Fig. 1
From: Observation of bound state self-interaction in a nano-eV atom collider
Feynman diagrams for resonant collisions. a The total scattering amplitude f(E) for asymptotically free particles A and B is the sum of the background contribution fbg and the resonant contribution fres. The lowest order contribution to fres has A and B forming the quasi-bound state AB which then decays back to the individual particles. The next order adds a self-energy correction to the bound state energy. AB decays into particles A and B which reform into the quasi-bound state AB. b Analogous self-energy correction for the mass of the Z0 boson in the elastic scattering of electrons and positrons
