First observation of the production and decay of the Σc

Abstract An event with the decay chain Σ c + → Λ c + + π 0 , Λ c + → K − + p + π + , has been observed in an exposure of BEBC, equipped with a track sensitive target, to the wide band neutrino beam from the SPS at CERN. The event has a unique three constraint kinematic fit to the ΔS = − ΔQ reaction v + p → μ − + p + K − + π + + π + + π 0 with both gammas from the π 0 decay detected. The proton and other final state particles are identified. The masses are M ( Λ c + ) = 2290 ± 3 MeV/ c 2 , M ( Σ c + ) = 2457 ± 4 MeV/ c 2 and M ( Σ c + ) − M ( Λ c + ) = 168 ± 3 MeV/ c 2 . Including other data one obtains M ( Σ c ++ ) − M ( Σ c + ) = 0 ± 4 MeV/ c 2 .