15 research outputs found
Cross-section-constrained top-quark mass measurement from dilepton events at the tevatron
No full textWe report the first top-quark mass measurement that uses a cross-section constraint to improve the mass determination. This measurement is made with a dilepton t (t) over bar event candidate sample collected with the Collider Detector II at Fermilab. From a data sample corresponding to an integrated luminosity of 1.2 fb(-1), we measure a top-quark mass of 170.7(-3.9)(+4.2)(stat)+/- 2.6(syst)+/- 2.4(theory) GeV/c(2). The measurement without the cross-section constraint is 169.7(-4.9)(+5.2)(stat)+/- 3.1(syst) GeV/c(2)
Observation of orbitally excited B-s mesons
No full textWe report the observation of two narrow resonances consistent with states of orbitally excited (L=1) B-s mesons using 1 fb(-1) of p (p) over bar collisions at root s =1.96 TeV collected with the Collider Detector at Fermilab II detector at the Fermilab Tevatron. We use two-body decays into K- and B+ mesons reconstructed as B+-> J/psi K+, J/psi ->mu(+)mu(-) or B+->(D) over bar (0)pi(+), (D) over bar (0)-> K+pi(-). We deduce the masses of the two states to be m(B-s1)=5829.4 +/- 0.7 MeV/c(2) and m(B-s2(*))=5839.6 +/- 0.7 MeV/c(2)
Polarizations of J/psi and psi(2S) mesons produced in p(p)over-bar collisins at root s-1.96 TeV
No full textWe have measured the polarizations of J/psi and psi(2S) mesons as functions of their transverse momentum p(T) when they are produced promptly in the rapidity range |y|= 5 GeV/c. The analysis is performed using a data sample with an integrated luminosity of about 800 pb(-1) collected by the CDF II detector. For both vector mesons, we find that the polarizations become increasingly longitudinal as p(T) increases from 5 to 30 GeV/c. These results are compared to the predictions of nonrelativistic quantum chromodynamics and other contemporary models. The effective polarizations of J/psi and psi(2S) mesons from B-hadron decays are also reported
Search for the Higgs boson in events with missing transverse energy and b quark jets produced in p(p)over-bar collisions at root s=1.96 TeV
No full textWe search for the standard model Higgs boson produced in association with an electroweak vector boson in events with no identified charged leptons, large imbalance in transverse momentum, and two jets where at least one contains a secondary vertex consistent with the decay of b hadrons. We use similar to 1 fb(-1) integrated luminosity of p (p) over bar collisions at root s = 1: 96 TeV recorded by the Collider Detector at Fermilab II experiment at the Tevatron. We find 268 (16) single (double) b-tagged candidate events, where 248 +/- 43 (14: 4 +/- 2: 7) are expected from standard model background processes. We observe no significant excess over the expected background and thus set 95% confidence level upper limits on the Higgs boson production cross section for several Higgs boson masses ranging from 110 to 140 GeV/c(2). For a mass of 115 GeV/c(2), the observed (expected) limit is 20.4 (14.2) times the standard model prediction
First run II measurement of the W boson mass at the Fermilab Tevatron
No full textWe describe a measurement of the W boson mass m(W) using 200 pb(-1) of root s=1.96 TeV p (p) over bar collision data taken with the CDF II detector. With a sample of 63 964 W -\u3e e nu candidates and 51 128 W -\u3e mu nu candidates, we measure m(W) = [80.413 +/- 0.034(stat) +/- 0.034(sys) = 80.413 +/- 0.048] GeV/c(2). This is the single most precise m(W) measurement to date. When combined with other measured electroweak parameters, this result further constrains the properties of new unobserved particles coupling to W and Z bosons
Search for pair production of scalar top quarks decaying to a tau lepton and a b quark in p(p)over-bar collisions at root s=1.96 TeV
No full textWe search for pair production of supersymmetric top quarks((t) over tilde (1)), followed by R-parity violating decay (t) over tilde (1)->tau b with a branching ratio beta, using 322 pb(-1) of p (p) over bar collisions at root s=1: 96 TeV collected by the upgraded Collider Detector at Fermilab. Two candidate events pass our final selection criteria, consistent with the standard model expectation. We set upper limits on the cross section sigma((t) over tilde (1)(t) over tilde (1)) x beta(2) as a function of the top-squark mass m((t) over tilde (1)). Assuming beta=1, we set a 95% confidence level limit m((t) over tilde (1)) > 153 GeV/c(2). The limits are also applicable to the case of a third-generation scalar leptoquark (LQ(3)) decaying LQ(3)->tau b
Search for heavy, long-lived neutralinos that decay to photons at CDF II using photon timing
No full textWe present the results of the first hadron collider search for heavy, long-lived neutralinos that decay via chi(0)(1)-\u3egamma G in gauge-mediated supersymmetry breaking models. Using an integrated luminosity of 570 +/- 34 pb(-1) of p (p) over bar collisions at root s=1.96 TeV, we select gamma+jet+missing transverse energy candidate events based on the arrival time of a high-energy photon at the electromagnetic calorimeter as measured with a timing system that was recently installed on the CDF II detector. We find 2 events, consistent with the background estimate of 1.3 +/- 0.7 events. While our search strategy does not rely on model-specific dynamics, we set cross section limits and place the world-best 95% C.L. lower limit on the chi(0)(1) mass of 101 GeV/c(2) at tau(0)(chi 1)=5 ns
Two-particle momentum correlations in jets produced in p(p)over-barcollisions at root s=1.96 TeV
No full textWe present the first measurement of two-particle momentum correlations in jets produced in p (p) over bar collisions at root s = 1.96 TeV. Results are obtained for charged particles within a restricted cone with an opening angle of 0.5 radians around the jet axis and for events with dijet masses between 66 and 563 GeV/c(2). A comparison of the experimental data to theoretical predictions obtained for partons within the framework of resummed perturbative QCD in the next-to-leading log approximation shows that the parton momentum correlations survive the hadronization stage of jet fragmentation, giving further support to the hypothesis of local parton-hadron duality. The extracted value of the next-to-leading-log-approximation parton shower cutoff scale Q(eff) set equal to Lambda(QCD) is found to be (1.4(-0.7)(+0.9)) x 100 MeV
Search for standard model Higgs Bosons produced in association with W Bosons
No full textWe report on the results of a search for standard model Higgs bosons produced in association with W bosons from pp̅ collisions at √s=1.96 TeV. The search uses a data sample corresponding to approximately 1 fb<sup>-1</sup> of integrated luminosity. Events consistent with the W→ℓν and H→bb̅ signature are selected by triggering on a high-p<sub>T</sub> electron or muon candidate and tagging one or two of the jet candidates as having originated from b quarks. A neural network filter rejects a fraction of tagged charm and light-flavor jets, increasing the b-jet purity in the sample. We observe no excess ℓνbb̅ production beyond the background expectation, and we set 95% confidence level upper limits on the production cross section times branching fraction σ(pp̅ →WH)Br(H→bb̅ ) ranging from 3.9 to 1.3 pb, for specific Higgs boson mass hypotheses in the range 110 to 150 GeV/c<sup>2</sup>, respectively
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
