Extended Lee model and three-particle equations

Abstract

The extended Lee model describes the interaction of two fermions, V and N, with a scalar boson θ and its antiparticle θ¯ through the virtual processes V⇄N+θ and N⇄V+θ¯. Here it is shown that the amplitudes for the physical processes V+θ→V+θ and V+θ→N+2θ can be obtained in a reasonable approximation from the solution of an Amado-Lovelace type of three-particle equation. The analysis presented gives some insight into the problem of extending a crossing symmetric, Chew-Low type of T matrix off the energy shell.