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arXiv · 1506.03484

New Vector-Like Fermions and Flavor Physics

Koji Ishiwata·Zoltan Ligeti·Mark B. Wise
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Abstract

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 fine- tunings. They can lead to, and are constrained by, a number of different flavor- changing processes involving leptons and quarks, as well as direct searches. An interesting feature of the models with strongly interacting vector-like fermions is that constraints from neutral meson mixings (apart from CP violation in neutral kaon mixing) are not sensitive to higher scales than other flavor-changing neutral-current processes. We identify order 1/(4 pi M)^2 (where M is the vector-like fermion mass) one-loop contributions to the coefficients of the four-quark operators for meson mixing, that are not suppressed by standard model quark masses and/or mixing angles.

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Koji Ishiwata, Zoltan Ligeti, Mark B. Wise. 2015-09-15. New Vector-Like Fermions and Flavor Physics. https://doi.org/10.1007/jhep10(2015)027

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