Master Thesis defense by Kevin Urquía Calderón

Title: Lepton collider sensitivity to Heavy Neutral Lepton from Left-Right Symmetric Models

Abstract:

Left-right symmetric models (LRSM) were initially proposed to reconcile violation of parity in weak interactions with our intrinsic notion of a fundamental parity symmetry. Very soon after their proposal, it was realized that LRSM can also fit small neutrino masses, in part due to the incorporation of right-handed neutrinos (or Heavy Neutral Leptons, HNLs), /N/.

In this thesis we review on fundamental concepts in LRSM, including relatively recent developments. Then we study for the first time the potential that different proposals for lepton colliders (FCC-ee, CEPC, ILC, CLIC and a Muon Collider) have for the production and discovery of a pair of HNLs. Of particular interest are the background free signals that the model can give: doubly-displaced vertices and lepton number violating signals.

We find that some of our results reach regions of the parameter space that are impossible to reach with current experiments.