On the recent anomalies in semileptonic B decays

Both BABAR and LHCb Collaborations have recently claimed signals of pos- sible deviations with respect to the Standard Model through the analyses of specific semileptonic B-meson decays. We firstly investigate the semileptonic b → c decay with a τ lepton in the final state for which new BABAR measurements are available, showing a deviation from the Standard Model at 3.4 σ level. We study the effects of a new ten- sor operator in the effective weak Hamiltonian on a set of observables, in semileptonic B → D (∗) modes as well as in semileptonic B and Bs decays to excited charmed mesons. Moreover, we discuss the phenomenology of the mode B → K ∗ � + � − , in the framework of a warped extra-dimensional model. Since a complete set of form factor almost in- dependent observables have been recently measured by the LHCb Collaboration, with few sizable deviations with respect to the Standard Model in some of them, it would be interesting to put constraints on such a scenario from the FCNC transition b → s� + � − . 1 Semileptonic B-meson decays with a τ lepton in the final states