Λ(1405) and meson-baryon interactions in a quark model

We investigate the mass spectra of p-wave Λ’s by means of the constituent quark model with the effect of coupling to meson-baryon channels. The quark wave function of the lowest p-wave ${\mathrm{\Lambda }}^{\mathrm{*}}$, i.e., Λ(1405), is found to be dominated by the antisymmetric flavor state which strongly couples to the K¯N and πΣ channels. The significant downward shift of the Λ(1405)’s mass is attributed to its large attractive self-energy due to the K¯N${\mathrm{\Lambda }}^{\mathrm{*}}$ and πΣ${\mathrm{\Lambda }}^{\mathrm{*}}$ coupling and its strong increase due to the presence of the cusp around the K¯N threshold.