$\Delta(1232)$ resonance in the $\vec{\gamma}p\rightarrow p\pi^0$ reaction at threshold

TL;DR

This paper uses covariant baryon chiral perturbation theory including the $
232$ resonance to analyze neutral pion photoproduction near threshold, showing improved convergence with the resonance included.

Contribution

It explicitly incorporates the $
232$ resonance in covariant baryon chiral perturbation theory up to order $p^{7/2}$, enhancing the theoretical description of the process.

Findings

Improved convergence of the chiral series with the $
232$ resonance inclusion.

Good agreement with recent Mainz Microtron data.

Enhanced accuracy in angular distributions and photon asymmetries.

Abstract

We calculate the neutral pion photoproduction on the proton near threshold in covariant baryon chiral perturbation theory, including the $\Delta(1232)$ resonance as an explicit degree of freedom, up to chiral order $p^{7/2}$ in the $\delta$ counting. We compare our results with recent low-energy data from the Mainz Microtron for angular distributions and photon asymmetries. The convergence of the chiral series of the covariant approach is found to improve substantially with the inclusion of the $\Delta(1232)$ resonance.