Pion photoproduction in chiral perturbation theory with explicit treatment of the ?(1232) resonance

We study the reaction of pion photoproduction on the nucleon in the framework of chiral perturbation theory with explicit delta(1232) degrees of freedom. In the covariant approach, we give results up to order epsilon(3) in the small scale expansion scheme. Furthermore, we provide delta-less and delta-full results obtained in the heavy-baryon scheme to analyze the differences from the covariant approach. Low-energy constants are fitted to multipole amplitudes using theoretical truncation errors estimated by a Bayesian approach. We also compare our findings to data of neutral pion production cross sections and polarization asymmetries. The description of the reaction is clearly improved by the explicit treatment of the delta(1232) resonance.

Automated summary

In this article, we study the reaction of pion photoproduction on the nucleon using chiral perturbation theory. We present results using both the covariant approach and the heavy-baryon scheme, and compare them to experimental data using Bayesian methods to estimate theoretical truncation errors. We find that the explicit treatment of the delta(1232) resonance significantly improves the description of the reaction.