Meson-exchange model for {pi}{ital N} scattering and {gamma}{ital N}{r_arrow}{pi}{ital N} reaction
- Physics Division, Argonne National Laboratory, Argonne, Illinois 60439-4843 Department of Physics, Osaka University, Toyonaka, Osaka 560 (Japan)
An effective Hamiltonian consisting of bare {Delta}{leftrightarrow}{pi}{ital N}, {gamma}{ital N} vertex interactions and energy-independent meson-exchange {pi}{ital N}{leftrightarrow}{pi}{ital N},{gamma}{ital N} transition operators is derived by applying a unitary transformation to a model Lagrangian with {ital N},{Delta},{pi}, {rho}, {omega}, and {gamma} fields. With appropriate phenomenological form factors and coupling constants for {rho} and {Delta}, the model can give a good description of {pi}{ital N} scattering phase shifts up to the {Delta} excitation energy region. It is shown that the best reproduction of the recent LEGS data of the photon-asymmetry ratios in {gamma}{ital p}{r_arrow}{pi}{sup 0}{ital p} reactions provides rather restricted constraints on the coupling strengths {ital G}{sub {ital E}} of the electric {ital E}2 and {ital G}{sub {ital M}} of the magnetic {ital M}1 transitions of the bare {Delta}{leftrightarrow}{gamma}{ital N} vertex and the less well-determined coupling constant {ital g}{sub {omega}{ital NN}} of {omega} meson. Within the ranges that {ital G}{sub {ital M}}=1.9{plus_minus}0.05, {ital G}{sub {ital E}}=0.0{plus_minus}0.025, and 7{le}{ital g}{sub {omega}{ital NN}}{le}10.5, the predicted differential cross sections and photon-asymmetry ratios are in an overall good agreement with the data of {gamma}{ital p}{r_arrow}{pi}{sup 0}{ital p}, {gamma}{ital p}{r_arrow}{pi}{sup +}{ital n}, and {gamma}{ital n}{r_arrow}{pi}{sup {minus}}{ital p} reactions from 180 MeV to the {Delta} excitation region. The predicted {ital M}{sub 1{sup +}} and {ital E}{sub 1{sup +}} multipole amplitudes are also in good agreement with the empirical values determined by the amplitude analyses. The constructed effective Hamiltonian is free of the nucleon renormalization problem and hence is suitable for nuclear many-body calculations. (Abstract Truncated)
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 389450
- Journal Information:
- Physical Review, C, Journal Name: Physical Review, C Journal Issue: 5 Vol. 54; ISSN 0556-2813; ISSN PRVCAN
- Country of Publication:
- United States
- Language:
- English
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