Searches for new phenomena in events with two leptons, jets, and missing transverse momentum in 139 fb$^{-1}$ of $ \sqrt{s}=13$ TeV $ pp$ collisions with the ATLAS detector

Searches for new phenomena inspired by supersymmetry in final statescontaining an $e^+e^-$ or $\mu^+\mu^-$ pair, jets, and missing transversemomentum are presented. These searches make use of proton-proton collision datawith an integrated luminosity of 139 $\text{fb}^{-1}$, collected during2015-2018 at a centre-of-mass energy $\sqrt{s}=13 $TeV by the ATLAS detector atthe Large Hadron Collider. Two searches target the pair production of charginosand neutralinos. One uses the recursive-jigsaw reconstruction technique tofollow up on excesses observed in 36.1 $\text{fb}^{-1}$ of data, and the otheruses conventional event variables. The third search targets pair production ofcoloured supersymmetric particles (squarks or gluinos) decaying through thenext-to-lightest neutralino $(\tilde\chi_2^0)$ via a slepton $(\tilde\ell)$ or$Z$ boson into $\ell^+\ell^-\tilde\chi_1^0$, resulting in a kinematic endpointor peak in the dilepton invariant mass spectrum. The data are found to beconsistent with the Standard Model expectations. Results are interpreted usingsimplified models and exclude masses up to 900 GeV for electroweakinos, 1550GeV for squarks, and 2250 GeV for gluinos.