Bounds for the mass of the heaviest right-handed neutrino in SO(10) theories

By relating the Dirac neutrino mass matrix to the mass of the charged fermions and assuming that the product of the masses of the two lightest left-handed neutrinos is of the order of $\Delta m^2_{\rm sol}$, we derive, within a leptogenesis scenario, a range of values for the mass of the heaviest right-handed neutrino, centered around the scale of B–L symmetry breaking in the SO(10) theory with Pati–Salam intermediate symmetry.