Radiative pion photoproduction in covariant chiral perturbation theory

TL;DR

This paper calculates radiative pion photoproduction using covariant chiral perturbation theory with explicit delta degrees of freedom, fitting experimental data to extract the delta+ magnetic moment and providing theoretical predictions.

Contribution

It introduces a covariant chiral perturbation theory approach with explicit delta(1232) degrees of freedom and applies the small scale expansion to analyze radiative pion photoproduction.

Findings

Extracted the $elta^+$ magnetic moment from data.

Compared covariant approach results with previous $elta$-less and $elta$-expansion schemes.

Provided predictions for radiative charged-pion photoproduction.

Abstract

We present a calculation of radiative pion photoproduction in the framework of covariant chiral perturbation theory with explicit $\Delta(1232)$ degrees of freedom. The analysis is performed employing the small scale expansion scheme adjusted for the $\Delta$ region. Depending on the channel, we include contributions up to next-to-next-to-leading order. We fit the available experimental data for the reaction $ \gamma p\to\gamma p\pi^0 $ and extract the value of the $\Delta^+$ magnetic moment. Errors from the truncation of the small scale expansion are estimated using the Bayesian approach. We compare our results both with the previous studies within the $\delta$-expansion scheme and with the $\Delta$-less theory. We also give predictions for radiative charged-pion photoproduction.