Low-scale seesaw with flavour and CP symmetries $\unicode{x2013}$ from colliders to leptogenesis

TL;DR

This paper explores a Standard Model extension with three right-handed neutrinos and specific flavour symmetries, analyzing heavy neutrino properties, lepton mixing patterns, and conditions for successful leptogenesis testable at experiments.

Contribution

It introduces a detailed study of low-scale seesaw models with flavour and CP symmetries, linking collider phenomenology to leptogenesis in a unified framework.

Findings

Heavy neutrinos are nearly mass-degenerate with measurable lifetimes.

Distinct lepton mixing patterns compatible with current data are identified.

Parameter regions for successful leptogenesis are mapped out for experimental testing.

Abstract

We consider an extension of the Standard Model with three right-handed neutrinos, endowed with a flavour symmetry $G_f$, $G_f=\Delta (3 \, n^2)$ or $G_f=\Delta (6 \, n^2)$, $n \geq 2$, 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.