02 09 07 7 v 1 2 7 Se p 20 02 1 W Boson Cross Section and Decay Properties at the Tevatron
نویسنده
چکیده
We present the first measurements of σ(p¯ p → W → ℓν) and σ(p¯ p → Z → ℓℓ) at √ s = 1.96 TeV, along with new measurements of W angular-decay distributions in p¯ p collisions at √ s = 1.8 TeV. W and Z boson production cross-section measurements in p¯ p collisions are a test of the consistency of Standard-Model couplings, constrain proton parton distribution functions, and provide information on higher-order QCD corrections. They also test the mettle of an experiment, as the measurements require good understanding of detection efficiencies, backgrounds, and lumi-nosity. If experimental uncertainties are small, and the cross sections can be well-estimated from theory, the boson production rates can be interpreted as a measure of luminosity, and can also be used to normalize measurements of other production cross sections. Finally, W and Z bosons provide a path to the physics of Run II at the Teva-tron, where many signatures of top-quark and Higgs-boson production can include these bosons. At the Tevatron, protons and antiprotons collide at a center-of-mass energy of 1.96 TeV. A W boson appears in the detector as a high-momentum lepton and large missing energy due to the undetected neutrino. As the z component of p ν is unmeasured, all quantites are measured in the transverse plane. A Z boson appears as two high-momentum opposite-signed leptons with an invariant mass around 90 GeV. The cross section can be expressed as σ · B = N obs − N bg Aǫ Ldt , (1) where N obs is the number of observed boson events, N bg is the estimated number of background events, A is the kinematic and geometric acceptance, ǫ is the total efficiency, and Ldt is the integrated luminosity. The lepton plus missing transverse-energy sample can be accounted for by W → ℓν, Z → ℓℓ, W → τ ν, QCD jets (fake leptons), and (for muons) cosmic rays, as illustrated in Figure 1. CDF measures the W cross section in the electron and muon decay channels, and D0 does so in the electron channel. (CDF also looks at mono-jet events with large missing energy, and sees an enhancement in the number of jets with one and three charged tracks, evidence for W → τ ν decays .) The inputs and results for the cross-section measurements are given in Table 1. The measurements are systematics-limited, with the overall uncertainty typically dominated by …
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ar X iv : 0 70 9 . 26 65 v 1 [ he p - ex ] 1 7 Se p 20 07 Top Quark Physics at the Tevatron ∗
The Tevatron proton-antiproton collider at Fermilab with its centre of mass energy of 1.96 TeV is currently the only source for the production of top quarks. Its increased luminosity and centre of mass energy in Run II allow both collider detectors CDF and D0 to study top quarks with unprecedented scrutiny. Recent results on the top quark’s pair production cross section and its properties such ...
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