Can the observed CP asymmetry in tau --> K pi nu_tau be due to Non-Standard Tensor interactions?

Abstract

An intriguing opposite sign of the CP violating asymmetry was recently measured in the tau decay modes tau -> Ks pi nutau by the BaBar collaboration, than that expected within the Standard Model. If this result is confirmed with higher precision, the observed decay rate asymmetry ACP, can only arise from some Non-Standard Interactions(NSI) occurring possibly in both the hadronic as well as in the leptonic sectors. We illustrate that while a simple charged scalar interaction cannot yield this rate asymmetry, it will be possible to generate this in the presence of a tensor interaction. Parameterizing the strength and weak phase of this NSI contribution, the observed branching ratio and the decay rate CP asymmetry for the particular mode tau -> Ks pi nutau, are used to determine the CP violating weak phase and the coupling of a tensorial interaction that can give a consistent sign and magnitude of the asymmetry.

18 pages, 8 figures; Major modifications in section V, including new clean relations for the observed asymmetry as well as the branching ratio, in terms of the indirect CPV from neutral K meson mixing and the direct CPV in the tau decay (appearing in the presence of the new tensor interaction). Version accepted in PRD

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• What can be learned from the Belle spectrum for the decay tau- -> nu_tau K_S pi-
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• Search for CP Violation in the Decay tau- -> pi- K^0_S (>= 0 pi0) nu_tau
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• $CP$ asymmetry in the angular distribution of $\tau \to K_S\pi {\nu }_{\tau }$ decays
• $CP$ asymmetry in the angular distributions of $\tau \to K_S\pi {\nu }_{\tau }$ decays -- II: general effective field theory analysis
• Feasibility study of $CP$ Violation in ${\tau }^{-}\to K_S{\pi }^{-}{\nu }_{\tau }$ decays at Super Tau Charm Facility
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