Off-shell resonances in coupled channel problems

Abstract

The coupled channel theory of nuclear reactions is extended off the energy shell so that the T-matrix can be constructed to include both the direct reaction contribution and the contribution from the off-shell background scattering. This has been shown to be important for (d,p) stripping reactions to unbound states. Three soluble two-channel models with square well, δ-function, and separable potentials, are presented and the resonance and bound state behaviour is discussed in some numerical detail. The importance of the off-shell background term is also studied.