Abstract: We present here two concrete examples of models where a sub-TeV scale breaking of their respective T-13 and A(5) flavor symmetries is able to account for the recently observed discrepancy in the muon anomalous magnetic moment, (g – 2)(mu). Similarities in the flavor structures of the charged-lepton Yukawa matrix and dipole matrix yielding (g – 2)(mu) give rise to strong constraints on low-scale flavor models when bounds from lepton flavor violation (LFV) are imposed. These constraints place stringent limits on the off- diagonal Yukawa structure, suggesting a mostly (quasi)diagonal texture for models with a low flavor breaking scale A(f). We argue that many of the popular flavor models in the literature designed to explain the fermion masses and mixings are not suitable for reproducing the observed discrepancy in (g – 2)(mu), which requires a delicate balance of maintaining a low flavor scale while simultaneously satisfying strong LFV constraints.

Abstract: We present a precise lattice computation of pseudoscalar and vector heavy-light meson masses for heavy-quark masses ranging from the physical charm mass up to similar or equal to 4 times the physical b-quark mass. We employ the gauge configurations generated by the European Twisted Mass Collaboration (ETMC) with N-f = 2 + 1 + 1 dynamical quarks at three values of the lattice spacing (a similar or equal to 0.062; 0.082; 0.089 fm) with pion masses in the range M-pi similar or equal to 210-450 MeV. The heavy-quark mass is simulated directly on the lattice up to similar or equal to 3 times the physical charm mass. The interpolation to the physical b-quark mass is performed using the ETMC ratio method, based on ratios of the meson masses computed at nearby heavy-quark masses, and adopting the kinetic mass scheme. The extrapolation to the physical pion mass and to the continuum limit yields m(b)(kin) (1 GeV) = 4.61(20) GeV, which corresponds to (m) over bar (b) ((m) over bar (b)) 4.26(18) GeV in the (MS) over bar scheme. The lattice data are analyzed in terms of the heavy-quark expansion (HQE) and the matrix elements of dimension-four and dimension-five operators are extracted with a good precision, namely,(Lambda) over bar = 0.552(26) GeV, mu(2)(pi) = 0.321(32) GeV2, and mu(2)(G)(m(b)) = 0.253(25) GeV2. The data also allow for a rough estimate of the dimension-six operator matrix elements. As the HQE parameters play a crucial role in the inclusive determination of the Cabibbo-Kobayashi-Maskawa matrix elements V-ub and V-cb, their precise determination on the lattice may eventually validate and improve the analyses based on fits to the semileptonic moments.

Abstract: The confirmation of the discrepancy with the Standard Model predictions in the anomalous magnetic moment by theMuon g-2 experiment at Fermilab points to a low scale of new physics. Flavour symmetries broken at low energies can account for this discrepancy but these models are much more restricted, as they would also generate offdiagonal entries in the dipole moment matrix. Therefore, if we assume that the observed discrepancy in the muon g – 2 is explained by the contributions of a low-energy flavor symmetry, lepton flavour violating processes can constrain the structure of the lepton mass matrices and therefore the flavour symmetries themselves predicting these structures. We apply these ideas to several discrete flavour symmetries popular in the leptonic sector, such as Delta(27), A(4), and A(5) proportional to CP.