Observation of and updated measurement of at Belle - Belle Collaboration

We report the first observation of the charmed-strange baryon with a significance greater than 5. The is found in its decay to in decays. The measured mass and width are  MeV/ and  MeV, respectively, and the product branching fraction is . We also measure with improved precision, and search for the charmonium-like state Y (4660) and its spin partner, , in the invariant mass spectrum. No clear signals of the Y (4660) nor its spin partner are observed and the 90% credibility level (C.L.) upper limits on their production rates are determined. These measurements are obtained from a sample of pairs collected at the resonance by the Belle detector at the KEKB asymmetric energy electron–positron collider.