Chiral effective-field theory in the $\Delta$(1232) region. II. Radiative pion photoproduction
Vladimir Pascalutsa and Marc Vanderhaeghen

We present a theoretical study of the radiative pion photoproduction on the nucleon ($\gamma N \rightarrow \pi N \gamma'$) in the $\De$-resonance region, with the aim to determine the magnetic dipole moment (MDM) of the $\Delta^+(1232)$. The study is done within the framework of chiral effective-field theory, where the expansion is performed (to next-to-leading order) in the $\delta$ power-counting scheme, an extension of chiral perturbation theory to the $\Delta$-resonance energy region. We present the results for the absorptive part of the $\Delta$ MDM, as well as perform a sensitivity study of the dependence of $\gamma N \rightarrow \pi N \gamma'$ observables on the real part of the $\Delta$ MDM. We find that an asymmetry for circular polarization of the photon beam may provide a model-independent way to measure the $\Delta$ MDM.

© 2008 The American Physical Society.