There is a surprising connection between the top quark and Higgs alignment
in Gildener-Weinberg multi-Higgs-doublet models. Were it not for the top
quark and its large mass, the coupling of the 125 GeV Higgs boson H
to gauge bosons and fermions would be indistinguishable from those of the
Standard Model Higgs. The top quark’s coupling to a single Higgs doublet
breaks this perfect alignment in higher orders of the Coleman-Weinberg loop
expansion of the effective potential, but the effect is still small, <O(1%).
The experimental consequence of this is that many popular searches for
Beyond-Standard-Model Higgs bosons will remain fruitless.
