  Neutrino flavor conversion is assumed to be induced by right-handed neutrino
flavor conversion via seesaw mechanism. Neutrino oscillation is the macroscopic
phenomenon before all neutrino flavor-flip interactions reaching equilibrium.
The model for the hypothesis is the extension by introducing large mass
Majorana right-handed neutrino into the Standard Model and exerting horizontal
symmetry only on the right-handed neutrino sector.
