Search for nucleon decay with final states l⁺η⁰, ν̄η⁰, and ν̄π^+,0 using Soudan 2

We have searched for nucleon decay into five two-body final states using a 4.4 kiloton-year fiducial exposure of the Soudan 2 iron tracking calorimeter. For proton decay into the fully visible final states μ⁺η⁰ and e⁺η⁰, we observe zero and one event, respectively, that satisfy our search criteria for nucleon decay. The lifetime lower limits (τ/B) thus implied are 89×10³⁰ years and 81×10³⁰ years at 90% confidence level. For neutron decay into ν̄η⁰, we obtain the lifetime lower limit 71×10³⁰ years. Limits are also reported for neutron decay into ν̄π⁰, and for proton decay into ν̄π⁺.