Pion-nucleon systems

The pion-nucleon interaction has been subject both to experimental and theoretical studies since the very beginning of the development of particle physics. On the theoretical side the description of the pion-nucleon system with QCD is considered to be a fundamental issue in the development of this theory. The understanding of strong interaction in the confinement regime has advanced recently, as chiral perturbation theory was developed to perform calculations at low energies [1,2]. 

B.H. Bransden and R.G. Moorhouse, The Pion-Nucleon System (Princeton University Press, Princeton, NJ, 1973) pp. 53-54. 

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