DOIAbstract
We investigated the meson-baryon scattering using time-order perturbation theory (TOPT) based on covariant chiral effective field theory. The effective potential is defined as the sum of two-particle irreducible contributions of time-ordered diagrams, and the renormalized scattering amplitude is obtained by solving the integral equation, which is derived self-consistently in TOPT. Our developed formalism has been successfully applied to the πN scattering at leading order, and it has been extended to the meson-baryon scattering in S = −1 sector and found the two-pole structure of the Λ(1405) resonance