Determination of the Δ++ magnetic dipole moment

We study the elastic and radiative π⁺p scattering within a full dynamical model which incorporates the finite width effects of the Δ⁺⁺. 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 Δ⁺⁺ obtained from the elastic cross section are m_Δ=(1211.2±0.4) MeV and Γ_Δ=(88.2±0.4) MeV. From a fit to the most sensitive observables in radiative π⁺p scattering, we obtain μ_Δ=(6.14±0.51)e/2m_p for the magnetic dipole moment of the Δ⁺⁺.