Observation of Ξ(1620)0 and Evidence for Ξ(1690)0 in Ξ+c→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 Ξ+c→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)+6.1−4.2 (syst) MeV/c2 and 59.9±4.8(stat)+2.8−7.1(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.