Description
The extension of the adjoint SU(5) model with a flavour symmetry based
on Z_4 group is investigated. The Z_4 symmetry is introduced with the
aim to lead the up- and down-quark mass matrices in the
Nearest-Neighbour-Interaction form. As consequence of the discrete
symmetry embedded in the SU(5) gauge group the charged lepton mass
matrix also gets the same form. Within this model, light neutrinos get
their masses through type-I, type-III and one-loop radiative seesaw
mechanisms, implemented, respectively, via a singlet, a triplet and an
octet from the adjoint fermionic 24 fields. It is demonstrated that
the neutrino phenomenology oblige the introduction of at least three
24 fermionic multiplets. The symmetry SU(5) X Z_4 allows only two
viable zero textures for the effective neutrino mass matrix. It is
showed that one texture is compatible with normal hierarchy, while the
other with inverted hierarchy in the light neutrino mass
spectrum. Finally, it is also demonstrated that Z_4 freezes out the
possibility of proton decay through exchange of colour Higgs triplets
at tree-level.
Author
David Emmanuel-Costa
(IST-ID, LISBOA, PORTUGAL)
