Search for CP violation in tau -> K^0_S pi nu_tau decays at Belle
  We report on a search for CP violation in tau -> K^0_S pi nu_tau decays using a data sample of 699 fb^{-1} collected in the Belle experiment at the KEKB electron-positron asymmetric-energy collider. The CP asymmetry is measured in four bins of the invariant mass of the K^0_S pi system and found to be compatible with zero with a precision of O(10^{-3}) in each mass bin. Limits for the CP violation parameter Im(eta_S) are given at a 90 % confidence level. These limits are |Im(eta_S)|<0.026 or better, depending on the parameterization used to describe the hadronic form factors and improve upon previous limits by one order of magnitude. 
M. Bischofberger, H. Hayashii, K. Adamczyk, H. Aihara, V. Aulchenko,   A. M. Bakich, V. Balagura, E. Barberio, K. Belous, A....
hep-ex