Search for new phenomena in the $Z(\rightarrow\ell\ell) + E_{\mathrm{T}}^{\mathrm{miss}}$ final state at $\sqrt{s}$ = 13 TeV with the ATLAS detector

A study of the $\ell\ell+E^{\mathrm{miss}}_{\mathrm{T}}$ ($\ell=\; e,\;\mu$) final state is performed using 13.3 fb$^{-1}$ of 13 TeV proton-proton collision data collected by the ATLAS experiment. The collisions were produced by the Large Hadron Collider in 2015 and the first half of 2016. The analysis is optimised to address three searches: 1) the search for new heavy resonances decaying to $ZZ\rightarrow \ell\ell\nu\nu$, 2) the search for dark matter in association with a leptonically decaying $Z$ boson and 3) the search for an invisibly decaying Higgs boson in the channel $ZH$, $Z\rightarrow \ell\ell$. New physics is searched for as an excess over the Standard Model predictions in the $ZZ$ transverse mass distribution and in the missing transverse momentum distribution. Results are found to be compatible with Standard Model expectations.