Search for a new leptonically decaying neutral vector boson in association with missing transverse energy in proton–proton collisions at $\sqrt{s}=13~$TeV with the ATLAS detector

A search for dark matter particles produced in association with a new neutral vector boson is performed using proton–proton collisions at $\sqrt{s} = 13$ TeV, corresponding to an integrated luminosity of 140 fb$^{−1}$ recorded by the ATLAS detector at the Large Hadron Collider. Decays of the Z′ boson to same-flavour light leptons ($e^+e^−$/$\mu^+\mu^−$) are studied for Z′ masses above 200 GeV. No significant excess over the Standard Model prediction is observed. The results of this search are interpreted for several dark-Higgs and light-vector benchmark model scenarios. Cross-section limits are set considering each benchmark scenario, as well as limits on the coupling of the Z′ with leptons.