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The CDF Collaboration

Publications and source records attributed to The CDF Collaboration.

At least 37 records · Page 2Linked to original sources

arXiv2010

Measurement of the Top Pair Production Cross Section in the Dilepton Decay Channel in ppbar Collisions at sqrt s = 1.96 TeV

A measurement of the $\ttbar$ production cross section in $\ppbar$ collisions at $\sqrt{\rm s}$ = 1.96 TeV using events with two leptons, missing transverse energy, and jets is reported. The data were collected with the CDF II Detector. The result in a data sample corresponding to an integrated luminosity 2.8 fb$^{-1}$ is: $σ_{\ttbar}$ = 6.27 $\pm$ 0.73(stat) $\pm$ 0.63(syst) $\pm$ 0.39(lum) pb. for an assumed top mass of 175 GeV/$c^{2}$.

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arXiv2010

Search for the supersymmetric partner of the top quark in ppbar collisions at sqrt(s) = 1.96 TeV

We present a search for the lightest supersymmetric partner of the top quark in proton-antiproton collisions at a center-of-mass energy sqrt(s)=1.96 TeV. This search was conducted within the framework of the R-parity conserving minimal supersymmetric extension of the standard model, assuming the stop decays dominantly to a lepton, a sneutrino, and a bottom quark. We searched for events with two oppositely-charged leptons, at least one jet, and missing transverse energy in a data sample corresponding to an integrated luminosity of 1fb^-1 collected by the CDF experiment. No significant evidence of a stop quark signal was found. Exclusion limits at 95% confidence level in the stop quark versus sneutrino mass plane are set. Stop quark masses up to 180 GeV/c^2 are excluded for sneutrino masses around 45 GeV/c^2, and sneutrino masses up to 116 GeV/c^2 are excluded for stop quark masses around 150 GeV/c^2.

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arXiv2010

Improved Search for a Higgs Boson Produced in Association with Z->l+l- in proton antiproton Collisions at sqrt(s) = 1.96 TeV

We present a search for the standard model Higgs boson produced with a Z boson in 4.1 fb^-1 of data collected with the CDF II detector at the Tevatron. In events consistent with the decay of the Higgs boson to a bottom-quark pair and the Z boson to electrons or muons, we set 95% credibility level upper limits on the ZH production cross section times the H -> b bbar branching ratio. Improved analysis methods enhance signal sensitivity by 20% relative to previous searches beyond the gain due to the larger data sample. At a Higgs boson mass of 115 GeV/c^2 we set a limit of 5.9 times the standard model value.

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arXiv2010

Updated Search for the Flavor-Changing Neutral-Current Decay D^0 \to μ + μ-

We report on a search for the flavor-changing neutral-current decay D0 \to μ+ μ- in pp collisions at \surd s = 1.96 TeV using 360 pb-1 of integrated luminosity collected by the CDF II detector at the Fermilab Tevatron collider. A displaced vertex trigger selects long-lived D0 candidates in the μ+ μ-, π+π-, and K-π+ decay modes. We use the Cabibbo-favored D0 \to K-π+ channel to optimize the selection criteria in an unbiased manner, and the kinematically similar D0 \toπ+ π- channel for normalization. We set an upper limit on the branching fraction (D0 --> μ+ μ-) < 2.1 E-7 (3.0 E-7) at the 90% (95%) confidence level.

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arXiv2010

Search for Anomalous Production of Events with Two Photons and Additional Energetic Objects at CDF

We present results of a search for anomalous production of two photons together with an electron, muon, $τ$ lepton, missing transverse energy, or jets using $p\bar{p}$ collision data from 1.1-2.0 fb$^{-1}$ of integrated luminosity collected by the Collider Detector at Fermilab (CDF). The event yields and kinematic distributions are examined for signs of new physics without favoring a specific model of new physics. The results are consistent with the standard model expectations. The search employs several new analysis techniques that significantly reduce instrumental backgrounds in channels with an electron and missing transverse energy.

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arXiv2010

Combined CDF and D0 Upper Limits on Standard Model Higgs-Boson Production with up to 6.7 fb-1 of Data

We combine results from CDF and D0 on direct searches for the standard model (SM) Higgs boson H in ppbar collisions at the Fermilab Tevatron at sqrt(s)=1.96 TeV. Compared to the previous Tevatron Higgs search combination more data have been added, additional new channels have been incorporated, and some previously used channels have been reanalyzed to gain sensitivity. We use the latest parton distribution functions and gg to H theoretical cross sections when comparing our limits to the SM predictions. With up to 5.9 fb-1 of data analyzed at CDF, and up to 6.7 fb-1 at D0, the 95% C.L. upper limits on Higgs boson production are factors of 1.56 and 0.68 the values of the SM cross section for a Higgs boson mass of m_H=115 GeV/c^2 and 165~GeVc^2. We exclude, at the 95% C.L., a new and larger region at high mass between 158<m_H<175 GeV/c^2.

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arXiv2010

Measurement of the ttbar Production Cross Section with an in situ Calibration of b-jet Identification Efficiency

A measurement of the top-quark pair-production cross section in ppbar collisions at sqrt{s}=1.96 TeV using data corresponding to an integrated luminosity of 1.12/fb collected with the Collider Detector at Fermilab is presented. Decays of top-quark pairs into the final states e nu + jets and mu nu + jets are selected, and the cross section and the b-jet identification efficiency are determined using a new measurement technique which requires that the measured cross sections with exactly one and multiple identified b-quarks from the top-quark decays agree. Assuming a top-quark mass of 175 GeV/c^2, a cross section of 8.5+/-0.6(stat.)+/-0.7(syst.) pb is measured.

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arXiv2010

Search for WW and WZ resonances decaying to electron, missing ET, and two jets in ppbar collisions at sqrt(s) = 1.96 TeV

Using data from 2.9/fb of integrated luminosity collected with the CDF II detector at the Tevatron, we search for resonances decaying into a pair of on-shell gauge bosons, WW or WZ, where one W decays into an electron and a neutrino, and the other boson decays into two jets. We observed no statistically significant excess above the expected standard model background, and we set cross section limits at 95% confidence level on G*(Randall-Sundrum graviton), Z', and W' bosons. By comparing these limits to theoretical cross sections, mass exclusion regions for the three particles are derived. The mass exclusion regions for Z' and W' are further evaluated as a function of their gauge coupling strength.

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arXiv2010

Search for R-parity Violating Decays of tau Sneutrinos to emu, mutau, and etau Pairs in ppbar Collisions at sqrt(s) = 1.96 TeV

We present a search for tau sneutrino production using the Tevatron ppbar collision data collected with the CDF II detector and corresponding to an integrated luminosity of 1 fb^-1. We focus on the scenarios predicted by the R-parity violating (RPV) supersymmetric models in which tau sneutrinos decay to two charged leptons of different flavor. With the data consistent with the standard model expectations, we set the upper limits on sigma(ppbar -> tau sneutrino)*BR(tau sneutrino ->emu,mutau,etau) and use these results to constrain the RPV couplings as a function of tau sneutrino mass.

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arXiv2010

Combined CDF and D0 upper limits on MSSM Higgs boson production in tau-tau final states with up to 2.2 fb-1

Combined results are presented on the search for a neutral Higgs boson in the di-tau final state using 1.8fb-1 and 2.2fb-1 of integrated luminosity collected at the CDF and D0 experiments respectively. Data were collected in ppbar collisions at a centre of mass energy of 1.96TeV during RunII of the Tevatron. Limits are set on the cross section times branching ratio ranging from 13.6pb to 0.653pb for Higgs masses from 90GeV to 200GeV respectively. The results are then interpreted as limits in four different benchmark scenarios within the framework of the MSSM.

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arXiv2010

Measurement of the Top Quark Mass and ppbar -> ttbar Cross Section in the All-Hadronic Mode with the CDFII Detector

We present a measurement of the top quark mass and of the top-antitop pair production cross section using p-pbar data collected with the CDFII detector at the Tevatron Collider at the Fermi National Accelerator Laboratory and corresponding to an integrated luminosity of 2.9 fb-1. We select events with six or more jets satisfying a number of kinematical requirements imposed by means of a neural network algorithm. At least one of these jets must originate from a b quark, as identified by the reconstruction of a secondary vertex inside the jet. The mass measurement is based on a likelihood fit incorporating reconstructed mass distributions representative of signal and background, where the absolute jet energy scale (JES) is measured simultaneously with the top quark mass. The measurement yields a value of 174.8 +- 2.4(stat+JES) ^{+1.2}_{-1.0}(syst) GeV/c^2, where the uncertainty from the absolute jet energy scale is evaluated together with the statistical uncertainty. The procedure measures also the amount of signal from which we derive a cross section, sigma_{ttbar} = 7.2 +- 0.5(stat) +- 1.0 (syst) +- 0.4 (lum) pb, for the measured values of top quark mass and JES.

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arXiv2010

Measurement of $dσ/dy$ of Drell-Yan $e^+e^-$ pairs in the $Z$ Mass Region from $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV

We report on a CDF measurement of the total cross section and rapidity distribution, $dσ/dy$, for $q\bar{q}\to γ^{*}/Z\to e^{+}e^{-}$ events in the $Z$ boson mass region ($66<M_{ee}<116$GeV/c$^2$) produced in $p\bar{p}$ collisions at $\sqrt{s}=1.96$TeV with 2.1fb$^{-1}$ of integrated luminosity. The measured cross section of $257\pm16$pb and $dσ/dy$ 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 $dσ/dy$ measurements with theoretical calculations with the most recent NNLO PDFs.

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arXiv2010

Search for Technicolor Particles Produced in Association with a W Boson at CDF

We present a search for the technicolor particles $ρ_{T}$ and $π_{T}$ in the process $p\bar{p} \to ρ_{T} \to Wπ_{T}$ at a center of mass energy of $\sqrt{s}=1.96 \mathrm{TeV}$. The search uses a data sample corresponding to approximately $1.9 \mathrm{fb}^{-1}$ of integrated luminosity accumulated by the CDF II detector at the Fermilab Tevatron. The event signature we consider is $W\to \ellν$ and $π_{T} \to b\bar{b}, b\bar{c}$ or $b\bar{u}$ depending on the $π_{T}$ charge. We select events with a single high-$p_T$ electron or muon, large missing transverse energy, and two jets. Jets corresponding to bottom quarks are identified with multiple $b$-tagging algorithms. The observed number of events and the invariant mass distributions are consistent with the standard model background expectations, and we exclude a region at 95% confidence level in the $ρ_T$-$π_T$ mass plane. As a result, a large fraction of the region $m(ρ_T) = 180$ - $250 \mathrm{GeV}/c^2$ and $m(π_T) = 95$ - $145 \mathrm{GeV}/c^2$ is excluded.

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arXiv2010

Studying the Underlying Event in Drell-Yan and High Transverse Momentum Jet Production at the Tevatron

We study the underlying event in proton-antiproton collisions by examining the behavior of charged particles (transverse momentum pT > 0.5 GeV/c, pseudorapidity |η| < 1) produced in association with large transverse momentum jets (~2.2 fb-1) or with Drell-Yan lepton-pairs (~2.7 fb-1) in the Z-boson mass region (70 < M(pair) < 110 GeV/c2) as measured by CDF at 1.96 TeV center-of-mass energy. We use the direction of the lepton-pair (in Drell-Yan production) or the leading jet (in high-pT jet production) in each event to define three regions of η-ϕspace; toward, away, and transverse, where ϕis the azimuthal scattering angle. For Drell-Yan production (excluding the leptons) both the toward and transverse regions are very sensitive to the underlying event. In high-pT jet production the transverse region is very sensitive to the underlying event and is separated into a MAX and MIN transverse region, which helps separate the hard component (initial and final-state radiation) from the beam-beam remnant and multiple parton interaction components of the scattering. The data are corrected to the particle level to remove detector effects and are then compared with several QCD Monte-Carlo models. The goal of this analysis is to provide data that can be used to test and improve the QCD Monte-Carlo models of the underlying event that are used to simulate hadron-hadron collisions.

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arXiv2010

A Search for the Higgs Boson Using Neural Networks in Events with Missing Energy and \boldit{b}-quark Jets in $p\bar p$ Collisions at $\sqrt{s}=1.96$ TeV

We report on a search for the standard model Higgs boson produced in association with a $W$ or $Z$ boson in $p\bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV recorded by the CDF II experiment at the Tevatron in a data sample corresponding to an integrated luminosity of 2.1 fb$^{-1}$. We consider events which have no identified charged leptons, an imbalance in transverse momentum, and two or three jets where at least one jet is consistent with originating from the decay of a $b$ hadron. We find good agreement between data and predictions. We place 95% confidence level upper limits on the production cross section for several Higgs boson masses ranging from 110$\gevm$ to 150$\gevm$. For a mass of 115$\gevm$ the observed (expected) limit is 6.9 (5.6) times the standard model prediction.

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arXiv2010

Measurement of the WW+WZ Production Cross Section Using the Lepton+Jets Final State at CDF II

We report two complementary measurements of the WW+WZ cross section in the final state consisting of an electron or muon, missing transverse energy, and jets, performed using p\bar{p} collision data at sqrt{s} = 1.96 TeV collected by the CDF II detector. The first method uses the dijet invariant mass distribution while the second more sensitive method uses matrix-element calculations. The result from the second method has a signal significance of 5.4 sigma and is the first observation of WW+WZ production using this signature. Combining the results gives sigma_{WW+WZ} = 16.0 +/- 3.3 pb, in agreement with the standard model prediction.

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arXiv2010

First Measurement of the b-jet Cross Section in Events with a W Boson in p-pbar Collisions at sqrt{s} = 1.96 TeV

The cross section for jets from b quarks produced with a W boson has been measured in ppbar collision data from 1.9/fb of integrated luminosity recorded by the CDF II detector at the Tevatron. The W+b-jets process poses a significant background in measurements of top quark production and prominent searches for the Higgs boson. We measure a b-jet cross section of 2.74 +- 0.27(stat.) +- 0.42(syst.) pb in association with a single flavor of leptonic W boson decay over a limited kinematic phase space. This measured result cannot be accommodated in several available theoretical predictions.

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arXiv2010

Measurement of W-Boson Polarization in Top-quark Decay in ppbar Collisions at sqrt(s) = 1.96 TeV

We report measurements of the polarization of W bosons from top-quark decays using 2.7 fb^-1 of ppbar collisions collected by the CDF II detector. Assuming a top-quark mass of 175 GeV/c^2, three measurements are performed. A simultaneous measurement of the fraction of longitudinal (f_0) and right-handed (f_+) W bosons yields the model-independent results f_0 = 0.88 \pm 0.11 (stat) \pm 0.06 (syst) and f_+ = -0.15 \pm 0.07 (stat) \pm 0.06 (syst) with a correlation coefficient of -0.59. A measurement of f_0 (f_+) constraining f_+ (f_0) to its standard model value of 0.0 (0.7) yields f_0 = 0.70 \pm 0.07 (stat) \pm 0.04 (syst) (f_+ = -0.01 \pm 0.02 (stat) \pm 0.05 (syst)). All these results are consistent with standard model expectations.

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