Unitary ambiguity in the extraction of the E2/M1 ratio for the $\gamma N\leftrightarrow \Delta$ transition

P. Wilhelm, Th. Wilbois, H. Arenhoevel

The resonant electric quadrupole amplitude in the transition $\gamma N\leftrightarrow \Delta (1232)$ is of great interest for the understanding of baryon structure. Various dynamical models hav…