Review of Rare and Forbidden $\tau$ Decays

TL;DR

This review summarizes recent experimental results on rare and forbidden $ au$ lepton decays, including new limits and observations, highlighting ongoing searches for physics beyond the Standard Model.

Contribution

It compiles and discusses the latest experimental bounds and observations on rare and forbidden $ au$ decays, proposing new decay channels for future searches.

Findings

New upper limits on $ au o au ho$ and $ au o au o au$ decays.

Observation of Cabibbo-suppressed $ au o K ar{K} o au$ decay.

Proposals for searches of previously unsearched forbidden decays.

Abstract

This is a review of rare and forbidden decays of the $\tau$ lepton. For the rare decays, this includes new results on the chiral anomaly decay $\taupietapio$, new upper limits on the second-class-current decay $\taupieta$, and the observations of the Cabibbo-suppressed decay $\tauketa$ and the internal conversion decay $\taueee$. For the forbidden decays, there are new upper limits on the radiative decays $\tauegamma$ and $\taumugamma$. Some forbidden decays which have not been previously searched for are also suggested.