On the leptonic decays of the $τ$

In view of potential future improvements in the branching fractions of leptonic $τ$ decays $τ\to\ellν_τ\barν_\ell$, $\ell=e,μ$, it is timely to derive the corresponding Standard-Model predictions beyond next-to-leading order. We provide such benchmark values for the fully inclusive decay widths, pro