Searching for New Physics with b→sτ^{+}τ^{-} Processes.

In recent years, intriguing hints for the violation of lepton flavor universality (LFU) have been accumulated in semileptonic B decays, both in the charged-current transitions b -> cl(-)(v)over-bar(l) (i.e., R-D, R-D*, and R-J/psi) and the neutral-current transitions b -> sl(+)l(-) (i.e., R-K and R-K* Hints for LFU violation in R-D(*) and R-J/psi point at large deviations from the standard model (SM) in processes involving tau leptons. Moreover, LHCb has reported deviations from the SM expectations in b -> s mu(+)mu(-)processes as well as in the ratios R-K and R-K*, which together point at new physics (NP) affecting muons with a high significance. These hints for NP suggest the possibility of huge LFU-violating effects in b -> s tau(+)tau(-) transitions. In this Letter, we predict the branching ratios of B -> K tau(+)tau(-), B -> K*tau(+)tau(-), and B-s -> phi tau(+)tau(-), taking into account NP effects in the Wilson coefficients C-9(')(tau tau) and C-10(')(tau tau). Assuming a common NP explanation of R-D, R-D(*), and R-J/psi we show that a very large enhancement of b -> s tau(+)tau(-) processes, of around 3 orders of magnitude compared to the SM, can be expected under fairly general assumptions. We find that the branching ratios of B-s -> tau(+)tau(-), B-s -> phi tau(+)tau(-), and B -> K-(*())tau(+)tau(-) under these assumptions are in the observable range for LHCb and Belle II.