Observation of $\hat{I}ž(1620{)}^0$ and evidence for $\hat{I}ž(1690{)}^0$ in $\hat{I}{ž}_c^{+}\to \hat{I}{ž}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{+}$ decays

Abstract

We report the first observation of the doubly-strange baryon $\hat{I}ž(1620{)}^0$ in its decay to $\hat{I}{ž}^{-}\ddot{I}{€}^{+}$ via $\hat{I}{ž}_c^{+}\to \hat{I}{ž}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{+}$ decays based on a $980{\mathrm{fb}}^{-1}$ data sample collected with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. The mass and width are measured to be 1610.4 $\pm$ 6.0 (stat) ${}_{-3.5}^{+5.9}$ (syst)~MeV$/c^2$ and 59.9 $\pm$ 4.8 (stat) ${}_{-3.0}^{+2.8}$ (syst)~MeV, respectively. We obtain 4.0$\ddot{I}ƒ$ evidence of the $\hat{I}ž(1690{)}^0$ with the same data sample. These results shed light on the structure of hyperon resonances with strangeness $S=-2$.

6 pages, 3 figures, To be submitted to Phys. Rev. Lett