Speaker
Description
We investigate type-I seesaw frameworks motivated by Grand Unification, focusing on the generic consequences of hierarchical Dirac neutrino masses as expected in many SO(10)-type constructions where neutrino Yukawa couplings are linked to the up-quark sector. Excluding the well-known highly fine-tuned crossing-level solutions and using current low-energy neutrino data, we show that these setups generically lead to a strongly hierarchical right-handed (RH) neutrino spectrum, with RH masses scaling approximately as M_i \propto m_{D i}^2; remarkably, this conclusion holds independently of any additional model-dependent assumptions on the Dirac neutrino mass matrix. If, moreover, the Dirac neutrino masses are not too different from the up-quark masses, as naturally suggested by GUT relations, the intermediate RH neutrino N_2 lies in the mass range required for successful N_2-leptogenesis, extending and strengthening the applicability of SO(10)-inspired leptogenesis beyond specific texture choices. We also include flavour coupling effects in the computation of the final asymmetry within this extended GUT-motivated leptogenesis class and discuss their quantitative impact on the viable parameter space.
