The combination of measurements of the W boson polarization in top quark decays performed by the ATLAS and CMS Collaborations is presented. The measurements are based on proton-proton collision data produced at the LHC at a centre-of-mass energy of 8 TeV, and corresponding to an integrated luminosity of about 20 fb$^{-1}$ for each experiment. The measurements used events containing one lepton and having different jet multiplicities in the final state. The results are quoted as fractions of W bosons with longitudinal ($F_0$), left-handed ($F_\mathrm{L}$), or right-handed ($F_\mathrm{R}$) polarizations. The resulting combined measurements of the polarization fractions are $F_0 =$ 0.693 $\pm$ 0.014 and $F_\mathrm{L} =$ 0.315 $\pm$ 0.011. The fraction $F_\mathrm{R}$ is calculated from the unitarity constraint to be $F_\mathrm{R} = -$0.008 $\pm$ 0.007. These results are in agreement with the standard model predictions at next-to-next-to-leading order in perturbative quantum chromodynamics and represent an improvement in precision of 25 (29)% for $F_0$ ($F_\mathrm{L}$) with respect to the most precise single measurement. A limit on anomalous right-handed vector ($V_{\text{R}}$), and left- and right-handed tensor ($g_{\text{L}},g_{\text{R}}$) tWb couplings is set while fixing all others to their standard model values. The allowed regions are [$-$0.11, 0.16] for $V_{\text{R}}$, [$-$0.08, 0.05] for $g_{\text{L}}$, and [$-$0.04, 0.02] for $g_{\text{R}}$, at 95% confidence level. Limits on the corresponding Wilson coefficients are also derived.
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.
Machine learning is essential in many aspects of top-quark related physics in the ATLAS and CMS Collaborations. This work aims to give a brief overview over current applications in the two collaborations as well as on-going studies for future applications. Copyright 2023 CERN for the benefit of the ATLAS and CMS Collaborations. Reproduction of this article or parts of it is allowed as specified in the CC-BY-4.0 license
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.
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.
Recent inclusive and differential cross section measurements of the associated production of top quark pairs with gauge bosons or heavy-flavor jets are reported. A search for physics beyond the standard model in the top quark sector is also presented. All measurements are based on data samples of proton-proton collisions at $\sqrt{s}=13$ TeV collected by the ATLAS and CMS experiments at the CERN LHC. No significant deviation from the standard model predictions is observed.
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.
