2,491 research outputs found
Invariant approach to flavour-dependent CP-violating phases in the MSSM
We use a new weak basis invariant approach to classify all the observable
phases in any extension of the Standard Model (SM). We apply this formalism to
determine the invariant CP phases in a simplified version of the Minimal
Supersymmetric SM with only three non-trivial flavour structures. We propose
four experimental measures to fix completely all the observable phases in the
model. After these phases have been determined from experiment, we are able to
make predictions on any other CP-violating observable in the theory, much in
the same way as in the Standard Model all CP-violation observables are
proportional to the Jarlskog invariant.Comment: 25 pages, 12 figure
Bifurcations in the Lozi map
We study the presence in the Lozi map of a type of abrupt order-to-order and
order-to-chaos transitions which are mediated by an attractor made of a
continuum of neutrally stable limit cycles, all with the same period.Comment: 17 pages, 12 figure
Flavour Changing Higgs Couplings in a Class of Two Higgs Doublet Models
We analyse various flavour changing processes like , as well as hadronic decays , in the framework of a class
of two Higgs doublet models where there are flavour changing neutral scalar
currents at tree level. These models have the remarkable feature of having
these flavour-violating couplings entirely determined by the CKM and PMNS
matrices as well as . The flavour structure of these scalar currents
results from a symmetry of the Lagrangian and therefore it is natural and
stable under the renormalization group. We show that in some of the models the
rates of the above flavour changing processes can reach the discovery level at
the LHC at 13 TeV even taking into account the stringent bounds on low energy
processes, in particular .Comment: 33 pages, 8 figures; matches version accepted for publicatio
What if the Masses of the First Two Quark Families are not Generated by the Standard Higgs?
We point out that, in the context of the SM, is
expected to be large, of order one. The fact that motivates the introduction of a symmetry S which
leads to , with only the third generation of
quarks acquiring mass. We consider two scenarios for generating the mass of the
first two quark generations and full quark mixing. One consists of the
introduction of a second Higgs doublet which is neutral under S. The second
scenario consists of assuming New Physics at a high energy scale , contributing
to the masses of light quark generations, in an effective field theory
approach. This last scenario leads to couplings of the Higgs particle to
and which are significantly enhanced with
respect to those of the SM. In both schemes, one has scalar-mediated flavour-
changing neutral currents which are naturally suppressed. Flavour violating top
decays are predicted in the second scenario at the level \mbox{Br} (t
\rightarrow h c ) \geq 5\times 10^{-5}.Comment: 11 pages, 1 figur
Controlled Flavour Changing Neutral Couplings in Two Higgs Doublet Models
We propose a class of Two Higgs Doublet Models where there are Flavour
Changing Neutral Currents (FCNC) at tree level, but under control due to the
introduction of a discrete symmetry in the full Lagrangian. It is shown that in
this class of models, one can have simultaneously FCNC in the up and down
sectors, in contrast to the situation encountered in BGL models. The intensity
of FCNC is analysed and it is shown that in this class of models one can
respect all the strong constraints from experiment without unnatural
fine-tuning. It is pointed out that the additional sources of flavour and CP
violation are such that they can enhance significantly the generation of the
Baryon Asymmetry of the Universe, with respect to the Standard Model.Comment: 29 pages, 3 figure
Vector-like Quarks at the Origin of Light Quark Masses and Mixing
We show how a novel fine-tuning problem present in the Standard Model can be
solved through the introduction of a single flavour symmetry G, together with
three quarks, three quarks, as well as a complex singlet
scalar. The symmetry G is extended to the additional fields and it is an exact
symmetry of the Lagrangian, only spontaneously broken by the vacuum. Specific
examples are given and a phenomenological analysis of the main features of the
model is presented. It is shown that even for vector-like quarks with masses
accessible at the LHC, one can have realistic quark masses and mixing, while
respecting the strict constraints on process arising from flavour changing
neutral currents (FCNC). The vector-like quark decay channels are also
described.Comment: 25 pages, no figure
Emergence of hierarchical networks and polysynchronous behaviour in simple adaptive systems
We describe the dynamics of a simple adaptive network. The network
architecture evolves to a number of disconnected components on which the
dynamics is characterized by the possibility of differently synchronized nodes
within the same network (polysynchronous states). These systems may have
implications for the evolutionary emergence of polysynchrony and hierarchical
networks in physical or biological systems modeled by adaptive networks.Comment: 4 pages, 4 figure
Reparametrization invariance of B decay amplitudes and implications for new physics searches in B decays
When studying B decays within the Standard Model, it is customary to use the
unitarity of the CKM matrix in order to write the decay amplitudes in terms of
only two of the three weak phases which appear in the various diagrams.
Occasionally, it is mentioned that those two weak phases can be used in order
to describe any decay amplitude, even beyond the Standard Model. Here we point
out that, when describing a generic decay amplitude, the two weak phases can be
chosen completely at will, and we study the behavior of the decay amplitudes
under changes in the two weak phases chosen as a basis. Of course, physical
observables cannot depend on such reparametrizations. This has an impact in
discussions of the SM and in attempts to parametrize new physics effects in the
decay amplitudes. We illustrate these issues by looking at B --> psi K_S and
the isospin analysis in B --> pi pi.Comment: 16 pages, RevTe
Bounds on gamma from CP violation measurements in B -> pi+ pi- and B -> psi K_S
We study the determination of gamma from CP-violating observables in B -> pi+
pi- and B -> psi K_S. This determination requires theoretical input to one
combination of hadronic parameters. We show that a mild assumption about this
quantity may allow bounds to be placed on gamma, but we stress the pernicious
effects that an eightfold discrete ambiguity has on such an analysis. The
bounds are discussed as a function of the direct (C) and interference (S)
CP-violating observables obtained from time-dependent B -> pi+ pi- decays, and
their behavior in the presence of new physics effects in B-Bbar mixing is
studied. (V2: Misprints corrected. Slightly improved discussion.)Comment: 11 pages, RevTex 4, 5 eps figures include
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