We have searched for tau lepton decays, tau- -> Lambda-bar pi- and tau- -> Lambda pi-, that simultaneously violate the conservation of the lepton and baryon number using a data sample of 154 fb^{ -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(tau^- -> Lambda-bar\pi-) < 1.4 * 10^{ -7} and B(tau^- -> Lambda pi^-) < 0.72 * 10^{ -7} at the 90% confidence level. This is the first search ever performed for these modes.
Categories: hep-ex