Upper limits on branching ratios of the lepton-flavor-violating decays $\tau \to \ell \gamma \gamma$ and $\tau \to \ell X$

Abstract

From analysis of data produced by the BABAR experiment, the first upper bounds (90% C.L.) were obtained on the branching ratios $Br(\tau \to e\gamma \gamma )<2.5\times 10^{-4}$ and $Br(\tau \to \mu \gamma \gamma )<5.8\times 10^{-4}$. In addition, improved upper bounds (95% C.L.) were found on branching ratios $Br(\tau \to eX)<1.4\times 10^{-3}$ and $Br(\tau \to \mu X)<2.0\times 10^{-3}$, where $X$ is an undetected weakly interacting boson with mass $m_X<1.6$ GeV/$c^2$.

Comments: 8 pages, 2 figures