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CDF Collaboration

Publications and source records attributed to CDF Collaboration.

At least 55 records · Page 3Linked to original sources

arXiv2014

Measurement of \boldmath $R = {\mathcal{B}\left(t \rightarrow Wb \right)/\mathcal{B}\left(t \rightarrow Wq \right)} $ in Top--Quark--Pair Decays using Dilepton Events and the Full CDF Run II Data Set

We present a measurement of the ratio of the top-quark branching fractions $R=\mathcal{B}(t\rightarrow Wb)/\mathcal{B}(t\rightarrow $ $q$ represents quarks of flavors $b$, $s$, or $d$, in the final state, in events with two charged leptons, missing transverse energy and at least two jets. The measurement uses $\sqrt{s}$ = 1.96 TeV proton--antiproton collision data corresponding to an integrated luminosity of 8.7 fb$^{-1}$ and collected with the Collider Detector at Fermilab during Run II of the Tevatron. We measure $R=0.87 \pm 0.07$ (stat+syst), and extract the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element, $\left|V_{tb}\right| = 0.93 \pm 0.04$ (stat+syst) assuming three generations of quarks. Under these assumptions, a lower limit of $|V_{tb}|>0.85$ at 95% credibility level is set.

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arXiv2014

Mass and lifetime measurements of bottom and charm baryons in $p\bar p$ collisions at $\sqrt{s}= 1.96 TeV

We report on mass and lifetime measurements of several ground state charmed and bottom baryons, using a data sample corresponding to 9.6 $\textrm{fb}^{-1}$ from $p\bar p$ collisions at $\sqrt{s}=1.96$ TeV, and recorded with the Collider Detector at Fermilab. Baryon candidates are reconstructed from data collected with an online event selection designed for the collection of long-lifetime heavy-flavor decay products and a second event selection designed to collect $J/ψ\rightarrow μ^+ \, μ^-$ candidates. First evidence for the process $Ω_b^- \rightarrow Ω_c^0 \, π^-$ is presented with a significance of $3.3σ$. We measure the following baryon masses: \begin{eqnarray} M(Ξ_c^{0}) = 2470.85\pm0.24(stat)\pm0.55(syst) \, MeV/c^2, \nonumber M(Ξ_c^{+}) = 2468.00\pm0.18(stat)\pm0.51(syst) \, MeV/c^2, \nonumber \\ M(Λ_b) = 5620.15\pm0.31(stat)\pm0.47(syst) \, MeV/c^2, \nonumber \\ M(Ξ_b^-) = 5793.4\pm1.8(stat)\pm0.7(syst) \, MeV/c^2, \nonumber \\ M(Ξ_b^0) = 5788.7\pm4.3(stat)\pm1.4(syst) \, MeV/c^2, \, and \nonumber \\ M(Ω_b^-) = 6047.5\pm3.8(stat)\pm0.6(syst) \, MeV/c^2. \nonumber \end{eqnarray} The isospin splitting of the $Ξ_b^{-,0}$ states is found to be $M(Ξ_b^-)-M(Ξ_b^0)=4.7\pm4.7(stat)\pm0.7(syst)$ MeV/$c^2$. The isospin splitting of the $Ξ_c^{0,+}$ states is found to be $M(Ξ_c^0)-M(Ξ_c^+)$ = $2.85\pm0.30(stat)\pm0.04(syst)$ MeV/$c^2$. The following lifetime measurements are made: \begin{eqnarray} τ(Λ_b) = 1.565\pm0.035(stat)\pm0.020(syst) \, ps, \nonumber \\ τ(Ξ_b^-) = 1.32\pm0.14(stat)\pm0.02(syst) \, ps, \nonumber \\ τ(Ω_b^-) = 1.66^{+0.53}_{-0.40}(stat)\pm0.02(syst) \, ps. \nonumber \end{eqnarray}

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arXiv2014

First Search for Exotic Z Boson Decays into Photons and Neutral Pions in Hadron Collisions

A search for forbidden and exotic Z boson decays in the diphoton mass spectrum is presented for the first time in hadron collisions, based on data corresponding to 10.0 fb^-1 of integrated luminosity from proton-antiproton collisions at sqrt(s) = 1.96 TeV collected by the CDF experiment. No evidence of signal is observed, and 95% credibility level Bayesian upper limits are set on the branching ratios of decays of the Z boson to a photon and neutral pion (which is detected as a photon), a pair of photons, and a pair of neutral pions. The observed branching ratio limits are 2.01 x 10^-5 for Z to π^0γ, 1.46 x 10^-5 for Z to γγ, and 1.52 x 10^-5 for Z to π^0π^0. The Z to π^0γ and Z to γγ limits improve by factors of 2.6 and 3.6, respectively, the most stringent results from other experiments. The Z to π^0π^0 branching ratio limit is the first experimental result on this decay.

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arXiv2014

Indirect measurement of $\sin^2 θ_W$ (or $M_W$) using $μ^+μ^-$ pairs from $γ^*/Z$ bosons produced in $p\bar{p}$ collisions at a center-of-momentum energy of 1.96 TeV

Drell-Yan lepton pairs are produced in the process $p\bar{p} \rightarrow μ^+μ^- + X$ through an intermediate $γ^*/Z$ boson. The forward-backward asymmetry in the polar-angle distribution of the $μ^-$ as a function of the invariant mass of the $μ^+μ^-$ pair is used to obtain the effective leptonic determination $\sin^2 θ^{lept}_{eff}$ of the electroweak-mixing parameter $\sin^2 θ_W$, from which the value of $\sin^2 θ_W$ is derived assuming the standard model. The measurement sample, recorded by the Collider Detector at Fermilab (CDF), corresponds to 9.2 fb-1 of integrated luminosity from $p\bar{p}$ collisions at a center-of-momentum energy of 1.96 TeV, and is the full CDF Run II data set. The value of $\sin^2 θ^{lept}_{eff}$ is found to be 0.2315 +- 0.0010, where statistical and systematic uncertainties are combined in quadrature. When interpreted within the context of the standard model using the on-shell renormalization scheme, where $\sin^2 θ_W = 1 - M_W^2/M_Z^2$, the measurement yields $\sin^2 θ_W$ = 0.2233 +- 0.0009, or equivalently a W-boson mass of 80.365 +- 0.047 GeV/c^2. The value of the W-boson mass is in agreement with previous determinations in electron-positron collisions and at the Tevatron collider.

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arXiv2014

Observation of s-channel production of single top quarks at the Tevatron

We report the first observation of single-top-quark production in the s channel through the combination of the CDF and D0 measurements of the cross section in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. The data correspond to total integrated luminosities of up to 9.7 fb-1 per experiment. The measured cross section is $σ_s = 1.29^{+0.26}_{-0.24}$ pb. The probability of observing a statistical fluctuation of the background to a cross section of the observed size or larger is $1.8 \times 10^{-10}$, corresponding to a significance of 6.3 standard deviations for the presence of an s-channel contribution to the production of single-top quarks.

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arXiv2014

Search for $s$-channel Single Top Quark Production in the Missing Energy Plus Jets Sample using the Full CDF II Data Set

The first search for single top quark production from the exchange of an $s$-channel virtual $W$ boson using events with an imbalance in the total transverse momentum, $b$-tagged jets, and no identified leptons is presented. The full data set collected by the Collider Detector at Fermilab, corresponding to an integrated luminosity of 9.45 fb$^{-1}$ from Fermilab Tevatron proton-antiproton collisions at a center of mass energy of 1.96 TeV, is used. Assuming the electroweak production of top quarks of mass 172.5 GeV/$c^2$ in the $s$-channel, a cross section of $1.12_{-0.57}^{+0.61}$ (stat+syst) pb, with a significance of 1.9 standard deviations, is measured. This measurement is combined with a previous result obtained from events with an imbalance in total transverse momentum, $b$-tagged jets, and exactly one identified lepton, yielding a cross section of $1.36_{-0.32}^{+0.37}$ (stat+syst) pb, with a significance of 4.2 standard deviations.

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arXiv2013

Measurement of the Differential Cross Section dσ/d(cos θt) for Top-Quark Pair Production in p-pbar Collisions at sqrt{s} = 1.96 TeV

We report a measurement of the differential cross section, dσ/d(cos θt), for top-quark-pair production as a function of the top-quark production angle in proton-antiproton collisions at sqrt{s} = 1.96 TeV. This measurement is performed using data collected with the CDF II detector at the Tevatron, corresponding to an integrated luminosity of 9.4/fb. We employ the Legendre polynomials to characterize the shape of the differential cross section at the parton level. The observed Legendre coefficients are in good agreement with the prediction of the next-to-leading-order standard-model calculation, with the exception of an excess linear-term coefficient, a1 = 0.40 +- 0.12, compared to the standard-model prediction of a1 = 0.15^{+0.07}_{-0.03}.

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arXiv2013

Observation of D0-D0bar Mixing using the CDF II Detector

We measure the time dependence of the ratio of decay rates for D0 -> K+ pi- to the Cabibbo-favored decay D0 -> K- pi+. The charge conjugate decays are included. A signal of 3.3 x 10^4 D*+ -> pi+ D0, D0 -> K+ pi- decays is obtained with D0 proper decay times between 0.75 and 10 mean D0 lifetimes. The data were recorded with the CDF II detector at the Fermilab Tevatron and correspond to an integrated luminosity of 9.6 fb-1 for p-pbar collisions at sqrt(s) = 1.96 TeV. Assuming CP conservation, we search for D0-D0bar mixing and measure the mixing parameters to be R_D = (3.51 +/- 0.35) x 10^{-3}, y' = (4.3 +/- 4.3) x 10^{-3}, and x'^2 = (0.08 +/- 0.18) x 10^{-3}. We report Bayesian probability intervals in the x'^2 - y' plane and find that the significance of excluding the no-mixing hypothesis is equivalent to 6.1 Gaussian standard deviations, providing the second observation of D0-D0bar mixing from a single experiment.

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arXiv2013

Search for a dijet resonance in events with jets and missing transverse energy in $p\bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV

We report on a search for a dijet resonance in events with only two or three jets and large imbalance in the total event transverse momentum. This search is sensitive to the possible production of a new particle in association with a $W$ or $Z$ boson, where the boson decays leptonically with one or more neutrinos in the final state. We use the full data set collected by the CDF II detector at the Tevatron collider at a proton-antiproton center-of-mass energy of 1.96 TeV. These data correspond to an integrated luminosity of 9.1 fb$^{-1}$. We study the invariant mass distribution of the two jets with highest transverse energy. We find good agreement between data and standard model background expectations and measure the combined cross section for WW, WZ, and ZZ production to be $13.8^{+3.0}_{-2.7}$ pb. No significant anomalies are observed in the mass spectrum and 95% credibility level upper limits are set on the production rates of a potential new particle in association with a $W$ or $Z$ boson.

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arXiv2013

Indirect measurement of $sin^2θ_W$ (M_W) using e+e- pairs in the Z-boson region with $p\bar{p}$ collisions at a center-of-momentum energy of 1.96 TeV

Drell-Yan lepton pairs are produced in the process $p\bar{p} \rightarrow e^+e^- + X$ through an intermediate $γ^*/Z$ boson. The lepton angular distributions are used to provide information on the electroweak-mixing parameter $sin^2θ_W$ via its observable effective-leptonic $sin^2θ_W$, or $sin^2θ^{lept}_{eff}$. A new method to infer $sin^2θ_W$, or equivalently, the W-boson mass M_W in the on-shell scheme, is developed and tested using a previous CDF Run II measurement of angular distributions from electron pairs in a sample corresponding to 2.1 fb-1 of integrated luminosity from $p\bar{p}$ collisions at a center-of-momentum energy of 1.96 TeV. The value of $sin^2θ^{lept}_{eff}$ is found to be 0.2328 +- 0.0010. Within a specified context of the standard model, this results in $sin^2θ_W$ = 0.2246 +- 0.0009 which corresponds to a W-boson mass of 80.297 +- 0.048 GeV/c^2, in agreement with previous determinations in electron-position collisions and at the Tevatron collider.

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arXiv2013

A Direct Measurement of the Total Decay Width of the Top Quark

We present a measurement of the total decay width of the top quark using events with top-antitop-quark pair candidates reconstructed in the final state with one charged lepton and four or more hadronic jets. We use the full Tevatron Run II data set of $\sqrt{s} = 1.96$ TeV proton-antiproton collisions recorded by the CDF II detector. The top-quark mass and the mass of the hadronically-decaying $W$ boson are reconstructed for each event and compared with distributions derived from simulated signal and background samples to extract the top-quark width (\gmt) and the energy scale of the calorimeter jets with {\it in-situ} calibration. For a top-quark mass $\mtop = \gevcc{172.5}$, we find $1.10<\gmt<\gev{4.05}$ at 68% confidence level, which is in agreement with the standard-model expectation of \gev{1.3} and is the most precise direct measurement of the top-quark width to date.

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arXiv2013

Measurement of the top-quark pair production cross-section in events with two leptons and bottom-quark jets using the full CDF data set

We present a measurement of the top-quark pair production cross-section in proton-antiproton collisions at $\sqrt{s}$=1.96 TeV. The data were collected at the Fermilab Tevatron by the CDF II detector and correspond to an integrated luminosity of 8.8 fb$^{-1}$, representing the complete CDF Run II data set. We select events consistent with the production of top-quark pairs by requiring the presence of two reconstructed leptons, an imbalance in the total event transverse momentum, and jets. At least one jet is required to be identified as consistent with the fragmentation of a bottom quark using a secondary-vertex-finding algorithm. The 246 candidate events are estimated to have a signal purity of 91%. We measure a cross section of $σ_{\ttbar}$ = 7.09 $\pm$ 0.84 pb, assuming a top-quark mass of 172.5 GeV/$c^{2}$. The results are consistent with the standard model as predicted by next-to-leading-order calculations.

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arXiv2013

Measurement of $B$ Baryon Properties at CDF

We report on mass and mean life measurements of several ground state $b-$baryons, using 9.6 $\textrm{fb}^{-1}$ of data from $p\bar p$ collisions at $\sqrt{s}=1.96$ TeV, and recorded with the Collider Detector at Fermilab. Data collected with triggers designed to collect events with $J/ψ\rightarrow μ^+ \, μ^-$ candidates and events with hadrons displaced from the beamline are used to measure the masses and lifetimes of $Λ_b, Ξ_b^-, Ξ_b^0$, and $Ω_b^-$. The first evidence for the process $Ω_b^- \rightarrow Ω_c^0 \, π^-$ is also shown. The results supersede our previous measurements of these quantities.

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arXiv2013

Search for the production of ZW and ZZ boson pairs decaying into charged leptons and jets in proton-antiproton collisions at sqrt(s)=1.96 TeV

We present a measurement of the production cross section for ZW and ZZ boson pairs in final states with a pair of charged leptons, from the decay of a Z boson, and at least two jets, from the decay of a W or Z boson, using the full sample of proton-antiproton collisions recorded with the CDF II detector at the Tevatron, corresponding to 8.9 fb^(-1) of integrated luminosity. We increase the sensitivity to vector boson decays into pairs of quarks using a neural network discriminant that exploits the differences between the spatial spread of energy depositions and charged-particle momenta contained within the jet of particles originating from quarks and gluons. Additionally, we employ new jet energy corrections to Monte Carlo simulations that account for differences in the observed energy scales for quark and gluon jets. The number of signal events is extracted through a simultaneous fit to the dijet mass spectrum in three classes of events: events likely to contain jets with a heavy-quark decay, events likely to contain jets originating from light quarks, and events that fail these identification criteria. We determine the production cross section to be 2.5 +2.0 -1.0 pb (< 6.1 pb at the 95% confidence level), consistent with the standard model prediction of 5.1 pb.

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arXiv2013

Combination of measurements of the top-quark pair production cross section from the Tevatron Collider

We combine six measurements of the inclusive top-quark pair (ttbar) production cross section (sigma_ttbar) from data collected with the CDF and D0 detectors at the Fermilab Tevatron with proton anti-proton collisions at sqrt{s} = 1.96 TeV. The data correspond to integrated luminosities of up to 8.8 fb^{-1}. We obtain a value of sigma_ttbar = 7.60 \pm 0.41 pb for a top-quark mass of m_t=172.5 GeV. The contributions to the uncertainty are 0.20 pb from statistical sources, 0.29 pb from systematic sources, and 0.21 pb from the uncertainty on the integrated luminosity. The result is in good agreement with the standard model expectation of 7.35^{+0.28}_{-0.33} pb at NNLO+NNLL in pertubative QCD.

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arXiv2013

Search for new physics in trilepton events and limits on the associated chargino-neutralino production at CDF

We perform a search for new physics using final states consisting of three leptons and a large imbalance in transverse momentum resulting from proton-antiproton collisions at 1.96 TeV center-of-mass energy. We use data corresponding to 5.8 fb-1 of integrated luminosity recorded by the CDF II detector at the Tevatron collider. Our main objective is to investigate possible new low-momentum (down to 5 GeV/c) multi-leptonic final states not investigated by LHC experiments. Relative to previous CDF analyses, we expand the geometric and kinematic coverage of electrons and muons and utilize tau leptons that decay hadronically. Inclusion of tau leptons is particularly important for supersymmetry (SUSY) searches. The results are consistent with standard-model predictions. By optimizing our event selection to increase sensitivity to the minimal supergravity (mSUGRA) SUSY model, we set limits on the associated production of chargino and neutralino, the SUSY partners of the electroweak gauge bosons. We exclude cross sections up to 0.1 pb and chargino masses up to 168 GeV/c^2 at 95% CL, for a suited set of mSUGRA parameters. We also exclude a region of the two-dimensional space of the masses of the neutralino and the supersymmetric partner of the tau lepton, not previously excluded at the Tevatron.

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arXiv2013

W boson polarization measurement in the ttbar dilepton channel using the CDF II Detector

We present a measurement of $W$ boson polarization in top-quark decays in $t\bar{t}$ events with decays to dilepton final states using $5.1 {\rm fb^{-1}}$ of integrated luminosity in $p\bar{p}$ collisions collected by the CDF II detector at the Tevatron. A simultaneous measurement of the fractions of longitudinal ($f_0$) and right-handed ($f_+$) $W$ bosons yields the results $f_0 = 0.71 ^{+0.18}_{-0.17} {\rm (stat)} \pm 0.06 {\rm (syst)}$ and $f_+ = -0.07 \pm 0.09 {\rm (stat)} \pm 0.03 {\rm (syst)}$. Combining this measurement with our previous result based on single lepton final states, we obtain $f_0 = 0.84 \pm 0.09 {\rm (stat)} \pm 0.05 {\rm (syst)}$ and $f_{+} = -0.16 \pm 0.05 {\rm (stat)} \pm 0.04 {\rm (syst)}$. The results are consistent with standard model expectation.

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arXiv2013

Evidence for a bottom baryon resonance Lambda_b* in CDF data

Using data from proton-antiproton collisions at Ecms=1.96 TeV recorded by the CDF II detector at the Fermilab Tevatron, evidence for the excited resonance state Lambda_b* is presented in its Lambda_b0 pi+ pi- decay, followed by the Lambda_b0 -->Lambda_c+ (-->proton K- pi+) pi- decays. The analysis is based on a data sample corresponding to an integrated luminosity of 9.6/fb collected by an online event selection based on charged-particle tracks displaced from the proton-antiproton interaction point. The significance of the observed signal is 3.5 Gaussian sigmas. The mass of the observed state is found to be 5919.22 +- 0.76 MeV in agreement with similar findings in proton-proton collision experiments.

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