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arXiv · 1301.5576

Threshold $\pi^0$ photoproduction in relativistic chiral perturbation theory

Marius Hilt·Stefan Scherer·Lothar Tiator
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Abstract

We present a calculation of $\pi^0$ photoproduction on the proton in manifestly Lorentz-invariant baryon chiral perturbation theory up to and including chiral order $q^4$. With the results we analyze the latest $\pi^0$ photoproduction data in the threshold region obtained at the Mainz Microtron. In the calculation of observables and the fit of the low-energy constants, we take $S$, $P$, and $D$ waves into account. We compare the results for the multipoles with the corresponding single-energy analysis. Furthermore, we also fit the $O(q^4)$ heavy-baryon chiral perturbation theory calculation and compare both results. We provide predictions for several polarization observables for future experiments. Finally, we discuss the $\beta$ parameter of the unitarity cusp which is related to the breaking of isospin symmetry.

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Marius Hilt, Stefan Scherer, Lothar Tiator. 2013-01-23. Threshold $\pi^0$ photoproduction in relativistic chiral perturbation theory. https://doi.org/10.1103/physrevc.87.045204

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