Three-Flavoured Non-Resonant Leptogenesis at Intermediate Scales

Abstract: Leptogenesis can successfully explain the matter-antimatter asymmetry via out-of-equilibrium decays of heavy Majorana neutrinos in the early Universe. In this article, we focus on non-resonant thermal leptogenesis and the possibility of lowering its scale. In order to do so, we calculate the lepton asymmetry produced from the decays of one and two heavy Majorana neutrinos using three-flavoured density matrix equations in an exhaustive exploration of the model parameter space. We find regions of the parameter space where thermal leptogenesis is viable at intermediate scales, $T\sim 10^{6}$ GeV. However, the viability of thermal leptogenesis at such scales requires a certain degree of cancellation between the tree and one-loop level contribution to the light neutrino mass matrix and we quantify such fine-tuning.