# Meson-baryon scattering to one-loop order in heavy baryon chiral perturbation theory

## TL;DR

This paper computes meson-baryon scattering amplitudes to one-loop order in heavy baryon chiral perturbation theory, fitting low-energy constants to experimental data, and predicts phase shifts, scattering lengths, and potential resonances.

## Contribution

It provides a detailed one-loop calculation of meson-baryon scattering in SU(3) heavy baryon chiral perturbation theory, including fits to data and predictions of phase shifts and resonances.

## Key findings

- Agreement with experimental phase shift difference at the Xi mass
- Strong phase shifts suggest possible dynamically generated resonances
- Predicted scattering lengths consistent with other methods

## Abstract

We calculate the T-matrices of pseudoscalar meson octet-baryon scattering to one-loop order in SU(3) heavy baryon chiral perturbation theory. The pertinent combinations of low-energy constants are determined by fitting to phase shifts of $\pi N$ and $K N$ scattering and the corresponding data. By using these low-energy constants, we obtain the strong phase shift difference of $\pi \Lambda$ scattering at the $\Xi$ mass, $\delta_P-\delta_S=(8.8 \pm 0.2)$ degrees, in agreement with experimental results. We find that the phase shifts in the $S_{01}$($\pi \Sigma$), $S_{01}$($K \Xi$), $S_{01}$($\overline{K} N$), and $S_{11}$($\overline{K} \Sigma$) waves are so strong that resonances may be generated dynamically in all these channels. We also predict the scattering lengths and make comparisons with the results obtained from the threshold T-matrices in heavy baryon chiral perturbation theory and the method of covariant infrared regularization. The issue of convergence is also discussed in detail.