21 research outputs found
Electron and muon anomalies in general flavour conserving two Higgs doublets models
In general two Higgs doublet models (2HDMs) without scalar flavour changing
neutral couplings (SFCNC) in the lepton sector, the electron, muon and tau
interactions can be decoupled in a robust framework, stable under
renormalization group evolution. In this framework, the breaking of lepton
flavour universality (LFU) goes beyond the mass proportionality, opening the
possibility to accommodate a different behaviour among charged leptons. We
analyze the electron and muon anomalies in the context of these general
flavour conserving models in the leptonic sector (gFC). We consider two
different models, I-gFC and II-gFC, in which the quark Yukawa
couplings coincide, respectively, with the ones in type I and in type II 2HDMs.
We find two types of solutions that fully reproduce both anomalies, and
which are compatible with experimental constraints from LEP and LHC, from LFU,
from flavour and electroweak physics, and with theoretical constraints in the
scalar sector. In the first type of solution, all the new scalars have masses
in the 1--2.5 TeV range, the vacuum expectation values (vevs) of both doublets
are quite similar in magnitude, and both anomalies are dominated by two loop
Barr-Zee contributions. This solution appears in both models. In a second type
of solution, one loop contributions are dominant in the muon anomaly, all new
scalars have masses below 1 TeV, and the ratio of vevs is in the range 10--100.
The second neutral scalar is the lighter among the new scalars, with a mass
in the 210--390 GeV range while the pseudoscalar is the heavier, with a
mass in the range 400--900 GeV. The new charged scalar is almost
degenerate either with the scalar or with the pseudoscalar. This second type of
solution only appears in the I-gFC model. Both solutions require the soft
breaking of the symmetry of the Higgs potential.Comment: 32 pages, 11 figure
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
Symmetry Constrained Two Higgs Doublet Models
We study Two-Higgs-Doublet Models (2HDM) where Abelian symmetries have been
introduced, leading to a drastic reduction in the number of free parameters in
the 2HDM. Our analysis is inspired in BGL models, where, as the result of a
symmetry of the Lagrangian, there are tree-level scalar mediated
Flavour-Changing-Neutral-Currents, with the flavour structure depending only on
the CKM matrix. A systematic analysis is done on the various possible schemes,
which are classified in different classes, depending on the way the extra
symmetries constrain the matrices of couplings defining the flavour structure
of the scalar mediated neutral currents. All the resulting flavour textures of
the Yukawa couplings are stable under renormalisation since they result from
symmetries imposed at the Lagrangian level. We also present a brief
phenomenological analysis of the most salient features of each class of
symmetry constrained 2HDM.Comment: 30 pages, 5 Table
Muon and electron
We consider a type I or type X two Higgs doublets model with a modified lepton sector. The generalized lepton sector is also flavor conserving but with the new Yukawa couplings completely decoupled from lepton mass proportionality. The model is one loop stable under renormalization group evolution and it allows to reproduce the muon anomaly together with the different scenarios one can consider for the electron anomaly, related to the Cesium and/or to the Rubidium recoil measurements of the fine structure constant. Thorough parameter space analyses are performed to constrain all the model parameters in the different scenarios, either including or not including the recent CDF measurement of the W boson mass. For light new scalars with masses in the 0.2–1.0 TeV range, the muon anomaly receives dominant one loop contributions; it is for heavy new scalars with masses above 1.2 TeV that two loop Barr–Zee diagrams are needed. The electron anomaly, if any, must always be obtained with the two loop contributions. The final allowed regions are quite sensitive to the assumptions about perturbativity of Yukawa couplings, which influence unexpected observables like the allowed scalar mass ranges. On that respect, intermediate scalar masses, highly constrained by direct LHC searches, are allowed provided that the new lepton Yukawa couplings are fully scrutinized, including values up to 250 GeV. In the framework of a complete model, fully numerically analysed, we show the implications of the recent measurement
Muon and electron anomalies in a flavor conserving 2HDM with an oblique view on the CDF value
We consider a type I or type X two Higgs doublets model with a modified
lepton sector. The generalized lepton sector is also flavor conserving but with
the new Yukawa couplings completely decoupled from lepton mass proportionality.
The model is one loop stable under renormalization group evolution and it
allows to reproduce the muon anomaly together with the different
scenarios one can consider for the electron anomaly, related to the
Cesium and/or to the Rubidium recoil measurements of the fine structure
constant. Thorough parameter space analyses are performed to constrain all the
model parameters in the different scenarios, either including or not including
the recent CDF measurement of the W boson mass. For light new scalars with
masses in the - TeV range, the muon anomaly receives dominant one
loop contributions; it is for heavy new scalars with masses above TeV
that two loop Barr-Zee diagrams are needed. The electron anomaly, if any,
must always be obtained with the two loop contributions. The final allowed
regions are quite sensitive to the assumptions about perturbativity of Yukawa
couplings, which influence unexpected observables like the allowed scalar mass
ranges. On that respect, intermediate scalar masses, highly constrained by
direct LHC searches, are allowed provided that the new lepton Yukawa couplings
are fully scrutinized, including values up to 250 GeV. In the framework of a
complete model, fully numerically analysed, we show the implications of the
recent measurement
The framework for a common origin of
We analyse a possible connection between CP violations in the quark and lepton sectors, parametrised by the CKM and PMNS phases. If one assumes that CP breaking arises from complex Yukawa couplings, both in the quark and lepton sectors, the above connection is not possible in general, since Yukawa couplings in the two sectors have independent flavour structures. We show that both the CKM and PMNS phases can instead be generated by a vacuum phase in a class of two Higgs doublet models, and in this case a connection may be established. This scenario requires the presence of scalar FCNC at tree level, both in the quark and lepton sectors. The appearance of these FCNC is an obstacle and a blessing. An obstacle since one has to analyse which models are able to conform to the strict experimental limits on FCNC, both in the quark and lepton sectors. A blessing, because this class of models is falsifiable since FCNC arise at a level which can be probed experimentally in the near future, specially in the processes and . The connection between CP violations in CKM and PMNS is explicitely illustrated in models with Minimal Flavour Violation
Cosmic topology. Part IVa. Classification of manifolds using machine learning: a case study with small toroidal universes
International audienceNon-trivial spatial topology of the Universe may give rise to potentially measurable signatures in the cosmic microwave background. We explore different machine learning approaches to classify harmonic-space realizations of the microwave background in the test case of Euclidean topology (the 3-torus) with a cubic fundamental domain of a size scale significantly smaller than the diameter of the last scattering surface. Different machine learning approaches are capable of classifying the harmonic-space realizations with accuracy greater than 99% if the topology scale is half of the diameter of the last-scattering surface and orientation of the topology is known. For distinguishing random rotations of these sky realizations from realizations of the covering space, the extreme gradient boosting classifier algorithm performs best with an accuracy of 88%. Slightly lower accuracies of 83% to 87% are obtained with the random forest classifier along with one- and two-dimensional convolutional neural networks. The techniques presented here can also accurately classify non-rotated cubic topology realizations with a topology scale slightly larger than the diameter of the last-scattering surface, if provided enough training data. This work identifies the prospects and the main challenges for developing machine learning techniques that are capable of accurately classifying observationally viable topologies