We propose a new model that combines the rigor of full-fledged loop calculations in field theory with the simplicity of the $K$-matrix formalism for channel-coupling effects. We show, for one example, the equivalence of this new model, the renormalized Im-$K$-matrix (RIK) model, with a more standard approach in which nonperturbative loop corrections are calculated. In the RIK model an analytic continuation of the $K$-matrix formalism is combined with a renormalization procedure to arrive at a scattering amplitude that obeys low-energy theorems and is also an analytic function in the complex momentum plane.

• Received 22 November 2006

DOI:https://doi.org/10.1103/PhysRevC.75.055203