New Predictions for Λ_{b}→Λ_{c} Semileptonic Decays and Tests of Heavy Quark Symmetry.

The heavy quark effective theory makes model independent predictions for semileptonic Λ_{b}→Λ_{c} decays in terms of a small set of parameters. No subleading Isgur-Wise function occurs at order Λ_{QCD}/m_{c,b}, and only two subsubleading functions enter at order Λ_{QCD}^{2}/m_{c}^{2}. These features allow us to fit the form factors and decay rates calculated up to order Λ_{QCD}^{2}/m_{c}^{2} to LHCb data and lattice QCD calculations. We derive a significantly more precise standard model prediction for the ratio B(Λ_{b}→Λ_{c}τν[over ¯])/B(Λ_{b}→Λ_{c}µν[over ¯]) than prior results, and find the expansion in Λ_{QCD}/m_{c} well behaved, addressing a long-standing question. Our results allow more precise and reliable calculations of Λ_{b}→Λ_{c}ℓν[over ¯] rates, and are systematically improvable with better data on the µ (or e) modes.

Disentangling Mass and Mixing Hierarchies.

We present a fully perturbative mechanism that naturally generates mass hierarchies for the standard model (SM) fermions in a flavor-blind sector. The dynamics generating the mass hierarchies can therefore be independent from the source of flavor violation, and hence this dynamics may operate at a much lower scale. This mechanism works by dynamically enforcing simultaneous diagonalization--alignment--among a set of flavor-breaking spurions, as well as generating highly singular spectra for them. It also has general applications in model building beyond the SM, wherever alignment between exotic and SM sources of flavor violation is desired.

Towards More Precise Determinations of the Quark Mixing Phase ß.

We derive a new flavor symmetry relation for the determination of the weak phase ß=ϕ_{1} from time-dependent CP asymmetries and B→J/ψP decay rates. In this relation, the contributions to sin2ß proportional to V_{ub} are parametrically suppressed compared to the contributions in the B→J/ψK^{0} time-dependent CP asymmetry alone. This relation uses only SU(3) flavor symmetry, and does not require further diagrammatic assumptions. The current data either fluctuate at the 2σ level from expectations, or may hint at effects of unexpected magnitude from contributions proportional to V_{ub} or from isospin breaking.