780 research outputs found
Perturbed Yukawa Textures in the Minimal Seesaw Model
\noindent We revisit the \textit{minimal seesaw model}, i.e., the type-I
seesaw mechanism involving only two right-handed neutrinos. % This model
represents an important minimal benchmark scenario for future experimental
updates on neutrino oscillations. % It features four real parameters that
cannot be fixed by the current data: two -violating phases, and
, as well as one complex parameter, , that is experimentally
inaccessible at low energies. % The parameter controls the structure of the
neutrino Yukawa matrix at high energies, which is why it may be regarded as a
label or index for all UV completions of the minimal seesaw model. % The fact
that encompasses only two real degrees of freedom allows us to
systematically scan the minimal seesaw model over all of its possible UV
completions. % In doing so, we address the following question: Suppose
and should be measured at particular values in the future---to what
extent is one then still able to realize approximate textures in the neutrino
Yukawa matrix? % Our analysis, thus, generalizes previous studies of the
minimal seesaw model based on the assumption of exact texture zeros. % In
particular, our study allows us to assess the theoretical uncertainty inherent
to the common texture ansatz. % One of our main results is that a normal
light-neutrino mass hierarchy is, in fact, still consistent with a two-zero
Yukawa texture, provided that the two texture zeros receive corrections at the
level of . % While our numerical
results pertain to the minimal seesaw model only, our general procedure appears
to be applicable to other neutrino mass models as well.Comment: 30 pages, 7 figures, 2 tables; v2: updated references, extended
discussion in the introduction and conclusions, new title, results unchanged,
content matches version published in JHE
Leptogenesis and low-energy CP violation in a type-II-dominated left-right seesaw model
We consider leptogenesis in a left-right-symmetric seesaw scenario in which
neutrino mass generation and leptogenesis are dominated by the type-II seesaw
term. Motivated by grand unification, we assume that the neutrino Dirac mass
matrix is dominated by a single entry of the order of the top-quark mass, which
leaves the low-energy phases of the lepton mixing matrix as the only sources of
CP violation. Working in a regime where the triplet scalar predominantly decays
into leptons, this results in a predictive scenario based on a minimal number
of parameters. We perform a detailed analysis of the flavored Boltzmann
equations within a revised density matrix framework and demonstrate that the
observed baryon asymmetry can be successfully generated in this simple model.
We point out that the significance of flavor effects is limited, and we discuss
the implications for low-energy observables such as the Dirac CP phase and
neutrinoless double beta decay.Comment: 40 pages, 9 figures, 3 tables; minor text revisions, new benchmark
values, plots and results updated, matches published version in NP
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