Speaker
Description
Models based on the type-I seesaw mechanism are among the most popular ones for explaining neutrino masses. These models predict that neutrinos are Majorana fermions, either through the explicit or the spontaneous breaking of lepton number. Furthermore, some models introduce seesaw mediators at very high energy scales, while others operate at energies not far from the electroweak scale. I will provide a comprehensive analysis of the Type-I Seesaw family of neutrino mass models, including the conventional type-I seesaw and its low-scale variants. After showing that all these models correspond to a particular form of the type-I seesaw when the breaking of lepton number is explicit, I will delve into the more interesting scenario of spontaneous lepton number violation, systematically categorizing all inequivalent minimal models. In the latter scenario, a Goldstone boson emerges in the spectrum, the majoron ($J$). This leads to a very rich phenomenology and allows for the differentiation among models. In particular, I will discuss models in which, despite having heavy mediators and not being visible in processes such as $\mu \to e \gamma$, could be tested in experiments looking for $\mu \to e J$.