Towards constraints on the SUSY seesaw from flavour-dependent leptogenesis

We systematically investigate constraints on the parameters of the supersymmetric type-I seesaw mechanism from the requirement of successful thermal leptogenesis in the presence of upper bounds on the reheat temperature $T_\mathrm{RH}$ of the early Universe. To this end, we solve the flavour-dependent Boltzmann equations in the MSSM, extended to include reheating. With conservative bounds on $T_\mathrm{RH}$, leading to mildly constrained scenarios for thermal leptogenesis, compatibility with observation can be obtained for extensive new regions of the parameter space, due to flavour-dependent effects. On the other hand, focusing on (normal) hierarchical light and heavy neutrinos, the hypothesis that there is no CP violation associated with the right-handed neutrino sector, and that leptogenesis exclusively arises from the CP-violating phases of the $U_\text{MNS}$ matrix, is only marginally consistent. Taking into account stricter bounds on $T_\mathrm{RH}$ further suggests that (additional) sources of CP violation must arise from the right-handed neutrino sector, further implying stronger constraints for the right-handed neutrino parameters.Comment: 42 pages, 12 figures; final version published in JCAP; numerical results for the efficiency factor can be downloaded from http://www.newphysics.eu/leptogenesis

Viability of Dirac phase leptogenesis

We discuss the conditions for a non-vanishing Dirac phase ? and mixing angle ?13, sources of CP violation in neutrino oscillations, to be uniquely responsible for the observed matter–antimatter asymmetry of the Universe through leptogenesis. We show that this scenario, that we call ?-leptogenesis, is viable when the degenerate limit for the heavy right-handed (RH) neutrino spectrum is considered. We derive an interesting joint condition on sin?13 and the absolute neutrino mass scale that can be tested in future neutrino oscillation experiments. In the limit of the hierarchical heavy RH neutrino spectrum, we strengthen the previous result that ?-leptogenesis is only very marginally allowed, even when the production from the two heavier RH neutrinos is taken into account. An improved experimental upper bound on sin?13 and/or an account of quantum kinetic effects could completely rule out this option in the future. Therefore, ?-leptogenesis can be also regarded as motivation for models with degenerate heavy neutrino spectrum