Speaker
Description
Neutrino mass models usually involve the breaking of a custodial symmetry related to the masslessness of neutrinos in the Standard Model. Focusing on low-scale seesaws, we will show how, in contrast with scenarios where the symmetry is explicitly broken, the case of spontaneous symmetry breaking introduces crucial distinct directions, mainly through the associated Nambu-Goldstone Boson ($G$). In this talk, we will explore how the NGB associated with the spontaneous breaking of a global $B-L$ symmetry (giving rise to the Majoron or the Diracon) is the key to testing and falsifying these models. In particular, we will discuss how flavour-violating processes such as $\mu \to e G$ become more relevant and experimentally accessible than the typical loop-induced cLFV signal $\mu \to e \gamma$, offering a sharp, distinct signature in both laboratory searches and cosmological bounds.