Search for fermion universality of the Dirac component of neutrino mass matrix

Abstract

An effective texture is presented for six Majorana neutrinos, three active and three (conventional) sterile, based on a 6x6 mass matrix, whose 3x3 active--sterile component (i.e., Dirac component) is conjectured to get a fermion universal form similar to the constructed previously 3x3 mass matrix for charged leptons and 3x3 mass matrices for up and down quarks. This is true, however, when the bimaximal mixing, specific for neutrinos, is transformed out unitarily from the neutrino mass matrix. The 3x3 active--active component (i.e., lefthanded component) of neutrino 6x6 mass matrix is diagonal and gets degenerate entries. It dominates over the whole neutrino mass matrix. In such a texture, three neutrino masses are nearly degenerate, $ m_1 \simeq m_2 \simeq m_3 $, but their mass-squared differences appear hierarchical, $\Delta m^2_{21} \ll \Delta m^2_{32} \simeq \Delta m^2_{31}$, while the remaining three neutrino masses can be constructed to vanish, $ m_4 = m_5 = m_6 = 0 $, in contrast to the familiar seesaw mechanism.