N→Δ(1232)E2transition and Siegert’s theorem

Until now, calculations of the $E2\mathrm{}$ amplitude in the $\overrightarrow{N}\Delta$ transition using the spatial current operator have differed considerably from those using the one-body charge operator and Siegert’s theorem. We show that this difference is almost entirely explained by spatial two-body exchange currents consistent with the chosen quark-quark potentials. These were not explicitly included in previous comparisons. Furthermore, using Siegert’s theorem we find that the main contribution to the $E2\mathrm{}$ amplitude comes from a two-quark spin-flip mechanism originating from pion and gluon degrees of freedom in the charge operator. Our results provide insight into the microscopic origin of the intrinsic deformation of the nucleon.