Eur. Phys. J. A (2005) 25: 419-425
https://doi.org/10.1140/epja/i2005-10144-9

Original Article

The Fubini-Furlan-Rosetti sum rule and related aspects in light of covariant baryon chiral perturbation theory^⋆

¹ Laboratoire de Physique Théorique, Université Louis Pasteur, F-67084, Strasbourg Cedex 2, France
² Helmholtz-Institut für Strahlen- und Kernphysik (Theorie), Universität Bonn, Nußallee 14-16, D-53115, Bonn, Germany
³ Institut für Kernphysik (Theorie), Forschungszentrum Jülich, D-52425, Jülich, Germany

Received: 12 June 2005
Accepted: 11 August 2005
Published online: 20 September 2005

Abstract

We analyze the Fubini-Furlan-Rosetti sum rule in the framework of covariant baryon chiral perturbation theory to leading one-loop accuracy and including next-to-leading-order polynomial contributions. We discuss the relation between the subtraction constants in the invariant amplitudes and certain low-energy constants employed in earlier chiral perturbation theory studies of threshold neutral pion photoproduction off nucleons. In particular, we consider the corrections to the sum rule due to the finite pion mass and show that below the threshold they agree well with determinations based on fixed-t dispersion relations. We also discuss the energy dependence of the electric dipole amplitude E₀₊.