Search for lepton and baryon number violating τ− decays into Λ¯π− and Λπ−

We have searched for τ lepton decays, τ−→Λ¯π− and τ−→Λπ−, that simultaneously violate the conservation of the lepton (L) and baryon (B) number using a data sample of 154fb−1 collected with the Belle detector at the KEKB e+e− asymmetric-energy collider. No evidence for a signal was found in either of the decay modes and we set the following upper limits for the branching fractions: B(τ−→Λ¯π−)<1.4×10−7 and B(τ−→Λπ−)<0.72×10−7 at the 90% confidence level. This is the first search ever performed for these modes.