Electromagnetic excitation of nucleon resonances
1 Institut für Kernphysik, Johannes Gutenberg-Universität, 55099 Mainz, Germany
2 Laboratory of Theoretical Physics, JINR Dubna, 141980 Moscow Region, Russia
Revised: 21 July 2011
Published online: 23 September 2011
Recent progress on the extraction of electromagnetic properties of nucleon resonance excitation through pion photo- and electroproduction is reviewed. Cross section data measured at MAMI, ELSA, and CEBAF are analyzed and compared to the analysis of other groups. On this basis, we derive longitudinal and transverse transition form factors for most of the four-star nucleon resonances. Furthermore, we discuss how the transition form factors can be used to obtain empirical transverse charge densities. Contour plots of the thus derived densities are shown for the Delta, Roper, S11, and D13 nucleon resonances.
© EDP Sciences, Springer-Verlag, 2011