9 research outputs found
Measurement of the cross section for t(t)over-bar production in p(p)over-bar collisions using the kinematics of lepton plus jets events
No full textWe present a measurement of the top pair production cross section in p (p) over bar collisions at root s=1.96 TeV. We collect a data sample with an integrated luminosity of 194 +/- 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 (t) over bar)=6.6 +/- 1.1 +/- 1.5 pb, where the first uncertainty is statistical and the second is systematic
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
Measurement of the top-quark mass in the lepton+jets channel using a matrix element technique with the CDF II detector
No full textA measurement of the top-quark mass is presented using Tevatron data from proton-antiproton collisions at center-of-mass energy √s=1.96 TeV collected with the CDF II detector. Events are selected from a sample of candidates for production of tt̅ pairs that decay into the lepton+jets channel. The top-quark mass is measured with an unbinned maximum likelihood method where the event probability density functions are calculated using signal and background matrix elements, as well as a set of parametrized jet-to-parton transfer functions. The likelihood function is maximized with respect to the top-quark mass, the signal fraction in the sample, and a correction to the jet energy scale (JES) calibration of the calorimeter jets. The simultaneous measurement of the JES correction (ΔJES) amounts to an additional in situ jet energy calibration based on the known mass of the hadronically decaying W boson. Using the data sample of 578 lepton+jets candidate events, corresponding to 3.2 fb-1 of integrated luminosity, the top-quark mass is measured to be mt=172.4±1.4(stat+ΔJES)±1.3(syst) GeV/c2.National Science Foundation (U.S.)United States. Dept. of EnergyAlfred P. Sloan Foundatio
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 a Heavy Top-Like Quark in p\bar{p} Collisions at {\surd}s = 1.96 TeV
No full textWe present the results of a search for pair production of a heavy top-like (t') quark decaying to Wq final states using data corresponding to an integrated luminosity of 5.6 fb-1 collected by the CDF II detector in pp collisions at {\surd}s = 1.96 TeV. We perform parallel searches for t' \to Wb and t' \to Wq (where q is a generic down-type quark) in events containing a lepton and four or more jets. By performing a fit to the two-dimensional distribution of total transverse energy versus reconstructed t quark mass, we set upper limits on the t \bar{t} production cross section and exclude a standard model fourth-generation t' quark decaying to W b (W q) with mass below 358 (340) GeV/c2 at 95% CL
Search for new heavy particles decaying to Z(0)Z(0)-> eeee in p(p)over-bar collisions at root s=1.96 TeV
No full textWe report the results of a search for the anomalous production of a massive particle decaying to four electrons via two Z0 bosons in 1.1fb-1 of pp̄ collisions at s=1.96TeV collected by the CDF II detector at Fermilab. We employ optimized electron identification criteria to maximize acceptance and efficiency. We estimate the backgrounds in the invariant mass range 500-1000GeV/c2 to be 0.028±0.009(stat)±0.011(syst) events. We observe zero events in this search region. Assuming a Randall-Sundrum graviton production model, we set 95% C.L. limits on σ×BF(G→Z0Z0)<4- 6pb, depending on the graviton mass. © 2008 The American Physical Society
Search for WZ+ZZ production with missing transverse energy+jets with b enhancement at √s=1.96 TeV
No full textDiboson production (WW+WZ+ZZ) has been observed at the Tevatron in hadronic decay modes dominated by the WW process. This paper describes the measurement of the cross section of WZ and ZZ events in final states with large E̸[subscript T] and using b-jet identification as a tool to suppress WW contributions. Because of the limited energy resolution, we cannot distinguish between partially hadronic decays of WZ and ZZ, and we measure the sum of these processes. The number of signal events is extracted using a simultaneous fit to the invariant mass distribution of the two jets for events with two b-jet candidates and events with fewer than two b-jet candidates. We measure a cross section σ(pp̅ →WZ,ZZ)=5.8[subscript -3.0][superscript +3.6] pb, in agreement with the standard model
Measurement of the ratios of branching fractions B (B-s(0)-> D-s(-) pi(+) pi(+) pi(-))/B(B-0 -> D- pi(+) pi(+) pi(-)) and B(B-s(0) -> D-s(-) pi(+))/B(B-0 -> D- pi(+))
No full textUsing 355 pb(-1) of data collected by the CDF II detector in p (p) over bar at collisions at root s = 1.96 TeV at the Fermilab Tevatron, we study the fully reconstructed hadronic decays B-(s)(0) -> D-(s)(-)pi(+) and B-(s)(0) -> D-(s)(-) pi(+)pi(+)pi(-). We present the first measurement of the ratio of branching fractions B(B-s(0) -> D-s(-) pi(+)pi(+)pi(-))/B(B-0 -> D-s(-) pi(+)pi(+)pi(-)) = 1.05 +/- 0.10(stat) +/- 0.22(syst). We also update our measurement of B(B-s(0) -> D-s(-)pi(+))/B(B-0 -> D-pi(+)) to 1.13 +/- 0.08(stat) +/- 0.23(syst), improving the statistical uncertainty by more than a factor of 2. We find B(B-s(0) -> D-s(-)pi(+)) = [3.8 +/- 0.3(stat) +/- 1.3(syst)] x 10(-3) and B(B-s(0) -> D-s(-) pi(+)pi(+)pi(-)) = [8.4 +/- 0.8 (stat) +/- 3.2(syst)] x 10(-3)
Study of multi-muon events produced in p (p)over-bar interactions at root s=1.96 TeV
No full textWe report the results of a study of multi-muon events produced at the Fermilab Tevatron collider and acquired with the CDF II detector using a dedicated dimuon trigger. The production cross section and kinematics of events in which both muon candidates are produced inside the beam pipe of radius 1.5 cm are successfully modeled by known processes which include heavy flavor production. In contrast, we are presently unable to fully account for the number and properties of the remaining events, in which at least one muon candidate is produced outside of the beam pipe, in terms of the same understanding of the CDF II detector, trigger, and event reconstruction
