Photo- and electro-excitation of the Δ-resonance at MAMI.

Over the last decade accurate experiments at MAMI played an essential role to improve our understanding of the nucleon to Δ(1232) transition. Originally to a large extent motivated through intraquark hyperfine interactions anticipated in QCD-inspired quark models they showed that pionic degrees of freedom are essential. The meson cloud is mainly responsible for the observed quadrupole excitation strength and affects the magnetic dipole transition strength as well [ABSTRACT FROM AUTHOR]