Search for lepton flavor violating decays τ−→τ−→ℓ−π0,ℓ−η,ℓ−η′ℓ−π0,ℓ−η,ℓ−η′

We have searched for lepton flavor violating semileptonic τ−τ− decays using a data sample of 153.8 fb−1 accumulated with the Belle detector at the KEKB e+e−e+e− collider. For the six decay modes studied, the observed yield is compatible with the estimated background and the following upper limits are set at the 90% confidence level: B(τ−→e−η)<2.3×10−7B(τ−→e−η)<2.3×10−7, B(τ−→μ−η)<1.5×10−7B(τ−→μ−η)<1.5×10−7, B(τ−→e−π0)<1.9×10−7B(τ−→e−π0)<1.9×10−7, B(τ−→μ−π0)<4.1×10−7B(τ−→μ−π0)<4.1×10−7, B(τ−→e−η′)<10×10−7B(τ−→e−η′)<10×10−7, and B(τ−→μ−η′)<4.7×10−7B(τ−→μ−η′)<4.7×10−7. These results are 10 to 64 times more restrictive than previous limits.