Revisiting vectorlike quark models with enhanced top Yukawa coupling

Abstract

We revisit a scenario with an enhanced top yukawa coupling in vector-like quark (VLQ) models, where the top yukawa coupling is larger than the standard model value and the lightest VLQ has a negative yukawa coupling. We find that the parameter space satisfying the LHC bounds of the Higgs signal strengths consistently with the precision measurements is rather wide. Because the Lagrangian parameters of the yukawa couplings are large, such scenario can be realized in some strongly interacting theories. It also turns out that there is a noticeable relation between the contributions of the triangle and box diagrams in the gg → hh process by using the lowest order of the 1/M expansion where M is the heavy mass running in the loops.

Constraining composite Higgs models using LHC data

“…where F(H † H/f 2 ) is a function of the SU(2) L doublet Higgs field (H). The contributions from the higher dimensional operators with independent coefficients, added to the SM dimension-4 Yukawa term, give rise to a modification in the couplings of the Higgs with the fermions (f f h), see also [47,48] in a different context. In the minimal model, the SM fermions couple to only one operator of the strong sector.…”

The W boson mass weighs in on the non-standard Higgs

“…This is a universal property of Goldstone Higgs models [33]. Only couplings to fermions can be enhanced compared to the SM values, for specific choices of the model details [34]. In all the other cases, κ V is naturally larger than unity when the new scale is somewhat smaller that v, or the coupling r π > 1.…”