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We present a three-site Pati-Salam gauge model able to explain the Standard Model flavor hierarchies while, at the same time, accommodating the recent experimental hints of lepton-flavor non-universality in B decays. The model is consistent with low-and high-energy bounds, and predicts a rich spectrum of new states at the TeV scale that could be probed in the near future by the high-pT experiments at the LHC.

The three-site Pati-Salam gauge model provides a consistent description for the hints of lepton-flavor non-universality observed in B decays, connecting the present pattern of "anomalies" to the origin of the Standard Model Yukawa couplings. We present here a detailed analysis of the model predictions for a series of low-energy observables, mainly in B and τ physics. The model is in good agreement with present data and predicts a well-defined pattern of non-standard effects in lowenergy observables that could allow us to test it in the near future. Particularly interesting are the predictions of large τ → µ Lepton Flavor Violating processes, such as τ → µγ, τ → 3µ, B → Kτ µ, and B s → τ µ. Also µ → 3e, µ → eγ, and K L → µe decays could be not far from the present exclusion bounds, although this conclusion is more model dependent.

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We carry out a comprehensive analysis of the full set ofBq → D ( * ) q form factors for spectator quarks q = u, d, s within the framework of the Heavy-Quark Expansion (HQE) to order O αs, 1/m b , 1/m 2 c . In addition to the available lattice QCD calculations we make use of two new sets of theoretical constraints: we produce for the first time numerical predictions for the full set ofBs → D ( * ) s form factors using Light-Cone Sum Rules with Bs-meson distribution amplitudes. Furthermore, we reassess the QCD three-point sum rule results for the Isgur-Wise functions entering all our form factors for both q = u, d and q = s spectator quarks. These additional constraints allow us to go beyond the commonly used assumption of SU (3)F symmetry for theBs → D ( * ) s form factors, especially in the unitarity constraints which we impose throughout our analysis. We find the coefficients of the IW functions emerging at O 1/m 2 c to be consistent with the naive O (1) expectation, indicating a good convergence of the HQE. While we do not find significant SU (3) breaking, the explicit treatment of q = s as compared to a simple symmetry assumption renders the unitarity constraints more effective. We find that the (pseudo)scalar bounds are saturated to a large degree, which affects our theory predictions. We analyze the phenomenological consequences of our improved form factors by extracting |V cb | fromB → D ( * ) ν decays and producing theoretical predictions for the lepton-flavour universality ratios R(D), R(D * ), R(Ds) and R(D * s ), as well as the τ -and D * q polarization fractions for theBq → D ( * ) q τ ν modes.