AbstractA 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
→
Z
H
)
×
B
(
H
→
b
b
or
H
→
W
W
)
are set. The upper limits are in the range 0.0062–0.380 pb for the $$H\rightarrow bb$$
H
→
b
b
channel and in the range 0.023–8.9 pb for the $$H\rightarrow WW$$
H
→
W
W
channel. An interpretation of the results in the context of two-Higgs-doublet models is also given.
Constraints on the off-shell Higgs boson signal strength in the high-mass ZZ and WW final states with the ATLAS detector