Measurements Of Top Quark Production Research Articles

A Monte Carlo global analysis of the Standard Model Effective Field Theory: the top quark sector

We present a novel framework for carrying out global analyses of the Standard Model Effective Field Theory (SMEFT) at dimension-six: SMEFiT. This approach is based on the Monte Carlo replica method for deriving a faithful estimate of the experimental and theoretical uncertainties and enables one to construct the probability distribution in the space of the SMEFT degrees of freedom. As a proof of concept of the SMEFiT methodology, we present a first study of the constraints on the SMEFT provided by top quark production measurements from the LHC. Our analysis includes more than 30 independent measurements from 10 different processes at sqrt{s} = 8 and 13 TeV such as inclusive toverline{t} and single-top production and the associated production of top quarks with weak vector bosons and the Higgs boson. State-of-the-art theoretical calculations are adopted both for the Standard Model and for the SMEFT contributions, where in the latter case NLO QCD corrections are included for the majority of processes. We derive bounds for the 34 degrees of freedom relevant for the interpretation of the LHC top quark data and compare these bounds with previously reported constraints. Our study illustrates the significant potential of LHC precision measurements to constrain physics beyond the Standard Model in a model-independent way, and paves the way towards a global analysis of the SMEFT.

Highlights of top quark cross-section measurements at ATLAS

The highlights of the measurements of top quark production in proton-proton collisions at the Large Hadron Collider with the ATLAS detector are presented. The inclusive measurements of the top-pair production cross section have reached high precision and are compared to the best available theoretical calculations. The differential cross section measurements, including results using boosted top quarks, probe our understanding of top-pair production in the TeV regime. The results are compared to Monte Carlo generators implementing LO and NLO matrix elements matched with parton showers. Measurements of the single top quark production cross section are presented in the t -channel and s -channel, and with associated production with a W boson. For the t -channel production, results on the ratio between top quark and antitop quark production cross sections and differential measurements are also included.

Top Quark Studies at DO

Years after its discovery in 1995 by CDF and D0, the top quark still undergoes intense investigations at the Tevatron. Using up to the full Run II data sample, new measurements of top quark production and properties by the D0 Collaboration are presented. In particular, the first observation of single top quark s-channel production, the measurement of differential tt̄ distributions, forward-backward tt̄ asymmetry, a new measurement of the top quark mass, and a measurement of the top quark charge are discussed.

Top-quark production in ATLAS

Measurements of the top-quark production cross-sections in proton-proton collisions with the ATLAS detector at the Large Hadron Collider are presented. The measurement require no, one or two electrons or muons in the final state (hadronic, single lepton or dilepton channel). In addition, the decay modes with tau leptons are presented (channels with tau leptons). Differential measurements of tt̄ final states are presented, in particular, measurements that are able to constrain the modelling of additional parton radiation. Measurements of single top-quark production in the t- and Wt-channels are presented and determination of the CKM matrix element |Vtb| is discussed. In addition, the s-channel production is explored and limits on exotic production in single top-quark processes are discussed. This also includes the search for flavour changing neutral currents and the search for additional W′ bosons in the s-channel.

Single top-quark production measurements with ATLAS at the LHC

We present cross-section measurements of single top-quark production in the t-channel and associated Wt production modes using pp collision data recorded with the ATLAS detector at the LHC. The t-channel total cross-section is measured at √s = 7 TeV and at √s = 8 TeV with an integrated luminosity of 1.04 fb−1 and 5.8 fb−1, respectively. The t-channel top-quark and top-antiquark production cross sections and their ratio are also measured at 7 TeV with 4.7 fb−1 of data. Evidence for the Wt associated production is found at 7 TeV in the dileptonic channel using a luminosity of 2.05 fb−1. The measured cross-sections as well as the top-antitop ratio are in good agreement with the Standard Model predictions. The coupling strength |Vtb| is determined from the ratio of the measured to the theoretically predicted cross sections assuming that |Vts| and |Vtd| are small. The extracted values are all compatible with the Standard Model and with previous measurements.

First Measurement of theb-Jet Cross Section in Events with aWBoson inpp¯Collisions ats=1.96 TeV

The cross section for jets from b quarks produced with a W boson has been measured in pp collision data from 1.9 fb(-1) of integrated luminosity recorded by the CDF II detector at the Tevatron. The W+b-jets process poses a significant background in measurements of top quark production and prominent searches for the Higgs boson. We measure a b-jet cross section of 2.74+/-0.27(stat)+/-0.42(syst) pb in association with a single flavor of leptonic W boson decay over a limited kinematic phase space. This measured result cannot be accommodated in several available theoretical predictions.