Search for lepton flavor violating τ− decays with a KS0 meson

We have searched for the lepton flavor violating decays τ−→ℓ−KS0 (ℓ=e or μ), using a data sample of 281 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(τ−→e−KS0)<5.6×10−8 and B(τ−→μ−KS0)<4.9×10−8 at the 90% confidence level. These results improve the previously published limits set by the CLEO Collaboration by factors of 16 and 19, respectively.