Lepton Flavor Violation Phenomenology Beyond the Standard Model

Abstract

Historically, experimental searches for flavor violating processes have been essential for the theoretical developments in Particle Physics. After the detection of neutrino oscillations, the most clear experimental evidence for new physics at present comes from lepton flavor violation (LFV) in the neutrino sector. Whereas a new window to physics beyond the Standard Model (SM) and even beyond neutrino masses can be opened if a positive signal from LFV processes in the charge sector is observed by ongoing or future facilities. The upper limits on these kind of processes serve as a very powerful probe to test new models of neutrino masses. In this thesis we analyze the LFV phenomenology generated by two models that induce neutrino masses through different mechanisms. In the first case, we investigate LFV in the the singlet-triplet scotogenic model in which neutrinos acquire non-zero masses at the 1-loop level. In contrast to the most popular variant of this setup, the singlet scotogenic model, this version includes a triplet fermion as well as a triplet scalar, leading to a scenario with a richer dark matter phenomenology. Taking into account results from neutrino oscillation experiments, we explore some aspects of the LFV phenomenology of the model. In particular, we study the relative weight of the dipole operators with respect to other contributions to the LFV amplitudes and determine the most constraining observables. We show that in large portions of the parameter space, the most promising experimental perspectives are found for LFV 3-body decays and for coherent μ-e conversion in nuclei. <br /> Given that in recent years several observables associated to semileptonic b→s processes have been found to depart from their predicted values in the SM, including a few tantalizing hints of lepton flavor universality violation. In the second work we consider an existing model with a massive Z' boson that addresses the anomalies in b→s transitions and extend it with a non-trivial embedding of neutrino masses. We analyze LFV effects induced by the non-universal interaction associated to the b→s anomalies and by the new physics associated to the neutrino mass generation, and determine the expected ranges for the most relevant observables.