Search for a heavy Higgs boson decaying into a $Z$ boson and another heavy Higgs boson in the $\ell\ell bb$ and $\ell\ell WW$ final states in $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

TL;DR

This paper reports a search for a heavy neutral Higgs boson decaying into a Z boson and another heavy Higgs, using 13 TeV proton-proton collision data from ATLAS, setting upper limits and interpreting results within two-Higgs-Doublet models.

Contribution

The study provides the first comprehensive search for $A o ZH$ decays in the $ ext{ll}bb$ and $ ext{ll}WW$ channels at 13 TeV, with new upper limits and model interpretations.

Findings

No significant excess observed over Standard Model background.

Upper limits on production cross-section times branching ratio are set.

Results constrain parameters of two-Higgs-Doublet models.

Abstract

A search for a heavy neutral Higgs boson, $A$, decaying into a $Z$ boson and another heavy Higgs boson, $H$, is performed using a data sample corresponding to an integrated luminosity of 139 fb$^{-1}$ from proton-proton collisions at $\sqrt{s}$ = 13 TeV recorded by the ATLAS detector at the LHC. The search considers the $Z$ boson decaying into electrons or muons and the $H$ boson into a pair of $b$-quarks or $W$ bosons. The mass range considered is 230-800 GeV for the $A$ boson and 130-700 GeV for the $H$ boson. The data are in good agreement with the background predicted by the Standard Model, and therefore 95% confidence-level upper limits for $\sigma \times B(A\rightarrow ZH) \times B(H\rightarrow bb$ or $H\rightarrow WW)$ are set. The upper limits are in the range 0.0062-0.380 pb for the $H\rightarrow bb$ channel and in the range 0.023-8.9 pb for the $H\rightarrow WW$ channel. An interpretation of the results in the context of two-Higgs-Doublet models is also given.