Two-nucleon processes in a coupled-channel approach to pion-nucleus single-charge-exchange reactions

L. C. Liu
Phys. Rev. C 23, 814 – Published 1 February 1981
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Abstract

A momentum space coupled-channel formalism is proposed for the study of pion-nucleus single-charge-exchange reactions at medium energies. Formal elimination of certain reaction channels leads to a reduced set of coupled equations with a complex and energy-dependent interaction. A nonperturbative method based upon unitarity considerations is then used to construct each order of this effective pion-nucleus interaction. Our analysis thus leads to a second-order pion-nucleus interaction with analytical properties very different from those obtained from multiple-scattering theory. The theory is applied to the study of pion-C13 elastic scattering and the single-charge-exchange reaction C13(π+,π0)N13(g.s). Included in our calculations are the first- and second-order pion-nucleus strong interactions, and the pion-nucleus Coulomb interaction. We have calculated the first-order interaction using a covariant, nonstatic theory and have evaluated contributions to the second-order interaction arising from two-nucleon processes related to true pion absorption and to the scattering of pions from a nucleon pair. We present a general relation connecting the second-order pion-nucleus strong interaction potentials of nuclei whose structure do not differ appreciably. Theoretical results for πC13 elastic scattering predicted by our theory are found to be in good agreement with the data. The calculated excitation function of the single-charge-exchange reaction exhibits a high sensitivity to the type of two-nucleon processes considered. Pion-nucleus single-charge-exchange reactions therefore have promise as a tool for investigating pion-nucleus reaction mechanisms.

NUCLEAR REACTIONS Coupled-channel theory, pion-nucleus single-charge-exchange reactions, pion absorption, nucleon-nucleon correlations, πC13 elastic cross sections at 50 and 180 MeV, excitation function of C13(π+,π0)N13(g.s) between 30 and 260 MeV.

  • Received 17 July 1980

DOI:https://doi.org/10.1103/PhysRevC.23.814

©1981 American Physical Society

Authors & Affiliations

L. C. Liu

  • Los Alamos Scientific Laboratory, University of California, Los Alamos, New Mexico 87545

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Issue

Vol. 23, Iss. 2 — February 1981

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