SEESAW AND LEPTOGENESIS: A TRIANGULAR ANSATZ

A triangular ansatz for the seesaw mechanism and baryogenesis via leptogenesis is explored. In a basis where both the charged lepton and the Majorana mass matrix are diagonal, the Dirac mass matrix can generally be written as the product of a unitary times a triangular matrix. We assume the unitary matrix to be the identity and then an upper triangular Dirac matrix. Constraints from bilarge lepton mixing and leptogenesis are studied.

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TRIBIMAXIMAL MIXING IN NEUTRINO MASS MATRICES WITH TEXTURE ZEROS OR VANISHING MINORS

Modern Physics Letters A ◽

10.1142/s0217732311034906 ◽

2011 ◽

Vol 26 (07) ◽

pp. 501-514 ◽

Cited By ~ 17

Author(s):

S. DEV ◽

SHIVANI GUPTA ◽

RADHA RAMAN GAUTAM

Keyword(s):

Neutrino Mass ◽

Mass Matrix ◽

Mass Scale ◽

Neutrino Mass Matrix ◽

Seesaw Mechanism ◽

Majorana Mass ◽

Absolute Mass ◽

Mass Matrices ◽

The One ◽

The Right

We study the existence of one/two texture zeros or one/two vanishing minors in the neutrino mass matrix with μτ symmetry. In the basis where the charged lepton mass matrix and the Dirac neutrino mass matrix are diagonal, the one/two zeros or one/two vanishing minors on the right-handed Majorana mass matrix having μτ symmetry will propagate via seesaw mechanism as one/two vanishing minors or one/two texture zeros in the neutrino mass matrix with μτ symmetry respectively. It is found that only five such texture structures of the neutrino mass matrix are phenomenologically viable. For tribimaximal mixing, these texture structures reduce the number of free parameters to one. Interesting predictions are obtained for the effective Majorana mass Mee, the absolute mass scale and the Majorana-type CP violating phases.

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Time Evolution of Lepton Number Carried by Majorana Neutrinos

Progress of Theoretical and Experimental Physics ◽

10.1093/ptep/ptab025 ◽

2021 ◽

Author(s):

Apriadi Salim Adam ◽

Nicholas J Benoit ◽

Yuta Kawamura ◽

Yamato Matsuo ◽

Takuya Morozumi ◽

...

Keyword(s):

Time Evolution ◽

Charged Lepton ◽

Mass Matrix ◽

Mass Term ◽

Big Bang ◽

Mass Hierarchy ◽

Majorana Mass ◽

Cosmic Neutrino Background ◽

Cosmic Neutrino ◽

Lepton Family

Abstract We revisit the time evolution of the lepton family number for a SU(2) doublet consisting of a neutrino and a charged lepton. The lepton family number is defined through the weak basis of the SU(2) doublet, where the charged lepton mass matrix is real and diagonal. The lepton family number carried by the neutrino is defined by the left-handed current of the neutrino family. For this work we assume the neutrinos have Majorana mass. This Majorana mass term is switched on at time t = 0 and the lepton family number is evolved. Since the operator in the avor eigenstate is continuously connected to that of the mass eigenstate, the creation and annihilation operators for the two eigenstates are related to each other. We compute the time evolution of all lepton family numbers by choosing a specific initial avor eigenstate for a neutrino. The evolution is studied for relativistic and nonrelativistic neutrinos. The nonrelativistic region is of particular interest for the Cosmic Neutrino Background predicted from big bang models. In that region we find the lepton family numbers are sensitive to Majorana and Dirac phases, the absolute mass, and mass hierarchy of neutrinos.

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NEUTRINO OSCILLATIONS IN A 3νL+3νR FRAMEWORK WITH FIVE LIGHT NEUTRINOS

International Journal of Modern Physics A ◽

10.1142/s0217751x00002822 ◽

2000 ◽

Vol 15 (25) ◽

pp. 3967-3991

Author(s):

DAIJIRO SUEMATSU

Keyword(s):

Dark Matter ◽

Matrix Model ◽

Charged Lepton ◽

Mass Matrix ◽

Atmospheric Neutrino ◽

Discrete Symmetry ◽

High Energy ◽

Energy Scale ◽

Seesaw Mechanism ◽

High Energy Scale

We propose a neutrino mass matrix model in which five neutrino species remain light through the seesaw mechanism within a supersymmetric 3νL+3νR framework. We construct such a model based on the nonrenormalizable terms in the superpotential constrained by the discrete symmetry which may be expected in the models at the high energy scale such as superstring. We study the possible oscillation phenomena by fixing mass parameters so as to explain the solar and atmospheric neutrino deficits and also include a candidate of the suitable dark matter. We also discuss the charged lepton mass matrix based on this neutrino model. LSND results may be consistently explained within this model.

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UNIVERSALITY OF QUARK–LEPTON MASS MATRIX

Modern Physics Letters A ◽

10.1142/s021773231350017x ◽

2013 ◽

Vol 28 (08) ◽

pp. 1350017 ◽

Cited By ~ 3

Author(s):

TAKESHI FUKUYAMA ◽

HIROYUKI NISHIURA

Keyword(s):

Charged Lepton ◽

Mass Matrix ◽

Unitary Matrix ◽

Mixing Angle ◽

Phase Parameter ◽

Quark Mixing ◽

Mass Matrices ◽

Mixing Matrix ◽

Best Fit

The recently observed lepton mixing angle θ13 of the MNS mixing matrix is well incorporated in a universal mixing hypothesis between quark and lepton sectors. This hypothesis asserts that, in the charged lepton diagonal base, all other mass matrices for up- and down-type quarks and light neutrinos are diagonalized by the same unitary matrix except for the phase elements. It is expressed as V CKM = U MNS (δ′)†PU MNS (δ) for quark mixing matrix V CKM and lepton mixing matrix U MNS (δ) in the phenomenological level. Here P is a diagonal phase mass matrix. δ′ is a slightly different phase parameter from the Dirac CP-violating phase δ = 1.1π (best fit) in the MNS lepton mixing matrix.

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What if θ13 is small?

Canadian Journal of Physics ◽

10.1139/p06-016 ◽

2006 ◽

Vol 84 (6-7) ◽

pp. 621-623

Author(s):

C S Lam

Keyword(s):

Mass Spectrum ◽

Neutrino Mass ◽

Charged Lepton ◽

Mass Matrix ◽

Neutrino Mass Matrix ◽

Inverted Hierarchy ◽

Seesaw Mechanism ◽

Mixing Angle ◽

Left Handed ◽

The Right

In the basis where the charged lepton mass matrix is diagonal, the left-handed neutrino mass matrix is invariant under the permutation of the second and third generations if, and only if, the reactor angle θ13 is zero and the atmospheric mixing angle θ23 is maximal. In the presence of the seesaw mechanism, this symmetry leads to an inverted hierarchy, with m3 = 0. This inverted mass spectrum is doubly protected if the right-handed neutrinos also have a 2–3 symmetry.PACS No.: 14.60Pq

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SO(10)-INSPIRED SEESAW MECHANISM

International Journal of Modern Physics A ◽

10.1142/s0217751x01003056 ◽

2001 ◽

Vol 16 (04) ◽

pp. 609-623 ◽

Cited By ~ 6

Author(s):

MARIO ABUD ◽

FRANCO BUCCELLA

Keyword(s):

Experimental Data ◽

Solar Neutrino ◽

Neutrino Oscillations ◽

Mass Matrix ◽

Neutrino Masses ◽

Matrix Elements ◽

Seesaw Mechanism ◽

Solar Neutrino Problem ◽

Majorana Mass ◽

The Matrix

We determine the νR Majorana mass matrix from the experimental data on neutrino oscillations in the framework of a see-saw SO(10) model, where we impose the condition (MR)33=0 to avoid too large fine-tunings in the see-saw formula. We find a class of solutions with the two lowest neutrino masses almost degenerate and the scale of the matrix elements of MR in the range 1011–1012 GeV in agreement with Pati–Salam intermediate symmetry. We find also solutions with smaller neutrino masses, for which the scale of MR depends on the solution to the "solar neutrino problem" and on the value of the component of νe along the highest mass eigenstate, Ue3.

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