Polarization Observables in the N→Δ(1232) Transition

In the simple SU(6) spherically symmetric quark model, the proton and the Δ(1232) are states of three quarks in an overall S-wave with spins coupled to 1/2 and 3/2 respectively. In this context, the transition has a pure magnetic dipole M 1+ nature resulting in the spin-flip of a single quark. However the measurements carried out in the late sixties and early seventies at DESY [1, 2, 3], NINA (Daresbury) [4] and CEA (Harvard) [5] have demonstrated already the inconsistency of the data with a pure magnetic dipole transition, indicating that, although small, other components were also needed.