Electromagnetic excitation of the Δ(1232)-resonance

• DOI: 10.1016/j.physrep.2006.09.006
• Publication Date: 2006-12-19T14:32:17Z
• Authors: Vladimir Pascalutsa; Marc Vanderhaeghen; Shin Nan Yang
• Keywords: Perturbative QCD

150 pp, 67 figs; final version - to appear in Physics Reports<br/>We review the description of the lowest-energy nucleon excitation -- the $��$(1232)-resonance. Much of the recent experimental effort has been focused on the precision measurements of the nucleon-to-$��$ transition by means of electromagnetic probes. We confront the results of these measuremnts with the state-of-the-art calculations based on chiral effective-field theories (EFT), lattice QCD, large-$N_c$ relations, perturbative QCD, and QCD-inspired models. We also discuss the link of the nucleon-to-$��$ form factors to generalized parton distributions (GPDs). Some of the theoretical approaches are reviewed in detail, in particular, recent dynamical and unitary-isobar models of pion electroproduction, which are extensively used in the interpretation of experiments. Also, the novel extension of chiral EFTs to the energy domain of the $��$-resonance is described in detail. The two-photon exchange effects in the electroexcitation of the $\De$-resonance are addressed here as well.<br/>