Aspects of Low Scale Leptogenesis and Connection to Dark Matter

Abstract

quotThe observed baryon asymmetry and dark matter (DM) in the universe have been two longstanding puzzles in particle physics and cosmology. While the standard model (SM) of particle physics can neither satisfy the required criteria to generate the observed baryon asymmetry of universe (BAU) dynamically nor offer a viable DM candidate. Among several popular mechanisms put forward to explain these observed phenomena, leptogenesis is one of the most popular one to explain the origin of BAU whereas particle DM of thermal or non-thermal origin having mass around the electroweak scale has been a popular DM paradigm. In this thesis, we aim to study a few leptogenesis scenarios which can also shed light on the origin of DM. A common framework for explaining both the BAU and DM is motivating due to its minimal and predictive nature. We consider a few realistic particle physics models where there exist new particles and symmetries beyond those in the SM. While canonical neutrino mass models, also known as seesaw models, predict high scale leptogenesis out of reach from direct search experiments, we focus on leptogenesis and DM scenarios where scale of leptogenesis can be brought down to TeV corner such that these scenarios can be tested at near future experiments. After giving introduction to the observed evidences and popular theoretical mechanisms for BAU and DM in chapter 1, we consider a radiative seesaw, known as the minimal scotogenic model in chapter 2, to study the possibility of thermal as well as non-thermal fermion singlet DM with the heavier singlet fermions being responsible for successful leptogenesis. In chapter 3, we study a novel scenario where lepton asymmetry is generated from three-body decay of a heavy fermion with DM as one of the final states. While phase-space suppression and involvement of new parameters independent of neutrino mass lead to sub-TeV scale leptogenesis, the DM sector naturally emerges as a two-component type. In chapter 4, we study the possibility of having successful TeV scale leptoge