UC Berkeley

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 s=13$$\sqrt{s}=13$$ TeV collected with the ATLAS detector during the LHC Run-2, corresponding to an integrated luminosity of 139 fb-1$$^{-1}$$. 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 (t~1$$\tilde{t}_1$$) or the heavier top squark (t~2$$\tilde{t}_2$$), excluding at 95% confidence level t~1$$\tilde{t}_1$$ and t~2$$\tilde{t}_2$$ masses up to about 1220 and 875 GeV, respectively.