Constraints on off-shell Higgs boson production and the Higgs boson total width in $ZZ\to4\ell$ and $ZZ\to2\ell2\nu$ final states with the ATLAS detector

TL;DR

This paper measures off-shell Higgs boson production in ZZ decay channels using ATLAS data at 13 TeV, setting limits on the Higgs total width and off-shell signal strength to test Standard Model predictions.

Contribution

It provides the first combined measurement of off-shell Higgs production and total width constraints using 13 TeV ATLAS data in ZZ decay channels.

Findings

Upper limit on off-shell Higgs signal strength: 3.8 at 95% CL

Upper limit on Higgs total width: 14.4 MeV at 95% CL

Consistent with Standard Model predictions

Abstract

A measurement of off-shell Higgs boson production in the $ZZ\to4\ell$ and $ZZ\to2\ell2\nu$ decay channels, where $\ell$ stands for either an electron or a muon, is performed using data from proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=13$ TeV. The data were collected by the ATLAS experiment in 2015 and 2016 at the Large Hadron Collider, and they correspond to an integrated luminosity of 36.1 fb$^{-1}$. An observed (expected) upper limit on the off-shell Higgs signal strength, defined as the event yield normalised to the Standard Model prediction, of 3.8 (3.4) is obtained at 95% confidence level (CL). Assuming the ratio of the Higgs boson couplings to the Standard Model predictions is independent of the momentum transfer of the Higgs production mechanism considered in the analysis, a combination with the on-shell signal-strength measurements yields an observed (expected) 95% CL upper limit on the Higgs boson total width of 14.4 (15.2) MeV.