The pole structure of the $\mathrm{\Lambda }(1405)$ is examined by fitting the couplings of an underlying Hamiltonian effective field theory to cross sections of $K^{-}p$ scattering in the infinite-volume limit. Finite-volume spectra are then obtained from the theory, and compared to lattice QCD results for the mass of the $\mathrm{\Lambda }(1405)$. Momentum-dependent, nonseparable potentials motivated by the well-known Weinberg-Tomozawa terms are used, with SU(3) flavor symmetry broken in the couplings and masses. In addition, we examine the effect on the behavior of the spectra from the inclusion of a bare triquarklike isospin-zero basis state. It is found that the cross sections are consistent with the experimental data with two complex poles for the $\mathrm{\Lambda }(1405)$, regardless of whether a bare-baryon basis state is introduced or not. However, it is apparent that the bare baryon is important for describing the results of lattice QCD at high pion masses.

• Received 25 July 2016

DOI:https://doi.org/10.1103/PhysRevD.95.014506