First observation of the exclusive decays Λ_c ⁺→Λ π⁺ π⁺ π^- π⁰ 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^- π⁰ 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^- π⁰)/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^- π⁰ 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^- π⁰)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.