Search for heavy resonances decaying into a pair of Z bosons in the $$\ell ^+\ell ^-\ell '^+\ell '^-$$ ℓ + ℓ - ℓ ′ + ℓ ′ - and $$\ell ^+\ell ^-\nu {{\bar{\nu }}}$$ ℓ + ℓ - ν ν ¯ final states using 139 $$\mathrm {fb}^{-1}$$ fb - 1 of proton–proton collisions at $$\sqrt{s} = 13\,$$ s = 13 TeV with the ATLAS detector

A search for heavy resonances decaying into a pair of Z bosons leading to $$\ell ^+\ell ^-\ell '^+\ell '^-$$ and $$\ell ^+\ell ^-\nu {{\bar{\nu }}}$$ final states, where $$\ell $$ 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 collected from 2015 to 2018 that corresponds to the integrated luminosity of 139 $$\mathrm {fb}^{-1}$$ recorded by the ATLAS detector during Run 2 of the Large Hadron Collider. Different mass ranges spanning 200 GeV to 2000 GeV for the hypothetical resonances are considered, depending on the final state and model. In the absence of a significant observed excess, 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, and the limits for the spin-2 resonance are used to constrain the Randall–Sundrum model with an extra dimension giving rise to spin-2 graviton excitations.