Coupled-channels study of ΛK and ΣK states in the chiral SU(3) quark model -: art. no. 064001

The S-wave Lambda K and Sigma K states with isospin I=1/2 are dynamically investigated within the framework of the chiral SU(3) quark model by solving a resonating group method equation. The model parameters are taken from our previous work, which gave a good description of the energies of the baryon ground states, the binding energy of the deuteron, and the experimental data of the nucleon-nucleon (NN) and nucleon-hyperon (NY) scattering. Assumed not to give important contributions in the scattering processes, the s-channel quark-antiquark (q (q) over bar) annihilation interactions are not included as a first step. The results show a strong attraction between Sigma and K, which consequently results in a Sigma K quasibound state with about 17-MeV binding energy, unlike the case of Lambda K, which is unbound. When the channel coupling of Lambda K and Sigma K is considered, a sharp resonance state near 1670 MeV with spin-parity J(P)=1/2(-) is found. The narrow gap of the Lambda K and Sigma K thresholds, the strong attraction between Sigma and K, and the sizable off-diagonal matrix elements of Lambda K and Sigma K are responsible for the appearance of this resonance.