John Bulava, Bárbara Cid-Mora, Andrew D. Hanlon, Ben Hörz, Daniel Mohler, Colin Morningstar, Joseph Moscoso, Amy Nicholson, Fernando Romero-López, Sarah Skinner, and André Walker-Loud, Two-Pole Nature of the Λ(1405) Resonance from Lattice QCD, Phys. Rev. Lett. 132, 051901 (2024), published in January 2024

We present the first lattice QCD computation of the coupled channel πΣ−KN scattering amplitudes at energies near 1405 MeV. These amplitudes contain the resonance Λ(1405) resonance with strangeness S=−1 and isospin, spin, and parity quantum numbers I(J^P)=0(1/2–). However, whether there is a single resonance or two nearby resonance poles in this region is controversial theoretically and experimentally. Using single-baryon and meson-baryon operators to extract the finite-volume stationary-state energies to obtain the scattering amplitudes at slightly unphysical quark masses corresponding to m_π≈200  MeV and m_K≈487  MeV, this study finds the amplitudes exhibit a virtual bound state below the πΣ threshold in addition to the established resonance pole just below the KN threshold. Several parametrizations of the two-channel K matrix are employed to fit the lattice QCD results, all of which support the two-pole picture suggested by SU(3) chiral symmetry and unitarity.

See also: Phys. Rev. D 109, 014511 (2024)