Search for Lepton Flavor Violating Decays $\tau^\pm \to \ell^\pm{\pi^0},   \ell^\pm\eta, \ell^\pm{\eta^\prime}$
  A search for lepton flavor violating decays of the $\tau$ lepton to a lighter mass lepton and a pseudoscalar meson has been performed using 339 fb$^{-1}$ of $e^+e^-$ annihilation data collected at a center-of-mass energy near 10.58 GeV by the BaBar detector at the SLAC PEP-II storage ring. No evidence of signal has been found, and upper limits on the branching fractions are set at $10^{-7}$ level. 
The BABAR Collaboration, B. Aubert, et al