How to extract the P{sub 33}(1232) resonance contributions from the amplitudes M{sub 1+}{sup 3/2},E{sub 1+}{sup 3/2},S{sub 1+}{sup 3/2} of pion electroproduction on nucleons
- Yerevan Physics Institute, Alikhanian Brothers St. 2, Yerevan, 375036 (Armenia)
Within the dispersion relation approach, solutions of integral equations for the multipoles M{sub 1+}{sup 3/2},E{sub 1+}{sup 3/2},S{sub 1+}{sup 3/2} are found at 0{le}Q{sup 2}{le}3GeV{sup 2}. These solutions should be used as input for the resonance and nonresonance contributions in the analyses of pion electroproduction data in the P{sub 33}(1232) resonance region. It is shown that the traditional identification of the amplitude M{sub 1+}{sup 3/2} (as well as the amplitudes E{sub 1+}{sup 3/2},S{sub 1+}{sup 3/2}) with the P{sub 33}(1232) resonance contribution is not right; there is a contribution in these amplitudes which has a nonresonance nature and is produced by rescattering effects in the diagrams corresponding to the nucleon and pion poles. This contribution is reproduced by the dispersion relations. Taking into account nonresonance contributions in the amplitudes M{sub 1+}{sup 3/2},E{sub 1+}{sup 3/2}, the helicity amplitudes A{sub p}{sup 1/2},A{sub p}{sup 3/2} and the ratio E2/M1 for the {gamma}N{r_arrow}P{sub 33}(1232) transition are extracted from experiment at Q{sup 2}=0. They are in good agreement with quark model predictions. {copyright} {ital 1998} {ital The American Physical Society}
- OSTI ID:
- 615255
- Journal Information:
- Physical Review, D, Vol. 57, Issue 5; Other Information: PBD: Mar 1998
- Country of Publication:
- United States
- Language:
- English
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