3,711 research outputs found
Intrinsic flavor violation for massive neutrinos
It is shown that intrinsic neutrino flavor violation invariably occurs when
neutrinos are created within the SM augmented by the known massive neutrinos,
with mixing and nondegenerate masses. The effects are very small but much
greater than the naive estimate or the branching ratio of
indirect flavor violating processes such as within the SM. We
specifically calculate the probability (branching ratio) of pion decay
processes with flavor violation, such as , showing
nonzero results.Comment: v3: published versio
Compatible abelian symmetries in N-Higgs-Doublet Models
We analyze the compatibility between abelian symmetries acting in two
different sectors of a theory using the Smith Normal Form method. We focus on
N-Higgs-doublet models (NHDMs) and on the compatibility between symmetries in
the Higgs potential and in the Yukawa interactions, which were separately
analyzed previous works. It is shown that two equal (isomorphic) symmetry
groups that act in two separate sectors are not necessarily compatible in the
whole theory and an upper bound is found for the size of the group that can be
implemented in the entire NHDM. We also develop useful techniques to analyze
compatibility and extend a symmetry from one sector to another. Consequences to
the supersymmetric case are briefly discussed.Comment: v2: 40pp; some modifications in text, brief discussion on the
supersymmetric case added; to appear in JHE
Custodial SO(4) symmetry and CP violation in N-Higgs-doublet potentials
We study the implementation of global
symmetry in general potentials with N-Higgs-doublets in order to obtain models
with custodial symmetry. We conclude that any implementation of the
custodial SO(4) symmetry is equivalent, by a basis transformation, to a
canonical one if is the gauge factor, is embedded in
and we require copies of the doublet representation of .
The invariance by SO(4) automatically leads to a CP invariant potential and the
basis of the canonical implementation of SO(4) is aligned to a basis where
CP-symmetry acts in the standard fashion. We show different but equivalent
implementations for the 2HDM, including an implementation not previously
considered.Comment: 22pp, REVTeX4. Published versio
Physical parameters and basis transformations in the Two-Higgs-Doublet model
A direct connection between physical parameters of general Two-Higgs-Doublet
Model (2HDM) potentials after electroweak symmetry breaking (EWSB) and the
parameters that define the potentials before EWSB is established. These
physical parameters, such as the mass matrix of the neutral Higgs bosons, have
well defined transformation properties under basis transformations transposed
to the fields after EWSB. The relations are also explicitly written in a basis
covariant form. Violation of these relations may indicate models beyond 2HDMs.
In certain cases the whole potential can be defined in terms of the physical
parameters. The distinction between basis transformations and
reparametrizations is pointed out. Some physical implications are discussed.Comment: 11 pages. 1 figure. v2: references and comments adde
Properties of the general NHDM. I. The orbit space
We study the scalar sector of the general N-Higgs-doublet model via geometric
constructions in the space of gauge orbits. We give a detailed description of
the shape of the orbit space both for general N and, in more detail, for N=3.
We also comment on remarkable analogies between NHDM and quantum information
theory.Comment: 27 pages, 2 figure
Solving the strong CP problem with non-conventional CP
A very simple model is presented where all CP violation in Nature is
spontaneous in origin. The CKM phase is generated unsuppressed and the strong
CP problem is solved with only moderately small couplings between the SM and
the CP violation sector or mediator sector because corrections to
arise only at two loops. The latter feature follows from an
underlying unconventional CP symmetry of order 4 imposed in the sectors beyond
the SM composed of only two vector-like quarks of charge and one complex
scalar singlet. No additional symmetry is necessary to implement the
Nelson-Barr mechanism.Comment: Comments added, comply with published versio
Implications of Flavored CP Symmetry of Leptons
We discuss gauge models incorporating flavored CP symmetry (called
CP in the text) in combination with invariance to
understand neutrino mixings and discuss their phenomenological implications. We
show that viable leptogenesis in this setting requires that the lightest
right-handed neutrino mass must be between GeV and for effective
two hierarchical right-handed neutrinos, leptogenesis takes place only in a
narrower range of GeV. A multi-Higgs realization of
this idea implies that there must be a pseudoscalar Higgs boson with mass less
than 300 GeV. Generically, the vev alignment problem can be naturally avoided
in our setting.Comment: 34pp. v3: matches journal versio
Flavor mixing in a Lee-type model
An exactly solvable Quantum Field Theory (QFT) model of Lee-type is
constructed to study how neutrino flavor eigenstates are created through
interactions and how the localization properties of neutrinos follows from the
parent particle that decays. The two-particle states formed by the neutrino and
the accompanying charged lepton can be calculated exactly as well as their
creation probabilities. We can show that the coherent creation of neutrino
flavor eigenstates follows from the common negligible contribution of neutrino
masses to their creation probabilities. On the other hand, it is shown that it
is not possible to associate a well defined "flavor" to mixed states of charged
leptons.Comment: v2: 25pp in preprint form, typos corrected and references added, one
paragraph around Eq.(90) added in conclusion
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