Mono-τ Signatures at the LHC Constrain Explanations of B-decay Anomalies.

We investigate the crossing-symmetry relation between b→cτ^{-}ν[over ¯] decay and bc[over ¯]→τ^{-}ν[over ¯] scattering to derive direct correlations of new physics in semitauonic B-meson decays and the mono-tau signature at the LHC (pp→τ_{h}X+MET). Using an exhaustive set of effective operators and heavy mediators we find that the current ATLAS and CMS data constrain scenarios addressing anomalies in B decays. Pure tensor solutions, completed by leptoquark, and right-handed solutions, completed by W_{R}^{'} or leptoquark, are challenged by our analysis. Furthermore, the sensitivity that will be achieved in the high-luminosity phase of the LHC will probe all the possible scenarios that explain the anomalies. Finally, we note that the LHC is also competitive in the b→u transitions and bounds in some cases are currently better than those from B decays.

Lifetime of B_{c}

We investigate a new constraint on new-physics interpretations of the anomalies observed in B→D^{(*)}τν decays making use of the lifetime of the B_{c}^{-} meson. A constraint is obtained by demanding that the rate for B_{c}^{-}→τ^{-}ν[over ¯] does not exceed the fraction of the total width that is allowed by the calculation of the lifetime in the standard model. This leads to a very strong bound on new-physics scenarios involving scalar operators since they lift the slight, but not negligible, chiral suppression of the B_{c}^{-}→τ^{-}ν[over ¯] amplitude in the standard model. The new constraint renders a scalar interpretation of the enhancement measured in R_{D^{*}} implausible, including explanations implementing extra Higgs doublets or certain classes of leptoquarks. We also discuss the complementarity of R_{D^{(*)}} and a measurement of the longitudinal polarization of the τ in the B→D^{*}τν decay in light of our findings.

Nonstandard semileptonic hyperon decays.

We investigate the discovery potential of semileptonic hyperon decays in terms of searches of new physics at teraelectronvolt scales. These decays are controlled by a small SU(3)-flavor breaking parameter that allows for systematic expansions and accurate predictions in terms of a reduced dependence on hadronic form factors. We find that muonic modes are very sensitive to nonstandard scalar and tensor contributions and demonstrate that these could provide a powerful synergy with direct searches of new physics at the LHC.