Low-scale seesaw with flavour and CP symmetries $–$ from colliders to leptogenesis

Abstract

We consider an extension of the Standard Model with three right-handed neutrinos, endowed with a flavour symmetry $G_f$, $G_f=\Delta (3n^2)$ or $G_f=\Delta (6n^2)$, $n\ge 2$, and CP. For large active-sterile mixing, we study the properties of the (nearly mass-degenerate) heavy neutrinos, such as their lifetimes and branching ratios. In doing so, we examine the four different cases, called Case 1) through Case 3 b.1), that lead to distinct lepton mixing patterns, all potentially compatible with current data. Furthermore, we comprehensively explore for each case the region of parameter space in which a sufficient amount of baryon asymmetry of the Universe can be generated via leptogenesis, while being testable at accelerator-based and potentially also precision flavour experiments.

Comments: 51 pages + 4 pages of appendices, 26 figures, 4 tables