Observation of Xi(1620)(0) and Evidence for Xi(1690)(0) in Xi(+)(c) -> Xi(-) pi(+) pi(+) Decays

We report the first observation of the double strange baryon Xi(1620)(0) in its decay to Xi(-) pi(+) via Xi(+)(c) -> Xi(-)pi(+)pi(+) decays based on a 980 fb(-1) data sample collected with the Belle detector at the KEKB asymmetricenergy e(+)e(-) collider. The mass and width are measured to be 1610.4 +/- 6.0(stat)(-4.2)(+6.1) (syst) MeV/c(2) and 59.9 +/- 4.8(stat)(-7.1)(+2.8)(syst) MeV, respectively. We obtain 4.0 sigma evidence of the Xi(1690)(0) with the same data sample. These results shed light on the structure of hyperon resonances with strangeness S = -2.