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See detailScalar and fermionic extensions of the Standard Model
Degée, Audrey ULg

Doctoral thesis (2013)

In this thesis several aspects of beyond SM physics schemes have been treated. In particular, two categories of models have been considered: ($i$) models with extra Higgs ElectroWeak (EW) doublets (multi ... [more ▼]

In this thesis several aspects of beyond SM physics schemes have been treated. In particular, two categories of models have been considered: ($i$) models with extra Higgs ElectroWeak (EW) doublets (multi-Higgs-doublet models), ($ii$) models with new fermion EW singlets (type-I seesawmodels). In the first category, two problems associated with the most general two-Higgs-Doublet Model (2HDM) and with the three-Higgs-Doublet Model (3HDM) have been tackled. In the former case the scalar mass spectrum has been derived in a basis-invariant fashion whereas in the later, after introducing a general procedure for the minimization of highly symmetric potentials, the minimization of an $S_4$ and of an $A_4$ 3HDM has been analyzed. In the second category, the possibility of envisaging seesaw-like models yielding sizeable lepton-flavor-violating decay rates has been investigated. With the models at hand, the corresponding charged lepton-flavor-violating phenomenology has been studied focusing on rare muon decays, for which forthcoming lepton-flavor-violating experiments will be able to prove large parts of their parameter space. [less ▲]

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See detailGeometric minimization of highly symmetric potentials
Degée, Audrey ULg; Ivanov, Igor ULg; Keus, Venus ULg

in Journal of High Energy Physics [=JHEP] (2013), 2013

In non-minimal Higgs mechanisms, one often needs to minimize highly symmetric Higgs potentials. Here we propose a geometric way of doing it, which, surprisingly, is often much more efficient than the ... [more ▼]

In non-minimal Higgs mechanisms, one often needs to minimize highly symmetric Higgs potentials. Here we propose a geometric way of doing it, which, surprisingly, is often much more efficient than the usual method. By construction, it gives the global minimum for any set of free parameters of the potential, thus offering an intuitive understanding of how they affect the vacuum expectation values. For illustration, we apply this method to the S_4 and A_4-symmetric three-Higgs-doublet models. We find that at least three recent phenomenological analyses of the A_4-symmetric model used a local, not the global minimum. We discuss coexistence of minima of different types, and comment on the mathematical origin of geometrical CP-violation and on a new symmetry linking different minima. [less ▲]

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See detailMinimal seesaw models and minimal lepton flavor violation.
Degée, Audrey ULg

in Frascati Physics Series Vol. LIV (2012), Frascati Phys.Ser. 55(2012), 31-36

We study the implications of the global U(1)R symmetry present in minimal lepton flavor violating implementations of the seesaw mechanism for neutrino masses. Our discussion is done in the context of ... [more ▼]

We study the implications of the global U(1)R symmetry present in minimal lepton flavor violating implementations of the seesaw mechanism for neutrino masses. Our discussion is done in the context of explicit minimal type-I seesaw scenarios, where depending on the R-charge assignment different models can be constructed. We study the charged lepton flavor violating phenomenology of a concrete realization paying special attention to μ → eγ and μ → 3e [less ▲]

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See detailMinimal Lepton Flavor Violating Realizations of Minimal Seesaw Models.
Aristizabal Sierra, Diego ULg; Degée, Audrey ULg; Kamenik, Jernej F.

in Journal of High Energy Physics [=JHEP] (2012), JHEP 1207 (2012) 135(2012), 135-156

We study the implications of the global U(1)R symmetry present in minimal lepton flavor violating implementations of the seesaw mechanism for neutrino masses. In the context of minimal type I seesaw ... [more ▼]

We study the implications of the global U(1)R symmetry present in minimal lepton flavor violating implementations of the seesaw mechanism for neutrino masses. In the context of minimal type I seesaw scenarios with a slightly broken U(1)R, we show that, depending on the R-charge assignments, two classes of generic models can be identi fied. Models where the right-handed neutrino masses and the lepton number breaking scale are decoupled, and models where the parameters that slightly break the U(1)R induce a suppression in the light neutrino mass matrix. We show that within the fi rst class of models, contributions of right-handed neutrinos to charged lepton flavor violating processes are severely suppressed. Within the second class of models we study the charged lepton flavor violating phenomenology in detail, focusing on \ mu->e \gamma , \mu->3e and \mu- e conversion in nuclei. We show that sizable contributions to these processes are naturally obtained for right-handed neutrino masses at the TeV scale. We then discuss the interplay with the eff ects of the right- handed neutrino interactions on primordial B- L asymmetries,fi nding that sizable right-handed neutrino contributions to charged lepton flavor violating processes are incompatible with the requirement of generating (or even preserving preexisting) B-L asymmetries consistent with the observed baryon asymmetry of the Universe. [less ▲]

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See detailHiggs boson masses of the general two-Higgs-doublet model in the Minkowski-space formalism
Degée, Audrey ULg; Ivanov, Igor ULg

in Physical Review. D : Particles and Fields (2010), 81

We study the masses of the Higgs bosons in the most general two-Higgs-doublet model in a basis-independent approach. We adapt the recently developed Minkowski-space formalism to this problem and calculate ... [more ▼]

We study the masses of the Higgs bosons in the most general two-Higgs-doublet model in a basis-independent approach. We adapt the recently developed Minkowski-space formalism to this problem and calculate traces of any power of the mass matrix in a compact and reparametrization-invariant form. Our results can be used to gain insight into the dynamics of the scalar sector of the general two-Higgs-doublet model. [less ▲]

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See detailHiggs mechanism in the general Two-Higgs-Doublet Model
Degée, Audrey ULg

Master's dissertation (2009)

We first review the standard Higgs mechanism of the standard model. Then, in the second chapter, we motivate the introduction of a second doublet in the theory. In the third chapter, we talk about the ... [more ▼]

We first review the standard Higgs mechanism of the standard model. Then, in the second chapter, we motivate the introduction of a second doublet in the theory. In the third chapter, we talk about the reasons to study the most general two Higgs doublet model and introduce the Minkowski formalism introduced by I.P. Ivanov to simplify this problem. Finally, we study the masses of the Higgs bosons in the most general two-Higgs-doublet model (2HDM) in a basis-independent approach. We adapt the recently developed Minkowski-space formalism to this problem and calculate traces of any power of the mass matrix in a compact and reparametrization-invariant form. Our results can be used to gain insight into the dynamics of the scalar sector of the general 2HDM. [less ▲]

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