First Observation of the Exclusive Decays Lambda_c to Lambda pi+pi+pi-pi0 and Lambda_c to Lambda omega pi+

Using data recorded by the CLEO III detector at CESR, we report on the first measurements of the branching fractions for decays of the Lambda_c^+ charmed baryon into (Lambda pi+ pi+ pi- pi0) and (Lambda omega pi+). All rates are measured with respect to the p K- pi+ decay mode. The relative branching fractions are 0.39 +- 0.09(stat.) +- 0.09(syst.) and 0.24 +- 0.06(stat.) +- 0.06(syst.) for the (Lambda pi+ pi+ pi- pi0) and (Lambda omega pi+) modes, respectively. The data also suggest decays of the Lambda_c^+ via (Lambda eta pi+, eta --> pi+ pi- pi0) with a rate which is consistent with previous measurements of the branching fraction of Lambda_c^+ to (Lambda eta pi+, eta --> gamma gamma). The measurements indicate that the omega and eta sub-modes comprise 87+-13% of the (Lambda pi+ pi+ pi- pi0) final state. We set an upper limit on the contribution from non-omega and non-eta modes of 0.13 at the 90% confidence level.