Heavy Seesaw Neutrinos as Long Lived Particles : A Phenomenological Perspective

Sammanfattning

In this thesis we explore two possible extensions of the Standard Model that is able to explain the origin of neutrino masses. The first model under consideration in this thesis is the Left-Right Symmetric Model where one extends the gauge group of the Standard Model by a $SU(2)_R$ gauge group and a modified $U(1)_{Y}$ group by the $U(1)_{B-L}$ group. This allows for the introduction of new scalar fields, gauge bosons and right-handed lepton doublets, including heavy right-handed neutrinos, that allows for Dirac and Majorana mass terms for neutrinos in the Lagrangian as well as providing possible interactions, such as the Keung-Senjanovic process, to explore in current and future colliders. The second model we consider is the $U(1)_{B-L}$ gauge extension of the Standard Model which introduces one extra singlet scalar, a new neutral gauge boson $Z'$ and heavy right-handed neutrinos. Here, we investigate the production of $Z'$ bosons after proton-proton collision which produces quarks and leptons in the final state through intermediate right-handed neutrinos. The processes under consideration in thesis has the possibility of displaying displaced vertices which are very promising features to look at when looking for new physics as the Standard Model has little background for these types of phenomenon. The primary goal of this thesis is to explore the possibility of finding these displaced vertices in current and future colliders. We used Monte-Carlo based event simulators such as MadGraph 5 and Pythia8 to generate events of the processes and a modified version of Delphes for detector simulations. We present the displaced results and reconstruct the invariant mass of the final-state objects and discuss our findings.