2,710 research outputs found
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
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