  gamma N->Delta transition form factors and threshold pi^0 photo- and
electroproduction are studied with the new version of MAID and a dynamical
model. By re-analyzing the recent Jlab data on p(e,e'p) pi^0 at Q^2 = 2.8 and
4.0 (GeV/c)^2, we find that the hadronic helicity conservation is not yet
observed in this region of Q^2. The extracted R_{EM}, starting from a small and
negative value at the real photon point, actually exhibits a clear tendency to
cross zero and change sign as Q^2 increases, while the absolute value of R_{SM}
is strongly increasing. Our analysis indicates that A_{1/2} and S_{1/2}, but
not A_{3/2}, starts exhibiting the pQCD scaling behavior at about Q^2 = 2.5
(GeV/c)^2. For the pi^0 photo- and electroproduction near threshold, results
obtained within the dynamical model with the use of a meson-exchange pi N model
for the final state interaction are in as good agreement with the data as ChPT.

Nuclear Theory