  After discovery of the Higgs boson at CERN the Standard Model acquired a
status of the theory of the elementary particles in the electroweak range (up
to about 300 GeV). What general conclusions can be inferred from the Standard
Model? It looks that the Standard Model teaches us that in the framework of
such general principles as local gauge symmetry, unification of weak and
electromagnetic interactions and Brout-Englert-Higgs spontaneous breaking of
the electroweak symmetry nature chooses the simplest possibilities.
Two-component left-handed massless neutrino fields play crucial role in the
determination of the charged current structure of the Standard Model. The
absence of the right-handed neutrino fields in the Standard Model is the
simplest, most economical possibility. In such a scenario Majorana mass term is
the only possibility for neutrinos to be massive and mixed. Such mass term is
generated by the lepton-number violating Weinberg effective Lagrangian. In this
approach three Majorana neutrino masses are suppressed with respect to the
masses of other fundamental fermions by the ratio of the electroweak scale and
a scale of a lepton-number violating physics. The discovery of the neutrinoless
double $\beta$-decay and absence of transitions of flavor neutrinos into
sterile states would be evidence in favor of the minimal scenario we advocate
here.
