Search for direct top squark pair production in events with a Higgs or $Z$ boson, and missing transverse momentum in $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS detector

Abstract

A search for direct top squark pair production resulting in events with either a same-flavour opposite-sign dilepton pair with invariant mass compatible with a $Z$ boson or a pair of jets compatible with a Standard Model (SM) Higgs boson ($h$) is presented. Requirements on additional leptons, jets, jets identified as originating from $b$-quarks, and missing transverse momentum are imposed to target the other decay products of the top squark pair. The analysis is performed using proton-proton collision data at $\sqrt{s}=13$ TeV collected with the ATLAS detector at the LHC in 2015--2016, corresponding to an integrated luminosity of 36.1 fb${}^{-1}$. No excess is observed in the data with respect to the SM predictions. The results are interpreted in two sets of models. In the first set, direct production of pairs of lighter top squarks (${\tilde{t}}_1$) with long decay chains involving $Z$ or Higgs bosons is considered. The second set includes direct pair production of the heavier top squark pairs (${\tilde{t}}_2$) decaying via ${\tilde{t}}_2\to Z{\tilde{t}}_1$ or ${\tilde{t}}_2\to h{\tilde{t}}_1$. The results exclude at 95\% confidence level ${\tilde{t}}_2$ and ${\tilde{t}}_1$ masses up to about 800 GeV, extending the exclusion region of supersymmetric parameter space covered by previous LHC searches.

arXiv comment29 pages plus author list + cover pages (46 pages total), 7 figures, 9 tables, submitted to JHEP, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/SUSY-2016-20/

References in corpus (53)

• PYTHIA 6.4 Physics and Manual
• PYTHIA 6.2 Physics and Manual
• The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
• The anti-k_t jet clustering algorithm
• A Brief Introduction to PYTHIA 8.1
• Parton distributions for the LHC
• Asymptotic formulae for likelihood-based tests of new physics
• A general framework for implementing NLO calculations in shower Monte Carlo programs: the POWHEG BOX
• New parton distributions for collider physics
• Event generation with SHERPA 1.1
• HERWIG 6.5: an event generator for Hadron Emission Reactions With Interfering Gluons (including supersymmetric processes)
• The ATLAS Simulation Infrastructure
• The total top quark pair production cross-section at hadron colliders through O(alpha_S^4)
• Top++: a program for the calculation of the top-pair cross-section at hadron colliders
• Tuning Monte Carlo Generators: The Perugia Tunes
• Performance of the ATLAS Trigger System in 2015
• Vector boson production at hadron colliders: a fully exclusive QCD calculation at NNLO
• Two-loop soft anomalous dimensions for single top quark associated production with a W- or H-
• Percent level precision physics at the Tevatron: first genuine NNLO QCD corrections to q qbar -> t tbar + X
• Top-pair production at hadron colliders with next-to-next-to-leading logarithmic soft-gluon resummation
• Muon reconstruction performance of the ATLAS detector in proton--proton collision data at $\sqrt{s}$=13 TeV
• NNLO corrections to top-pair production at hadron colliders: the all-fermionic scattering channels
• NNLO corrections to top pair production at hadron colliders: the quark-gluon reaction
• Next-to-next-to-leading-order collinear and soft gluon corrections for t-channel single top quark production
• NNLL resummation for s-channel single top quark production
• Performance of pile-up mitigation techniques for jets in $pp$ collisions at $\sqrt{s}=8$ TeV using the ATLAS detector
• Improved luminosity determination in pp collisions at sqrt(s) = 7 TeV using the ATLAS detector at the LHC
• Stop Production at Hadron Colliders
• Performance of $b$-Jet Identification in the ATLAS Experiment
• Threshold resummation for squark-antisquark and gluino-pair production at the LHC
• Simplified Models for a First Characterization of New Physics at the LHC
• Squark and gluino hadroproduction
• Soft gluon resummation for the production of gluino-gluino and squark-antisquark pairs at the LHC
• Soft-gluon resummation for squark and gluino hadroproduction
• Squark and gluino production cross sections in pp collisions at $\sqrt{s}$ = 13, 14, 33 and 100 TeV
• HistFitter software framework for statistical data analysis
• One-Loop Analysis of the Electroweak Breaking in Supersymmetric Models and the Fine-Tuning Problems
• Search for top-squark pair production in the single-lepton final state in pp collisions at sqrt(s) = 8 TeV
• Electron efficiency measurements with the ATLAS detector using 2012 LHC proton-proton collision data
• Supersymmetric top and bottom squark production at hadron colliders
• Matching Tree-Level Matrix Elements with Interleaved Showers
• Measurement of the top quark-pair production cross section with ATLAS in pp collisions at $\sqrt{s}=7\TeV$
• ATLAS Run 1 searches for direct pair production of third-generation squarks at the Large Hadron Collider
• Searching for Directly Decaying Gluinos at the Tevatron
• Searches for supersymmetry using the MT2 variable in hadronic events produced in pp collisions at 8 TeV
• Search for supersymmetry using razor variables in events with b-tagged jets in pp collisions at sqrt(s) = 8 TeV
• Search for top-squark pairs decaying into Higgs or Z bosons in pp collisions at sqrt(s) = 8 TeV
• Search for top squarks in final states with one isolated lepton, jets, and missing transverse momentum in $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS detector
• Measurement of the top quark pair production cross section in pp collisions at sqrt(s) = 7 TeV in dilepton final states with ATLAS
• Search for direct top squark pair production in events with a Z boson, b-jets and missing transverse momentum in sqrt(s)=8 TeV pp collisions with the ATLAS detector
• Search for scalar top quark pair production in natural gauge mediated supersymmetry models with the ATLAS detector in pp collisions at sqrt(s) = 7 TeV
• Search for supersymmetry in events with soft leptons, low jet multiplicity, and missing transverse momentum in proton-proton collisions at sqrt(s) = 8 TeV
• Search for direct pair production of supersymmetric top quarks decaying to all-hadronic final states in pp collisions at sqrt(s) = 8 TeV

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