Constraint on the total width of the Higgs boson from Higgs boson and four-top-quark measurements in $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

TL;DR

This paper constrains the total width of the Higgs boson by combining on-shell and four-top-quark production measurements at 13 TeV, avoiding assumptions about off-shell production rates, and sets upper limits of 450 MeV and 160 MeV.

Contribution

It introduces a novel method to constrain the Higgs width using combined measurements that do not rely on assumptions about off-shell production rates.

Findings

Observed 95% CL upper limit on Higgs width is 450 MeV.

Considering Higgs-top Yukawa coupling constraints yields an upper limit of 160 MeV.

Method avoids assumptions about off-shell Higgs production rates.

Abstract

This Letter presents a constraint on the total width of the Higgs boson ($\Gamma_H$) using a combined measurement of on-shell Higgs boson production and the production of four top quarks, which involves contributions from off-shell Higgs boson-mediated processes. This method relies on the assumption that the tree-level Higgs-top Yukawa coupling strength is the same for on-shell and off-shell Higgs boson production processes, thereby avoiding any assumptions about the relationship between on-shell and off-shell gluon fusion Higgs production rates, which were central to previous measurements. The result is based on up to 140 fb$^{-1}$ of proton-proton collisions at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV collected with the ATLAS detector at the Large Hadron Collider. The observed (expected) 95% confidence level upper limit on $\Gamma_H$ is 450 MeV (75 MeV). Additionally, considering the constraint on the Higgs-top Yukawa coupling from loop-induced Higgs boson production and decay processes further yields an observed (expected) upper limit of 160 MeV (55 MeV).