https://doi.org/10.1140/epja/i2007-10510-7
Regular Article - Theoretical Physics
Invariant amplitudes for pion electroproduction
1
Dipartimento di Fisica Nucleare e Teorica, Università degli Studi di Pavia and INFN, Sezione di Pavia, Pavia, Italy
2
Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099, Mainz, Germany
* e-mail: tiator@kph.uni-mainz.de
Received:
14
December
2007
Accepted:
19
December
2007
Published online:
18
January
2008
The invariant amplitudes for pion electroproduction on the nucleon are evaluated by dispersion relations at constant t with MAID as input for the imaginary parts of these amplitudes. In the threshold region these amplitudes are confronted with the predictions of several low-energy theorems derived in the soft-pion limit. In general agreement with chiral perturbation theory, the dispersive approach yields large corrections to these theorems because of the finite pion mass.
PACS: 11.55.Fv Dispersion relations – / 11.55.Hx Sum rules – / 13.40.Gp Electromagnetic form factors – / 13.60.Le Meson production –
© Società Italiana di Fisica and Springer-Verlag, 2008
