Search for a CP-odd Higgs boson decaying into a heavy CP-even Higgs boson and a <i>Z</i> boson in the <i>l</i>+<i>l</i>-<i>t</i>(<i>t</i>)over-bar and ν(ν)over-bar<i>b</i>(<i>b</i>)over-bar final states using 140 fb-1 of data collected with the ATLAS detector

Abstract

<p>A search for a heavy CP-odd Higgs boson, <em>A</em>, decaying into a <em>Z</em> boson and a heavy CP-even Higgs boson, <em>H</em>, is presented. It uses the full LHC Run 2 dataset of <em>pp</em> collisions at 𝑠 = 13 TeV collected with the ATLAS detector, corresponding to an integrated luminosity of 140 fb^{<em>−</em>1}. The search for <em>A</em> → <em>ZH</em> is performed in the ℓ+ℓ−𝑡𝑡¯ and 𝜈𝜈¯𝑏𝑏¯ final states and surpasses the reach of previous searches in different final states in the region with <em>m</em>_<em>H</em> > 350 GeV and <em>m</em>_<em>A</em> > 800 GeV. No significant deviation from the Standard Model expectation is found. Upper limits are placed on the production cross-section times the decay branching ratios. Limits with less model dependence are also presented as functions of the reconstructed <em>m</em>(𝑡𝑡¯) and <em>m</em>(𝑏𝑏¯) distributions in the ℓ+ℓ−𝑡𝑡¯ and 𝜈𝜈¯𝑏𝑏¯ channels, respectively. In addition, the results are interpreted in the context of two-Higgs-doublet models.<br></p>