Experimental upper limits on branching fractions for unexpected decay modes of theτlepton
Citations Over TimeTop 12% of 1982 papers
Abstract
Searches for 12 neutrinoless decay modes of the $\ensuremath{\tau}$ which violate lepton-number conservation have been made using the reaction ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$. No evidence for lepton-number violation is observed, and we have set upper limits (90% C.L.) on the branching ratio for each decay mode. The branching-ratio limits on the radiative decays $\ensuremath{\tau}\ensuremath{\rightarrow}\ensuremath{\mu}\ensuremath{\gamma}$ and $\ensuremath{\tau}\ensuremath{\rightarrow}e\ensuremath{\gamma}$ are 0.055 and 0.064%, respectively. For the charged lepton decays $\ensuremath{\tau}\ensuremath{\rightarrow}\mathrm{eee}$, $\ensuremath{\tau}\ensuremath{\rightarrow}e\ensuremath{\mu}\ensuremath{\mu}$, $\ensuremath{\tau}\ensuremath{\rightarrow}\ensuremath{\mu}\mathrm{ee}$, and $\ensuremath{\tau}\ensuremath{\rightarrow}\ensuremath{\mu}\ensuremath{\mu}\ensuremath{\mu}$, the branching ratio limits are 0.040, 0.033, 0.044, and 0.049%, respectively. Upper limits on the branching ratios for the following charged lepton + neutral hadron decays are $\ensuremath{\tau}\ensuremath{\rightarrow}e{\ensuremath{\rho}}^{0} (0.037%)$, $\ensuremath{\tau}\ensuremath{\rightarrow}\ensuremath{\mu}{\ensuremath{\rho}}^{0} (0.044%)$, $\ensuremath{\tau}\ensuremath{\rightarrow}e{K}^{0} (0.13%)$, $\ensuremath{\tau}\ensuremath{\rightarrow}\ensuremath{\mu}{K}^{0} (0.10%)$, $\ensuremath{\tau}\ensuremath{\rightarrow}e{\ensuremath{\pi}}^{0} (0.21%)$, and $\ensuremath{\tau}\ensuremath{\rightarrow}\ensuremath{\mu}{\ensuremath{\pi}}^{0} (0.082%)$. We also use these data to search for the pair production in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation of some unconventional particles with masses less than about 3 GeV/${\mathit{c}}^{2}$.