Observation of Cabibbo-suppressed and W-exchange Λ c + baryon decays

Abstract We present measurements of the Cabibbo-suppressed decays Λ c + → Λ 0 K + and Λ c + → Σ 0 K + (both first observations), Λ c + → Σ + K + π − (seen with large statistics for the first time), Λ c + → pK + K − and Λ c + → pφ (measured with improved accuracy). Improved branching ratio measurements for the decays Λ c + → Σ + K + K − and Λ c + → Σ + φ , which are attributed to W-exchange diagrams, are shown. We also present the first evidence for Λ c + → Ξ (1690) 0 K + and set an upper limit on the non-resonant decay Λ c + → Σ + K + K − . This analysis was performed using 32.6 fb −1 of data collected by the Belle detector at the asymmetric e + e − collider KEKB.