Searches for $B^0\to K^{+}{\pi }^{-}{\tau }^{+}{\tau }^{-}$ and $B_s^0\to K^{+}{K}^{-}{\tau }^{+}{\tau }^{-}$ decays

The first searches for $B^0\to K^{+}{\pi }^{-}{\tau }^{+}{\tau }^{-}$ and $B_s^0\to K^{+}{K}^{-}{\tau }^{+}{\tau }^{-}$ decays at the LHCb experiment are conducted with $pp$ collision data corresponding to an integrated luminosity of $5.4{\text{ fb}}^{-1}$. The tau leptons are reconstructed using the ${\tau }^{+}\to {\mu }^{+}{\bar{\nu }}_{\tau }{\nu }_{\mu }$ decay and the results are presented in bins of $K^{+}{\pi }^{-}$ or $K^{+}{K}^{-}$ mass. No signal is observed and upper limits are set on the branching fractions. The searches result in the first upper limits for $B^0\to K^{+}{\pi }^{-}{\tau }^{+}{\tau }^{-}$ decays outside the $K^{\ast }(892{)}^0$ region in $K^{+}{\pi }^{-}$ mass and the first limits for $B_s^0\to K^{+}{K}^{-}{\tau }^{+}{\tau }^{-}$ decays. The searches are recast into limits on the decays $B^0\to K^{\ast }(892{)}^0{\tau }^{+}{\tau }^{-}$ and $B_s^0\to \phi (1020){\tau }^{+}{\tau }^{-}$, yielding $2.8\times {10}^{-4}$ ($2.5\times {10}^{-4}$) and $4.7\times {10}^{-4}$ ($4.1\times {10}^{-4}$) at the $95\mathrm{\%}$ ($90\mathrm{\%}$) confidence level, respectively. For the decay $B^0\to K^{\ast }(892{)}^0{\tau }^{+}{\tau }^{-}$, this result improves on the current best upper limit by an order of magnitude.