Probing Neutrino Physics with Effective Field Theories

Abstract

Despite the robust evidence provided by various experiments confirming the phenomenon of neutrino oscillations, which indicates the existence of neutrino masses and mixing, the underlying origin of these masses remains a mystery. One of the simplest ways to address this problem is by introducing right-handed neutrinos (RHN), which are allowed to have a Lepton Number Violation (LNV) Majorana mass. The inclusion of such particles can be realized via different scenarios, including some alternatives in which we have a lower RHN mass scale, while still explaining the smallness of neutrino masses. In this case, the RHNs can be light enough to be included in the low energy spectrum of the theory. Such RHNs can also be used to explain baryogenesis, via a leptogenesis-assisted framework. In this work, by using the Effective Field Theory (EFT) approach, we propose to study the effect of higher-dimensional LNV operators on the mechanism of low-scale leptogenesis and other related low-energy observables, such as the effective Majorana neutrino mass. By including the RHNs in the lower-energy spectrum, we can explore such operators in the neutrino Standard Model EFT (nuSMEFT) and also in the neutrino low-energy EFT (nuLEFT). In this context, we will explore experimental constraints coming from lepton flavor-violating processes, colliders, neutrino measurements, as well as cosmology.