  Within the dispersion relation approach, solutions of integral equations for
the multipoles M_{1+}^{3/2},E_{1+}^{3/2},S_{1+}^{3/2} are found at 0 < Q^2 < 3
GeV^2. These solutions should be used as input for the resonance and
nonresonance contributions in the analyses of pion electroproduction data in
the P_{33}(1232) resonance region. It is shown that the traditional
identification of the amplitude M_{1+}^{3/2} (as well of the amplitudes
E_{1+}^{3/2},S_{1+}^{3/2}) with the P_{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_{1+}^{3/2},E_{1+}^{3/2}, the helicity amplitudes A_p^{1/2},~A_p^{3/2} and the
ratio E2/M1 for the gamma N -> P_{33}(1232) transition are extracted from
experiment at Q^2=0. They are in good agreement with quark model predictions.

High Energy Physics - Phenomenology