Nucleon mass and pion loops

Poincaré covariant Faddeev equations for the nucleon and $\Delta$ are solved to illustrate that an internally consistent description in terms of confined-quark and non-point-like confined-diquark correlations can be obtained. $\pi N$-loop induced self-energy corrections to the nucleon’s mass are analyzed and shown to be independent of whether a pseudoscalar or pseudovector coupling is used. Phenomenological constraints suggest that this self-energy correction reduces the nucleon’s mass by up to several hundred MeV. That effect does not qualitatively alter the picture, suggested by the Faddeev equation, that baryons are quark-diquark composites. However, neglecting the $\pi$ loops leads to a quantitative overestimate of the nucleon’s axial-vector diquark component.