Higgs alignment and the top quark

TL;DR

This paper explores the subtle influence of the top quark on Higgs alignment in multi-Higgs models, showing that its effect slightly breaks the perfect alignment predicted by simpler models, but remains experimentally challenging to detect.

Contribution

It reveals a small but fundamental connection between the top quark and Higgs alignment in Gildener-Weinberg multi-Higgs doublet models, highlighting the top quark's role in higher-order corrections.

Findings

Top quark coupling slightly breaks Higgs alignment

Effect size is less than 1%

Potentially inaccessible experimentally

Abstract

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, $< {\cal{O}}(1\%)$, and probably experimentally inaccessible.