scholarly journals LEPTON MIXING AND SEESAW MECHANISM

2006 ◽  
Vol 21 (13n14) ◽  
pp. 3015-3020 ◽  
Author(s):  
D. FALCONE
Keyword(s):  
Fermion Mass ◽  
Type I ◽  
Type Ii ◽  
Seesaw Mechanism ◽  
Mixing Angle ◽  
Mass Matrices ◽  
Typical Model

In the context of a typical model for fermion mass matrices, possibly based on the horizontal U (2) symmetry, we explore the effect of the type II seesaw mechanism on lepton mixings. We find that the combined contribution of type I and type II terms is able to explain the large but not maximal 1-2 mixing and the near maximal 2-3 mixing, while the 1-3 mixing angle is predicted to be small.

scholarly journals Investigating two heavy neutral leptons neutrino seesaw mechanism at SHiP

2019 ◽  
Vol 34 (08) ◽  
pp. 1950047
Author(s):  
Marco Chianese ◽  
Damiano F. G. Fiorillo ◽  
Gennaro Miele ◽  
Stefano Morisi
Keyword(s):  
Neutrino Mass ◽  
Double Beta Decay ◽  
Type I ◽  
Mass Generation ◽  
Seesaw Mechanism ◽  
Mixing Angle ◽  
Mechanism Model ◽  
Neutrino Mass Generation ◽  
Generation Mechanisms ◽  
The Masses

One of the main purposes of SHiP experiment is to shed light on neutrino mass generation mechanisms like the so-called seesaw. We consider a minimal type-I seesaw neutrino mass mechanism model with two heavy neutral leptons (right-handed or sterile neutrinos) with arbitrary masses. Extremely high active-sterile mixing angle requires a correlation between the phases of the Dirac neutrino couplings. Actual experimental limits on the half-life of neutrinoless double beta decay [Formula: see text]-rate on the active-sterile mixing angle are not significative in constraining the masses or the mixing measurable by SHiP.

scholarly journals Type II seesaw origin of nonzero θ13, δCP and leptogenesis

2014 ◽  
Vol 29 (22) ◽  
pp. 1450108 ◽  
Author(s):  
Debasish Borah
Keyword(s):  
Neutrino Mass ◽  
Mass Matrix ◽  
Neutrino Mass Matrix ◽  
Type I ◽  
Type Ii ◽  
Mixing Angle ◽  
Yukawa Couplings ◽  
Minimal Structure ◽  
Reactor Mixing ◽  
The Universe

We discuss the possible origin of nonzero reactor mixing angle θ13 and Dirac CP phase δ CP in the leptonic sector from a combination of type I and type II seesaw mechanisms. Type I seesaw contribution to neutrino mass matrix is of tri-bimaximal (TBM) type which gives rise to vanishing θ13 leaving the Dirac CP phase undetermined. If the Dirac neutrino mass matrix is assumed to take the diagonal charged lepton (CL) type structure, such a TBM type neutrino mass matrix originating from type I seesaw corresponds to real values of Dirac Yukawa couplings in the terms [Formula: see text]. This makes the process of right-handed heavy neutrino decay into a light neutrino and Higgs (N → νH) CP preserving ruling out the possibility of leptogenesis. Here we consider the type II seesaw term as the common origin of nonzero θ13 and δ CP by taking it as a perturbation to the leading order TBM type neutrino mass matrix. First, we numerically fit the type I seesaw term by taking oscillation as well as cosmology data and then compute the predictions for neutrino parameters after the type II seesaw term is introduced. We consider a minimal structure of the type II seesaw term and check whether the predictions for neutrino parameters lie in the 3σ range. We also compute the predictions for baryon asymmetry of the universe by considering type II seesaw term as the only source of CP violation and compare it with the latest cosmology data.

scholarly journals TEXTURE-ZERO MODEL FOR THE LEPTON MASS MATRICES

2012 ◽  
Vol 27 (28) ◽  
pp. 1250159 ◽  
Author(s):  
P. M. FERREIRA ◽  
L. LAVOURA
Keyword(s):  
Mass Spectrum ◽  
Neutrino Mass ◽  
Mass Matrix ◽  
Type I ◽  
Mixing Angle ◽  
Mass Matrices ◽  
Neutrino Mass Spectrum ◽  
Texture Zero ◽  
Vanishing Elements ◽  
Reactor Mixing

We suggest a simple model, based on the type-I seesaw mechanism, for the lepton mass matrices. The model hinges on an Abelian symmetry which leads to mass matrices with some vanishing matrix elements. The model predicts one massless neutrino and Meμ = 0 (M is the effective light-neutrino Majorana mass matrix). We show that these predictions agree with the present experimental data if the neutrino mass spectrum is inverted, i.e. if m3 = 0, provided the Dirac phase δ is very close to maximal (±π/ 2). In the case of a normal neutrino mass spectrum, i.e. when m1 = 0, the agreement of our model with the data is imperfect — the reactor mixing angle θ13 is too small in our model. Minimal leptogenesis is not an option in our model due to the vanishing elements in the Yukawa-coupling matrices.

B−L model based on Q4 symmetry for fermion spectrum with normal neutrino mass ordering

2021 ◽  
Vol 36 (07) ◽  
pp. 2150047
Author(s):  
V. V. Vien
Keyword(s):  
Neutrino Mass ◽  
Type I ◽  
Effective Parameters ◽  
Seesaw Mechanism ◽  
Mixing Angle ◽  
Mixing Angles ◽  
Neutrino Sector ◽  
Quark Sector ◽  
The Standard Model ◽  
Experimental Values

We propose a renormalizable gauge [Formula: see text] extension of the Standard Model (SM) based on [Formula: see text] symmetry and an auxiliary [Formula: see text] symmetry which can explain the observed quark and lepton masses and mixing angles associated to normal neutrino mass ordering through type-I seesaw mechanism. The relation between the atmospheric mixing angle [Formula: see text] and the effective parameters in neutrino sector is analyzed. Two Majorana phases are predicted to be [Formula: see text] and [Formula: see text] and the model also predicts the effective neutrino mass parameters of [Formula: see text], [Formula: see text] which is well consistent with the planning of future experiments. In the quark sector, the model is predictive since it has ten effective parameters that allow to successfully reproduce the experimental values of the experimental values of the ten physical observables of the quark sector.

scholarly journals Anomaly-free Abelian gauge symmetries with Dirac seesaws

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
Nicolás Bernal ◽  
Diego Restrepo
Keyword(s):  
Unconditional Stability ◽  
Tree Level ◽  
Neutrino Masses ◽  
Type I ◽  
Type Ii ◽  
Abelian Gauge ◽  
Seesaw Mechanism ◽  
Gauge Symmetries ◽  
New States ◽  
Additional Anomaly

AbstractWe perform a systematic analysis of Standard Model extensions with an additional anomaly-free gauge U(1) symmetry, to generate tree-level Dirac neutrino masses. An anomaly-free symmetry demands nontrivial conditions on the charges of the unavoidable new states. An intensive scan was performed, looking for solutions generating neutrino masses by the type-I and type-II tree-level Dirac seesaw mechanism, via operators with dimension 5 and 6, that correspond to active or dark symmetries. Special attention was paid to the cases featuring no extra massless chiral fermions or multicomponent dark matter with unconditional stability.

scholarly journals Singlet Fermion Assisted Dominant Seesaw with Lepton Flavor and Number Violations and Leptogenesis

2017 ◽  
Vol 2017 ◽  
pp. 1-24 ◽  
Author(s):  
M. K. Parida ◽  
Bidyut Prava Nayak
Keyword(s):  
Neutrino Mass ◽  
Experimental Tests ◽  
Fine Tuning ◽  
Type I ◽  
Type Ii ◽  
Mass Generation ◽  
Lepton Flavor ◽  
Mass Matrices ◽  
Neutrino Mass Generation ◽  
High Degree

Embedding type I seesaw in GUTs, left-right gauge theories, or even in extensions of the SM requires large right-handed neutrino masses making the neutrino mass generation mechanism inaccessible for direct experimental tests. This has been circumvented by introducing additional textures or high degree of fine-tuning in the Dirac neutrino or right-handed neutrino mass matrices. In this work we review another new mechanism that renders type I seesaw vanishing but other seesaw mechanisms dominant. Such mechanisms include extended seesaw, type II, linear, or double seesaw. The linear seesaw, double seesaw, and extended seesaw are directly verifiable at TeV scale. New observable predictions for lepton flavor and lepton number violations by ongoing searches are noted. Type II embedding in SO(10) also predicts these phenomena in addition to new mechanism for leptogenesis and displaced vertices mediated by gauge singlet fermions.

Understanding of two-zero textures of neutrino mass matrices in minimal extended seesaw mechanism and their symmetry realization

2019 ◽  
Vol 34 (11) ◽  
pp. 1950059 ◽  
Author(s):  
Mahadev Patgiri ◽  
Priyanka Kumar
Keyword(s):  
Neutrino Mass ◽  
Mass Matrix ◽  
Scalar Fields ◽  
Fermion Mass ◽  
Type I ◽  
Number Of Zeros ◽  
Mass Matrices ◽  
Texture Zero ◽  
Minimum Number ◽  
The Right

We study the texture zeros of [Formula: see text] neutrino mass matrices [Formula: see text] in the minimal extended type-I seesaw (MES) mechanism, incorporating one extra gauge singlet field “[Formula: see text]”. The [Formula: see text]  MES model deals with [Formula: see text]  [Formula: see text], [Formula: see text]  [Formula: see text] and [Formula: see text] mass matrix [Formula: see text] which couples the right-handed neutrinos and the singlet field “[Formula: see text]”. We carry out the mapping of all possible zero textures of [Formula: see text], [Formula: see text] and [Formula: see text] with the restriction to phenomenologically predictive cases having total eight zeros of [Formula: see text] and [Formula: see text] studied in the literature. If [Formula: see text], the sterile neutrino mass, is subject to any limit, further block diagonalization of [Formula: see text] shall not be allowed to reduce it to a [Formula: see text] matrix. In [Formula: see text]  [Formula: see text] scenario, the study of texture zero is totally different and interesting. With this motivation, we consider the [Formula: see text] scheme where the digits of the pair represent the number of zeros of [Formula: see text] and [Formula: see text], respectively, along with the one/two-zero textures of [Formula: see text]. There are a large number of possibilities of zeros of fermion mass matrices, but the implementation of [Formula: see text] transformations reduces it to a very minimum number of basic structures. As the [Formula: see text] MES matrix is a matrix of rank 3, so we consider only those textures with two zeros which are of rank 3 whereby the number of feasible zero textures reduces to 12, out of 15. On realizing these 12 textures under MES mechanism with [Formula: see text] picture, we arrive at certain correlations for each texture. We examine the viability of each texture by scanning their respective correlations under recent neutrino oscillation data. Also, we discuss the interplay of Dirac and Majorana CP phases in determining the viability of a texture. The allowed two-zero textures are finally realized using a discrete Abelian flavor symmetry group [Formula: see text] with the extension of Standard Model to include some scalar fields.

scholarly journals Adjoint SU(5) GUT model with modular S4 symmetry

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Ya Zhao ◽  
Hong-Hao Zhang
Keyword(s):  
Modular Forms ◽  
Experimental Result ◽  
Fermion Mass ◽  
Neutrino Masses ◽  
Type I ◽  
Neutrino Sector ◽  
Horizontal Symmetry ◽  
Mass Matrices ◽  
Two Generations ◽  
Charged Leptons

Abstract We study the textures of SM fermion mass matrices and their mixings in a supersymmetric adjoint SU(5) Grand Unified Theory with modular S4 being the horizontal symmetry. The Yukawa entries of both quarks and leptons are expressed by modular forms with lower weights. Neutrino sector has an adjoint SU(5) representation 24 as matter superfield, which is a triplet of S4. The effective light neutrino masses is generated through Type-III and Type-I seesaw mechanism. The only common complex parameter in both charged fermion and neutrino sectors is modulus τ . Down-type quarks and charged leptons have the same joint effective operators with adjoint scalar in them, and their mass discrepancy in the same generation depends on Clebsch-Gordan factor. Especially for the first two generations the respective Clebsch-Gordan factors made the double Yukawa ratio 𝒴d𝒴μ/𝒴e𝒴s = 12, in excellent agreement with the experimental result. We reproduce proper CKM mixing parameters and all nine Yukawa eigenvalues of quarks and charged leptons. Neutrino masses and MNS parameters are also produced properly with normal ordering is preferred.

scholarly journals Data driven flavour model

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
F. Arias-Aragón ◽  
C. Bouthelier-Madre ◽  
J. M. Cano ◽  
L. Merlo
Keyword(s):  
Scalar Potential ◽  
Majorana Neutrino ◽  
Double Beta Decay ◽  
Fermion Mass ◽  
Type I ◽  
Minimal Flavour Violation ◽  
Seesaw Mechanism ◽  
Charged Fermion ◽  
Fermion Masses ◽  
Flavour Violation

AbstractA bottom-up approach has been adopted to identify a flavour model that agrees with present experimental measurements. The charged fermion mass hierarchies suggest that only the top Yukawa term should be present at the renormalisable level. Similarly, describing the lightness of the active neutrinos through the type-I Seesaw mechanism, right-handed neutrino mass terms should also be present at the renormalisable level. The flavour symmetry of the Lagrangian including the fermionic kinetic terms and only the top Yukawa is then a combination of U(2) and U(3) factors. Once considering the Majorana neutrino terms, the associated symmetry is O(3). Lighter charged fermion and active neutrino masses and quark and lepton mixings arise considering specific spurion fields à la Minimal Flavour Violation. The associated phenomenology is investigated and the model turns out to have almost the same flavour protection as the Minimal Flavour Violation in both quark and lepton sectors. Promoting the spurions to dynamical fields, the associated scalar potential is also studied and a minimum is identified such that fermion masses and mixings are correctly reproduced. Very precise predictions for the Majorana phases follow from the minimisation of the scalar potential and thus the neutrinoless-double-beta decay may represent a smoking gun for the model.

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