Energy dependence of K̄N interactions and resonance pole of strange dibaryons

We study the resonance energy of the strange dibaryons using two models with the energy-independent and energy-dependent potentials for the s-wave K̄N interaction, both of which are derived by certain reductions from the leading order term of the effective chiral Lagrangian. These potential models produce rather different off-shell behaviors of the two-body K̄N - πnΣ amplitudes in J = 0 channel, i.e., the model with energy-independent (energy-dependent) potential predicts one (two) resonance pole in the Λ1(1405) region, while they describe the available data equally well. We find that the energy-independent potential model predicts one resonance pole of the strange dibaryons, whereas the energy-dependent potential model predicts two resonance poles: one is the shallow quasi-bound state of the K̄NN, and the other is the resonance of the πtYN with large width. An investigation of the binding energy of the strange dibaryons will make a significant contribution to clarify resonance structure of s-wave K̄N - πΣ around the Λ(1405) region.