Search for Lepton-Flavor Violation in Narrow $\Upsilon$ Resonance Decays

Charged lepton-flavor violating processes are extremely rare in the Standard Model, but they are predicted to occur in several beyond-the-Standard Model theories, including Supersymmetry or models with leptoquarks or compositeness. We present searches for such processes in narrow $\Upsilon$ resonance decays. From a sample of 117 million $\Upsilon(3S)$ decays recorded with the {\it B{\footnotesize A}B{\footnotesize AR}} detector, we place upper limits on the branching fractions ${\cal B}(\Upsilon(3S) \rightarrow e \tau) < 5.0\times 10^{-6}$ and ${\cal B}(\Upsilon(3S) \rightarrow \mu \tau) < 4.1\times 10^{-6}$ at 90\% confidence level. These results are used to place lower limits on the mass scale of beyond-the-Standard Model physics contributing to lepton-flavor violating decays of the $\Upsilon(3S)$.