# Overview - Form Factors, Polarizabilities and Sum Rules

## Lothar Tiator

*Institut für Kernphysik, Universität Mainz*

In this overview I will present the status on nucleon form factors,
polarizabilities and electromagnetic sum rules.
Electromagnetic form factors from elastic electron scattering on
proton, deuteron and 3He targets will be briefly discussed. Real and
virtual Compton scattering will be introduced and the nucleon
polarizabilities and generalized polarizabilities will be shown from
theoretical investigations in terms of dispersion relations. From forward
Compton scattering electromagnetic sum rules will be derived both for real
and virtual photons. In particular I will show recent analyses and
predictions of the Gerasimov-Drell-Hearn (GDH) sum rule and the forward
spin polarizability sum rule (FSP).
References:

- A.W. Thomas, W. Weise,
The structure of the nucleon,
WILEY-VCH, Berlin 2001.
- D. Drechsel,
The structure of the nucleon,
Lecture notes of HUGS, JLab 1999 [nucl-th/0003061].
- Nucleon form factors:
- H.-W. Hammer, U.-G. Meissner and D. Drechsel,
Dispersion theoretical analysis of the nucleon electromagnetic form factors,
Nucl. Phys. A 596, 367 (1996) [hep-ph 9506375].
- H. Schmieden,
Form factors of the neutron,
Proceedings Baryons'98 (Bonn), ed. by D.W. Menze and B. Ch. Metsch,
World Scientific (1999), p. 356.

- Nucleon polarizabilities:
- S. Scherer,
Real and virtual Compton scattering at low energies,
Czech J. Phys. 49, 1307 (1999) [nucl-th/9901056].
- A.I. L'vov, S. Scherer, B. Pasquini, C. Unkmeir and D. Drechsel,
Generalized dipole polarizabilities and the spatial structure of hadrons,
Phys. Rev. C 64, 015203 (2001) [hep-ph/0103172].

- Pion electroproduction and electromagnetic sum rules:
- D. Drechsel, O. Hanstein, S.S. Kamalov and L. Tiator,
A unitary isobar model for pion photo- and electroproduction on the proton
up to 1 GeV, Nucl. Phys. A 645, 145 (1998) [nucl-th/9807001].
- D. Drechsel, S.S. Kamalov and L. Tiator,
Gerasimov-Drell-Hearn sum rule and related integrals,
Phys. Rev. D 63, 114010 (2001) [hep-ph/0008306].