Search for the Decay B+→K+τ∓μ±

Le résumé fourni par la source

We present a search for the lepton flavor violating decay ${B}^{+}\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\tau}}^{\ensuremath{\mp}}{\ensuremath{\mu}}^{\ifmmode\pm\else\textpm\fi{}}$ using $383\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ events collected by the BABAR experiment. The branching fraction for this decay can be substantially enhanced in new physics models. The kinematics of the tau from the signal $B$ decay are inferred from the ${K}^{+}$, $\ensuremath{\mu}$, and other $B$ in the event, which is fully reconstructed in one of a variety of hadronic decay modes, allowing the signal $B$ candidate to be fully reconstructed. We observe no excess of events over the expected background and set a limit of $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{K}^{+}\ensuremath{\tau}\ensuremath{\mu})<7.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ at 90% confidence level, where the branching fraction is for the sum of the ${K}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}{\ensuremath{\mu}}^{+}$ and ${K}^{+}{\ensuremath{\tau}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ final states. We use this result to improve a model-independent bound on the energy scale of flavor-changing new physics.

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