Flavour predictions in the Standard Model and beyond

This thesis reports on two projects concerning flavour physics. In the first project it is shown how approximate Minimal Flavour Violation (MFV) can emerge from an SU(5) Supersymmetric Grand Unified Theory (SUSY GUT) supplemented by an S4 x U(1) family symmetry, which provides a good description of all quark and lepton (including neutrino) masses, mixings and CP violation. Assuming a SUSY breaking mechanism which respects the family symmetry, the low energy mass insertion parameters are calculated in full explicit detail in the super-CKM basis, including the effects of canonical normalisation and renormalisation group running. It is found that the very simple family symmetry S4 x U(1) is sufficient to approximately reproduce the effects of low energy MFV where required but there is also a suggestion of testable new physics. Numerical estimates of the low energy mass insertion parameters are presented for well-defined ranges of SUSY parameters and the naive model expectations are compared to the numerical scans and the experimental bounds. The results are then used to estimate the predictions for Electric Dipole Moments (EDMs), Lepton Flavour Violation (LFV), B and K meson mixing as well as rare B decays. The largest observable deviations from MFV come from the LFV process μ → eγ and the EDMs. In the second project, matrix elements of the chromomagnetic operator, often denoted by O 8 , between B/D-states and light mesons plus an off-shell photon are calculated, by employing the method of light-cone sum rules (LCSR) at leading twist 2. These matrix elements are relevant for flavour changing transition processes, such as B → K*l+l- and they can be seen as the analogues of the well-known penguin form factors T 1;2;3 and f T . A large CP-even phase is found, for which a long-distance (LD) interpretation is given. Results are compared to QCD factorisation (QCDF), for which the spectator photon emission is end-point divergent. The analytic structure of the correlation function used in the LCSR method, admits a complex anomalous threshold on the physical sheet, the meaning and handling of which is discussed.