Search for the decays $B_s^0\to\tau^+\tau^-$ and $B^0\to\tau^+\tau^-$

Understand

A search for the rare decays $B_s^0\to\tau^+\tau^-$ and $B^0\to\tau^+\tau^-$ is performed using proton--proton collision data collected with the LHCb detector.

• The data sample corresponds to an integrated luminosity of 3fb$^{-1}$ collected in 2011 and 2012.
• The $\tau$ leptons are reconstructed through the decay $\tau^-\to\pi^-\pi^+\pi^-\nu_{\tau}$.
• Assuming no contribution from $B^0\to\tau^+\tau^-$ decays, an upper limit is set on the branching fraction $\mathcal{B}(B_s^0\to\tau^+\tau^-) < 6.8\times 10^{-3}$ at 95% confidence level.