Evidence for W exchange in charmed baryon decays

Abstract Using the detector ARGUS at the e + e − storage ring DORIS II at DESY, we have observed the decays Λ c + → Ξ − K + π + and Λ c + → Ξ ∗0 K + and obtained evidence for the decay Ξ c 0 → ΛK s 0 . All three of these decays are of interest as they provide information about W -exchange processes. The products of cross sections and branching ratios for Λ c + → Ξ − K + π + and Λ c + → Ξ ∗0 K + are (1.7±0.3±0.3) pb and (0.6±0.2±0.1) pb, respectively, which implies that (35±17) % of the Ξ − K + π + final state is generated through a two-body decay via intermediate W -exchange. The product of production cross section and branching ratio for Ξ c 0 → Λ K s 0 is (2.1 ± 1.0 ± 0.6) pb.