Local field corrections in. pi. -nucleus scattering

Journal Article · Thu May 01 04:00:00 EDT 1980 · Phys. Rev., C; (United States)

DOI:https://doi.org/10.1103/PhysRevC.21.1996· OSTI ID:5446556

Banerjee, M K; Wallace, S J

The local field correction to the ..pi..-nucleus optical potential is calculated taking recoil into account. The correction arises from the triple scattering matrix element <0;k vertical-bartau/sub 1/Gtau/sub 2/Gtau/sub 1/vertical-bar 0;k'>, where tau/sub i/ are ..pi..N amplitudes. The recoil energy of nucleon 1 affects the pion Green's function G and the intermediate scattering amplitude tau/sub 2/. The recoil of nucleon 2 affects only tau/sub 2/ and has not been included to save computational time. Effects of antisymmetry of the two nucleons, spin flip, and charge exchange have been included, but not those of pair correlation and Pauli blocking. Inclusion of recoil is found to reduce the local field correction by a factor of 7 from the result of fixed scatterer calculations. Nevertheless, the local field correction remains sizable. In the ..pi..-/sup 16/O case it represents a correction 2/3 as large as the first-order optical potential near the ..pi..N resonant energy. Nucleon 1 typically recoils through approx. 1 fm while in terms of the internucleon separation r/sub 12/ the effect is very long ranged. Thus the P-wave nature of the ..pi..N interaction which enhances the reflection of the pion from nucleon 2 back to nucleon 1 is the main reason why the local field correction is so important in ..pi..-nucleus scattering. The imaginary part of the local field correction part of the optical potential is analyzed and its reactive content is shown to arise from two competing mechanisms. The first, and dominant, mechanism is a reduction of the single nucleon knockout contribution that is overestimated in the first-order optical potential while the second mechanism is the two-nucleon knockout. The analysis suggests very slow convergence of multiple scattering expansions near the ..pi..N resonance energy.

• Research Organization: Department of Physics and Astronomy, University of Maryland, College Park, Maryland 20742
• OSTI ID: 5446556
• Journal Information: Phys. Rev., C; (United States), Journal Name: Phys. Rev., C; (United States) Vol. 21:5; ISSN PRVCA
• Country of Publication: United States
• Language: English

Related Subjects

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73 NUCLEAR PHYSICS AND RADIATION PHYSICS
AMPLITUDES
CHARGE-EXCHANGE REACTIONS
CHARGED-PARTICLE REACTIONS
CROSS SECTIONS
DIRECT REACTIONS
ELASTIC SCATTERING
FUNCTIONS
GREEN FUNCTION
HADRON REACTIONS
KINETICS
KNOCK-OUT REACTIONS
MATRIX ELEMENTS
MESON REACTIONS
MULTIPLE SCATTERING
NUCLEAR REACTION KINETICS
NUCLEAR REACTIONS
OPTICAL MODELS
OXYGEN 16 TARGET
P WAVES
PARTIAL WAVES
PION REACTIONS
REACTION KINETICS
RECOILS
SCATTERING
SCATTERING AMPLITUDES
SPIN FLIP
TARGETS
TOTAL CROSS SECTIONS