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Search for CP Violation in $τ\to ππ^{0}ν_τ$ Decay

We search for CP non-conservation in the decays of tau leptons produced via $e^+ e^-$ annihilation at $\sqrt{s}\sim$ 10.6 GeV. The method uses correlated decays of pairs of tau leptons, each decaying to the $ππ^0 ν_τ$ final state. The search is done within the framework of a model with a scalar boson exchange. In an analysis of a data sample corresponding to 12.2 million produced tau pairs collected with the CLEO detector, we find no evidence of violation of CP symmetry. We obtain a limit on the imaginary part of the coupling constant parameterizing the relative contribution of diagrams that would lead to CP violation to be $-0.046 <\Im(Λ) < 0.022$ at 90% C.L. This result provides a restriction on CP non-conservation in the tau lepton decays. As a cross check, we study the decay angular distribution and perform a model-independent search for a CP violation effect of a scalar exchange in single $τ\to ππ^0ν_τ$ decays. The limit on the imaginary part of the $τ$ scalar coupling is $-0.033 < \Im(Λ) < 0.089$ at 90% C.L.