Upper limits on branching ratios of the lepton-flavor-violating decays <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>τ</mml:mi><mml:mo stretchy="false">→</mml:mo><mml:mo>ℓ</mml:mo><mml:mi>γ</mml:mi><mml:mi>γ</mml:mi></mml:mrow></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>τ</mml:mi><mml:mo stretchy="false">→</mml:mo><mml:mo>ℓ</mml:mo><mml:mi>X</mml:mi></mml:mrow></mml:math>
D. Bryman, S. Ito, Robert Shrock
Abstract
From analysis of data produced by the BABAR experiment, the first upper bounds (90% C.L.) were obtained on the branching ratios $\mathrm{Br}(\ensuremath{\tau}\ensuremath{\rightarrow}e\ensuremath{\gamma}\ensuremath{\gamma})<2.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ and $\mathrm{Br}(\ensuremath{\tau}\ensuremath{\rightarrow}\ensuremath{\mu}\ensuremath{\gamma}\ensuremath{\gamma})<5.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$. In addition, improved upper bounds (95% C.L.) were found on branching ratios $\mathrm{Br}(\ensuremath{\tau}\ensuremath{\rightarrow}eX)<1.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ and $\mathrm{Br}(\ensuremath{\tau}\ensuremath{\rightarrow}\ensuremath{\mu}X)<\phantom{\rule{0ex}{0ex}}2.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$, where $X$ is an undetected weakly interacting boson with mass ${m}_{X}<1.6\text{ }\text{ }\mathrm{GeV}/{c}^{2}$.