• effective field theory
• phenomenology
• seesaw models

This thesis studies the phenomenology of the type II seesaw model, an extension of the Standard Model (SM) that explains neutrino masses through the introduction of an SU(2)L scalar triplet Δ. Our main focus is the study of its effective field theory extension, the ΔEFT, which includes non-renormalizable operators. We first investigate the role of dimension-five operators, deriving new interaction vertices and computing their effects on decay widths and production cross-sections. This allows us to determine whether their contributions can significantly modify predictions in different regions of the parameter space. The analysis is then extended to dimension-five and -six operators at low energies, with constraints on Wilson coefficients obtained by matching the ΔEFT onto the SMEFT and by fitting electroweak precision observables. A collider proto-analysis is also performed, where a dimension-five vertex is implemented in FeynRules and simulated with MadGraph5, to assess its impact on kinematic distributions. Finally, we discuss possible mediators from which dimension-five operators could arise and examine their embedding within unified frameworks.