Aspects of Models with vector-like singlet quarks

Vector-like quarks are simple extensions of the Standard Model (SM) with the potential to solve some of the open questions of the Standard Model. These are, in some sense, minimal extensions of the SM that can be probed in the next round of experiments. There is an analogy between vector-like quarks and right-handed neutrinos In both cases tree level Z mediated flavour changing neutral currents and scalar mediated flavour changing neutral currents are violated in a controlled way. Deviations from unitarity of the Cabibbo-Kobayashi-Maskawa matrix also arise. These new effects are naturally suppressed by the masses of the new quarks, that are constrained to be above the electroweak scale. In addition, striking new effects can be achieved with the inclusion of an extra complex scalar singlet. Such a "minimal" extension of the SM can give rise to new sources of CP violation with profound theoretical implications, allowing for a solution to the strong CP problem and a possible explanation for the baryon asymmetry of the Universe.