Majorana neutrinos in an effective field theory approach

The discovery of neutrino oscillations and non-vanishing neutrino masses is one of the key recent advances made in particle physics. Tiny neutrino masses are very difficult to generate in a natural way in the Standard Model, based in the SU(3)C x SU(2)L x U(1)Y gauge group. Standard Yukawa interactions cannot explain the huge mass difference between the neutrinos and other fermions, and a very attractive scheme is the seesaw mechanism, incorporating right-handed Majorana neutrino species that allow for the lepton number violation. However, in typical seesaw scenarios, the couplings between the Majorana neutrinos and the light neutrinos must be vanishingly small in order to obtain tiny observed masses, leading to the decoupling of the former, and thus their detection (e.g., via lepton number violating processes) would be a signal of physics beyond the minimal seesaw framework. Here we consider a model independent scenario with one Majorana neutrino N with negligible mixing with the standard vL, introducing its interactions via an effective Lagrangian involving N and the standard fields and preserving SM symmetry. This leads to a very rich N phenomenology, and we have studied its decay, production, and detection mechanisms in present and future collider experiments.