Bound states, resonances, and poles in low-energyK¯Ninteraction models

The locations of the dynamic poles in the complex energy plane of the s-wave T matrix for the coupled (K¯N,Σπ) system are calculated. Investigated are a quark bag model and several potential models, including one that agrees with the strong interaction shift in kaonic hydrogen as well as scattering data. Each potential model is found to support either one or no poles, while the bag model is found to support two. The poles energies are found to be quite different from the energy of the ${\mathrm{\Lambda }}^{\mathrm{*}}$(1405) determined by phenomenological analyses along the real energy axis.