An overview is presented of the measurements of the top quark mass performed by the ATLAS experiment at the LHC with an integrated luminosity varying between 35 pb$^{-1}$ and 4.7 fb$^{-1}$. Different techniques are used to measure the top quark mass looking at events in all three signatures: fully-hadronic, lepton+jets and di-leptonic ones. The most precise measurement, using a template method on lepton+jets events, yields a top quark mass of 174.5 $\pm$ 0.6 (stat) $\pm$ 2.3 (syst) GeV. The dominant systematic uncertainties are related to the determination of the $b-$jet energy scale and the modelling of additional radiation accompanying the $t\bar{t}$ pair production.
These proceedings present the first observation of single top-quark production associated with a photon using the full Run2 proton-proton dataset collected by the ATLAS experiment at the LHC.
The top-quark mass measurements carried out by the LHC experiments, ATLAS and CMS, are summarized. Results of different approaches to the top-quark mass reconstruction are presented. Masses from different measurements are in good agreement within uncertainties. Precision of the measurements with the directly measured top-quark mass is now better than 0.5%. Progress in determination of the top-quark pole mass is reported and the relation between the directly measured top-quark mass and top-quark pole mass is discussed.
The top-quark mass is one of the fundamental parameters of the Standard Model of particle physics. The latest ATLAS measurements of the top-quark mass in top quark pair final states are presented. Measurements use di-lepton, lepton+jets and all-jets final states and their combination is performed. Measurements of the top-quark pole mass based on precision theoretical QCD calculations for lepton kinematic distribution and for top quark pair production with an additional jet are also presented.
This article presents a review of recent results on direct top quark mass measurements performed by the ATLAS and CMS collaborations on $pp$ collisions collected during Run 2 of the LHC at $\sqrt{s}=$13 TeV.
Latest results on inclusive top-quark pair production cross-sections are presented using collision data collected by ATLAS and CMS experiments at the LHC. Inclusive and differential measurements of top-quark pair production cross-sections from ATLAS and CMS are presented in the resolved and boosted kinematic regions. The cross-sections are measured as a function of various kinematic observables of the top quarks, the jets and leptons of the event final state.
A search for new heavy quarks focusing on recent vector-like quark searches with the ATLAS detector at the CERN Large Hadron Collider is presented. Two recent searches targeting the pair production of type vector-like quarks are described. The first search is sensitive to vector-like up-type quark ($T$) decays to a $t$ quark and either a Standard Model Higgs boson or a $Z$ boson. The second search is primarily sensitive to $T$ decays to $W$ boson and a $b$ quark. Additionally, the results can be interpreted for alternative VLQ decays.
Recent results on top quark modelling and tuning are presented. In particular, the focus of this talk is on the studies on the definition and commissioning of the common Monte Carlo effort carried out by ATLAS and CMS within the LHCtopWG. An overview of current recommendations for modelling uncertainties is also presented.
Many models beyond the standard model predict the existence of vector-like quarks or other types of heavy resonances. Using proton-proton collision data at center-of-mass energies of 8 and 13 TeV, the ATLAS and CMS Collaborations have performed a multitude of searches for pair and singly produced vector-like quarks decaying to W, Z, or Higgs bosons. Heavy gauge and (pseudo)scalar resonances decaying to top quarks have been searched for as well. No evidence for any of these hypothetical particles has been found yet, and stringent exclusion limits are derived on their masses, cross sections and …
The top quark is the heaviest known fundamental particle. As it is the only quark that decays without hadronisation, it provides the unique opportunity to probe the properties of bare quarks at the Large Hadron Collider (LHC). This article will present two recent measurements of the top quark using 13TeV collision data with the ATLAS experiment: the top and anti-top quark pair charge asymmetry measurement alongside the first test of lepton flavour universality (LFU) of leptons to W bosons from tt events.
An overview of recent searches with top quarks in the final state using up to 36 fb$^{-1}$ of pp collision data at $\sqrt{s}$ = 13 TeV collected with the ATLAS and CMS experiments at the LHC is presented. In particular, searches for heavy resonances decaying into third generation quarks, searches for production of vector-like quarks and searches for dark-matter produced in association with top quarks are summarised. No significant excess over the SM prediction is found and 95% CL exclusion limits are set in a variety of models.
Recent analyses of top quark production in association with vector bosons are summarized, representing the most precise inclusive and differential cross section measurements of these processes to date. Proton-proton collision data at a center-of-mass energy of $\sqrt{s}=13$ TeV, recorded by the ATLAS and CMS detectors at the LHC are analyzed, corresponding to an integrated luminosity of up to 139 fb$^{-1}$ for each experiment. Comparisons with theory calculations are performed and overall good agreement with standard model predictions are obtained.
The ATLAS and CMS Collaborations have performed a variety of measurements of the top quark mass, taking advantage of the abundant production of top quarks at the LHC. The most recent measurements are reported here, based on data collected at 8 and 13 TeV, with particular emphasis on the distinction between the so-called "direct" measurements and the "indirect" evaluations obtained from cross sections and differential cross sections.
ATLAS has made several measurements of the top quark mass using proton-proton collision data recorded in 2012 at the LHC with a centre-of-mass energy of 8 TeV. Those summarised here include an indirect determination of the top quark pole mass from lepton differential cross-sections; previous direct measurements of the top quark mass in the $t\bar{t}\to\textrm{dilepton}$ and $t\bar{t}\to\textrm{all-jets}$ decay channels as well as in the $t$-channel of single-top-quark production; and lastly, the new direct measurement of the top quark mass in the $t\bar{t}\to\textrm{lepton+jets}$ decay channel…
A set of measurements of top quark pair and single top quark production in association with standard model (SM) bosons performed by the CMS and ATLAS Collaborations is presented. The consistency of these results among themselves and with the SM prediction is discussed. The latest results on four top quark production are also shown.
Top quarks are produced copiously at the LHC, and a variety of related measurements has been made in the recent years by the two collaborations ATLAS and CMS. The most recent measurements of the top quark mass by the two collaborations are reported here. The top quark mass has been measured with a relative uncertainty smaller than 0.3%, making the top quark the most accurately measured quark.
The production of top quarks through single or rare production modes has become important due to the large amount of data collected by both ATLAS and CMS at the LHC. Many searches are now studying these processes either as a targeted signal or as an important source of background. This document reviews the Monte Carlo simulations used to model these processes in ATLAS and CMS, and how the modeling systematic uncertainties are estimated. Many analyses have also recently released a large variety of unfolded distributions. These distributions are shown and the modeling from various Monte Carlo ge…
These proceedings highlight a selection of recent ATLAS and CMS measurements which target either the production of a single top quark or the associated production of a top-antitop quark pair together with a $W$ boson, a $Z$ boson, or a photon ($γ$). The highlighted analyses are based predominantly on proton-proton collision data collected by the two experiments during Run 2 of the LHC at a centre-of-mass energy of $\sqrt{s}=13$ TeV with datasets corresponding to integrated luminosities of up to 77.5 fb$^{-1}$. One combination of ATLAS and CMS single top quark measurements employing the full Ru…
Measurement of the top quark mass in topologies enhanced with single top quarks produced in the $t$-channel at $\sqrt{s}=8\,\mathrm{TeV}$ using the ATLAS experiment
Measurements of differential cross sections of top quark pair production in association with jets by the ATLAS experiment at the LHC are presented. The measurements are performed as functions of the top quark transverse momentum, the transverse momentum of the top quark-antitop quark system and the out-of-plane transverse momentum using data from $pp$ collisions at $\sqrt{s}=13$ TeV collected by the ATLAS detector at the LHC in 2015 and corresponding to an integrated luminosity of 3.2 fb$^{-1}$. The top quark pair events are selected in the lepton (electron or muon) + jets channel. The measure…
With the large data set delivered during the second run of the CERN LHC, inclusive and differential measurements of the top quark-antiquark production cross section at the ATLAS and CMS experiments often reach a precision that is comparable or superior to that of the corresponding theoretical calculations. The results of these measurements can be used to test the validity of perturbative quantum chromodynamics (QCD), and to precisely extract the values of parameters of the QCD Lagrangian such as the top quark mass ($m_\mathrm{t}$). The value of $m_\mathrm{t}$ can also be measured, with higher …
Recent measurements of top quark properties with ${\rm t{\bar t}}$ events collected by the ATLAS experiment in proton-proton collisions at the center of mass energy $\sqrt{s}=8$ and $13$ TeV, are presented. The measurements of the top quark width, spin and spin correlations, polarisation, the $W$ boson helicity fractions, charge and CP asymmetries are discussed. Finally, recent results obtained on colour flow effects in ${\rm t{\bar t}}$ events are presented. All the measurements are consistent with the Standard Model expectations.
Preliminary results of two differential cross-section measurements in the ATLAS experiment at CERN are presented. Measurements are focused on the top-antitop quark pair production in the~lepton+jets and the~all-hadronic channels in the kinematic region with high transverse momentum top quarks. Both measurements use the full Run 2 data of 13 TeV proton-proton collisions from the Large Hadron Collider collected by the ATLAS detector in 2015-2018, corresponding to an integrated luminosity of 139 fb$^{-1}$. The measured spectra are compared with the Standard Model predictions. They are also used t…
Top-quark pairs in association with final state particles are produced in large quantities at the LHC due to the high centre-of-mass energy available in proton-proton collisions. One such topology is that of a prompt photon radiated from the top quark in addition to the final state particles from the top quark decay. Using 36.1 fb$^{-1}$ of data collected at $\sqrt{s}$ = 13 TeV with the ATLAS detector, fiducial cross-section results are shown in the single-lepton and dilepton channels. Object-level and event-level neural networks are used to increase sensitivity.
Absolute and normalised differential cross-sections of single top quarks produced in the $t$-channel are presented. 20.2 fb$^{-1}$ of proton-proton collision data at a centre-of-mass energy of 8 TeV collected by the ATLAS experiment at the LHC are used. Differential cross-sections as a function of the transverse momentum and the absolute value of the rapidity of the top quarks and the top antiquarks are measured at both parton level and particle level. The transverse momentum and rapidity differential cross-sections of the scattered light-quark jets are extracted at particle level. The measure…
