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

TL;DR

This paper reports on searches for supersymmetric particles in proton-proton collision data at 13 TeV, finding no evidence of new phenomena and setting exclusion limits on particle masses.

Contribution

It introduces new search strategies for supersymmetric particles using advanced reconstruction techniques and analyzes a large dataset to improve exclusion limits.

Findings

No significant excess observed over Standard Model predictions.

Excluded electroweakinos up to 900 GeV, squarks up to 1550 GeV, and gluinos up to 2250 GeV.

Enhanced analysis methods improve sensitivity to new physics.

Abstract

Searches for new phenomena inspired by supersymmetry in final states containing an $e^+e^-$ or $\mu^+\mu^-$ pair, jets, and missing transverse momentum are presented. These searches make use of proton-proton collision data with an integrated luminosity of 139 $\text{fb}^{-1}$, collected during 2015-2018 at a centre-of-mass energy $\sqrt{s}=13 $TeV by the ATLAS detector at the Large Hadron Collider. Two searches target the pair production of charginos and neutralinos. One uses the recursive-jigsaw reconstruction technique to follow up on excesses observed in 36.1 $\text{fb}^{-1}$ of data, and the other uses conventional event variables. The third search targets pair production of coloured supersymmetric particles (squarks or gluinos) decaying through the next-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 endpoint or peak in the dilepton invariant mass spectrum. The data are found to be consistent with the Standard Model expectations. Results are interpreted using simplified models and exclude masses up to 900 GeV for electroweakinos, 1550 GeV for squarks, and 2250 GeV for gluinos.