This repository contains my Bachelor's thesis work document, titled "Thermal leptogenesis in the type-I Dirac seesaw extension to the DFSZ axion model for dark matter". Link in Google Drive: https://drive.google.com/file/d/1ZKikk7BBdSC9gHrxAvJtC4-r57_cjog4/view?usp=sharing
Abstract:
The type-I Dirac seesaw extension is made to the DFSZ axion model, where light active neutrinos are Dirac particles and acquire mass through the canonical seesaw mechanism after the Peccei-Quinn and electroweak symmetry breaking, finding that neutrino mass can be approximated to m_{\nu}≈vf_{a}/Λ_{UV}, result which relates the three energy scales involved in the model: the mass of the heavy sterile Dirac fermions introduced (Λ_{UV}), the Peccei-Quinn spontaneous symmetry breaking scale given by the axion coupling constant (f_{a}), and the electroweak scale (v). As a consequence, it was found that 10^{3}f_{a}∼Λ_{UV}, hence neutrino Yukawa coupling associated to the QCD axion, which is candidate to dark matter, is highly suppressed (up to 10^{−10}) in comparison to the Higgs. Dirac neutrino effective mass matrix is computed explicitly, whose components depend on active-sterile mixing parameters, the latter being new sources of CP violation. Therefore, the CP asymmetry factor and the baryon-antibaryon density are computed for the unflavoured leptogenesis, linking neutrino physics, QCD axion, and cosmological parameters into a same theoretical model.