Search for the Decay<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>B</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:mo>→</mml:mo><mml:msup><mml:mi>K</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>τ</mml:mi><mml:mo>∓</mml:mo></mml:msup><mml:msup><mml:mi>μ</mml:mi><mml:mo>±</mml:mo></mml:msup></mml:math>

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.

Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.