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

Understand

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.