251 research outputs found
Minimal archi-texture for neutrino mass matrices
The origin of the observed masses and mixing angles of quarks and leptons is
one of imperative subjects in and beyond the standard model. Toward a deeper
understanding of flavor structure, we investigate in this paper the minimality
of fermion mass (Yukawa) matrices in unified theory. That is, the simplest
matrix form is explored in light of the current experimental data for quarks
and leptons, including the recent measurements of quark CP violation and
neutrino oscillations. Two types of neutrino mass schemes are particularly
analyzed; (i) Majorana masses of left-handed neutrinos with unspecified
mechanism and (ii) Dirac and Majorana masses introducing three right-handed
neutrinos. As a result, new classes of neutrino mass matrices are found to be
consistent to the low-energy experimental data and high-energy unification
hypothesis. For distinctive phenomenological implications of the minimal
fermion mass textures, we discuss flavor-violating decay of charged leptons,
the baryon asymmetry of the universe via thermal leptogenesis, neutrino-less
double beta decay, and low-energy leptonic CP violation.Comment: 37 pages, 6 figure
Relation between CKM and MNS Matrices Induced by Bi-Maximal Rotations in the Seesaw Mechanism
It is found that the seesaw mechanism not only explains the smallness of
neutrino masses but also accounts for the large mixing angles simultaneously,
even if the unification of the neutrino Dirac mass matrix with that of up-type
quark sector is realized. In this mechanism, we show that the mixing matrix of
the Dirac-type mass matrix gets extra rotations from the diagonalization of
Majorana mass matrix. Assuming that the mixing angles to diagonalize the
Majorana mass matrix are extremely small, we find that the large mixing angles
of leptonic sector found in atmospheric and long baseline reactor neutrino
oscillation experiments can be explained by these extra rotations. We also find
that provided the mixing angle around y-axis to diagonalize the Majorana mass
matrix vanishes, we can derive the information about the absolute values of
neutrino masses and Majorana mass responsible for the neutrinoless double beta
decay experiment through the data set of neutrino experiments. In the
simplified case that there is no CP phase, we find that the neutrino masses are
decided as and that there are no solution which
satisfy (inverted mass spectrum). Then, including all CP phases,
we reanalyze the absolute values of neutrino masses and Majorana mass
responsible for the neutrinoless double beta decay experiment.Comment: 19 pages, 7 figures, revtex4, to appear in J.PHYS.SOC.JA
On Neutrinos and Fermionic Mass Patterns
Recent data on neutrino mass differences are consistent with a hierarchical
neutrino mass structure strikingly similar to what is observed for the other
fermionic masses.Comment: 8pages, 2figure
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