Probing Higgs Width and Top Quark Yukawa Coupling from $t\bar{t}H$ and $t\bar{t}t\bar{t}$ Productions

TL;DR

This paper shows that four top-quark production processes can effectively constrain the Higgs boson width and top Yukawa coupling at the LHC, independent of Higgs decay modes, with projected bounds improving with higher luminosity.

Contribution

It introduces a novel approach using four top-quark production to constrain Higgs width and top Yukawa coupling without relying on Higgs decay channels.

Findings

Bound on Higgs width: $oxed{ ext{up to } 3.1 imes ext{SM}}$ at 14 TeV with 300 fb$^{-1}$

Improved bound: $oxed{ ext{up to } 2.1 imes ext{SM}}$ at 14 TeV with 500 fb$^{-1}$

Demonstrates robustness of constraints against Higgs decay assumptions.

Abstract

We demonstrate that four top-quark production is a powerful tool to constrain the top Yukawa coupling. The constraint is robust in the sense that it does not rely on the Higgs boson decay. Taking into account the projection of the $t\bar{t}H$ production by the ATLAS collaobration, we obtain a bound on Higgs boson width, $\Gamma_H\leq 3.1~\Gamma_H^{\rm SM}$, at the 14 TeV LHC with an integrated luminosity of $300~{\rm fb}^{-1}$. Increasing the luminosity to $500~{\rm fb}^{-1}$ yields $\Gamma_H\leq 2.1~\Gamma_H^{\rm SM}$.