Search for top squarks in events with a Higgs or $Z$ boson using 139 fb${}^{-1}$ of $pp$ collision data at $\sqrt{s}=13$ TeV with the ATLAS detector

Abstract

This paper presents a search for direct top squark pair production in events with missing transverse momentum plus either a pair of jets consistent with Standard Model Higgs boson decay into $b$-quarks or a same-flavour opposite-sign dilepton pair with an invariant mass consistent with a $Z$ boson. The analysis is performed using the proton-proton collision data at $\sqrt{s}=13$ TeV collected with the ATLAS detector during the LHC Run-2, corresponding to an integrated luminosity of 139 fb${}^{-1}$. No excess is observed in the data above the Standard Model predictions. The results are interpreted in simplified models featuring direct production of pairs of either the lighter top squark (${\tilde{t}}_1$) or the heavier top squark (${\tilde{t}}_2$), excluding at 95% confidence level ${\tilde{t}}_1$ and ${\tilde{t}}_2$ masses up to about 1220 and 875 GeV, respectively.

arXiv comment48 pages in total, author list starting page 32, 12 figures, 12 tables, published in Eur. Phys. J. C. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/SUSY-2018-21

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