Searches for B ⁰ →k ⁺π ^-τ ⁺τ ^- and B _s ⁰ →k ⁺K ^-τ ⁺τ ^- Decays

The first searches for B0→K+π-τ+τ- and Bs0→K+K-τ+τ- decays at the LHCb experiment are conducted with pp collision data corresponding to an integrated luminosity of 5.4 fb-1. The tau leptons are reconstructed using the τ+→μ+ν¯τνμ decay and the results are presented in bins of K+π- 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 B0→K+π-τ+τ- decays outside the K∗(892)0 region in K+π- mass and the first limits for Bs0→K+K-τ+τ- decays. The searches are recast into limits on the decays B0→K∗(892)0τ+τ- and Bs0→φ(1020)τ+τ-, yielding 2.8×10-4 (2.5×10-4) and 4.7×10-4 (4.1×10-4) at the 95% (90%) confidence level, respectively. For the decay B0→K∗(892)0τ+τ-, this result improves on the current best upper limit by an order of magnitude.