Mikhail Shapkin (IHEP)
The tau lepton lifetime is measured using the process e^+ e^- --> tau^+ tau^-, where both tau leptons decay to 3 pi nu. An upper limit on the relative lifetime difference between positive and negative tau-leptons is given. The obtained results are based on a large data sample collected on the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^+e^- collider. We also present the results of a search for CP violation in tau --> nu K_S pi. CP violation in semileptonic tau decays is generally forbidden in the Standard Model but can be induced by the exchange of an exotic scalar such as a charged Higgs in supersymmetric models. Exploiting the large statistics of the Belle data set, we report a model-independent limit for CP violation as well as a significantly improved measurement of the CP violation parameters for specific parameterizations of the hadronic structure functions.
Collaboration BELLE (KEK)