The B -- TAU FCNC connection in SUSY Unified Theories

In the context of SUSY grand unification a link is established between the hadronic and leptonic soft breaking sectors. Such relation is here exploited in particular for FCNC processes in B physics. It is shown how bounds on leptonic FCNC involving the third generation translate into constraints on FC B decays. In the second part of the contribution we show that tests of lepton universality in K and B decays can represent an interesting handle to obtain relevant information on the amount of FCNC in the second and third fermion generation.Comment: 9 pages, 4 figures. Based on talks given at: DIF06, International Workshop on discoveries in flavour physics at e+e- colloders, Laboratori Nazionali di Frascati (Italy), February 28- March 03, 2006; XLIst Rencontres de Moriond, La Thuile, 5-11 March 2006; CORFU2005, Corfu Summer Institute on EPP, Corfu, Greece, September 4-26, 200

Higgs-Mediated e -> mu transitions in II Higgs doublet Model and Supersymmetry

We study the phenomenology of the e-mu lepton flavour violation (LFV) in a general two Higgs Doublet Model (2HDM) including the supersymmetric case. We compute the decay rate expressions of mu -> e gamma, mu -> eee, and mu -> e conversion in nuclei at two loop level. In particular, it is shown that mu -> e gamma is generally the most sensitive channel to probe Higgs-mediated LFV. The correlations among the decay rates of the above processes are also discussed.Comment: v2=published version: 16 pages, 2 figures. Discussions and references added. Results and conclusions unchange

The SUSY CP Problem and the MFV Principle

We address the SUSY CP problem in the framework of Minimal Flavor Violation (MFV), where the SUSY flavor problem finds a natural solution. By contrast, the MFV principle does not solve the SUSY CP problem as it allows for the presence of new {\it flavor blind} CP-violating phases. Then, we generalize the MFV ansatz accounting for a natural solution of it. The phenomenological implications of the generalized MFV ansatz are explored for MFV scenarios defined both at the electroweak (EW) and at the GUT scales.Comment: 8 pages, 6 figures. V2: one comment added, published version in PL

Revisiting Lepton Flavour Universality in B Decays

Lepton flavour universality (LFU) in B-decays is revisited by considering a class of semileptonic operators defined at a scale Lambda above the electroweak scale v. The importance of quantum effects, so far neglected in the literature, is emphasised. We construct the low-energy effective Lagrangian taking into account the running effects from Lambda down to v through the one-loop renormalization group equations (RGE) in the limit of exact electroweak symmetry and QED RGEs from v down to the 1 GeV scale. The most important quantum effects turn out to be the modification of the leptonic couplings of the vector boson Z and the generation of a purely leptonic effective Lagrangian. Large LFU breaking effects in Z and tau decays and visible lepton flavour violating (LFV) effects in the processes tau -> mu ll, tau -> mu rho, tau -> mu pi and tau -> mu eta^(') are induced.Comment: 5 pages, 2 figures. V2: Minor text improvements. Published PRL versio

On the Importance of Electroweak Corrections for B Anomalies

The growing experimental indication of Lepton Flavour Universality Violation (LFUV) both in charged- and neutral-current semileptonic B-decays, has triggered many theoretical interpretations of such non-standard phenomena. Focusing on popular scenarios where the explanation of these anomalies requires New Physics at the TeV scale, we emphasise the importance of including electroweak corrections to obtain trustable predictions for the models in question. We find that the most important quantum effects are the modifications of the leptonic couplings of the W and Z vector bosons and the generation of a purely leptonic effective Lagrangian. As a result, the tight experimental bounds on Z-pole observables and tau decays challenge an explanation of the current non-standard data. We illustrate how these effects arise, by providing a detailed discussion of the running and matching procedure which is necessary to derive the low-energy effective Lagrangian.Comment: 38 pages, 7 figures. V2: Text improvments. Published versio

Higgs--mediated K -> pi nu nu-bar in the MSSM at large tan(beta)

We analyze the impact of Higgs-mediated amplitudes on the rare decays KL -> pi0 nu nu-bar and K+ -> pi+ nu nu-bar in the MSSM with large tan(beta) and general flavour mixing. We point out that, going beyond the minimal flavour violation hypothesis, Z-penguin amplitudes generated by charged-Higgs exchange can induce sizable modifications of K -> pi nu nu-bar rates. Interestingly, these effects scale as tan^4(beta) at the amplitude level. For large values of tan(beta), this mechanism allows deviations from the SM expectations even for tiny (CKM-type) off-diagonal mixing terms in the right-handed squark sector.Comment: 9 pages, 2 figure