Top Pair Production Cross Section Research Articles

Measurement of thett¯production cross section inpp¯collisions ats=1.96 TeVusing kinematic characteristics oflepton+jetsevents

We present a measurement of the top quark pair production cross section in ppbar collisions at sqrt(s)=1.96 TeV utilizing 425 pb-1 of data collected with the D0 detector at the Fermilab Tevatron Collider. We consider the final state of the top quark pair containing one high-pT electron or muon and at least four jets. We exploit specific kinematic features of ttbar events to extract the cross section. For a top quark mass of 175 GeV, we measure sigma_ttbar = 6.4 +1.3-1.2(stat} +/- 0.7(syst)+/- 0.4(lum) pb in good agreement with the standard model prediction.

Measurement of thepp¯→tt¯+Xproduction cross section ats=1.96 TeVin the fully hadronic decay channel

A measurement of the top quark pair production cross section in proton antiproton collisions at an interaction energy of root s=1.96 TeV is presented. This analysis uses 405 +/- 25 pb(-1) of data collected with the D0 detector at the Fermilab Tevatron Collider. Fully hadronic t (t) over bar decays with final states of six or more jets are separated from the multijet background using secondary vertex tagging and a neural network. The t (t) over bar cross section is measured as sigma(t (t) over bar)=4.5(-1.9)(+2.0)(stat)(-1.1)(+1.4)(syst)+/- 0.3(lumi) pb for a top quark mass of m(t)=175 GeV/c(2).

Top pair production cross section measurements into multijet final states

The measurements of the top quark pair production cross section in pp̄ collision at √s = 1.96 TeV into multijet final states are provided. A multijet triggered data set is used to measure the tt̄ production cross section in the missing Er+jets and all-hadronic final states. Optimized kinematical and topological selections, with additional requirement on the identification of heavy flavor jets from top quark decay, are applied in order to select tt̄ events in the respective final states. From 311 pb−1 of data collected by the Collider Detector at Fermilab, the measurements, σ(tt̄) = 5.8+1.5−1.4 pb and σ(tt̄) = 7.5+3.7−2.8 pb, for the ET+jets and all-hadronic final states respectively, are reported assuming a top quark mass of 178 GeV/c2. Results are in agreement with Standard Model prediction and previous determinations.

Measurement of thett¯Production Cross Section inpp¯Collisions ats=1.96 TeV

We present a measurement of the top quark pair production cross section in ppbar collisions at sqrt(s)=1.96 TeV using 318 pb^{-1} of data collected with the Collider Detector at Fermilab. We select ttbar decays into the final states e nu + jets and mu nu + jets, in which at least one b quark from the t-quark decays is identified using a secondary vertex-finding algorithm. Assuming a top quark mass of 178 GeV/c^2, we measure a cross section of 8.7 +-0.9 (stat) +1.1-0.9 (syst) pb. We also report the first observation of ttbar with significance greater than 5 sigma in the subsample in which both b quarks are identified, corresponding to a cross section of 10.1 +1.6-1.4(stat)+2.0-1.3 (syst) pb.

Measurement of the cross section fortt¯production inpp¯collisions using the kinematics of lepton+jets events

We present a measurement of the top pair production cross section in $p\bar{p}$ collisions at $\sqrt{s}$=1.96 TeV. We collect a data sample with an integrated luminosity of 194$\pm$11 pb$^{-1}$ with the CDF II detector at the Fermilab Tevatron. We use an artificial neural network technique to discriminate between top pair production and background processes in a sample of 519 lepton+jets events, which have one isolated energetic charged lepton, large missing transverse energy and at least three energetic jets. We measure the top pair production cross section to be $\sigma_{t\bar{t}}= 6.6$$\pm 1.1 \pm 1.5$ pb, where the first uncertainty is statistical and the second is systematic.

Measurement of the [formula omitted] production cross section in [formula omitted] collisions at [formula omitted] using kinematic characteristics of lepton + jets events

We present a measurement of the top quark pair (tt¯) production cross section (σtt¯) in pp¯ collisions at a center-of-mass energy of 1.96 TeV using 230 pb−1 of data collected by the DØ detector at the Fermilab Tevatron Collider. We select events with one charged lepton (electron or muon), large missing transverse energy, and at least four jets, and extract the tt¯ content of the sample based on the kinematic characteristics of the events. For a top quark mass of 175 GeV, we measure σtt¯=6.7−1.3+1.4(stat)−1.1+1.6(syst)±0.4(lumi) pb, in good agreement with the standard model prediction.

Measurement of the [formula omitted] production cross section in [formula omitted] collisions at [formula omitted] using lepton + jets events with lifetime b-tagging

We present a measurement of the top quark pair (tt¯) production cross section (σtt¯) in pp¯ collisions at s=1.96 TeV using 230 pb−1 of data collected by the DØ experiment at the Fermilab Tevatron Collider. We select events with one charged lepton (electron or muon), missing transverse energy, and jets in the final state. We employ lifetime-based b-jet identification techniques to further enhance the tt¯ purity of the selected sample. For a top quark mass of 175 GeV, we measure σtt¯=8.6−1.5+1.6(stat.+syst.)±0.6(lumi.) pb, in agreement with the standard model expectation.

Measurement of the [formula omitted] production cross section in [formula omitted] collisions at [formula omitted] in dilepton final states

We present a measurement of the top quark pair (tt¯) production cross section in pp¯ collisions at s=1.96 TeV using events with two charged leptons in the final state. This analysis utilizes an integrated luminosity of 224–243 pb−1 collected with the DØ detector at the Fermilab Tevatron Collider. We observe 13 events in the e+e−, eμ and μ+μ− channels with an expected background of 3.2±0.7 events. For a top quark mass of 175 GeV, we measure a tt¯ production cross section of σtt¯=8.6−2.7+3.2(stat)±1.1(syst)±0.6(lumi) pb, consistent with the standard model prediction.

Third-order Coulomb corrections to the S-wave Green function, energy levels and wave functions at the origin

We obtain analytic expressions for the third-order corrections due to the strong interaction Coulomb potential to the S-wave Green function, energy levels and wave functions at the origin for arbitrary principal quantum number n. Together with the known non-Coulomb correction this results in the complete spectrum of S-states up to order α s 5 . The numerical impact of these corrections on the upsilon spectrum and the top quark pair production cross section near threshold is estimated.

Supersymmetric correction to top quark pair production near threshold

We studied the leading supersymmetric contribution to top–antitop threshold production using the NRQCD framework. The one-loop matching to the potential and the Wilson coefficient of the leading 3S1 production current were considered. We point out that the leading correction to the potential is zero due to SU(3)c gauge invariance. This is true in general for any new physics that enters above the electroweak scale. The shape of the top quark pair production cross section is therefore almost unaffected near threshold, allowing a precise determination of the top quark mass based on the Standard Model calculations. The supersymmetric correction to the Wilson coefficient c1 of the production current decouples for heavy super particles. Its contribution is smaller than the Standard Model next-to-next-leading-log results.

Measurement of the Top Quark Pair Production Cross Section in the All-Jets Decay Channel

We present a measurement of $t\overline{t}$ production in $p\overline{p}$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$ from $110{\mathrm{pb}}^{\ensuremath{-}1}$ of data collected in the all-jets decay channel with the D0 detector at Fermilab. A neural network analysis yields a cross section of $7.1\ifmmode\pm\else\textpm\fi{}2.8(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}1.5(\mathrm{syst})\mathrm{pb}$ at a top quark mass $({m}_{t})$ of $172.1\mathrm{GeV}{/c}^{2}$. Using previous D0 measurements from dilepton and single lepton channels, the combined D0 result for the $t\overline{t}$ production cross section is $5.9\ifmmode\pm\else\textpm\fi{}1.2(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}1.1(\mathrm{syst})\mathrm{pb}$ for ${m}_{t}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}172.1\phantom{\rule{0ex}{0ex}}\mathrm{GeV}{/c}^{2}$.

Top quark physics and searches for new phenomena at the Tevatron

The CDF and DØ collaborations each have collected over 110pb −1 of data. The following article will describe near final results from two currently topical analyses: results from top quark physics and searches for first generation leptoquarks (LQ), using the entire statistics of these large data sets. After careful selection, both collaborations have collected top quark data samples consisting of several dozen events each. From these events both experiments have measured the top quark mass and pair production cross section in a variety of decay channels, including the so-called dilepton, lepton plus jets, and all jets channels. The combined top quark mass from both experiments in the lepton plus jets channels is m t = 175.6 ± 5.5GeV/ c 2. CDF and DØ have also performed optimized searches for the pair production of first generation leptoquarks. No candidate events were found. Combining the results from the ee+jets, eν+jets, and νν+jets channels both experiments set 95% confidence level (CL) upper limits on the LQ pair production cross section as a function of mass and of β, the branching fraction to a charged lepton.

Top quark results from the Tevatron

The CDF and DØ collaborations have collected top quark data samples consisting of several dozen events each. Using these data samples, the two Tevatron experiments have measured the top quark mass and pair production cross section in a variety of decay channels, including the so-called dilepton, lepton plus jets and all jets channels. The combined top quark mass from both experiments in the lepton plus jets channels is m t = 175.6 ± 5.5 GeV/ c 2. Additionally, upper limits have been obtained for certain rare or nonstandard (FCNC and charge Higgs) top quark decays.