and can interact with each other only through quark loops. To evaluate the meson exchange current contribution, the form factors of the two-pion decay modes of the {rho},{sigma}, and f{sub 0} mesons have been used in the calculations. The contribution of the four-quark box diagram has been taken into account as well as a contact diagram. The contributions of the {rho},{sigma}, and f{sub 0} mesons increase the forward scattering cross section, which depends weakly on the energy.},
doi = {10.1103/PHYSREVC.75.015203},
journal = {Physical Review. C, Nuclear Physics},
number = 1,
volume = 75,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}
  • We examine the influence of meson exchange currents (MEC) on pion double charge exchange (DCX) using the Weinberg Lagrangian. We calculate the corresponding amplitude for DCX and examine its interplay with more conventional mechanisms of DCX for {sup 14}C at incident energies of 10 to 110 MeV and for the Ca isotopes at 35 MeV. The MEC effect includes the pion pole term and the contact term. In comparison to previous estimates, we find smaller but nevertheless non-negligible contributions of these effects to DCX. We stress the fact that the MEC contribution to DCX is strongly {ital A} dependent, withmore » its effect in light nuclei comparatively larger than in heavy ones.« less
  • The magnitude of the effect of meson exchange currents on low-energy pion nucleus double charge exchange is reexamined. In particular, the role of chiral symmetry in limiting the size of the effect is studied, using the method of effective Lagrangians. The equivalence of two commonly used versions of the theory is shown, which resolves some of the disagreements in the literature. The effect is calculated for the case of {sup 42}Ca, and found to be smaller than that of ordinary multiple scattering.
  • We have measured the differential cross section d/sup 2/sigma/d..cap omega.. dT and estimated the total cross section sigma/sub T/ for the double charge exchange reaction /sup 4/He(..pi../sup +/,..pi../sup -/)4p at 140, 200, and 295 MeV. The values for sigma/sub T/ are at least an order of magnitude larger than predictions based on sequential single charge exchange ..pi..-N scatterings. It is possible, therefore, that /sup 4/He(..pi../sup +/,..pi../sup -/) is dominated by other processes, such as the formation of a ..delta.. in the intermediate state or scattering from meson exchange currents.
  • Based on the Lagrangian of Olsson and Turner, contributions of the second kind of meson exchange current to pion-nucleus double-charge-exchange reactions /sup 18/O(..pi../sup +/,..pi../sup -/)/sup 18/N/sub e//sub (g.s))/ and /sup 14/C(..pi../sup +/,..pi../sup -/)/sup 14/O/sub g.s./ have been evaluated. The calculated results show that the second kind of meson exchange current makes the forward theoretical cross section closer to the experimental data but the long-standing puzzling problem of the location of the minimum of the angular distribution at the energy of 164 MeV has not been solved.
  • We predict a narrow resonance structure (GAMMAapprox. =10 MeV) in the excitaton function of (..pi../sup +/,..pi../sup -/) double-charge-exchange reactions at a pion kinetic energy of --419 MeV. This structure is due to the interference between the usual ..pi../sup +/..--> pi../sup 0/..--> pi../sup -/ double-charge-exchange amplitudes, which have a smooth energy dependence, and a resonant ..pi../sup +/..-->..eta/sup 0/..--> pi../sup -/ high-energy double-charge-exchange amplitude associated with the formation of a strongly bound eta-nucleus system. The latter process leads to a novel feature of the pion-nucleus interaction, the mesonic compound nucleus resonance.