Professor Daniela Bortoletto

Abstract:

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 $$^{-1}$$ -1 from proton–proton collisions at $$\sqrt{s} = 13$$ s=13 $$\text {TeV}$$ 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 $$\text {GeV}$$ GeV for the A boson and 130–700 $$\text {GeV}$$ 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 $$\sigma \times B(A\rightarrow ZH)\times B(H\rightarrow bb \; \text {or} \; H \rightarrow WW)$$ σ×B(A→ZH)×B(H→bborH→WW) are set. The upper limits are in the range 0.0062–0.380 pb for the $$H\rightarrow bb$$ H→bb channel and in the range 0.023–8.9 pb for the $$H\rightarrow WW$$ H→WW channel. An interpretation of the results in the context of two-Higgs-doublet models is also given.