Compositeness of hadronic states in coupled-channel separable potential model

Abstract

The compositeness of coupled-channel hadronic interactions is explored by considering virtual and bound states in higher or lower channel. Since the pole is expected to move across the Riemann sheets, we investigate how Weinberg's compositeness criterion applies to initially composite states. To account for virtual states, the modified compactness formula is used because the compositeness criterion was originally designed to evaluate bound states. We first experiment on the simple nucleon-nucleon system using separable potential model to derive exact amplitude. Since the model potential is energy independent, we expect the system to remain composite despite the changing value of the compactness Z. However, there is one interesting case where, at some given coupling strength, the system becomes dominantly compact.