Elastic and inelastic pion-nucleon scattering to fourth order in chiral perturbation theory

We extend our previous study of elastic pion-nucleon scattering in the framework of chiral perturbation theory by performing a combined analysis of the reactions $πN \to πN$ and $πN \to ππN$. The calculation is carried out to fourth order in the chiral expansion using the heavy baryon approach and the covariant formulation supplemented with a modified version of the extended on-mass-shell renormalization scheme. We demonstrate that a combined fit to experimental data in both channels leads to a reduced amount of correlations between the low-energy constants. A satisfactory description of the experimental data in both channels is obtained, which is further improved upon including tree-level contributions of the $Δ$(1232) resonance. We also explore a possibility of using the empirical information about $πN$ subthreshold parameters obtained recently by means of the Roy-Steiner equations to stabilize the fits.

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