Determination of the Delta++ magnetic dipole moment

We study the elastic and radiative pi+ p scattering within a full dynamical model which incorporates the finite width effects of the Delta++. The scattering amplitudes are invariant under contact transformations of the spin 3/2 field and gauge-invariance is fulfilled for the radiative case. The pole parameters of the Delta++ obtained from the elastic cross section are m_Delta = 1211.2 \pm 0.4 MeV and Gamma_Delta = 88.2 \pm 0.4 MeV. From a fit to the most sensitive observables in radiative pi+ p scattering, we obtain mu_Delta = 6.14 \pm 0.51 e/2m_p for the magnetic dipole moment of the Delta++.