6 research outputs found
Combination of CDF and D0 results on the W boson mass and width
No full textThe results based on 1992–95 data (Run 1) from the CDF and D0 experiments on the measurements of the W boson mass and width are presented, along with the combined results. We report a Tevatron collider average MW=80.456±0.059  GeV. We also report the Tevatron collider average of the directly measured W boson width ΓW=2.115±0.105  GeV. We describe a new joint analysis of the direct W mass and width measurements. Assuming the validity of the standard model, we combine the directly measured W boson width with the width extracted from the ratio of W and Z boson leptonic partial cross sections. This combined result for the Tevatron is ΓW=2.135±0.050  GeV. Finally, we use the measurements of the direct total W width and the leptonic branching ratio to extract the leptonic partial width Γ(W→eν)=224±13  MeV
Direct Top-Quark Width Measurement at CDF
No full textWe present a measurement of the top-quark width in the lepton + jets decay channel of t (t) over bar events produced in p (p) over bar collisions at Fermilab's Tevatron collider and collected by the CDF II detector. From a data sample corresponding to 4.3 fb(-1) of integrated luminosity, we identify 756 candidate events. The top-quark mass and the mass of the hadronically decaying W boson that comes from the top-quark decay are reconstructed for each event and compared with templates of different top-quark widths (Gamma(t)) and deviations from nominal jet energy scale (Delta(JES)) to perform a simultaneous fit for both parameters, where Delta(JES) is used for the in situ calibration of the jet energy scale. By applying a Feldman-Cousins approach, we establish an upper limit at 95% confidence level (CL) of Gamma(t) < 7.6 GeV and a two-sided 68% CL interval of 0.3 GeV < Gamma(t) < 4.4 GeV for a top-quark mass of 172.5 GeV/c(2), which are consistent with the standard model prediction
Measurement of d sigma/dy of Drell-Yan e(+)e(-) pairs in the Z mass region from p(p)over-bar collisions at root s=1.96 TeV
No full textWe report on a CDF measurement of the total cross section and rapidity distribution, d sigma/dy, for gamma*/Z -\u3e e(+)e(-) events in the Z boson mass region (66 \u3c M-ee \u3c 116 GeV/c(2)) produced in p (p) over bar collisions at root s = 1.96 TeV with 2.1 fb(-1) of integrated luminosity. The measured cross section of 257 +/- 16 pb and d sigma/dy distribution are compared with Next-to-Leading-Order (NLO) and Next-to-Next-to-Leading-Order (NNLO) QCD theory predictions with CTEQ and MRST/MSTW parton distribution functions (PDFs). There is good agreement between the experimental total cross section and d sigma/dy measurements with theoretical calculations with the most recent NNLO PDFs. (C) 2010 Elsevier B.V. All rights reserved
Search for new physics in lepton plus photon plus X events with 305 pb(-1) of p(p)over-bar collisions at root s=1.96 TeV
No full textWe present results of a search for anomalous production of events containing a charged lepton (l, either e or mu) and a photon (gamma), both with high transverse momentum, accompanied by additional signatures X, including missing transverse energy (is not an element of(T)) and additional leptons and photons. We use the same selection criteria as in a previous CDF search but with a substantially larger data set, 305 pb(-1), a p (p) over bar collision energy of 1.96 TeV, and the CDF II detector. We find 42 l gamma E-T events versus an expectation of 37.3 +/- 5.4 events. We observe 31 ll is not an element of gamma+X events versus an expectation of 23.0 +/- 2.7 events. We find no events similar to the run I ll gamma gamma is not an element of(T) event
Search for chargino-neutralino production in p(p)over-bar collisions at root s=1.96 TeV
No full textWe present a search for associated production of the chargino and neutralino supersymmetric particles using up to 1.1 fb(-1) of integrated luminosity collected by the CDF II experiment at the Tevatron p (p) over bar collider at root s=1.96 TeV. We analyze events with a large transverse momentum imbalance and either three charged leptons or two charged leptons of the same electric charge. The numbers of observed events are consistent with standard model expectations. Upper limits on the production cross section are derived in different theoretical models
Observation of single top quark production and measurement of |V subscript tb| with CDF
No full textWe report the observation of electroweak single top quark production in 3.2 fb-1 [fb superscript -1] of pp̅ collision data collected by the Collider Detector at Fermilab at √s=1.96 TeV [square root of s=1.96 TeV]. Candidate events in the W+jets topology with a leptonically decaying W boson are classified as signal-like by four parallel analyses based on likelihood functions, matrix elements, neural networks, and boosted decision trees. These results are combined using a super discriminant analysis based on genetically evolved neural networks in order to improve the sensitivity. This combined result is further combined with that of a search for a single top quark signal in an orthogonal sample of events with missing transverse energy plus jets and no charged lepton. We observe a signal consistent with the standard model prediction but inconsistent with the background-only model by 5.0 standard deviations, with a median expected sensitivity in excess of 5.9 standard deviations. We measure a production cross section of 2.3-0.5+0.6(stat+sys) [2.3 subscript -0.5 superscript +0.6 (stat + sys)] pb, extract the value of the Cabibbo-Kobayashi-Maskawa matrix element |Vtb|=0.91-0.11+0.11(stat+sys)±0.07 [|V subscript tb|=0.91 subscript -0.11 superscript +0.11 (stat + sys)±0.07] (theory), and set a lower limit |Vtb|>0.71 [|V subscript tb|>0.71] at the 95% C.L., assuming mt=175 [m subscript t =175] GeV/c2 [GeV / c superscript 2].United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio
