10 research outputs found
Electromagnetic Form Factors of the Nucleon and Compton Scattering
We review the experimental and theoretical status of elastic electron
scattering and elastic low-energy photon scattering (with both real and virtual
photons) from the nucleon. As a consequence of new experimental facilities and
new theoretical insights, these subjects are advancing with unprecedented
precision. These reactions provide many important insights into the spatial
distributions and correlations of quarks in the nucleon.Comment: 47 pages, 18 figures, includes corrections and updates to published
manuscrip
Measurement of the Electric and Magnetic Polarizabilities of the Proton
The Compton scattering cross section on the proton has been measured at
laboratory angles of 90 and 135 using tagged photons in the
energy range 70--100 MeV and simultaneously using untagged photons in the range
100--148~MeV. With the aid of dispersion relations, these cross sections were
used to extract the electric and magnetic polarizabilities, and
respectively, of the proton. We find
in agreement with a model-independent dispersion sum rule, and
where the errors shown are statistical, systematic, and model-dependent,
respectively. A comparison with previous experiments is given and global values
for the polarizabilities are extracted.Comment: 35 pages, 11 PostScript figures, uses RevTex 3.
Dispersion relations in real and virtual Compton scattering
A unified presentation is given on the use of dispersion relations in the
real and virtual Compton scattering processes off the nucleon. The way in which
dispersion relations for Compton scattering amplitudes establish connections
between low energy nucleon structure quantities, such as polarizabilities or
anomalous magnetic moments, and the nucleon excitation spectrum is reviewed. We
discuss various sum rules for forward real and virtual Compton scattering, such
as the Gerasimov-Drell-Hearn sum rule and its generalizations, the
Burkhardt-Cottingham sum rule, as well as sum rules for forward nucleon
polarizabilities, and review their experimental status. Subsequently, we
address the general case of real Compton scattering (RCS). Various types of
dispersion relations for RCS are presented as tools for extracting nucleon
polarizabilities from the RCS data. The information on nucleon polarizabilities
gained in this way is reviewed and the nucleon structure information encoded in
these quantities is discussed. The dispersion relation formalism is then
extended to virtual Compton scattering (VCS). The information on generalized
nucleon polarizabilities extracted from recent VCS experiments is described,
along with its interpretation in nucleon structure models. As a summary, the
physics content of the existing data is discussed and some perspectives for
future theoretical and experimental activities in this field are presented.Comment: 120 pages, 42 figures, to appear in Phys. Re