Experimental review of τ lepton studies at the B factories

Recent results of a high-statistics τ lepton studies at B factories are reported. Reviewed are the measurements of Michel parameters in leptonic and radiative leptonic τ decays at Belle, as well as the measurement of the branching fractions of the radiative leptonic τ decays at BABAR. Searches for CP symmetry violation in hadronic decays with $ \mathop K\nolimits_S^0 $ are also briefly discussed.

On spin asymmetry in muon and tau decays

The angular asymmetry in decays of polarized muons and tau leptons is discussed. Both the standard [Formula: see text] Fermi model and the general parametrization via Michel parameters are considered. Numerical importance of contributions suppressed by charged lepton mass ratio is underlined. Contribution of the second order QED correction is estimated in the leading logarithm approximation.

Study of the Lorentz Structure of the Charged Weak Interaction in Tau Decays at Belle

To test the Lorentz structure of the charged weak interaction, we study leptonic decays of tau lepton in the Belle experiment. We perform this test through the measurement of Michel parameters which appear in the differential decay widths of leptonic tau decays. In this paper, we discuss the preliminary results of the measurement of Michel parameters at Belle.