Semi-leptonic $B$-physics anomalies: a general EFT analysis within $U(2)^n$ flavor symmetry

Understand

We analyse the recent hints of Lepton Flavor Universality violations in semi-leptonic $B$ decays within a general EFT based on a $U(2)^n$ flavor symmetry acting on the light generations of SM fermions.

• We analyse in particular the consistency of these anomalies with the tight constraints on various low-energy observables in $B$ and $\tau$ physics.
• We show that, with a moderate fine-tuning, a consistent picture for all low-energy observables can be obtained under the additional dynamical assumption that the NP sector is coupled preferentially to third generation SM fermions.
• We discuss how this dynamical assumption can be implemented in general terms within the EFT, and we identify a series of observables in $\tau$ decays which could provide further evidences of this NP framework.