Measurement Of Single Top Quark Production Research Articles

Measurement of single top-quark production in the s-channel in proton–proton collisions at sqrt{s} = 13 TeV with the ATLAS detector

A measurement of single top-quark production in the s-channel is performed in proton–proton collisions at a centre-of-mass energy of 13 TeV with the ATLAS detector at the CERN Large Hadron Collider. The dataset corresponds to an integrated luminosity of 139 fb−1. The analysis is performed on events with an electron or muon, missing transverse momentum and exactly two b-tagged jets in the final state. A discriminant based on matrix element calculations is used to separate single-top-quark s-channel events from the main background contributions, which are top-quark pair production and W-boson production in association with jets. The observed (expected) signal significance over the background-only hypothesis is 3.3 (3.9) standard deviations, and the measured cross-section is sigma ={8.2}_{-2.9}^{+3.5} pb, consistent with the Standard Model prediction of {sigma}^{textrm{SM}}={10.32}_{-0.36}^{+0.40} pb.

Measurement of single top-quark production in association with a W boson in the single-lepton channel at sqrt{s} = 8,text {TeV} with the ATLAS detector

The production cross-section of a top quark in association with a W boson is measured using proton–proton collisions at sqrt{s} = 8,text {TeV}. The dataset corresponds to an integrated luminosity of 20.2,text {fb}^{-1}, and was collected in 2012 by the ATLAS detector at the Large Hadron Collider at CERN. The analysis is performed in the single-lepton channel. Events are selected by requiring one isolated lepton (electron or muon) and at least three jets. A neural network is trained to separate the tW signal from the dominant t{bar{t}} background. The cross-section is extracted from a binned profile maximum-likelihood fit to a two-dimensional discriminant built from the neural-network output and the invariant mass of the hadronically decaying W boson. The measured cross-section is sigma _{tW} = 26 pm 7,text {pb}, in good agreement with the Standard Model expectation.

Single top-quark productioncross-section at the LHC in ATLAS

Measurements of the single top-quark production cross-sections with the AT- LAS detector in ppcollisions at the Large Hadron Collider (LHC) are presented. Results of measurements of single top-quark production in the t- and Wt-channel, as well as the determination of the CKM matrix element |Vtb| are shown. Further, the separate mea- surement of the top- and antitop-quark t-channel production cross-section and the ratio of the two are presented, and several searches for exotic processes in single top-quark production are discussed. The latter include results from searches for flavour changing neutral currents, extra heavy charged gauge bosons (W � ), excited quarks, and searches for anomalous CP-violating couplings in the Wtb vertex.

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-quarks at the LHC

This article summarises the status of measurements of single top-quark production in all channels at the LHC for a centre-of-mass energy of 7 TeV with the full 2011 data set and for a centre-of-mass of 8 TeV for the t-channel cross-section. Results are reported from the ATLAS and CMS experiments. Both experiments also report evidence for the W t-channel production which has never been observed before. ATLAS also sets a limit on the s-channel cross-section. So far, the measured cross sections are in good agreement with the predictions by the Standard Model.

Top quark production at ATLAS

We present various studies of the production of top quarks in proton-proton collisions at 7 TeV with the ATLAS detector at the Large Hadron Collider. The cross-section of top-quark pair production is measured in the single lepton, dilepton, all hadronic channel and channels with tau leptons. Top-quark pairs are also studied in the context of additional radiation. Measurements of single top-quark production in the t-channel and Wt-channel are also presented. Several extensions of the SM predict the presence of new particles that couple to top quarks. We report on searches for such resonance decaying to top-antitop quark pairs.

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.

Top-Quark Physics at the Tevatron

The Tevatron experiments, CDF and DO have by now analysed collision data corresponding an integrated luminosity of more than 2 fb −1 and the selected data sets comprise several hundreds of reconstructed t t ¯ pairs. Run II of the Tevatron has thus paved the way for a new era in top quark physics focussing on the precise measurement of top quark properties. This article gives a concise overview on the status of measurements in the top quark sector by CDF and DO including t t ¯ cross section measurements, the measurement of the charge asymmetry in top-antitop events, the search for top-antitop resonances, the measurement of the W helicity in top quark decays, and the search for flavor-changing neutral current top quark decays. The measurements of intrisic top quark properties, mass, width and charge, are discussed. The article concludes with a presentation of first measurements of single top-quark production.