Chiral effective-field theory in the Delta(1232) region: II. radiative pion photoproduction

TL;DR

This paper uses chiral effective-field theory to analyze radiative pion photoproduction near the Delta(1232) resonance, aiming to determine its magnetic dipole moment through polarization asymmetries.

Contribution

It extends chiral perturbation theory to the Delta-resonance region and proposes a model-independent method to measure the Delta's magnetic dipole moment via polarization asymmetries.

Findings

The absorptive part of the Delta MDM is calculated.

Circular polarization asymmetry can measure the Delta MDM.

Sensitivity of observables to the real part of the Delta MDM is analyzed.

Abstract

We present a theoretical study of the radiative pion photoproduction on the nucleon ($\gamma N \to \pi N \gamma'$) 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 which is 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 $\gamma N \to \pi N \gamma'$ 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.