Observation of Ξ (1620)0 and Evidence for Ξ (1690)0 in Ξc+ → Ξ-π+π+ Decays

Abstract

We report the first observation of the double strange baryon Ξ(1620)0 in its decay to Ξ-π+ via Ξc+→Ξ-π+π+ decays based on a 980 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±6.0(stat)-4.2+6.1 (syst) MeV/c2 and 59.9±4.8(stat)-7.1+2.8(syst) MeV, respectively. We obtain 4.0σ evidence of the Ξ(1690)0 with the same data sample. These results shed light on the structure of hyperon resonances with strangeness S=-2.