Abstract
We study the supersymmetric extension of SO(10)-inspired thermal leptogenesis showing the constraints on neutrino parameters and on the reheat temperature TRH 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 tan β 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 10 ≲ m1/meV ≲ 30 (corresponding to 75≲ Σi mi/meV ≲ 120). Inverted ordering is still disfavoured, but an allowed region satisfying strong thermal leptogenesis opens up at large tan β values. We also study in detail the lower bound on TRH finding TRH ≳ 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 TRH ≳ 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.
Highlights
In this paper we extend the study of SO(10)-inspired leptogenesis to the supersymmetric case, showing how the constraints derived in the non-supersymmetric case change, with a particular focus on the lower bound on TRH
This result could somehow suggest that in the supersymmetric case one can expect a similar or even more stringent lower bound because of the increased washout, leading in this case to a tension with the gravitino problem upper bound that, as discussed in the introduction, in a conservative way can be assumed to be TRH 1010 GeV in order not to overproduce the gravitino abundance.11. This potential tension was confirmed by a dedicated analysis made in the supersymmetric case [60]. It was obtained TRH 1011 GeV, a result that would suggest that SO(10)-inspired thermal leptogenesis is incompatible with the upper bound from the gravitino problem unless, as discussed in the introduction, one assumes very specific supersymmetric models
We extended the study of SO(10)-inspired leptogenesis, previously discussed in a non-supersymmetric framework, to the supersymmetric case calculating the constraints on the low energy neutrino parameters and the lower bound on TRH that has a particular importance because of the tension with the upper bound from the gravitino problem
Summary
We extend the calculation of the asymmetry in the N2-dominated scenario, as rising from SO(10)-inspired conditions, to a supersymmetric framework. On the other hand for sufficiently large tan β values, such that M2 5 × 108 GeV (1 + tan β), the production occurs in the thee-flavoured regime and in this case the relic value of the final flavoured asymmetries are modified by the replacement K1μ → K1μ + K2μ and K1e → K1e + K2e in the exponentials In this way the conditions for the wash-out of the pre-existing asymmetry are less stringent since one has to impose K2τ , K1μ +K2μ, K1e +K2e 1, so that one can have K2μ 1 and K1μ 1, washing-out the pre-existing asymmetry and having a final muon (instead of tauon) dominated asymmetry, a new situation compared to the non-supersymmetric case
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