2,237 research outputs found
Tree-level metastability bounds for the most general two Higgs doublet model
Within two Higgs doublet models, it is possible that the current vacuum is
not the global minimum, in which case it could possibly decay at a later stage.
We discuss the tree-level conditions which must be obeyed by the most general
scalar potential in order to preclude that possibility. We propose a new
procedure which is not only more general but also easier to implement than the
previously published one, including CP conserving as well as CP violating
scalar sectors. We illustrate these conditions within the context of the Z2
model, softly broken by a complex, CP violating parameter.Comment: RevTex, 13 pages, 3 figure
A CP-conserving multi-Higgs model without real basis
Models beyond the Standard Model (bSM) often involve elaborate Higgs sectors,
which can be a source of CP-violation. It brings up the question of recognizing
in an efficient way whether a model is CP-violating. There is a diffuse belief
that the issue of explicit CP invariance can be linked to the existence of a
basis in which all coefficients are real; with even a theorem proposed a decade
ago claiming that the scalar sector of any multi-Higgs doublet model is
explicitly CP-conserving if and only if all of its coefficients can be made
real by a basis change. This is compounded by the fact that in all specific
multi Higgs models considered so far, the calculations complied with this
claim. Here, we present the first counterexample to this statement: a
CP-conserving three-Higgs-doublet model for which no real basis exists. We
outline the phenomenological consequences of this model, and notice that the
extra neutral Higgs bosons are neither CP-even nor CP-odd but are "half-odd"
under the generalized CP-symmetry of the model.Comment: 6 pages; v2: abstract, introduction, conclusions reformulated, all
the results stay unchange
Generalized CP Invariance and the Yukawa sector of Two-Higgs Models
We analyze generalized CP symmetries of two-Higgs doublet models, extending
them from the scalar to the fermion sector of the theory. We show that, with a
single exception, those symmetries imply massless fermions. The single model
which accommodates a fermionic mass spectrum compatible with experimental data
possesses a remarkable feature. It displays a new type of spontaneous CP
violation, which occurs not in the scalar sector responsible for the symmetry
breaking mechanism but, rather, in the fermion sector.Comment: RevTex, 4 pages, no figures Version2: Remarkable additional
conclusion => title & text changes; section adde
Neutrino masses and mixing in A4 models with three Higgs doublets
We study neutrino masses and mixing in the context of flavor models with A4
symmetry, three scalar doublets in the triplet representation, and three lepton
families. We show that there is no representation assignment that yields a
dimension-five mass operator consistent with experiment. We then consider a
type-I seesaw with three heavy right-handed neutrinos, explaining in detail why
it fails, and showing with a numerical example that agreement with the present
neutrino oscillation data can be recovered with the inclusion of
dimension-three heavy neutrino mass terms that break softly the A4 symmetry.Comment: 10 pages, RevTex, 3 figures. v2: much expanded section on softly
broken A4; refs adde
Implications of the LHC two-photon signal for two-Higgs-doublet models
We study the implications for Two Higgs Doublet Models of the recent
announcement at the LHC giving a tantalizing hint for a Higgs boson of mass 125
GeV decaying into two photons. We require that the experimental result be
within a factor of two of the theoretical Standard Model prediction, and
analyze the type I and type II models as well as the lepton-specific and
flipped models, subject to this requirement. It is assumed that there is no new
physics other than two Higgs doublets. In all of the models, we display the
allowed region of parameter space taking the recent LHC announcement at face
value, and we analyze the , , and
expectations in these allowed regions. Throughout the entire range of parameter
space allowed by the constraint, the number of events for Higgs
decays into , and are not changed from the Standard Model
by more than a factor of two. In contrast, in the Lepton Specific model, decays
to are very sensitive across the entire -allowed region.Comment: Latex, 6 pages, 4 figures; v2 - added 2 reference
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