Rare decays of the tau lepton as a probe of the left-right-symmetric theories of weak interactions.

Abstract

We consider the flavor-changing rare decays of the $\ensuremath{\tau}$ lepton as a probe on the left-right-symmetric theories of weak interactions manifesting at the TeV energy scale. We find the branching ratios for the rare decays such as $\ensuremath{\tau}\ensuremath{\rightarrow}3\ensuremath{\mu}$ and $\ensuremath{\tau}\ensuremath{\rightarrow}\ensuremath{\mu}\mathrm{ee}$, etc., as large as ${10}^{\ensuremath{-}5}$ and those for the radiative decays such as $\ensuremath{\tau}\ensuremath{\rightarrow}\ensuremath{\mu}\ensuremath{\gamma}$ and $\ensuremath{\tau}\ensuremath{\rightarrow}e\ensuremath{\gamma}$ as large as 4 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}6}$, consistent with the existing bounds on the model if the neutrino is a Majorana fermion with its small mass accounted for by the seesaw mechanism. On the other hand, for the case of Dirac neutrinos with a small ${m}_{\ensuremath{\nu}}$ accounted for by the loop mechanism, these rare decay modes are suppressed to the level of ${10}^{\ensuremath{-}10}$ or less.