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

TL;DR

This paper reports a search for top squarks in events with Higgs or Z bosons using 139 fb$^{-1}$ of 13 TeV proton-proton collision data, finding no evidence of new particles and setting mass exclusion limits.

Contribution

First search to analyze top squark pair production with Higgs or Z bosons using the full Run-2 ATLAS dataset, providing new mass exclusion limits.

Findings

No excess observed above Standard Model predictions.

Excluded top squark masses up to about 1220 GeV for $ ilde{t}_1$.

Excluded top squark masses up to about 875 GeV for $ ilde{t}_2$.

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.