Search for lepton flavor violating τ decays into three leptons

We search for lepton flavor violating τ decays into three leptons (electron or muon) using 535 fb−1 of data collected with the Belle detector at the KEKB asymmetric-energy e+e−e+e− collider. No evidence for these decays is observed, and we set 90% confidence level upper limits on the branching fractions of (2.0–4.1)×10−8(2.0–4.1)×10−8. These results improve upon our previously published upper limits by factors of 4.9 to 10.