First observation of the exclusive decays Λ _c ⁺→Λ π ⁺ π ⁺ π ^- π ⁰ and Λ _c ⁺Λ ωπ ⁺

Using data collected by the CLEO III detector at CESR, we report on the first observation of the decays Λ _c ⁺→Λ π ⁺ π ⁺ π ^- π ⁰ and Λ _c ⁺→Λ ωπ ⁺. The branching fractions are measured relative to the pK ^- π ⁺ mode; we find B(Λ _c ⁺→Λ π ⁺ π ⁺ π ^- π ⁰)/B(Lambda; _c ⁺→pK ^- π ⁺) = 0.36±0.09(stat) ±0.09(syst) and B(Λ _c ⁺→Λ ωπ ⁺)/B(Λ _c ⁺→pK ^- π ⁺) = 0.24±0.06(stat)±0.06(syst). We also observe a small excess of events in Λ _c ⁺→Λ ηπ ⁺, η→π ⁺ π ^- π ⁰ from which we find B(Λ _c ⁺→Λ ηπ ⁺)/B(Λ _c ⁺→pK ^- π ⁺) = 0.41±0.17±0. 10 with a corresponding limit of <0.65% at 90% confidence level. This rate is consistent with previous measurements of Λ _c ⁺→Λ ηπ ⁺, η-γ γ. We find that the combined branching fractions for Λ _c ⁺→Lambda; ωπ ⁺ and Λ _c ⁺→Λπ ⁺ π ⁺ π ^- π ⁰)B(Λ _c ⁺ comprise (87±13) of the total Λ rate. We set an upper limit on B(Λ _c ⁺→Λπ ⁺ π ⁺ π ^{- 0})/BΛ _c ⁺→pK ^- π ⁺ for non-ω and non-η modes of 0.13 at 90% confidence level.