Search for Lepton-Flavor-Violating and Lepton-Number-Violating tau to   lhh' Decay Modes
  We search for lepton-flavor-violating and lepton-number-violating tau decays into a lepton (l = electron or muon) and two charged mesons (h, h' = pion or Kaon) using 854 fb^{-1} of data collected with the Belle detector at the KEKB asymmetric-energy e^+e^- collider. We obtain 90% confidence level upper limits on the tau to lhh' branching fractions in the range (2.0-8.4)*10^{-8}. These results improve upon our previously published upper limits by factors of about 1.8 on average. 
Y. Miyazaki, I. Adachi, H. Aihara, D. M. Asner, V. Aulchenko, T.   Aushev, A. M. Bakich, A. Bay, V. Bhardwaj, B. Bhuyan, M. ...
hep-ex