The ${\vec{\Lambda (1405)}}$ in resummed chiral effective field theory

We study the unitarized meson–baryon scattering amplitude at leading order in the strangeness S=−1 sector using time-ordered perturbation theory for a manifestly Lorentz-invariant formulation of chiral effective field theory. By solving the coupled-channel integral equations with the full off-shell dependence of the effective potential and applying subtractive renormalization, we analyze the renormalized scattering amplitudes and obtain the two-pole structure of the Λ(1405) resonance. We also point out the necessity of including higher-order terms