Dynamical correlations in low-energy pion double charge exchange

E. R. Siciliano, Mikkel B. Johnson, H. Sarafian

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We consider various processes that contribute to low-energy pion double charge exchange (DCX), and we study their sensitivity to short-range correlations. Within the framework of the fixed-nucleon field theory, we derive a general expression for the following two-nucleon DCX processes: two sequential single charge exchanges via intermediate π (SEQ-π) plus ρ{variant} (SEQ-ρ{variant}) exchange and the lowest-order Δ33-nucleon (Δ-N) interactions via explicit π + ρ{variant} exchange. We retain the full spin dependence of the various contributions, and we present the results in a form that can be used for any transition whose corresponding two-body density matrix elements are known. Detailed evaluations are made for 14C to illustrate the importance of short-range correlations. We show the effects on the calculated DCX cross sections that result from three different wave functions: two defined entirely within the p-shell and the other involving configuration mixing with the sd-shell. Our results indicate that SEQ-π is the dominant mechanism for low-energies and that the inclusion of the short-range correlation function decreases the cross section by nearly 50% for standard choices of the pion-nucleon interaction. The largest contribution to the cross section from configuration mixing occurs in off-diagonal transitions [e.g., (0p)2 to (0d)2]. Pairs of nucleons coupled to spin S = 0.are substantially more sensitive to the short-range correlations than pairs coupled to S = 1. The size of the ρ{variant}-meson contribution to the SEQ mechanism is somewhat model-dependent, but the size of the Δ-N interaction is fixed from other sources. The SEQ-ρ{variant} contribution and the Δ-N interaction are about 5-20% effects, and they may increase or decrease the cross section, depending upon details such as the energy or the amount of configuration mixing.

Original languageEnglish (US)
Pages (from-to)1-75
Number of pages75
JournalAnnals of Physics
Issue number1
StatePublished - Oct 1990

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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