Eur. Phys. J. A 11, 185-208 (2001)

Dispersion relation formalism for virtual Compton scattering off the proton

B. Pasquini¹, M. Gorchtein², D. Drechsel², A. Metz³ and M. Vanderhaeghen<sup>2

1</sup>  ECT*, I-38050 Villazzano, Trento, and INFN, Trento, Italy
²  Institut für Kernphysik, Johannes-Gutenberg-Universität, D-55099 Mainz, Germany
³  Division of Physics and Astronomy, Faculty of Science, Vrije Universiteit, 1081 HV Amsterdam, The Netherlands

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(Received: 14 March 2001 Communicated by V. Vento)

Abstract
We present in detail a dispersion relation formalism for virtual Compton scattering (VCS) off the proton from threshold into the -resonance region. Such a formalism can be used as a tool to extract the generalized polarizabilities of the proton from both unpolarized and polarized VCS observables over a larger energy range. We present calculations for existing and forthcoming VCS experiments and demonstrate that the VCS observables in the energy region between pion production threshold and the -resonance show an enhanced sensitivity to the generalized polarizabilities.

PACS
11.55.Fv - Dispersion relations.
13.40.-f - Electromagnetic processes and properties.
13.60.Fz - Elastic and Compton scattering.
14.20.Dh - Protons and neutrons.

© Società Italiana di Fisica, Springer-Verlag 2001