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

TL;DR

This paper investigates whether non-standard tensor interactions could explain the observed CP asymmetry in tau decays, which deviates from Standard Model predictions, by analyzing experimental data and theoretical models.

Contribution

It demonstrates that tensor interactions, unlike scalar ones, can produce the observed CP asymmetry in tau decays and constrains their parameters based on experimental results.

Findings

Tensor interactions can generate the observed CP asymmetry.

Scalar interactions cannot account for the asymmetry.

Constraints on tensor coupling and phase are derived from data.

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.