Summary of ATLAS 13 TeV results using the full 2015−2018 (Run 2) dataset

This page provides a compact summary of published and preliminary ATLAS physics and performance results on 13 TeV proton–proton collision data based on the Run-2 data-set taken between 2015 and 2018. For questions, please, contact the ATLAS physics coordinators. See the central publications page for other results from ATLAS.

This page also provides links to ATLAS Physics Briefings for specific results. These are intended to provide a general introduction to ATLAS physics results for a non-specialist audience.

Physics results

  GroupFormatShort TitleDate√s (TeV)LLinks
EXOTConference noteDjiet resonance search   Full Title: Search for New Phenomena in Dijet Events using 139 fb$^{-1}$ of $pp$ collisions at $\sqrt{s}=13$ TeV collected with the ATLAS Detector

Abstract: A search for new resonances decaying into two hadronic jets is reported using the entire dataset of proton-proton collisions recorded at $\sqrt{s}$ = 13 TeV with the ATLAS detector at the Large Hadron Collider between 2015 and 2018, corresponding to an integrated luminosity of 139 fb$^{−1}$ . The dijet invariant mass distribution is compared to a smoothly-falling background prediction obtained by fitting the data. No significant excess is observed. Excited quarks with masses below 6.7 TeV are excluded at the 95% confidence level. Model-independent limits on Gaussian-shaped signals of various widths in dijet mass distribution are also set.

Keywords: 13 TeV,BSM resonance,BSM search,2 jets

17-MAR-1913139 fb-1Documents | Internal
EXOTPaperDilepton Resonance Search   Full Title: Search for high-mass dilepton resonances using 139 fb$^{-1}$ of pp collision data collected at $\sqrt{s}= $13 TeV with the ATLAS detector

Abstract: A search for high-mass dielectron and dimuon resonances in the mass range of 250 GeV to 6 TeV is presented. The data were recorded by the ATLAS experiment in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=13$ TeV during Run 2 of the Large Hadron Collider and correspond to an integrated luminosity of 139 fb$^{-1}$. A functional form is fitted to the dilepton invariant-mass distribution to model the contribution from background processes, and a generic signal shape is used to determine the significance of observed deviations from this background estimate. No significant deviation is observed and upper limits are placed at the 95% confidence level on the fiducial cross-section times branching ratio for various resonance width hypotheses. The derived limits are shown to be applicable to spin-0, spin-1 and spin-2 signal hypotheses. For a set of benchmark models, the limits are converted into lower limits on the resonance mass and reach 4.5 TeV for the E6-motivated $Z^\prime_\psi$ boson. Also presented are limits on Heavy Vector Triplet model couplings.

Keywords: 13 TeV,Contact interactions,BSM resonance,BSM search,2 leptons

14-MAR-1913139 fb-1Documents | 1903.06248 | Inspire
Briefing | Internal
HDBSConference noteDiboson resonance search in the all-hadronic final state   Full Title: Diboson resonance search in the all-hadronic final state

Abstract: Narrow resonances decaying into $WW$, $WZ$ or $ZZ$ boson pairs are searched for in 139 fb$^{-1}$ of proton-proton data at a centre-of-mass energy of $\sqrt{s}=13$ TeV recorded with the ATLAS detector at the Large Hadron Collider from 2015 to 2018. The diboson system is reconstructed using pairs of high transverse momentum, large-radius jets. These jets are built from a combination of calorimeter- and tracker-inputs compatible with the hadronic decay of a boosted $W$ or $Z$ boson, using jet mass and substructure properties. The search is performed for diboson resonances with masses greater than 1.3 TeV. No significant deviations from the background expectations are observed. Exclusion limits at the $95\%$ confidence level are set on the production cross-section times branching ratio into dibosons for a range of theories beyond the Standard Model, with the highest excluded mass of a new gauge boson at 4.4 TeV in the context of mass-degenerate resonances that couple predominantly to gauge bosons.

Keywords: 13 TeV,BSM resonance,BSM search,ZZ,WZ,WW,Boosted,All hadronic,2 jets

17-MAR-1913139 fb-1Documents | Internal
HIGGConference notettH(125) H->gammagammaFull Title: Measurement of Higgs boson production in association with a tt quark-antiquark pair in the diphoton decay channel using 139 fb$^{-1}$ of LHC data collected at $\sqrt{s}$ = 13 TeV by the ATLAS experiment

Abstract: The measurement of Higgs boson production in association with a top quark-antiquark pair in the diphoton decay channel ($H \to \gamma \gamma$) is presented, based on the analysis of 139~fb$^{-1}$ of proton-proton collision data with center-of-mass energy $\sqrt{s}=13$ TeV recorded with the ATLAS detector at the Large Hadron Collider. The analysis is performed using a simultaneous fit in seven signal-enriched event categories. The $t\bar{t}H$ process is observed in the diphoton decay mode with a significance of 4.9 standard deviations relative to the background-only hypothesis. The expected significance is 4.2 standard deviations. The $t\bar{t}H$ cross-section times the $H \to \gamma \gamma$ branching ratio is measured to be $\sigma_{t\bar{t}H}\times B_{\gamma\gamma } = 1.59_{-0.39}^{+0.43}$~fb, in agreement with the Standard Model prediction.

Keywords: 13 TeV,Coupling measurements,H(125) measurements,ttH production,Higgs to 2 photons,Cross-section measurement,Higgs,Top pair,Di-photon,b-jets,Photons

18-MAR-1813139 fb-1Documents | Briefing | Internal
SUSYConference noteChargino pair, slepton pair; 2 leptons   Full Title: Search for electroweak production of charginos and sleptons decaying in final states with two leptons and missing transverse momentum in $\sqrt{s}=13$ $pp$ collisions using the ATLAS detector

Abstract: A search for the electroweak production of charginos and sleptons decaying into final states with two electrons or muons is presented. The analysis is based on 139~fb$^{-1}$ of proton-proton collisions recorded by the ATLAS detector at the Large Hadron Collider at $\sqrt{s}=13$ TeV. Three R-parity conserving scenarios where the lightest neutralino is the lightest supersymmetric particle are considered: the production of chargino pairs with decays via either $W$ bosons or sleptons, and the direct production of slepton pairs. The analysis is optimised to target the first of these scenarios, but its results are also interpreted in the other ones. No significant deviations from the Standard Model expectations are observed and stringent limits at 95\% confidence level are set on the masses of relevant supersymmetric particles in each of these scenarios. For a massless lightest neutralino, masses up to 420 GeV are excluded for the production of the lightest chargino pairs assuming $W$ boson mediated decays and up to 1 TeV for slepton mediated decays, whereas for slepton-pair production masses up to 700 GeV are excluded assuming three generations of mass-degenerate sleptons.

Keywords: 13 TeV,Chargino/neutralino pair production,Slepton pair production,BSM search,MET,1 jet,0 jets,2 leptons

18-MAR-1913139 fb-1Documents | Internal
SUSYConference noteStop pair, long-lived; displaced vertex and displaced muon   Full Title: Search for long-lived, massive particles in events with a displaced vertex and muon in $pp$ collisions at $\sqrt{s } = 13$ TeV with the ATLAS detector

Abstract: A search for long-lived particles decaying into at least one muon and hadrons is presented. The analysis selects events that pass a muon or missing-transverse-momentum trigger and contain a displaced muon and a displaced vertex with at least three tracks and a visible invariant vertex mass of at least 20~GeV. The analyzed dataset of proton--proton collisions at $\sqrt{s } = 13$~TeV was collected with the ATLAS detector and corresponds to 136~fb$^{-1}$. The search employs dedicated reconstruction techniques that significantly increase the sensitivity to long-lived particle decays. Background estimates for Standard Model processes and instrumental effects are extracted entirely from data. The observed event yields are compatible with those expected from background processes. The results are presented as limits at 95\% confidence level on model-independent cross sections for processes beyond the Standard Model, and interpreted as exclusion limits on scenarios with pair-production of long-lived top squarks that decay via a small $R$-parity-violating coupling to a quark and a muon. Top squarks with masses up to 1.7~TeV are excluded for a lifetime of 0.1~ns, and masses below 1.3~TeV are excluded for all lifetimes between 0.01~ns and 30~ns.

Keywords: 13 TeV,Stop pair production,Displaced vertex,Long-lived massive particles,BSM search,Long-lived massive particle,MET,1 lepton

18-MAR-1913136 fb-1Documents | Internal

Object Performance and Trigger results

Topic Document type Short title Reference and Link Release conference
MCP Public plots Muon reconstruction and identification efficiency with 15.8 fb−1 of data collected in 2018 with the ATLAS detector MUON-2018-006 LHCC
Jet/Etmiss CP Public plots Missing transverse energy performance in 2017 and 2018 data JETM-2018-004/ ICHEP
E/gamma CP Public plots Z to ee mass distribution for early 2018 data EGAM-2018-003 LHCP
Muon CP Public plots Muon performance plots with first 2018 data: efficiency, scale and resolution MUON-2018-001/ LHCP

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Topic revision: r6 - 2019-02-27 - AndreasHoecker
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