Enhancing the Higgs associated production with a top quark pair

TL;DR

This paper proposes models similar to type-II 2HDM where Higgs production with top quarks can be significantly enhanced, aligning with experimental excesses, without conflicting with existing constraints.

Contribution

It introduces a mechanism within NMSSM with light stops that can boost the $tth$ signal, matching observed experimental excesses.

Findings

$tth$ production rate can be twice the SM prediction.

Higgs coupling modifications allow compatibility with experimental data.

Light stops influence gluon fusion rates and Higgs decay channels.

Abstract

It is pointed out that in a wide class of models reminiscent of type-II Two-Higgs-Doublet Models (2HDM) the signal of the Higgs produced in association with a top-antitop quark pair ($tth$) and decaying into gauge bosons can be significantly larger than the Standard Model (SM) prediction without violating any experimental constraints. The crucial feature of these models is enhanced (suppressed) Higgs coupling to top (bottom) quarks and existence of light colored particles that give negative contribution to the effective Higgs coupling to gluons resulting in the gluon fusion rates in the gauge boson decay channels close to SM predictions. We demonstrate this mechanism in NMSSM with light stops and show that $tth$ signal in the $WW$ decay channel can be two times larger than the SM prediction, as suggested by the excesses observed by ATLAS and CMS, provided that the Higgs-singlet superpotential coupling $\lambda\gtrsim0.8$ and the MSSM-like Higgs boson masses are in the range of 160 to 300 GeV.