The octet meson and octet baryon interaction with strangeness and the Λ(1405)

The octet meson and baryon interaction with strangeness [Formula: see text] is studied fully relativistically with chiral Lagrangian. In this paper, a Bethe–Salpeter equation (BSE) approach with spectator quasipotential approximation is applied to study the reactions [Formula: see text] with [Formula: see text] and [Formula: see text] with all possible partial waves and theoretical results are comparable with experimental data. It is found that the Weinberg–Tomozawa potential derived from the lowest order chiral Lagrangian only provides the contributions from partial waves with spin-parities [Formula: see text] and [Formula: see text]. Two-pole structure of the [Formula: see text] is confirmed with poles at [Formula: see text] and [Formula: see text] MeV. The lower and higher poles originate from [Formula: see text] interaction as a resonance and [Formula: see text] interaction as a bound state, respectively.