New Vector-Like Fermions and Flavor Physics

We study renormalizable extensions of the standard model that contain vector-like fermions in a (single) complex representation of the standard model gauge group. There are 11 models where the vector-like fermions Yukawa couple to the standard model fermions via the Higgs field. These models do not introduce additional finetunings. They can lead to, and are constrained by, a number of different flavorchanging processes involving leptons and quarks, as well as direct searches. Contrary to many other extensions of the standard model, an interesting feature of the models with strongly interacting vector-like fermions is that constraints from neutral meson mixings (apart from CP violation in K0 − K̄0 mixing) are not sensitive to higher scales than other flavor-changing neutral-current processes.