Electromagnetic form factors of the ∆ baryon

We develop a methodology that enables us to extract accurately the electromagnetic ∆ form factors and their momentum dependence. We test our approach in the quenched approximation as a preparation for a study using dynamical fermions. Our calculation of the four form factors covers pion masses between about 410 MeV and 560 MeV on lattices with a size of 2.9 fm and a lattice spacing ∼ 0.09 fm. From the form factors we are able to obtain estimates of the magnetic moment and the charge radius of the ∆, which we compare to existing experimental and theoretical results. Our non-zero result for the electric quadrupole form factor signals a deformation of the ∆, pointing to an oblate charge distribution.