Vector-like quarks with a scalar triplet

Abstract

We study a minimal extension to the Standard Model with an additional real scalar triplet, $\Sigma$, and a single vector-like quark, $T$. This class of models appear naturally in extensions of the Littlest Higgs model that incorporate dark matter without the need of $T$-parity. We assume the limit that the triplet does not develop a vacuum expectation value and that all dimension five operators coupling the triplet to Standard Model fields and the vector-like quarks are characterized by the scale $\Lambda$ at which we expect new physics to arise. We introduce new non-renormalizable interactions between the new scalar sector and fermion sector that allow mixing between the Standard Model third generation up-type quark and the vector-like quark in a way that leads to the cancellation of the leading quadratic divergences to the one-loop corrections from the top quark to the mass of the Higgs boson. Within this framework, new decay modes of the vector-like quark to the real scalar triplet and SM particles arise and bring forth an opportunity to probe this model with existing and future LHC data. We contrast constraints from direct colliders searches with low energy precision measurements and find that heavy vector-like top quarks with a mass as low as $650$ GeV are consistent with current experimental constraints in models where new physics arises at scales below $2$ TeV

Electroweak baryogenesis with vector-like leptons and scalar singlets

“…This correction is many orders of magnitude smaller than those found in vector-like quark models [52], as the latter feature factors of m t /M ψ rather than m τ /M ψ , and generally consider much larger Yukawa couplings than those considered here. Corrections to the weak gauge couplings of this order of magnitude are easily small enough to avoid existing constraints on lepton universality and Z-coupling measurements [53,54].…”

Impact of Yukawa-like dimension-five operators on the Georgi-Machacek model

“…We note that the presence of higher dimensional Yukawa-like operators is, in fact, a generic feature of a large class of BSM theories. They can arise, for example, when heavy vector-like fermions are integrated out [29,30]. A broad class of composite Higgs models (e.g.…”