Electromagnetic properties of the Delta(1232)

We calculate the electromagnetic moments and radii of the Delta(1232) in the nonrelativistic quark model, including two-body exchange currents. We show that two-body exchange currents lead to nonvanishing Delta and N-->Delta transition quadrupole moments even if the wave function shave no D-state admixture. The usual explanation based on the single-quark transition model involves D-state admixtures but no exchange currents. We derive a parameter-free relation between the N-->Delta transition quadrupole moment and the neutron charge radius, namely Q(N-->Delta)=(1/root 2)r(n)(2). Furthermore, we calculate the M1 and E2 amplitudes for the process gamma+N-->Delta. We find the E2 amplitude receives sizable contributions from exchange currents. These are more important than the ones that result from D-state admixtures due to tensor forces between quarks if a reasonable quark core radius of about 0.6 fm is used. We obtain a ration of E2/M1=-3.5%.