Search for new phenomena with top quark pairs in final states with one lepton, jets, and missing transverse momentum in $pp$ collisions at $\sqrt{s}$= 13 TeV with the ATLAS detector

Abstract

A search for new phenomena with top quark pairs in final states with one isolated electron or muon, multiple jets, and large missing transverse momentum is performed. Signal regions are designed to search for two-, three-, and four-body decays of the directly pair-produced supersymmetric partner of the top quark (stop). Additional signal regions are designed specifically to search for spin-0 mediators that are produced in association with a pair of top quarks and decay into a pair of dark-matter particles. The search is performed using the Large Hadron Collider proton-proton collision dataset at a centre-of-mass energy of $\sqrt{s}$=13 TeV recorded by the ATLAS detector from 2015 to 2018, corresponding to an integrated luminosity of 139 fb${}^{-1}$. No significant excess above the Standard Model background is observed, and limits at 95 % confidence level are set in the stop-neutralino mass plane and as a function of the mediator mass or the dark-matter particle mass. Stops are excluded up to 1200 GeV (710 GeV) in the two-body (three-body) decay scenario. In the four-body scenario stops up to 640 GeV are excluded for a stop-neutralino mass difference of 60 GeV. Scalar and pseudoscalar dark-matter mediators are excluded up to 200 GeV when the coupling strengths of the mediator to Standard Model and dark-matter particles are both equal to one and when the mass of the dark-matter particle is 1 GeV.

68 pages in total, author list starting page 52, 15 figures, 14 tables, published in JHEP. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/SUSY-2018-07/

References in corpus (32)

• Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC
• Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC
• The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
• Parton distributions for the LHC
• Event generation with SHERPA 1.1
• Herwig++ Physics and Manual
• A parton shower algorithm based on Catani-Seymour dipole factorisation
• Pileup subtraction using jet areas
• Vector boson production at hadron colliders: a fully exclusive QCD calculation at NNLO
• Single-top Wt-channel production matched with parton showers using the POWHEG method
• Two-loop soft anomalous dimensions for single top quark associated production with a W- or H-
• Automatic spin-entangled decays of heavy resonances in Monte Carlo simulations
• Single-top hadroproduction in association with a W boson
• The Catchment Area of Jets
• 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
• Luminosity determination in pp collisions at $\sqrt{s}$ = 8 TeV using the ATLAS detector at the LHC
• Simplified Models for a First Characterization of New Physics at the LHC
• Jet energy measurement and its systematic uncertainty in proton-proton collisions at $\sqrt{s}=7$ TeV with the ATLAS detector
• Squark and gluino production cross sections in pp collisions at $\sqrt{s}$ = 13, 14, 33 and 100 TeV
• Evaluation of three methods for calculating statistical significance when incorporating a systematic uncertainty into a test of the background-only hypothesis for a Poisson process
• Search for top squark pair production in final states with one isolated lepton, jets, and missing transverse momentum in $\sqrt{s}=$ 8 TeV pp collisions with the ATLAS detector
• Searching for Directly Decaying Gluinos at the Tevatron
• NNLL-fast: predictions for coloured supersymmetric particle production at the LHC with threshold and Coulomb resummation
• Identification and energy calibration of hadronically decaying tau leptons with the ATLAS experiment in $pp$ collisions at $\sqrt{s}$=8 TeV
• Search for a scalar partner of the top quark in the jets plus missing transverse momentum final state at $\sqrt{s}$=13 TeV with the ATLAS detector
• Search for dark matter produced in association with bottom or top quarks in $\sqrt{s}$ = 13 TeV pp collisions with the ATLAS detector
• Polarized Tops from Stop Decays at the LHC
• Search for top squark pair production in pp collisions at sqrt(s) = 13 TeV using single lepton events
• Search for direct production of supersymmetric partners of the top quark in the all-jets final state in proton-proton collisions at sqrt(s) = 13 TeV
• Search for dark matter produced in association with heavy-flavor quarks in proton-proton collisions at sqrt(s) = 13 TeV
• Inclusive search for supersymmetry using razor variables in pp collisions at sqrt(s) = 13 TeV

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• Exploration at the high-energy frontier: ATLAS Run~2 searches investigating the exotic jungle beyond the Standard Model
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• Phenomenology of unusual top partners in composite Higgs models
• The THDMa revisited
• Constraints on spin-0 dark matter mediators and invisible Higgs decays using ATLAS 13 TeV $pp$ collision data with two top quarks and missing transverse momentum in the final state
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• Status of searches for electroweak-scale supersymmetry after LHC Run 2
• Probing mild-tempered neutralino dark matter through top-squark production at the LHC
• Dark Matter Freeze-In with a Heavy Mediator: Beyond the EFT Approach
• Deconstructing squark contributions to di-Higgs production at the LHC
• The Hierarchy Problem and the Top Yukawa: An Alternative to Top Partner Solutions
• Spinning No-Scale $\mathcal{F}$-$SU$(5) in the Right Direction
• NNLL-fast 2.0: Coloured Sparticle Production at the LHC Run 3 with $\sqrt{S}$ = 13.6 TeV
• Collider fingerprints of freeze-in dark matter produced during the fast expansion phase of Universe
• LHC Run-3, $b-\tau$ Yukawa Unification and Dark Matter Implications in SUSY 4-2-2 model
• Dark Matter Searches with Top Quarks
• Calibration of a soft secondary vertex tagger using proton-proton collisions at $\sqrt{s}=$13 TeV with the ATLAS detector
• Markov Chain Monte Carlo analysis to probe trilinear $R$-parity violating SUSY scenarios and possible LHC signatures
• General search for supersymmetric particles in scenarios with compressed mass spectra using proton-proton collisions at $\sqrt{s}$ = 13 TeV
• The THDMa revisited -- A preview
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• Cross-section measurements for the production of a $W$-boson in association with high-transverse-momentum jets in $pp$ collisions at $\sqrt{s}$= 13 TeV with the ATLAS detector