D-state effects in the electromagnetic N-Delta transition

Understand

We consider here a manifestly covariant quark model of the nucleon and the Delta, where one quark is off-shell and the other two quarks form an on-shell diquark pair.

• Using this model, we have shown previously that the nucleon form factors and the dominant form factor for the gamma N -> Delta transition (the magnetic dipole (M1) form factor) can be well described by nucleon and Delta wave functions with S-state components only.
• In this paper we show that non-vanishing results for the small electric (E2) and Coulomb (C2) quadrupole form factors can be obtained if D-state components are added to the Delta valence quark wave function.
• We present a covariant definition of these components and compute their contributions to the form factors.