Lattice QCD study of πΣ-K̅N scattering and the Λ(1405) resonance

A lattice QCD computation of the coupled channel πΣ-K̅N scattering amplitudes in the Λ(1405) region is detailed. Results are obtained using a single ensemble of gauge field configurations with N_ f = 2+1 dynamical quark flavors and m_π≈ 200 MeV and m_K≈487 MeV. Hermitian correlation matrices using both single baryon and meson-baryon interpolating operators for a variety of different total momenta and irreducible representations are used. Several parametrizations of the two-channel scattering K-matrix are utilized to obtain the scattering amplitudes from the finite-volume spectrum. The amplitudes, continued to the complex energy plane, exhibit a virtual bound state below the πΣ threshold and a resonance pole just below the K̅N threshold.