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arXiv · hep-ph/9707399

On-Shell Approach to Pion-Nucleon Physics

James V. Steele·Hidenaga Yamagishi·Ismail Zahed
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Abstract

We discuss an on-shell approach to pion-nucleon physics that is consistent order by order in a $1/f_π$ expansion with the chiral reduction formula, crossing, and relativistic unitarity. A number of constraints between the on-shell low-energy parameters are derived at tree level in the presence of the pion-nucleon sigma term, and found to be in fair agreement with experiment. We analyze the nucleon form factors, and the $πN\to πN$ scattering amplitude to one-loop, as well as $πN\toππN$ to tree level. We use the latter to derive a new constraint for the pion-nucleon sigma term at threshold. We compare our results to both relativistic and non-relativistic chiral perturbation theory, and discuss the convergence character of the expansion in light of experiment.

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James V. Steele, Hidenaga Yamagishi, Ismail Zahed. 1997-07-19. On-Shell Approach to Pion-Nucleon Physics. https://doi.org/10.1103/physrevd.57.1703

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