Full angular spectrum analysis of tensor current contribution to $A_{cp}(\tau \rightarrow K_{s} \pi \nu_{\tau})$

TL;DR

This paper investigates the potential tensor current contribution to the CP asymmetry in tau decay, analyzing the angular spectrum to explain the Babar collaboration's observed sign anomaly, and fits the new physics coupling to experimental data.

Contribution

It provides a comprehensive angular spectrum analysis of tensor current effects on CP asymmetry in tau decay, fitting the NP coupling to experimental results within 1 sigma.

Findings

Tensor current can account for the sign anomaly in CP asymmetry.

The imaginary part of the NP tensor coupling fits experimental data within 1 sigma.

Analysis supports tensor current as a possible source of new physics in tau decay.

Abstract

Babar collaboration has reported an intriguing opposite sign in the integrated decay rate asymmetry $A_{cp}(\tau \rightarrow K_{s} \pi \nu_{\tau})$ than that of SM prediction from the known $K^{0}$ - $\bar{K^{0}}$ mixing. Babar's result deviate from the SM prediction by about 2.7$\sigma$. If the result stands with higher precision in the future experiments, the observed sign anomaly in the $A_{cp}(\tau \rightarrow K_{s} \pi \nu_{\tau})$ can most likely come only from a NP. In this work we present a full angular spectrum analysis on the contribution to $A_{cp}(\tau \rightarrow K_{s} \pi \nu_{\tau})$ coming from the tensorial term. Assuming the real part of the NP tensorial coupling is negligible compare to its imaginary part and with $A_{cp}(\tau \rightarrow K_{s} \pi \nu_{\tau})$ and $Br(\tau \rightarrow K_{s} \pi \nu_{\tau})$ as data points to fit the imaginary part of the NP coupling, we have been able to fit the result within 1$\sigma$ of the experimental values.