Supersymmetric SO(10)-inspired leptogenesis and a new N₂-dominated scenario

We study the supersymmetric extension of SO(10)-inspired thermal leptogenesis showing the constraints on neutrino parameters and on the reheat temperature T_RH that derive from the condition of successful leptogenesis from next-to-lightest right handed (RH) neutrinos (N₂) decays and the more stringent ones when independence of the initial conditions (strong thermal leptogenesis) is superimposed. In the latter case, the increase of the lightest right-handed neutrino (N₁) decay parameters helps the wash-out of a pre-existing asymmetry and constraints relax compared to the non-supersymmetric case. We find significant changes especially in the case of large tanβ values (∼> 15). In particular, for normal ordering, the atmospheric mixing angle can now be also maximal. The lightest left-handed neutrino mass is still constrained within the range 010 ∼< m₁/meV ∼< 3 (corresponding to 075∼< ∑_i m_i/meV ∼< 12). Inverted ordering is still disfavoured, but an allowed region satisfying strong thermal leptogenesis opens up at large tanβ values. We also study in detail the lower bound on T_RH finding T_RH∼> 1 × 10¹⁰ GeV independently of the initial N₂ abundance. Finally, we propose a new N₂-dominated scenario where the N₁ mass is lower than the sphaleron freeze-out temperature. In this case there is no N₁ wash-out and we find T_RH ∼> 1× 10⁹ GeV . These results indicate that SO(10)-inspired thermal leptogenesis can be made compatible with the upper bound from the gravitino problem, an important result in light of the role often played by supersymmetry in the quest of a realistic model of fermion masses