High-spin study of (128)Ce and systematics of quasiparticle pair alignment

We analyze elastic pion-nucleon scattering to fourth order in heavy-baryon chiral perturbation theory, extending the third-order study published in Nucl. Phys. A 640 (1998) 199. We use various partial-wave analyses to pin down the low-energy constants from data in the physical region. The S-wave scattering lengths are consistent with recent determinations from pionic hydrogen and deuterium. We find an improved description of the P-waves. We also discuss the pion-nucleon sigma term and problems related to the prediction of the subthreshold parameters.