Handbook of vectorlike quarks: Mixing and single production

TLDR

The study constrains vector‑like quark mixing with the third generation and examines its impact on LHC phenomenology, including heavy‑quark decays, single production, and indirect modifications of top and bottom couplings. The authors analyze seven vector‑like quark representations, deriving constraints from electroweak oblique parameters and LEP/SLC Z→bb data, and assess their effects on single Higgs production and decay at the LHC. They find that a hypercharge –5/6 doublet can account for the anomalous forward‑backward asymmetry observed in Z→bb at LEP.

Abstract

We obtain constraints on the mixing of vector-like quarks coupling predominantly to the third generation. We consider all (seven) relevant types of vector-like quarks, individually. The constraints are derived from oblique corrections and Z -> b bbar measurements at LEP and SLC. We investigate the implications of these constraints on LHC phenomenology, concerning the decays of the heavy quarks and their single production. We also explore indirect effects of heavy quark mixing in top and bottom couplings. A remarkable effect is the possibility of explaining the anomalous forward-backward asymmetry in Z -> b bbar at LEP, with a hypercharge -5/6 doublet. We also study the impact of the new quarks on single Higgs production at the LHC and Higgs decay.