A search for heavy resonances decaying into a
pair of Z bosons leading to ℓ+ℓ−ℓ+ℓ− and ℓ+ℓ−νν¯ final
states, where stands for either an electron or a muon, is
presented. The search uses proton–proton collision data at a
centre-of-mass energy of 13 TeV corresponding to an integrated
luminosity of 36.1 fb−1 collected with the ATLAS
detector during 2015 and 2016 at the Large Hadron Collider.
Different mass ranges for the hypothetical resonances are
considered, depending on the final state and model. The different
ranges span between 200 and 2000 GeV. The results
are interpreted as upper limits on the production cross section
of a spin-0 or spin-2 resonance. The upper limits for
the spin-0 resonance are translated to exclusion contours in
the context of Type-I and Type-II two-Higgs-doublet models,
while those for the spin-2 resonance are used to constrain
the Randall–Sundrum model with an extra dimension giving
rise to spin-2 graviton excitations.