On the spin, parity and nature of the $\mathrm{\Xi }(1620)$ resonance

Using a unitary extension of chiral perturbation theory with a lowest-order s-wave SU(3) chiral Lagrangian we study low-energy meson-baryon scattering in the strangeness $S=-2$ sector. A scattering-matrix pole is found around 1606 MeV which corresponds to an s-wave $\mathrm{\Xi }$ resonance with $J^P=1\mathrm{/}{2}^{-}$. We identify this resonance with the $\mathrm{\Xi }(1620)$ state, quoted in the Particle Data Book with $I=1\mathrm{/}2$ but with unknown spin and parity. The addition of the $S=-2$ state to the recently computed $\mathrm{\Lambda }(1670)$, $\mathrm{\Sigma }(1620)$ and N(1535) states completes the octet of $J^P=1\mathrm{/}{2}^{-}$ resonances dynamically generated in this chiral unitary approach.