Antikaon-Nucleon Molecular Structure of Λ(1405) Resonance from Lattice QCD
The structure of the lowest-lying excitation of the baryon, the resonance, was examined and determined to exhibit a meson-baryon molecular structure. While the baryon has quantum numbers , the , in a meson-baryon molecular state, would form either a proton bound state or a neutron bound state. The could also, potentially, be a state or an elementary three-quark state, but such results would require that the strange quark form factor of the by sizable, which would not be the case for the or states. For the first time, Lattice QCD techniques were applied which observed a vanishing strange quark magnetic form factor, suggesting the structure of the is dominated by a molecular bound state. As further evidence of a meson-baryon molecular structure, a finite volume Hamiltonian Effective Field Theory (EFT) model was used with a basis of single- and two-particle noninteracting meson-baryon states. Through examining the overlap of the basis state with the energy eigenstate for the , it was found that the state component was dominant, at physical pion masses, in the finite-volume EFT Hamiltonian treatment which, along with the vanishing strange quark magnetic form factor, corroborate the molecular bound state structure of the . Extending the model to the infinite-volume limit yielded results consistent with nature.
References: Jonathon M. M. Hall, et al., Phys. Rev. Lett. 114, 132002 (2015)
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