Dispersion-theoretical analysis of the electromagnetic form factors of the nucleon

• Applicant: Professor Dr. Ulf-G. Meißner, since 8/2005
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: from 2003 to 2005
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5407632

We plan to perform a new dispersion-theoretical analysis of the electromagnetic form factors of the nucleon. The form factors, which encode the electromagnetic structure of the nucleon, are not only interesting by themselves, but a precise knowledge is mandatory for many other experiments such as the measurement of the nucleon's strange form factors and fundamental tests of Quantum Electrodynamics. The dispersive approach allows for a simultaneous description of all four nucleon electromagnetic form factors. Furthermore, vector-meson-nucleon coupling constants can be extracted from the form factor data. Many new data from precise polarization experiments at ELSA (Bonn), MAMI (Mainz), MIT-Bates (USA), and Jefferson Lab (USA) have appeared since we have performed the last analysis in 1996. In particular, there are new data for the ratio of the electric and magnetic form factors of the proton and the timelike neutron form factors that cannot be described by previous analyses. A major part of the new analysis is also to improve its theoretical foundation. Particularly important are the constraints from perturbative QCD and the singularity structure of the form factors in the complex plane. We also plan to extract an accurate parametrization of the form factors which is often required as input in other calculations. Finally, we want to investigate the consequences for the strange form factors of the nucleon.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr. Hans-Werner Hammer, until 8/2005