https://doi.org/10.1140/epja/i2004-10114-9
The Fubini-Furlan-Rossetti sum rule revisited
1
Dipartimento di Fisica Nucleare e Teorica, Università degli Studi di Pavia, Pavia, Italy
2
Sezione di Pavia, INFN, Pavia, Italy
3
ECT*, Villazzano (Trento), Italy
4
Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099, Mainz, Germany
* e-mail: drechsel@kph.uni-mainz.de
Received:
1
December
2004
Accepted:
4
December
2004
Published online:
20
December
2004
The Fubini-Furlan-Rossetti sum rule for pion photoproduction on the nucleon is evaluated by dispersion relations at constant t, and the corrections to the sum rule due to the finite pion mass are calculated. Near threshold these corrections turn out to be large due to pion-loop effects, whereas the sum rule value is closely approached if the dispersion integrals are evaluated for sub-threshold kinematics. This extension to the unphysical region provides a unique framework to determine the low-energy constants of chiral perturbation theory by global properties of the excitation spectrum.
PACS: 11.55.Fv Dispersion relations – / 11.55.Hx Sum rules – / 12.39.Fe Chiral Lagrangians – / 13.60.Le Meson production –
© Società Italiana di Fisica and Springer-Verlag, 2005
