Towards the (Mexican) discovery of second class currents at Belle-II

TL;DR

This paper discusses the potential to discover second class current decays involving tau leptons at Belle-II, highlighting Mexican contributions and predicting branching ratios within experimental reach.

Contribution

It provides QCD-based predictions for tau decay branching ratios involving eta and eta prime mesons, emphasizing Mexican involvement in the Belle-II experiment.

Findings

Predicted branching ratio for tau decay with eta meson is ~1.7×10^{-5}.

Decay with eta prime meson is predicted to be one to two orders of magnitude more suppressed.

The predicted decay rates are within Belle-II's detection capabilities.

Abstract

Within the SM, the yet unmeasured $\tau^-\to\pi^-\eta^{(\prime)}\nu_\tau$ decays are predicted as a suppressed, isospin-violating effect with branching ratios $\lesssim\mathcal{O}(10^{-5})$. However, they can also proceed through other mechanisms (such as charged Higgs exchange) at comparable rates. This has motivated several studies of the corresponding QCD predictions for these second class current processes. In this contribution we discuss the prospects for the discovery of these decays at Belle-II emphasizing the Mexican involvement in this project. Our branching ratio prediction $\sim1.7\cdot10^{-5}$ (decay channel with an $\eta$ meson) is well within the reach of Belle-II. The branching fraction for the decay channel with an $\eta^\prime$ meson is expected to be between one and two orders of magnitude more suppressed.