Seesaw model in SO(10) with an upper limit on right-handed neutrino masses

Understand

In the framework of SO(10) gauge unification and the seesaw mechanism, we show that the upper bound on the mass of the heaviest right-handed neutrino $M_{R_3} < 3 \times 10^{11}$ GeV, given by the Pati-Salam intermediate scale of $B-L$ spontaneous symmetry breaking, constrains the observables related to the left-handed light neutrino mass matrix.

• We assume such an upper limit on the masses of right-handed neutrinos and, as a first approximation, a Cabibbo form for the matrix $V^L$ that diagonalizes the Dirac neutrino matrix $m_D$.
• Using the inverse seesaw formula, we show that our hypotheses imply a triangular relation in the complex plane of the light neutrino masses with the Majorana phases.
• We obtain normal hierarchy with an absolute scale for the light neutrino spectrum.