Cosmological constraints on sub-GeV dark vectors

Abstract

The purpose of this thesis is to recognize the effects of electromagnetic energy injection into the early Universe from decaying sub-GeV dark vectors. Decay widths and energy spectra for the most prominent channels in the sub-GeV region are calculated for various dark vector models. The models include the kinetic mixing of the dark photon with the Standard Model photon, U(1)_A' , a dark vector boson which couples to the baryon minus the lepton current, U(1)_B-L, and the last three are dark vector bosons which couple one lepton's current minus a different lepton's current, U(1)_Li-Lj where i != j = e, mu, tau . Measurements from Big Bang Nucleosynthesis and the Cosmic Microwave Background are used to constrain the lifetime, mass and coupling constant of the dark vectors.